Android 自定义View 进阶

Posted 2020-07-05

转载请标明出处：http://blog.csdn.net/lmj623565791/article/details/24300125

继续自定义View之旅，前面已经介绍过一个自定义View的基础的例子，Android 自定义View (一)，如果你还对自定义View不了解可以去看看。今天给大家带来一个稍微复杂点的例子。

自定义View显示一张图片，下面包含图片的文本介绍，类似相片介绍什么的，不过不重要，主要是学习自定义View的用法么。

还记得上一篇讲的4个步骤么:

 

1、自定义View的属性
2、在View的构造方法中获得我们自定义的属性
[ 3、重写onMesure ]
4、重写onDraw

直接切入正题：

1、在res/values/attr.xml

<?xml version="1.0" encoding="utf-8"?>  
<resources>  
  
    <attr name="titleText" format="string" />  
    <attr name="titleTextSize" format="dimension" />  
    <attr name="titleTextColor" format="color" />  
    <attr name="image" format="reference" />  
    <attr name="imageScaleType">  
        <enum name="fillXY" value="0" />  
        <enum name="center" value="1" />  
    </attr>  
  
    <declare-styleable name="CustomImageView">  
        <attr name="titleText" />  
        <attr name="titleTextSize" />  
        <attr name="titleTextColor" />  
        <attr name="image" />  
        <attr name="imageScaleType" />  
    </declare-styleable>  
  
</resources>  

2、在构造中获得我们的自定义属性：

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

        TypedArray a = context.getTheme().obtainStyledAttributes(attrs, R.styleable.CustomImageView, defStyle, 0);

        int n = a.getIndexCount();

        for (int i = 0; i < n; i++) {
            int attr = a.getIndex(i);

            switch (attr) {
            case R.styleable.CustomImageView_image:
                mImage = BitmapFactory.decodeResource(getResources(), a.getResourceId(attr, 0));
                break;
            case R.styleable.CustomImageView_imageScaleType:
                mImageScale = a.getInt(attr, 0);
                break;
            case R.styleable.CustomImageView_titleText:
                mTitle = a.getString(attr);
                break;
            case R.styleable.CustomImageView_titleTextColor:
                mTextColor = a.getColor(attr, Color.BLACK);
                break;
            case R.styleable.CustomImageView_titleTextSize:
                mTextSize = a.getDimensionPixelSize(attr, (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, 16, getResources().getDisplayMetrics()));
                break;

            }
        }
        a.recycle();
        rect = new Rect();
        mPaint = new Paint();
        mTextBound = new Rect();
        mPaint.setTextSize(mTextSize);
        // 计算了描绘字体需要的范围
        mPaint.getTextBounds(mTitle, 0, mTitle.length(), mTextBound);
    }

3、重写onMeasure

@Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        // super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        /**
         * 设置宽度
         */
        int specMode = MeasureSpec.getMode(widthMeasureSpec);
        int specSize = MeasureSpec.getSize(widthMeasureSpec);

        if (specMode == MeasureSpec.EXACTLY)// match_parent , accurate
        {
            Log.e("xxx", "EXACTLY");
            mWidth = specSize;
        } else {
            // 由图片决定的宽
            int desireByImg = getPaddingLeft() + getPaddingRight() + mImage.getWidth();
            // 由字体决定的宽
            int desireByTitle = getPaddingLeft() + getPaddingRight() + mTextBound.width();

            if (specMode == MeasureSpec.AT_MOST)// wrap_content
            {
                int desire = Math.max(desireByImg, desireByTitle);
                mWidth = Math.min(desire, specSize);
                Log.e("xxx", "AT_MOST");
            }
        }

        /***
         * 设置高度
         */

        specMode = MeasureSpec.getMode(heightMeasureSpec);
        specSize = MeasureSpec.getSize(heightMeasureSpec);
        if (specMode == MeasureSpec.EXACTLY)// match_parent , accurate
        {
            mHeight = specSize;
        } else {
            int desire = getPaddingTop() + getPaddingBottom() + mImage.getHeight() + mTextBound.height();
            if (specMode == MeasureSpec.AT_MOST)// wrap_content
            {
                mHeight = Math.min(desire, specSize);
            }
        }
        setMeasuredDimension(mWidth, mHeight);

    }

4、重写onDraw

    @Override
    protected void onDraw(Canvas canvas) {
        // super.onDraw(canvas);
        /**
         * 边框
         */
        mPaint.setStrokeWidth(4);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setColor(Color.CYAN);
        canvas.drawRect(0, 0, getMeasuredWidth(), getMeasuredHeight(), mPaint);

        rect.left = getPaddingLeft();
        rect.right = mWidth - getPaddingRight();
        rect.top = getPaddingTop();
        rect.bottom = mHeight - getPaddingBottom();

        mPaint.setColor(mTextColor);
        mPaint.setStyle(Style.FILL);
        /**
         * 当前设置的宽度小于字体需要的宽度，将字体改为xxx...
         */
        if (mTextBound.width() > mWidth) {
            TextPaint paint = new TextPaint(mPaint);
            String msg = TextUtils.ellipsize(mTitle, paint, (float) mWidth - getPaddingLeft() - getPaddingRight(), TextUtils.TruncateAt.END).toString();
            canvas.drawText(msg, getPaddingLeft(), mHeight - getPaddingBottom(), mPaint);

        } else {
            // 正常情况，将字体居中
            canvas.drawText(mTitle, mWidth / 2 - mTextBound.width() * 1.0f / 2, mHeight - getPaddingBottom(), mPaint);
        }

        // 取消使用掉的快
        rect.bottom -= mTextBound.height();

        if (mImageScale == IMAGE_SCALE_FITXY) {
            canvas.drawBitmap(mImage, null, rect, mPaint);
        } else {
            // 计算居中的矩形范围
            rect.left = mWidth / 2 - mImage.getWidth() / 2;
            rect.right = mWidth / 2 + mImage.getWidth() / 2;
            rect.top = (mHeight - mTextBound.height()) / 2 - mImage.getHeight() / 2;
            rect.bottom = (mHeight - mTextBound.height()) / 2 + mImage.getHeight() / 2;

            canvas.drawBitmap(mImage, null, rect, mPaint);
        }

    }

代码，结合注释和第一篇View的使用，应该可以看懂，不明白的留言。下面我们引入我们的自定义View:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
    xmlns:tools="http://schemas.android.com/tools"  
    xmlns:zhy="http://schemas.android.com/apk/res/com.zhy.customview02"  
    android:layout_width="match_parent"  
    android:layout_height="match_parent"  
    android:orientation="vertical" >  
  
    <com.zhy.customview02.view.CustomImageView  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:layout_margin="10dp"  
        android:padding="10dp"  
        zhy:image="@drawable/ic_launcher"  
        zhy:imageScaleType="center"  
        zhy:titleText="hello andorid ! "  
        zhy:titleTextColor="#ff0000"  
        zhy:titleTextSize="30sp" />  
  
    <com.zhy.customview02.view.CustomImageView  
        android:layout_width="100dp"  
        android:layout_height="wrap_content"  
        android:layout_margin="10dp"  
        android:padding="10dp"  
        zhy:image="@drawable/ic_launcher"  
        zhy:imageScaleType="center"  
        zhy:titleText="helloworldwelcome"  
        zhy:titleTextColor="#00ff00"  
        zhy:titleTextSize="20sp" />  
  
    <com.zhy.customview02.view.CustomImageView  
        android:layout_width="wrap_content"  
        android:layout_height="wrap_content"  
        android:layout_margin="10dp"  
        android:padding="10dp"  
        zhy:image="@drawable/lmj"  
        zhy:imageScaleType="center"  
        zhy:titleText="妹子~"  
        zhy:titleTextColor="#ff0000"  
        zhy:titleTextSize="12sp" />  
  
</LinearLayout>  

我特意让显示出现3中情况：

 

1、字体的宽度大于图片，且View宽度设置为wrap_content

2、View宽度设置为精确值，字体的长度大于此宽度

3、图片的宽度大于字体，且View宽度设置为wrap_content

看看显示效果：