滑动的Button

Posted 2020-08-22 希小风

在介绍SwitchButton之前，先来看一下系统Button是如何实现的。源码如下：

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1. @RemoteView  
2. public class Button extends TextView {  
3.     public Button(Context context) {  
4.         this(context, null);  
5.     }  
6.   
7.     public Button(Context context, AttributeSet attrs) {  
8.         this(context, attrs, com.android.internal.R.attr.buttonStyle);  
9.     }  
10.   
11.     public Button(Context context, AttributeSet attrs, int defStyle) {  
12.         super(context, attrs, defStyle);  
13.     }  
14.   
15.     @Override  
16.     public void onInitializeAccessibilityEvent(AccessibilityEvent event) {  
17.         super.onInitializeAccessibilityEvent(event);  
18.         event.setClassName(Button. class.getName());  
19.     }  
20.   
21.     @Override  
22.     public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) {  
23.         super.onInitializeAccessibilityNodeInfo(info);  
24.         info.setClassName(Button. class.getName());  
25.     }  
26. }  

@RemoteView
public class Button extends TextView {
    public Button(Context context) {
        this(context, null);
    }

    public Button(Context context, AttributeSet attrs) {
        this(context, attrs, com.android.internal.R.attr.buttonStyle);
    }

    public Button(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    public void onInitializeAccessibilityEvent(AccessibilityEvent event) {
        super.onInitializeAccessibilityEvent(event);
        event.setClassName(Button. class.getName());
    }

    @Override
    public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) {
        super.onInitializeAccessibilityNodeInfo(info);
        info.setClassName(Button. class.getName());
    }
}

  是直接继承于TextView，所不同的是在构造方法中添加了Button的样式，并且在初始化可见性方面交由Button类自己来处理。虽然Button的实现比较简单，但是它的子类并不是这样。看一下：

  直接子类只有有一个，CompoundButton。它是一个抽象类，而实现这个类的控件正是CheckBox, RadioButton, Switch, ToggleButton这四个，所以先重点说一下它。源码如下：

  

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1. /**  
2.  * <p>  
3.  * A button with two states, checked and unchecked. When the button is pressed  
4.  * or clicked, the state changes automatically.  
5.  * </p>  
6.  *  
7.  * <p><strong>XML attributes </strong></p>  
8.  * <p>  
9.  * See {@link android.R.styleable#CompoundButton  
10.  * CompoundButton Attributes}, {@link android.R.styleable#Button Button  
11.  * Attributes}, {@link android.R.styleable#TextView TextView Attributes}, {@link  
12.  * android.R.styleable #View View Attributes}  
13.  * </p>  
14.  */  
15. public abstract class CompoundButton extends Button implements Checkable {  
16.     private boolean mChecked ;  
17.     private int mButtonResource ;  
18.     private boolean mBroadcasting ;  
19.     private Drawable mButtonDrawable;  
20.     private OnCheckedChangeListener mOnCheckedChangeListener;  
21.     private OnCheckedChangeListener mOnCheckedChangeWidgetListener ;  
22.   
23.     private static final int[] CHECKED_STATE_SET = {  
24.         R.attr.state_checked  
25.     };  
26.   
27.     public CompoundButton(Context context) {  
28.         this(context, null);  
29.     }  
30.   
31.     public CompoundButton(Context context, AttributeSet attrs) {  
32.         this(context, attrs, 0);  
33.     }  
34.   
35.     public CompoundButton(Context context, AttributeSet attrs, int defStyle) {  
36.         super(context, attrs, defStyle);  
37.   
38.         TypedArray a =  
39.                 context.obtainStyledAttributes(  
40.                         attrs, com.android.internal.R.styleable.CompoundButton, defStyle, 0);  
41.   
42.         Drawable d = a.getDrawable(com.android.internal.R.styleable.CompoundButton_button);  
43.         if (d != null ) {  
44.             setButtonDrawable(d);  
45.         }  
46.   
47.         boolean checked = a  
48.                 .getBoolean(com.android.internal.R.styleable.CompoundButton_checked, false);  
49.         setChecked(checked);  
50.   
51.         a.recycle();  
52.     }  
53.   
54.     public void toggle() {  
55.         setChecked(! mChecked);  
56.     }  
57.   
58.     @Override  
59.     public boolean performClick() {  
60.         /*  
61.          * XXX: These are tiny, need some surrounding ‘expanded touch area‘,  
62.          * which will need to be implemented in Button if we only override  
63.          * performClick()  
64.          */  
65.   
66.         /* When clicked, toggle the state */  
67.         toggle();  
68.         return super .performClick();  
69.     }  
70.   
71.     @ViewDebug.ExportedProperty  
72.     public boolean isChecked() {  
73.         return mChecked ;  
74.     }  
75.   
76.     /**  
77.      * <p>Changes the checked state of this button.</p>  
78.      *  
79.      * @param checked true to check the button, false to uncheck it  
80.      */  
81.     public void setChecked(boolean checked) {  
82.         if (mChecked != checked) {  
83.             mChecked = checked;  
84.             refreshDrawableState();  
85.             notifyViewAccessibilityStateChangedIfNeeded(  
86.                     AccessibilityEvent.CONTENT_CHANGE_TYPE_UNDEFINED );  
87.   
88.             // Avoid infinite recursions if setChecked() is called from a listener  
89.             if (mBroadcasting ) {  
90.                 return;  
91.             }  
92.   
93.             mBroadcasting = true ;  
94.             if (mOnCheckedChangeListener != null) {  
95.                 mOnCheckedChangeListener.onCheckedChanged(this, mChecked);  
96.             }  
97.             if (mOnCheckedChangeWidgetListener != null) {  
98.                 mOnCheckedChangeWidgetListener .onCheckedChanged(this, mChecked);  
99.             }  
100.   
101.             mBroadcasting = false ;             
102.         }  
103.     }  
104.   
105.     /**  
106.      * Register a callback to be invoked when the checked state of this button  
107.      * changes.  
108.      *  
109.      * @param listener the callback to call on checked state change  
110.      */  
111.     public void setOnCheckedChangeListener(OnCheckedChangeListener listener) {  
112.         mOnCheckedChangeListener = listener;  
113.     }  
114.   
115.     /**  
116.      * Register a callback to be invoked when the checked state of this button  
117.      * changes. This callback is used for internal purpose only.  
118.      *  
119.      * @param listener the callback to call on checked state change  
120.      * @hide  
121.      */  
122.     void setOnCheckedChangeWidgetListener(OnCheckedChangeListener listener) {  
123.         mOnCheckedChangeWidgetListener = listener;  
124.     }  
125.   
126.     /**  
127.      * Interface definition for a callback to be invoked when the checked state  
128.      * of a compound button changed.  
129.      */  
130.     public static interface OnCheckedChangeListener {  
131.         /**  
132.          * Called when the checked state of a compound button has changed.  
133.          *  
134.          * @param buttonView The compound button view whose state has changed.  
135.          * @param isChecked  The new checked state of buttonView.  
136.          */  
137.         void onCheckedChanged(CompoundButton buttonView, boolean isChecked);  
138.     }  
139.   
140.     /**  
141.      * Set the background to a given Drawable, identified by its resource id.  
142.      *  
143.      * @param resid the resource id of the drawable to use as the background  
144.      */  
145.     public void setButtonDrawable(int resid) {  
146.         if (resid != 0 && resid == mButtonResource ) {  
147.             return;  
148.         }  
149.   
150.         mButtonResource = resid;  
151.   
152.         Drawable d = null;  
153.         if (mButtonResource != 0) {  
154.             d = getResources().getDrawable(mButtonResource );  
155.         }  
156.         setButtonDrawable(d);  
157.     }  
158.   
159.     /**  
160.      * Set the background to a given Drawable  
161.      *  
162.      * @param d The Drawable to use as the background  
163.      */  
164.     public void setButtonDrawable(Drawable d) {  
165.         if (d != null ) {  
166.             if (mButtonDrawable != null) {  
167.                 mButtonDrawable.setCallback(null);  
168.                 unscheduleDrawable( mButtonDrawable);  
169.             }  
170.             d.setCallback( this);  
171.             d.setVisible(getVisibility() == VISIBLE, false);  
172.             mButtonDrawable = d;  
173.             setMinHeight(mButtonDrawable .getIntrinsicHeight());  
174.         }  
175.   
176.         refreshDrawableState();  
177.     }  
178.   
179.     @Override  
180.     public void onInitializeAccessibilityEvent(AccessibilityEvent event) {  
181.         super.onInitializeAccessibilityEvent(event);  
182.         event.setClassName(CompoundButton.class .getName());  
183.         event.setChecked( mChecked);  
184.     }  
185.   
186.     @Override  
187.     public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) {  
188.         super.onInitializeAccessibilityNodeInfo(info);  
189.         info.setClassName(CompoundButton.class .getName());  
190.         info.setCheckable( true);  
191.         info.setChecked( mChecked);  
192.     }  
193.   
194.     @Override  
195.     public int getCompoundPaddingLeft() {  
196.         int padding = super.getCompoundPaddingLeft();  
197.         if (!isLayoutRtl()) {  
198.             final Drawable buttonDrawable = mButtonDrawable;  
199.             if (buttonDrawable != null) {  
200.                 padding += buttonDrawable.getIntrinsicWidth();  
201.             }  
202.         }  
203.         return padding;  
204.     }  
205.   
206.     @Override  
207.     public int getCompoundPaddingRight() {  
208.         int padding = super.getCompoundPaddingRight();  
209.         if (isLayoutRtl()) {  
210.             final Drawable buttonDrawable = mButtonDrawable;  
211.             if (buttonDrawable != null) {  
212.                 padding += buttonDrawable.getIntrinsicWidth();  
213.             }  
214.         }  
215.         return padding;  
216.     }  
217.   
218.     /**  
219.      * @hide  
220.      */  
221.     @Override  
222.     public int getHorizontalOffsetForDrawables() {  
223.         final Drawable buttonDrawable = mButtonDrawable ;  
224.         return (buttonDrawable != null) ? buttonDrawable.getIntrinsicWidth() : 0;  
225.     }  
226.   
227.     @Override  
228.     protected void onDraw(Canvas canvas) {  
229.         super.onDraw(canvas);  
230.   
231.         final Drawable buttonDrawable = mButtonDrawable ;  
232.         if (buttonDrawable != null) {  
233.             final int verticalGravity = getGravity() & Gravity.VERTICAL_GRAVITY_MASK ;  
234.             final int drawableHeight = buttonDrawable.getIntrinsicHeight();  
235.             final int drawableWidth = buttonDrawable.getIntrinsicWidth();  
236.   
237.             int top = 0;  
238.             switch (verticalGravity) {  
239.                 case Gravity.BOTTOM :  
240.                     top = getHeight() - drawableHeight;  
241.                     break;  
242.                 case Gravity.CENTER_VERTICAL :  
243.                     top = (getHeight() - drawableHeight) / 2;  
244.                     break;  
245.             }  
246.             int bottom = top + drawableHeight;  
247.             int left = isLayoutRtl() ? getWidth() - drawableWidth : 0;  
248.             int right = isLayoutRtl() ? getWidth() : drawableWidth;  
249.   
250.             buttonDrawable.setBounds(left, top, right, bottom);  
251.             buttonDrawable.draw(canvas);  
252.         }  
253.     }  
254.   
255.     @Override  
256.     protected int[] onCreateDrawableState(int extraSpace) {  
257.         final int [] drawableState = super.onCreateDrawableState(extraSpace + 1);  
258.         if (isChecked()) {  
259.             mergeDrawableStates(drawableState, CHECKED_STATE_SET);  
260.         }  
261.         return drawableState;  
262.     }  
263.   
264.     @Override  
265.     protected void drawableStateChanged() {  
266.         super.drawableStateChanged();  
267.          
268.         if (mButtonDrawable != null) {  
269.             int[] myDrawableState = getDrawableState();  
270.              
271.             // Set the state of the Drawable  
272.             mButtonDrawable.setState(myDrawableState);  
273.              
274.             invalidate();  
275.         }  
276.     }  
277.   
278.     @Override  
279.     protected boolean verifyDrawable(Drawable who) {  
280.         return super .verifyDrawable(who) || who == mButtonDrawable;  
281.     }  
282.   
283.     @Override  
284.     public void jumpDrawablesToCurrentState() {  
285.         super.jumpDrawablesToCurrentState();  
286.         if (mButtonDrawable != null) mButtonDrawable.jumpToCurrentState();  
287.     }  
288.   
289.     static class SavedState extends BaseSavedState {  
290.         boolean checked ;  
291.   
292.         /**  
293.          * Constructor called from {@link CompoundButton#onSaveInstanceState()}  
294.          */  
295.         SavedState(Parcelable superState) {  
296.             super(superState);  
297.         }  
298.          
299.         /**  
300.          * Constructor called from {@link #CREATOR}  
301.          */  
302.         private SavedState(Parcel in) {  
303.             super(in);  
304.             checked = (Boolean)in.readValue( null);  
305.         }  
306.   
307.         @Override  
308.         public void writeToParcel(Parcel out, int flags) {  
309.             super.writeToParcel(out, flags);  
310.             out.writeValue( checked);  
311.         }  
312.   
313.         @Override  
314.         public String toString() {  
315.             return "CompoundButton.SavedState{"  
316.                     + Integer.toHexString(System.identityHashCode(this))  
317.                     + " checked=" + checked + "}" ;  
318.         }  
319.   
320.         public static final Parcelable.Creator<SavedState> CREATOR  
321.                 = new Parcelable.Creator<SavedState>() {  
322.             public SavedState createFromParcel(Parcel in) {  
323.                 return new SavedState(in);  
324.             }  
325.   
326.             public SavedState[] newArray(int size) {  
327.                 return new SavedState[size];  
328.             }  
329.         };  
330.     }  
331.   
332.     @Override  
333.     public Parcelable onSaveInstanceState() {  
334.         // Force our ancestor class to save its state  
335.         setFreezesText( true);  
336.         Parcelable superState = super.onSaveInstanceState();  
337.   
338.         SavedState ss = new SavedState(superState);  
339.   
340.         ss. checked = isChecked();  
341.         return ss;  
342.     }  
343.   
344.     @Override  
345.     public void onRestoreInstanceState(Parcelable state) {  
346.         SavedState ss = (SavedState) state;  
347.    
348.         super.onRestoreInstanceState(ss.getSuperState());  
349.         setChecked(ss. checked);  
350.         requestLayout();  
351.     }  
352. }  

/**
 * <p>
 * A button with two states, checked and unchecked. When the button is pressed
 * or clicked, the state changes automatically.
 * </p>
 *
 * <p><strong>XML attributes </strong></p>
 * <p>
 * See {@link android.R.styleable#CompoundButton
 * CompoundButton Attributes}, {@link android.R.styleable#Button Button
 * Attributes}, {@link android.R.styleable#TextView TextView Attributes}, {@link
 * android.R.styleable #View View Attributes}
 * </p>
 */
public abstract class CompoundButton extends Button implements Checkable {
    private boolean mChecked ;
    private int mButtonResource ;
    private boolean mBroadcasting ;
    private Drawable mButtonDrawable;
    private OnCheckedChangeListener mOnCheckedChangeListener;
    private OnCheckedChangeListener mOnCheckedChangeWidgetListener ;

    private static final int[] CHECKED_STATE_SET = {
        R.attr.state_checked
    };

    public CompoundButton(Context context) {
        this(context, null);
    }

    public CompoundButton(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public CompoundButton(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

        TypedArray a =
                context.obtainStyledAttributes(
                        attrs, com.android.internal.R.styleable.CompoundButton, defStyle, 0);

        Drawable d = a.getDrawable(com.android.internal.R.styleable.CompoundButton_button);
        if (d != null ) {
            setButtonDrawable(d);
        }

        boolean checked = a
                .getBoolean(com.android.internal.R.styleable.CompoundButton_checked, false);
        setChecked(checked);

        a.recycle();
    }

    public void toggle() {
        setChecked(! mChecked);
    }

    @Override
    public boolean performClick() {
        /*
         * XXX: These are tiny, need some surrounding ‘expanded touch area‘,
         * which will need to be implemented in Button if we only override
         * performClick()
         */

        /* When clicked, toggle the state */
        toggle();
        return super .performClick();
    }

    @ViewDebug.ExportedProperty
    public boolean isChecked() {
        return mChecked ;
    }

    /**
     * <p>Changes the checked state of this button.</p>
     *
     * @param checked true to check the button, false to uncheck it
     */
    public void setChecked(boolean checked) {
        if (mChecked != checked) {
            mChecked = checked;
            refreshDrawableState();
            notifyViewAccessibilityStateChangedIfNeeded(
                    AccessibilityEvent.CONTENT_CHANGE_TYPE_UNDEFINED );

            // Avoid infinite recursions if setChecked() is called from a listener
            if (mBroadcasting ) {
                return;
            }

            mBroadcasting = true ;
            if (mOnCheckedChangeListener != null) {
                mOnCheckedChangeListener.onCheckedChanged(this, mChecked);
            }
            if (mOnCheckedChangeWidgetListener != null) {
                mOnCheckedChangeWidgetListener .onCheckedChanged(this, mChecked);
            }

            mBroadcasting = false ;           
        }
    }

    /**
     * Register a callback to be invoked when the checked state of this button
     * changes.
     *
     * @param listener the callback to call on checked state change
     */
    public void setOnCheckedChangeListener(OnCheckedChangeListener listener) {
        mOnCheckedChangeListener = listener;
    }

    /**
     * Register a callback to be invoked when the checked state of this button
     * changes. This callback is used for internal purpose only.
     *
     * @param listener the callback to call on checked state change
     * @hide
     */
    void setOnCheckedChangeWidgetListener(OnCheckedChangeListener listener) {
        mOnCheckedChangeWidgetListener = listener;
    }

    /**
     * Interface definition for a callback to be invoked when the checked state
     * of a compound button changed.
     */
    public static interface OnCheckedChangeListener {
        /**
         * Called when the checked state of a compound button has changed.
         *
         * @param buttonView The compound button view whose state has changed.
         * @param isChecked  The new checked state of buttonView.
         */
        void onCheckedChanged(CompoundButton buttonView, boolean isChecked);
    }

    /**
     * Set the background to a given Drawable, identified by its resource id.
     *
     * @param resid the resource id of the drawable to use as the background
     */
    public void setButtonDrawable(int resid) {
        if (resid != 0 && resid == mButtonResource ) {
            return;
        }

        mButtonResource = resid;

        Drawable d = null;
        if (mButtonResource != 0) {
            d = getResources().getDrawable(mButtonResource );
        }
        setButtonDrawable(d);
    }

    /**
     * Set the background to a given Drawable
     *
     * @param d The Drawable to use as the background
     */
    public void setButtonDrawable(Drawable d) {
        if (d != null ) {
            if (mButtonDrawable != null) {
                mButtonDrawable.setCallback(null);
                unscheduleDrawable( mButtonDrawable);
            }
            d.setCallback( this);
            d.setVisible(getVisibility() == VISIBLE, false);
            mButtonDrawable = d;
            setMinHeight(mButtonDrawable .getIntrinsicHeight());
        }

        refreshDrawableState();
    }

    @Override
    public void onInitializeAccessibilityEvent(AccessibilityEvent event) {
        super.onInitializeAccessibilityEvent(event);
        event.setClassName(CompoundButton.class .getName());
        event.setChecked( mChecked);
    }

    @Override
    public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) {
        super.onInitializeAccessibilityNodeInfo(info);
        info.setClassName(CompoundButton.class .getName());
        info.setCheckable( true);
        info.setChecked( mChecked);
    }

    @Override
    public int getCompoundPaddingLeft() {
        int padding = super.getCompoundPaddingLeft();
        if (!isLayoutRtl()) {
            final Drawable buttonDrawable = mButtonDrawable;
            if (buttonDrawable != null) {
                padding += buttonDrawable.getIntrinsicWidth();
            }
        }
        return padding;
    }

    @Override
    public int getCompoundPaddingRight() {
        int padding = super.getCompoundPaddingRight();
        if (isLayoutRtl()) {
            final Drawable buttonDrawable = mButtonDrawable;
            if (buttonDrawable != null) {
                padding += buttonDrawable.getIntrinsicWidth();
            }
        }
        return padding;
    }

    /**
     * @hide
     */
    @Override
    public int getHorizontalOffsetForDrawables() {
        final Drawable buttonDrawable = mButtonDrawable ;
        return (buttonDrawable != null) ? buttonDrawable.getIntrinsicWidth() : 0;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        final Drawable buttonDrawable = mButtonDrawable ;
        if (buttonDrawable != null) {
            final int verticalGravity = getGravity() & Gravity.VERTICAL_GRAVITY_MASK ;
            final int drawableHeight = buttonDrawable.getIntrinsicHeight();
            final int drawableWidth = buttonDrawable.getIntrinsicWidth();

            int top = 0;
            switch (verticalGravity) {
                case Gravity.BOTTOM :
                    top = getHeight() - drawableHeight;
                    break;
                case Gravity.CENTER_VERTICAL :
                    top = (getHeight() - drawableHeight) / 2;
                    break;
            }
            int bottom = top + drawableHeight;
            int left = isLayoutRtl() ? getWidth() - drawableWidth : 0;
            int right = isLayoutRtl() ? getWidth() : drawableWidth;

            buttonDrawable.setBounds(left, top, right, bottom);
            buttonDrawable.draw(canvas);
        }
    }

    @Override
    protected int[] onCreateDrawableState(int extraSpace) {
        final int [] drawableState = super.onCreateDrawableState(extraSpace + 1);
        if (isChecked()) {
            mergeDrawableStates(drawableState, CHECKED_STATE_SET);
        }
        return drawableState;
    }

    @Override
    protected void drawableStateChanged() {
        super.drawableStateChanged();
       
        if (mButtonDrawable != null) {
            int[] myDrawableState = getDrawableState();
           
            // Set the state of the Drawable
            mButtonDrawable.setState(myDrawableState);
           
            invalidate();
        }
    }

    @Override
    protected boolean verifyDrawable(Drawable who) {
        return super .verifyDrawable(who) || who == mButtonDrawable;
    }

    @Override
    public void jumpDrawablesToCurrentState() {
        super.jumpDrawablesToCurrentState();
        if (mButtonDrawable != null) mButtonDrawable.jumpToCurrentState();
    }

    static class SavedState extends BaseSavedState {
        boolean checked ;

        /**
         * Constructor called from {@link CompoundButton#onSaveInstanceState()}
         */
        SavedState(Parcelable superState) {
            super(superState);
        }
       
        /**
         * Constructor called from {@link #CREATOR}
         */
        private SavedState(Parcel in) {
            super(in);
            checked = (Boolean)in.readValue( null);
        }

        @Override
        public void writeToParcel(Parcel out, int flags) {
            super.writeToParcel(out, flags);
            out.writeValue( checked);
        }

        @Override
        public String toString() {
            return "CompoundButton.SavedState{"
                    + Integer.toHexString(System.identityHashCode(this))
                    + " checked=" + checked + "}" ;
        }

        public static final Parcelable.Creator<SavedState> CREATOR
                = new Parcelable.Creator<SavedState>() {
            public SavedState createFromParcel(Parcel in) {
                return new SavedState(in);
            }

            public SavedState[] newArray(int size) {
                return new SavedState[size];
            }
        };
    }

    @Override
    public Parcelable onSaveInstanceState() {
        // Force our ancestor class to save its state
        setFreezesText( true);
        Parcelable superState = super.onSaveInstanceState();

        SavedState ss = new SavedState(superState);

        ss. checked = isChecked();
        return ss;
    }

    @Override
    public void onRestoreInstanceState(Parcelable state) {
        SavedState ss = (SavedState) state;
 
        super.onRestoreInstanceState(ss.getSuperState());
        setChecked(ss. checked);
        requestLayout();
    }
}

  先从构造方法开始，在构造方法中，

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1. public CompoundButton(Context context, AttributeSet attrs, int defStyle) {  
2.        super(context, attrs, defStyle);  
3.   
4.        TypedArray a =  
5.                context.obtainStyledAttributes(  
6.                        attrs, com.android.internal.R.styleable.CompoundButton, defStyle, 0);  
7.   
8.        Drawable d = a.getDrawable(com.android.internal.R.styleable.CompoundButton_button);  
9.        if (d != null ) {  
10.            setButtonDrawable(d);  
11.        }  
12.   
13.        boolean checked = a  
14.                .getBoolean(com.android.internal.R.styleable.CompoundButton_checked, false);  
15.        setChecked(checked);  
16.   
17.        a.recycle();  
18.    }  
19.    

 public CompoundButton(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

        TypedArray a =
                context.obtainStyledAttributes(
                        attrs, com.android.internal.R.styleable.CompoundButton, defStyle, 0);

        Drawable d = a.getDrawable(com.android.internal.R.styleable.CompoundButton_button);
        if (d != null ) {
            setButtonDrawable(d);
        }

        boolean checked = a
                .getBoolean(com.android.internal.R.styleable.CompoundButton_checked, false);
        setChecked(checked);

        a.recycle();
    }
  

  先是从attrs中读取定义的属性，一个是Drawable用于设置背景；一个是布尔类型变量用于判断是否check过。设置背景使用的是setButtonDrawable()方法，代码如下：

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1. /**  
2.      * Set the background to a given Drawable  
3.      *  
4.      * @param d The Drawable to use as the background  
5.      */  
6.     public void setButtonDrawable(Drawable d) {  
7.         if (d != null ) {  
8.             if (mButtonDrawable != null) {  
9.                 mButtonDrawable.setCallback(null);  
10.                 unscheduleDrawable( mButtonDrawable);  
11.             }  
12.             d.setCallback( this);  
13.             d.setVisible(getVisibility() == VISIBLE, false);  
14.             mButtonDrawable = d;  
15.             setMinHeight(mButtonDrawable .getIntrinsicHeight());  
16.         }  
17.   
18.         refreshDrawableState();  
19.     }  

/**
     * Set the background to a given Drawable
     *
     * @param d The Drawable to use as the background
     */
    public void setButtonDrawable(Drawable d) {
        if (d != null ) {
            if (mButtonDrawable != null) {
                mButtonDrawable.setCallback(null);
                unscheduleDrawable( mButtonDrawable);
            }
            d.setCallback( this);
            d.setVisible(getVisibility() == VISIBLE, false);
            mButtonDrawable = d;
            setMinHeight(mButtonDrawable .getIntrinsicHeight());
        }

        refreshDrawableState();
    }

  这个方法写的就比较完善，可以作为一个学习的典范。首先判断传递过来的Drawable是否为空，如果不为空并且默认的Drawable也不为空，那么取消默认Drawable的callback，然后调用unscheduleDrawable方法。这个方法代码如下：

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1. /**  
2.     * Unschedule any events associated with the given Drawable.  This can be  
3.     * used when selecting a new Drawable into a view, so that the previous  
4.     * one is completely unscheduled.  
5.     *  
6.     * @param who The Drawable to unschedule.  
7.     *  
8.     * @see #drawableStateChanged  
9.     */  
10.    public void unscheduleDrawable(Drawable who) {  
11.        if (mAttachInfo != null && who != null) {  
12.            mAttachInfo.mViewRootImpl .mChoreographer.removeCallbacks(  
13.                    Choreographer.CALLBACK_ANIMATION, null, who);  
14.        }  
15.    }  

 /**
     * Unschedule any events associated with the given Drawable.  This can be
     * used when selecting a new Drawable into a view, so that the previous
     * one is completely unscheduled.
     *
     * @param who The Drawable to unschedule.
     *
     * @see #drawableStateChanged
     */
    public void unscheduleDrawable(Drawable who) {
        if (mAttachInfo != null && who != null) {
            mAttachInfo.mViewRootImpl .mChoreographer.removeCallbacks(
                    Choreographer.CALLBACK_ANIMATION, null, who);
        }
    }

  从方法注释中可以看出它的用途，正是更换Drawable时候使用的。接下来开始重新设置Drawable，包括回调、可见性、最小高度。最后调用refreshDrawableState()方法，这个是View类的方法，用于更新Drawable状态。

  然后再回过头看一下setChecked(checked)方法，这个用于设置check，也就是button的点击状态。代码如下：

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1. /**  
2.      * <p>Changes the checked state of this button.</p>  
3.      *  
4.      * @param checked true to check the button, false to uncheck it  
5.      */  
6.     public void setChecked( boolean checked) {  
7.         if (mChecked != checked) {  
8.             mChecked = checked;  
9.             refreshDrawableState();  
10.             notifyViewAccessibilityStateChangedIfNeeded(  
11.                     AccessibilityEvent.CONTENT_CHANGE_TYPE_UNDEFINED );  
12.   
13.             // Avoid infinite recursions if setChecked() is called from a listener  
14.             if (mBroadcasting ) {  
15.                 return;  
16.             }  
17.   
18.             mBroadcasting = true ;  
19.             if (mOnCheckedChangeListener != null) {  
20.                 mOnCheckedChangeListener.onCheckedChanged(this, mChecked);  
21.             }  
22.             if (mOnCheckedChangeWidgetListener != null) {  
23.                 mOnCheckedChangeWidgetListener .onCheckedChanged(this, mChecked);  
24.             }  
25.             mBroadcasting = false ;             
26.         }  
27.     }  

/**
     * <p>Changes the checked state of this button.</p>
     *
     * @param checked true to check the button, false to uncheck it
     */
    public void setChecked( boolean checked) {
        if (mChecked != checked) {
            mChecked = checked;
            refreshDrawableState();
            notifyViewAccessibilityStateChangedIfNeeded(
                    AccessibilityEvent.CONTENT_CHANGE_TYPE_UNDEFINED );

            // Avoid infinite recursions if setChecked() is called from a listener
            if (mBroadcasting ) {
                return;
            }

            mBroadcasting = true ;
            if (mOnCheckedChangeListener != null) {
                mOnCheckedChangeListener.onCheckedChanged(this, mChecked);
            }
            if (mOnCheckedChangeWidgetListener != null) {
                mOnCheckedChangeWidgetListener .onCheckedChanged(this, mChecked);
            }
            mBroadcasting = false ;           
        }
    }

  在这个方法中多出了一个接口，这个接口真是check的一个回调接口，代码如下：

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1. /**  
2.      * Interface definition for a callback to be invoked when the checked state  
3.      * of a compound button changed.  
4.      */  
5.     public static interface OnCheckedChangeListener {  
6.         /**  
7.          * Called when the checked state of a compound button has changed.  
8.          *  
9.          * @param buttonView The compound button view whose state has changed.  
10.          * @param isChecked  The new checked state of buttonView.  
11.          */  
12.         void onCheckedChanged(CompoundButton buttonView, boolean isChecked);  
13.     }  

/**
     * Interface definition for a callback to be invoked when the checked state
     * of a compound button changed.
     */
    public static interface OnCheckedChangeListener {
        /**
         * Called when the checked state of a compound button has changed.
         *
         * @param buttonView The compound button view whose state has changed.
         * @param isChecked  The new checked state of buttonView.
         */
        void onCheckedChanged(CompoundButton buttonView, boolean isChecked);
    }

  这种回调接口在Android中处处可见，之前的文章也有介绍过。但是在上面的方法，它使用了一个mBroadcasting变量，进而巧妙地避免了重复递归的问题，大家自己感受一下。

  然后就是ondraw()方法了，把之前的drawable画出来。代码如下：

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1. @Override  
2.   protected void onDraw(Canvas canvas) {  
3.       super.onDraw(canvas);  
4.   
5.       final Drawable buttonDrawable = mButtonDrawable ;  
6.       if (buttonDrawable != null) {  
7.           final int verticalGravity = getGravity() & Gravity.VERTICAL_GRAVITY_MASK ;  
8.           final int drawableHeight = buttonDrawable.getIntrinsicHeight();  
9.           final int drawableWidth = buttonDrawable.getIntrinsicWidth();  
10.   
11.           int top = 0;  
12.           switch (verticalGravity) {  
13.               case Gravity.BOTTOM :  
14.                   top = getHeight() - drawableHeight;  
15.                   break;  
16.               case Gravity.CENTER_VERTICAL :  
17.                   top = (getHeight() - drawableHeight) / 2;  
18.                   break;  
19.           }  
20.           int bottom = top + drawableHeight;  
21.           int left = isLayoutRtl() ? getWidth() - drawableWidth : 0;  
22.           int right = isLayoutRtl() ? getWidth() : drawableWidth;  
23.   
24.           buttonDrawable.setBounds(left, top, right, bottom);  
25.           buttonDrawable.draw(canvas);  
26.       }  
27.   }  

  @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        final Drawable buttonDrawable = mButtonDrawable ;
        if (buttonDrawable != null) {
            final int verticalGravity = getGravity() & Gravity.VERTICAL_GRAVITY_MASK ;
            final int drawableHeight = buttonDrawable.getIntrinsicHeight();
            final int drawableWidth = buttonDrawable.getIntrinsicWidth();

            int top = 0;
            switch (verticalGravity) {
                case Gravity.BOTTOM :
                    top = getHeight() - drawableHeight;
                    break;
                case Gravity.CENTER_VERTICAL :
                    top = (getHeight() - drawableHeight) / 2;
                    break;
            }
            int bottom = top + drawableHeight;
            int left = isLayoutRtl() ? getWidth() - drawableWidth : 0;
            int right = isLayoutRtl() ? getWidth() : drawableWidth;

            buttonDrawable.setBounds(left, top, right, bottom);
            buttonDrawable.draw(canvas);
        }
    }

  看得出来，在onDrawable()方法中，最主要的部分还是如何确定上下左右四个参数。确定完后就可以画出来了。但是，CompoundButton是一个抽象类，并不能直接使用，那看一下它的子类是如何实现的：

 

1、CheckBox

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1.  public class CheckBox extends CompoundButton {  
2.     public CheckBox(Context context) {  
3.         this(context, null);  
4.     }  
5.      
6.     public CheckBox(Context context, AttributeSet attrs) {  
7.         this(context, attrs, com.android.internal.R.attr.checkboxStyle);  
8.     }  
9.   
10.     public CheckBox(Context context, AttributeSet attrs, int defStyle) {  
11.         super(context, attrs, defStyle);  
12.     }  
13.   
14.     @Override  
15.     public void onInitializeAccessibilityEvent(AccessibilityEvent event) {  
16.         super.onInitializeAccessibilityEvent(event);  
17.         event.setClassName(CheckBox. class.getName());  
18.     }  
19.   
20.     @Override  
21.     public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) {  
22.         super.onInitializeAccessibilityNodeInfo(info);  
23.         info.setClassName(CheckBox. class.getName());  
24.     }  
25. }  

 public class CheckBox extends CompoundButton {
    public CheckBox(Context context) {
        this(context, null);
    }
   
    public CheckBox(Context context, AttributeSet attrs) {
        this(context, attrs, com.android.internal.R.attr.checkboxStyle);
    }

    public CheckBox(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    public void onInitializeAccessibilityEvent(AccessibilityEvent event) {
        super.onInitializeAccessibilityEvent(event);
        event.setClassName(CheckBox. class.getName());
    }

    @Override
    public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) {
        super.onInitializeAccessibilityNodeInfo(info);
        info.setClassName(CheckBox. class.getName());
    }
}

  和Button的实现差不多，使用了一个自己的样式。并且也是重写了那两个方法。再来看一下RadioButton，

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1. public class RadioButton extends CompoundButton {  
2.      
3.     public RadioButton(Context context) {  
4.         this(context, null);  
5.     }  
6.      
7.     public RadioButton(Context context, AttributeSet attrs) {  
8.         this(context, attrs, com.android.internal.R.attr.radioButtonStyle);  
9.     }  
10.   
11.     public RadioButton(Context context, AttributeSet attrs, int defStyle) {  
12.         super(context, attrs, defStyle);  
13.     }  
14.   
15.     /**  
16.      * {@inheritDoc}  
17.      * <p>  
18.      * If the radio button is already checked, this method will not toggle the radio button.  
19.      */  
20.     @Override  
21.     public void toggle() {  
22.         // we override to prevent toggle when the radio is already  
23.         // checked (as opposed to check boxes widgets)  
24.         if (!isChecked()) {  
25.             super.toggle();  
26.         }  
27.     }  
28.   
29.     @Override  
30.     public void onInitializeAccessibilityEvent(AccessibilityEvent event) {  
31.         super.onInitializeAccessibilityEvent(event);  
32.         event.setClassName(RadioButton. class.getName());  
33.     }  
34.   
35.     @Override  
36.     public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) {  
37.         super.onInitializeAccessibilityNodeInfo(info);  
38.         info.setClassName(RadioButton. class.getName());  
39.     }  
40. }  

public class RadioButton extends CompoundButton {
   
    public RadioButton(Context context) {
        this(context, null);
    }
   
    public RadioButton(Context context, AttributeSet attrs) {
        this(context, attrs, com.android.internal.R.attr.radioButtonStyle);
    }

    public RadioButton(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    /**
     * {@inheritDoc}
     * <p>
     * If the radio button is already checked, this method will not toggle the radio button.
     */
    @Override
    public void toggle() {
        // we override to prevent toggle when the radio is already
        // checked (as opposed to check boxes widgets)
        if (!isChecked()) {
            super.toggle();
        }
    }

    @Override
    public void onInitializeAccessibilityEvent(AccessibilityEvent event) {
        super.onInitializeAccessibilityEvent(event);
        event.setClassName(RadioButton. class.getName());
    }

    @Override
    public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) {
        super.onInitializeAccessibilityNodeInfo(info);
        info.setClassName(RadioButton. class.getName());
    }
}

  和CheckBox实现差不多，区别在于多重写了一个方法，用于防止按钮被重复点击。另外还有ToggleButton以及Switch，前者实现也比较简单，后者稍微麻烦了一些，感兴趣可以自己分析。

  最后切入正题，看看滑动Button要如何实现呢？首先看一下效果图：

 图1-1

  

 图1-2

  图1-1所示的滑动Button实现的思路是这样的，背景图片有开和关的文字，一个按钮在其上面左右滑动，遮住相应的部分，使其在一个位置时候只能看到一个开关。

  如图1-3，在实现的时候，先画一个开关背景图片只，然后在其上面画一个按钮，滑动开关的时候对上面的按钮进行处理即可。

  准备：

 

    1、按钮图片

       

      

    2、背景图片       

       

 编码：

    在自定义滑动按钮控件的时候，可以有多种选择，可以继承于Button，也可以继承于Button的子类，也可以继承于View类等。我们知道滑动按钮是一个很简单的控件，就是左右滑动改变显示内容，不需要其他的额外东西在里面，所以直接继承于View来实现即可。如果继承于系统的一些控件，那么有很多东西用不到，会造成浪费。

    1、定义一个类继承于View，初始化构造方法，在构造方法中加载图片及其信息。

    2、重写onMeasure()方法，计算控件的大小。

    3、重写onTouchEvent()方法，对滑动事件进行判别处理。

    4、定义接口，实现回调。

    5、重写onDraw()方法，动态画出按钮。

代码如下：

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1. /**  
2. *  
3. */  
4. package com.kince.slidebutton;  
5.   
6. import android.content.Context;  
7. import android.graphics.Bitmap;  
8. import android.graphics.BitmapFactory;  
9. import android.graphics.Canvas;  
10. import android.util.AttributeSet;  
11. import android.util.Log;  
12. import android.view.MotionEvent;  
13. import android.view.View;  
14.   
15. /**  
16. * @author kince  
17. * @category 左右手势滑动button  
18. * @serial 1.0.0  
19. * @since 2014.5.17  
20. * @see http://blog.csdn.net/wangjinyu501  
21. *  
22. */  
23. public class SlideButton extends View {  
24.   
25.      private Bitmap slideBitMap;// 滑动图片  
26.      private Bitmap switchBitMap;// 背景图片  
27.   
28.      private int slideBitMapWidth;// 滑动图片宽度  
29.      private int switchBitMapWidth;// 背景图片宽度  
30.      private int switchBitMapHeight;// 背景图片高度  
31.   
32.      private boolean currentState;// 开关状态  
33.      private boolean isSliding = false; // 是否正在滑动中  
34.   
35.      private int currentX; // 当前开关的位置  
36.   
37.      private OnToggleStateChangedListener mChangedListener;// 回调接口  
38.   
39.      /**  
40.      * @param context  
41.      *            在java代码中直接调用使用此构造方法  
42.      */  
43.      public SlideButton(Context context) {  
44.           this(context, null);  
45.           // TODO Auto-generated constructor stub  
46.      }  
47.   
48.      /**  
49.      * @param context  
50.      * @param attrs  
51.      *            在xml中使用要用到这个方法  
52.      */  
53.      public SlideButton(Context context, AttributeSet attrs) {  
54.           this(context, attrs, 0);  
55.           // TODO Auto-generated constructor stub  
56.      }  
57.   
58.      /**  
59.      * @param context  
60.      * @param attrs  
61.      * @param defStyleAttr  
62.      *            指定一个样式  
63.      */  
64.      public SlideButton(Context context, AttributeSet attrs, int defStyleAttr) {  
65.           super(context, attrs, defStyleAttr);  
66.           initBitmap();  
67.      }  
68.   
69.      /**  
70.      * @category 加载背景图片以及开关图片 然后获取各自的宽高  
71.      *  
72.      */  
73.      private void initBitmap() {  
74.           // TODO Auto-generated method stub  
75.           slideBitMap = BitmapFactory.decodeResource(getResources(),  
76.                     R.drawable.slide_button_background);  
77.           switchBitMap = BitmapFactory.decodeResource(getResources(),  
78.                     R.drawable.switch_background);  
79.           slideBitMapWidth = slideBitMap.getWidth();  
80.           switchBitMapWidth = switchBitMap.getWidth();  
81.           switchBitMapHeight = switchBitMap.getHeight();  
82.           Log.i("switchBitMapWidth", switchBitMapWidth + "");  
83.      }  
84.   
85.      @Override  
86.      protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {  
87.           // TODO Auto-generated method stub  
88.           super.onMeasure(widthMeasureSpec, heightMeasureSpec);  
89.           setMeasuredDimension(switchBitMapWidth, switchBitMapHeight);// 设置控件的宽高  
90.      }  
91.   
92.      @Override  
93.      protected void onDraw(Canvas canvas) {  
94.           // 绘制button背景图片  
95.           canvas.drawBitmap(switchBitMap, 0, 0, null);  
96.           // 绘制滑动开关  
97.           if (isSliding) {// 如果当前状态是滑动中 则动态绘制开关  
98.                int dis = currentX - slideBitMapWidth / 2;  
99.                if (dis < 0) {  
100.                     dis = 0;  
101.                } else if (dis > switchBitMapWidth - slideBitMapWidth) {  
102.                     dis = switchBitMapWidth - slideBitMapWidth;  
103.                }  
104.                canvas.drawBitmap(slideBitMap, dis, 0, null);  
105.           } else {  
106.                if (currentState) { // 绘制开关为开的状态  
107.                     canvas.drawBitmap(slideBitMap, switchBitMapWidth  
108.                               - slideBitMapWidth, 0, null);  
109.                } else { // 绘制开关为关的状态  
110.                     canvas.drawBitmap(slideBitMap, 0, 0, null);  
111.                }  
112.           }  
113.           super.onDraw(canvas);  
114.      }  
115.   
116.      @Override  
117.      public boolean onTouchEvent(MotionEvent event) {  
118.           // 手势识别 判断滑动方向  
119.           int action = event.getAction();  
120.           switch (action) {  
121.           case MotionEvent.ACTION_DOWN:  
122.                isSliding = true;  
123.                currentX = (int) event.getX();  
124.                break;  
125.   
126.           case MotionEvent.ACTION_MOVE:  
127.                currentX = (int) event.getX();  
128.                Log.i("currentX", currentX + "");  
129.   
130.                break;  
131.           case MotionEvent.ACTION_UP:  
132.                isSliding = false;  
133.                int bgCenter = switchBitMapWidth / 2;  
134.                boolean state = currentX > bgCenter; // 改变后的状态  
135.                if (state != currentState && mChangedListener != null) {// 添加回调  
136.                     mChangedListener.onToggleStateChanged(state);  
137.                }  
138.                currentState = state;  
139.                break;  
140.           default:  
141.                break;  
142.           }  
143.           invalidate();  
144.           return true;  
145.      }  
146.   
147.      public OnToggleStateChangedListener getmChangedListener() {  
148.           return mChangedListener;  
149.      }  
150.   
151.      public void setmChangedListener(  
152.                OnToggleStateChangedListener mChangedListener) {  
153.           this.mChangedListener = mChangedListener;  
154.      }  
155.   
156.      public boolean isToggleState() {  
157.           return currentState;  
158.      }  
159.   
160.      public void setToggleState(boolean currentState) {  
161.           this.currentState = currentState;  
162.      }  
163.   
164. }  

/**
*
*/
package com.kince.slidebutton;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;

/**
* @author kince
* @category 左右手势滑动button
* @serial 1.0.0
* @since 2014.5.17
* @see http://blog.csdn.net/wangjinyu501
*
*/
public class SlideButton extends View {

     private Bitmap slideBitMap;// 滑动图片
     private Bitmap switchBitMap;// 背景图片

     private int slideBitMapWidth;// 滑动图片宽度
     private int switchBitMapWidth;// 背景图片宽度
     private int switchBitMapHeight;// 背景图片高度

     private boolean currentState;// 开关状态
     private boolean isSliding = false; // 是否正在滑动中

     private int currentX; // 当前开关的位置

     private OnToggleStateChangedListener mChangedListener;// 回调接口

     /**
     * @param context
     *            在java代码中直接调用使用此构造方法
     */
     public SlideButton(Context context) {
          this(context, null);
          // TODO Auto-generated constructor stub
     }

     /**
     * @param context
     * @param attrs
     *            在xml中使用要用到这个方法
     */
     public SlideButton(Context context, AttributeSet attrs) {
          this(context, attrs, 0);
          // TODO Auto-generated constructor stub
     }

     /**
     * @param context
     * @param attrs
     * @param defStyleAttr
     *            指定一个样式
     */
     public SlideButton(Context context, AttributeSet attrs, int defStyleAttr) {
          super(context, attrs, defStyleAttr);
          initBitmap();
     }

     /**
     * @category 加载背景图片以及开关图片 然后获取各自的宽高
     *
     */
     private void initBitmap() {
          // TODO Auto-generated method stub
          slideBitMap = BitmapFactory.decodeResource(getResources(),
                    R.drawable.slide_button_background);
          switchBitMap = BitmapFactory.decodeResource(getResources(),
                    R.drawable.switch_background);
          slideBitMapWidth = slideBitMap.getWidth();
          switchBitMapWidth = switchBitMap.getWidth();
          switchBitMapHeight = switchBitMap.getHeight();
          Log.i("switchBitMapWidth", switchBitMapWidth + "");
     }

     @Override
     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
          // TODO Auto-generated method stub
          super.onMeasure(widthMeasureSpec, heightMeasureSpec);
          setMeasuredDimension(switchBitMapWidth, switchBitMapHeight);// 设置控件的宽高
     }

     @Override
     protected void onDraw(Canvas canvas) {
          // 绘制button背景图片
          canvas.drawBitmap(switchBitMap, 0, 0, null);
          // 绘制滑动开关
          if (isSliding) {// 如果当前状态是滑动中 则动态绘制开关
               int dis = currentX - slideBitMapWidth / 2;
               if (dis < 0) {
                    dis = 0;
               } else if (dis > switchBitMapWidth - slideBitMapWidth) {
                    dis = switchBitMapWidth - slideBitMapWidth;
               }
               canvas.drawBitmap(slideBitMap, dis, 0, null);
          } else {
               if (currentState) { // 绘制开关为开的状态
                    canvas.drawBitmap(slideBitMap, switchBitMapWidth
                              - slideBitMapWidth, 0, null);
               } else { // 绘制开关为关的状态
                    canvas.drawBitmap(slideBitMap, 0, 0, null);
               }
          }
          super.onDraw(canvas);
     }

     @Override
     public boolean onTouchEvent(MotionEvent event) {
          // 手势识别 判断滑动方向
          int action = event.getAction();
          switch (action) {
          case MotionEvent.ACTION_DOWN:
               isSliding = true;
               currentX = (int) event.getX();
               break;

          case MotionEvent.ACTION_MOVE:
               currentX = (int) event.getX();
               Log.i("currentX", currentX + "");

               break;
          case MotionEvent.ACTION_UP:
               isSliding = false;
               int bgCenter = switchBitMapWidth / 2;
               boolean state = currentX > bgCenter; // 改变后的状态
               if (state != currentState && mChangedListener != null) {// 添加回调
                    mChangedListener.onToggleStateChanged(state);
               }
               currentState = state;
               break;
          default:
               break;
          }
          invalidate();
          return true;
     }

     public OnToggleStateChangedListener getmChangedListener() {
          return mChangedListener;
     }

     public void setmChangedListener(
               OnToggleStateChangedListener mChangedListener) {
          this.mChangedListener = mChangedListener;
     }

     public boolean isToggleState() {
          return currentState;
     }

     public void setToggleState(boolean currentState) {
          this.currentState = currentState;
     }

}

  回调接口，

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1.  package com.kince.slidebutton;  
2.   
3. **  
4. * @author kince  
5. *  
6. */  
7. ublic interface OnToggleStateChangedListener {  
8.   
9.     /**  
10.      * @category  
11.      * @param state  
12.      */  
13.     public void onToggleStateChanged(boolean state);  

  package com.kince.slidebutton;

/**
 * @author kince
 *
 */
public interface OnToggleStateChangedListener {

     /**
      * @category
      * @param state
      */
     public void onToggleStateChanged(boolean state);

}

  Activity代码，

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1. package com.kince.slidebutton;  
2.   
3. import android.support.v7.app.ActionBarActivity;  
4. import android.support.v7.app.ActionBar;  
5. import android.support.v4.app.Fragment;  
6. import android.support.v4.app.FragmentActivity;  
7. import android.os.Bundle;  
8. import android.view.LayoutInflater;  
9. import android.view.Menu;  
10. import android.view.MenuItem;  
11. import android.view.View;  
12. import android.view.ViewGroup;  
13. import android.widget.Toast;  
14. import android.os.Build;  
15.   
16. public class MainActivity extends ActionBarActivity {  
17.   
18.      @Override  
19.      protected void onCreate(Bundle savedInstanceState) {  
20.           super.onCreate(savedInstanceState);  
21.           setContentView(R.layout.activity_main);  
22.   
23.           if (savedInstanceState == null) {  
24.                getSupportFragmentManager().beginTransaction()  
25.                          .add(R.id.container, new PlaceholderFragment()).commit();  
26.           }  
27.      }  
28.   
29.      @Override  
30.      public boolean onCreateOptionsMenu(Menu menu) {  
31.   
32.           // Inflate the menu; this adds items to the action bar if it is present.  
33.           getMenuInflater().inflate(R.menu.main, menu);  
34.           return true;  
35.      }  
36.   
37.      @Override  
38.      public boolean onOptionsItemSelected(MenuItem item) {  
39.           // Handle action bar item clicks here. The action bar will  
40.           // automatically handle clicks on the Home/Up button, so long  
41.           // as you specify a parent activity in AndroidManifest.xml.  
42.           int id = item.getItemId();  
43.           if (id == R.id.action_settings) {  
44.                return true;  
45.           }  
46.           return super.onOptionsItemSelected(item);  
47.      }  
48.   
49.      /**  
50.      * A placeholder fragment containing a simple view.  
51.      */  
52.      public static class PlaceholderFragment extends Fragment implements  
53.                OnToggleStateChangedListener {  
54.   
55.           private SlideButton slidebutton;  
56.   
57.           public PlaceholderFragment() {  
58.           }  
59.   
60.           @Override  
61.           public View onCreateView(LayoutInflater inflater, ViewGroup container,  
62.                     Bundle savedInstanceState) {  
63.                View rootView = inflater.inflate(R.layout.fragment_main, container,  
64.                          false);  
65.                slidebutton = (SlideButton) rootView.findViewById(R.id.slidebutton1);  
66.                // 设置一下开关的状态  
67.                slidebutton.setToggleState(true); // 设置开关的状态为打开  
68.                slidebutton.setmChangedListener(this);  
69.                return rootView;  
70.           }  
71.   
72.           @Override  
73.           public void onToggleStateChanged(boolean state) {  
74.                // TODO Auto-generated method stub  
75.                FragmentActivity activity = getActivity();  
76.                if (state) {  
77.                     Toast.makeText(activity, "开关打开", 0).show();  
78.                } else {  
79.                     Toast.makeText(activity, "开关关闭", 0).show();  
80.                }  
81.           }  
82.      }  
83.   
84. }  

package com.kince.slidebutton;

import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;
import android.os.Build;

public class MainActivity extends ActionBarActivity {

     @Override
     protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);

          if (savedInstanceState == null) {
               getSupportFragmentManager().beginTransaction()
                         .add(R.id.container, new PlaceholderFragment()).commit();
          }
     }

     @Override
     public boolean onCreateOptionsMenu(Menu menu) {

          // Inflate the menu; this adds items to the action bar if it is present.
          getMenuInflater().inflate(R.menu.main, menu);
          return true;
     }

     @Override
     public boolean onOptionsItemSelected(MenuItem item) {
          // Handle action bar item clicks here. The action bar will
          // automatically handle clicks on the Home/Up button, so long
          // as you specify a parent activity in AndroidManifest.xml.
          int id = item.getItemId();
          if (id == R.id.action_settings) {
               return true;
          }
          return super.onOptionsItemSelected(item);
     }

     /**
     * A placeholder fragment containing a simple view.
     */
     public static class PlaceholderFragment extends Fragment implements
               OnToggleStateChangedListener {

          private SlideButton slidebutton;

          public PlaceholderFragment() {
          }

          @Override
          public View onCreateView(LayoutInflater inflater, ViewGroup container,
                    Bundle savedInstanceState) {
               View rootView = inflater.inflate(R.layout.fragment_main, container,
                         false);
               slidebutton = (SlideButton) rootView.findViewById(R.id.slidebutton1);
               // 设置一下开关的状态
               slidebutton.setToggleState(true); // 设置开关的状态为打开
               slidebutton.setmChangedListener(this);
               return rootView;
          }

          @Override
          public void onToggleStateChanged(boolean state) {
               // TODO Auto-generated method stub
               FragmentActivity activity = getActivity();
               if (state) {
                    Toast.makeText(activity, "开关打开", 0).show();
               } else {
                    Toast.makeText(activity, "开关关闭", 0).show();
               }
          }
     }

}

  未完待续。

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