Android UI学习之NoticeView实现文字轮播效果

Posted 2022-12-05 Steven Jon

今天搬砖赚了500，你以为我要给你450，然后留50吃泡面。
不！！！ 你格局小了！！！
我会再向朋友再借20凑520给你。

—广州 · 14℃ · 阴天 · 天暗下来，你就是阳光~

效果展示

如何实现？

首先感谢一下编写NoticeView控件的作者，GitHub传送门：https://github.com/czy1121/noticeview ，喜欢的朋友可以为他点下star。

为了方便大家使用，在下面贴出控件源码，直接复制过去就可以使用：

• NoticeView控件的属性，在res/values文件下定义一个attrs.xml文件，代码如下：

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <declare-styleable name="NoticeView">
        <!-- 图标 -->
        <attr name="nvIcon" format="reference"/>
        <!-- 图标与内容的间隙 -->
        <attr name="nvIconPadding" format="dimension"/>
        <!-- 图标颜色 -->
        <attr name="nvIconTint" format="color"/>

        <!-- 文本尺寸 -->
        <attr name="nvTextSize" format="dimension"/>
        <!-- 文本颜色 -->
        <attr name="nvTextColor" format="color"/>
        <!-- 文本最大行数 -->
        <attr name="nvTextMaxLines" format="integer"/>
        <!-- 文本对齐方式 -->
        <attr name="nvTextGravity" format="integer">
            <enum name="left" value="3"/>
            <enum name="center" value="17"/>
            <enum name="right" value="5"/>
        </attr>

        <!-- 切换动画间隔时间，毫秒 -->
        <attr name="nvInterval" format="integer"/>
        <!-- 切换动画持续时间，毫秒 -->
        <attr name="nvDuration" format="integer"/>
    </declare-styleable>


</resources>

• NoticeView源码：

public class NoticeView extends TextSwitcher 

    private Animation mInUp = anim(1.5f, 0);
    private Animation mOutUp = anim(0, -1.5f);

    private List<String> mDataList = new ArrayList<>();

    private int mIndex = 0;
    private int mInterval = 4000;
    private int mDuration = 900;

    private Drawable mIcon;
    private int mIconTint = 0xff999999;
    private int mIconPadding = 0;
    private int mPaddingLeft = 0;

    private boolean mIsVisible = false;
    private boolean mIsStarted = false;
    private boolean mIsResumed = true;
    private boolean mIsRunning = false;
    private final TextFactory mDefaultFactory = new TextFactory();
    private final Runnable mRunnable = new Runnable() 
        @Override
        public void run() 
            if (mIsRunning) 
                show(mIndex + 1);
                postDelayed(mRunnable, mInterval);
            
        
    ;

    public NoticeView(Context context) 
        this(context, null);
    

    public NoticeView(Context context, AttributeSet attrs) 
        super(context, attrs);
        initWithContext(context, attrs);
        setInAnimation(mInUp);
        setOutAnimation(mOutUp);
        setFactory(mDefaultFactory);
        mInUp.setDuration(mDuration);
        mOutUp.setDuration(mDuration);
    

    private void initWithContext(Context context, AttributeSet attrs) 
        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.NoticeView);
        mIcon = a.getDrawable(R.styleable.NoticeView_nvIcon);
        mIconPadding = (int)a.getDimension(R.styleable.NoticeView_nvIconPadding, 0);

        boolean hasIconTint = a.hasValue(R.styleable.NoticeView_nvIconTint);

        if (hasIconTint) 
            mIconTint = a.getColor(R.styleable.NoticeView_nvIconTint, 0xff999999);
        

        mInterval = a.getInteger(R.styleable.NoticeView_nvInterval, 4000);
        mDuration = a.getInteger(R.styleable.NoticeView_nvDuration, 900);

        mDefaultFactory.resolve(a);
        a.recycle();

        if (mIcon != null) 
            mPaddingLeft = getPaddingLeft();
            int realPaddingLeft = mPaddingLeft + mIconPadding + mIcon.getIntrinsicWidth();
            setPadding(realPaddingLeft, getPaddingTop(), getPaddingRight(), getPaddingBottom());

            if (hasIconTint) 
                mIcon = mIcon.mutate();
                DrawableCompat.setTint(mIcon, mIconTint);
            
        
    


    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) 
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        if (mIcon != null) 
            int y = (getMeasuredHeight() - mIcon.getIntrinsicWidth()) / 2;
            mIcon.setBounds(mPaddingLeft, y, mPaddingLeft + mIcon.getIntrinsicWidth(), y + mIcon.getIntrinsicHeight());
        
    

    @Override
    protected void onDraw(Canvas canvas) 
        super.onDraw(canvas);
        if (mIcon != null) 
            mIcon.draw(canvas);
        
    

    public int getIndex() 
        return mIndex;
    

    public void start(List<String> list) 
        mDataList = list;
        if (mDataList == null || mDataList.size() < 1) 
            mIsStarted = false;
            update();
         else 
            mIsStarted = true;
            update();
            show(0);
        
    

    @Override
    protected void onDetachedFromWindow() 
        super.onDetachedFromWindow();
        mIsVisible = false;
        update();
    

    @Override
    protected void onWindowVisibilityChanged(int visibility) 
        super.onWindowVisibilityChanged(visibility);
        mIsVisible = visibility == VISIBLE;
        update();
    

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) 
        int action = ev.getAction();
        switch (action) 
        case MotionEvent.ACTION_DOWN:
            mIsResumed = false;
            update();
            break;
        case MotionEvent.ACTION_UP:
        case MotionEvent.ACTION_CANCEL:
            mIsResumed = true;
            update();
            break;

        
        return super.dispatchTouchEvent(ev);
    

    private void update() 
        boolean running = mIsVisible && mIsResumed && mIsStarted;
        if (running != mIsRunning) 
            if (running) 
                postDelayed(mRunnable, mInterval);
             else 
                removeCallbacks(mRunnable);
            
            mIsRunning = running;
        
        Log.e("ezy", "update() visible=" + mIsVisible + ", started=" + mIsStarted + ", running=" + mIsRunning);
    

    private void show(int index) 
        mIndex = index % mDataList.size();
        setText(html.fromHtml(mDataList.get(mIndex)));
    

    private Animation anim(float from, float to) 
        final TranslateAnimation anim = new TranslateAnimation(0, 0f, 0, 0f, Animation.RELATIVE_TO_PARENT, from, Animation.RELATIVE_TO_PARENT, to);
        anim.setDuration(mDuration);
        anim.setFillAfter(false);
        anim.setInterpolator(new LinearInterpolator());
        return anim;
    

    class TextFactory implements ViewFactory 
        DisplayMetrics dm = getContext().getResources().getDisplayMetrics();

        float size = dp2px(14);
        int color = 1;
        int lines = 1;
        int gravity = Gravity.LEFT;

        void resolve(TypedArray ta) 
            lines = ta.getInteger(R.styleable.NoticeView_nvTextMaxLines, lines);
            size = ta.getDimension(R.styleable.NoticeView_nvTextSize, size);
            color = ta.getColor(R.styleable.NoticeView_nvTextColor, color);
            gravity = ta.getInteger(R.styleable.NoticeView_nvTextGravity, gravity);
        

        private int dp2px(float dp) 
            return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp, dm);
        
        @Override
        public View makeView() 
            TextView tv = new TextView(getContext());
            tv.setTextSize(TypedValue.COMPLEX_UNIT_PX, size);
            tv.setMaxLines(lines);
            if (color != 1) 
                tv.setTextColor(color);
            
            tv.setEllipsize(TextUtils.TruncateAt.END);
            tv.setGravity(Gravity.CENTER_VERTICAL | gravity);
            tv.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
            return tv;
        
    

使用起来非常简单：

        final String[] test = new String[]
                "须知少时凌云志，",
                "曾许人间第一流。",
                "哪晓岁月蹉跎过，",
                "依然名利两无收。"
        ;
        noticeView = findViewById(R.id.nv_notice);
        noticeView.start(Arrays.asList(test));
        noticeView.setOnClickListener(new View.OnClickListener() 
            @Override
            public void onClick(View v) 
                // TODO: 2021/3/21  
                Toast.makeText(XXActivity.this, test[noticeView.getIndex()], Toast.LENGTH_SHORT).show();
            
        );
        

但是需要注意一点，如果没给NoticeView设置setOnClickListener点击事件，那么当NoticeView在轮播时被点击后会出现暂停现象，并且它也不会自动恢复轮播，无论再怎么点击NoticeView，它都会一直处于停止状态。
如果NoticeView只是用于显示信息轮播，不需要监听其点击事件，那可以在NoticeView里面将dispatchTouchEvent()删掉就好了。

非常感谢你能看到这里，如果能够帮助到你是我的荣幸！