Android学习研究(四)通过PorterDuffXfermode形成简单的圆角和圆形图片

我们之前学习了PorterDuffXfermode了,现在我们来用它做一下简单的圆角和圆形图片
首先自定义属性:

<resources>
    <declare-styleable name="RoundImageView">
        <attr name="backgroundresource" format="reference"></attr>
    </declare-styleable>
</resources>

添加图片资源属性,然后建一个类集成ImageView.,初始化画笔和属性

  private int backgroundresource;
    /**
     * 控件宽度
     */
    private int mWidth;
    /**
     * 控件高度
     */
    private int mHeight;
    private Bitmap bitmap;
    private Paint paint;

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

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

    public RoundImageView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        TypedArray array = context.obtainStyledAttributes(attrs,R.styleable.RoundImageView);
        backgroundresource = array.getResourceId(R.styleable.RoundImageView_backgroundresource,0);
        array.recycle();
        initPaint();
    }

    private void initPaint() {
        bitmap = BitmapFactory.decodeResource(getResources(),backgroundresource);
        paint = new Paint();
        paint.setAntiAlias(true);
    }

然后我们应该计算控件的高度:

 @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);

        if (widthMode == MeasureSpec.EXACTLY){ //matchparent 自定义
            mWidth = widthSize;
        }else {

            int imageWidth = getPaddingLeft() + getPaddingLeft() + bitmap.getWidth();

            if (widthMode == MeasureSpec.AT_MOST){//wrapcontent
                mWidth = Math.min(imageWidth,widthSize);
            }else {
                mWidth = imageWidth;
            }
        }


        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);

        if (heightMode == MeasureSpec.EXACTLY){
            mHeight = heightSize;
        }else {

            int imageHeight = getPaddingBottom() + getPaddingTop() + bitmap.getHeight();
            if (heightMode == MeasureSpec.AT_MOST){
                mHeight = Math.min(imageHeight,heightSize);
            }else {
                mHeight = imageHeight;
            }

        }

        setMeasuredDimension(mWidth,mHeight);

    }

再然后,我们应该开始作画了:

 @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        int centerRadius = Math.min(mWidth,mHeight);
        //通过最小值进行缩放
        bitmap = Bitmap.createScaledBitmap(bitmap,centerRadius,centerRadius,false);
        canvas.drawBitmap(createRoundBitmap(bitmap),0,0,null);
    }

 /**
     * 圆形图片
     * @param bitmap
     * @return
     */
    private Bitmap createRoundBitmap(Bitmap bitmap){
        Bitmap copyBitmap = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Bitmap.Config.ARGB_8888);
        //获取与图片大小的相同的画布
        Canvas canvas = new Canvas(copyBitmap);
        //先画圆
        canvas.drawCircle(bitmap.getWidth()/2,bitmap.getHeight()/2,bitmap.getHeight()/2,paint);
        //设置Xfermode模式
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));

        canvas.drawBitmap(bitmap,0,0,paint);

        return copyBitmap;
    }

通过代码可以知道,我们是先画圆,再画图片,这样就能显示圆形图片了,然后,我们也可以显示出圆角图片:

  /**
     * 圆角图片
     * @param bitmap
     * @return
     */
    private Bitmap createRectBitmap(Bitmap bitmap){
        Bitmap copyBitmap = Bitmap.createBitmap(bitmap.getWidth(),bitmap.getHeight(), Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(copyBitmap);
        RectF rectf = new RectF(0,0,bitmap.getWidth(),bitmap.getHeight());
        //画圆角
         canvas.drawRoundRect(rectf,50,50,paint);
        //设置模式
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
        canvas.drawBitmap(bitmap,0,0,paint);
        return copyBitmap;
    }

效果图我就不添加了,你通过我的代码肯定能实现圆角和圆形图片的,有什么问题欢迎留言