自定义ImageView实现圆形头像

public class MyImageView extends ImageView {
    public MyImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    private Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    private Bitmap mBitmap;
    private BitmapShader mBitmapShader;
    private Matrix mMatrix = new Matrix();


    @Override
    protected void onDraw(Canvas canvas) {
        Bitmap bitmap = getBitmap(getDrawable());
        if (bitmap != null) {
            int width = getWidth();
            int height = getHeight();
            int minSize = Math.min(width, height);
            float dstWidth = minSize;
            float dstHeight = minSize;
            if (mBitmapShader == null || !bitmap.equals(mBitmap)) {
                mBitmap = bitmap;
                mBitmapShader = new BitmapShader(mBitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
            }
            if (mBitmapShader != null) {
                mMatrix.setScale(dstWidth / bitmap.getWidth(), dstHeight / bitmap.getHeight());
                mBitmapShader.setLocalMatrix(mMatrix);
            }
            mPaint.setShader(mBitmapShader);
            float radius = minSize / 2.0f;
            canvas.drawCircle(radius, radius, radius, mPaint);
        } else {
            super.onDraw(canvas);
        }
    }



    private Bitmap getBitmap(Drawable drawable) {
        if (drawable instanceof BitmapDrawable) {
            return ((BitmapDrawable) drawable).getBitmap();
        } else if (drawable instanceof ColorDrawable) {
            Rect rect = drawable.getBounds();
            int width = rect.right - rect.left;
            int height = rect.bottom - rect.top;
            int color = ((ColorDrawable) drawable).getColor();
            Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
            Canvas canvas = new Canvas(bitmap);
            canvas.drawARGB(Color.alpha(color), Color.red(color), Color.green(color), Color.blue(color));
            return bitmap;
        } else {
            return null;
        }

    }
}

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