自定义圆形ImageView(解决Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap();报错问题)

package com.bottle.bottlelilibrary.view;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.graphics.PorterDuff.Mode;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;

/**
 * 自定义ImageView，将图片转换为圆形
 */
public class XCRoundImageView extends android.support.v7.widget.AppCompatImageView {

    private Paint paint;

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

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

    public XCRoundImageView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        paint = new Paint();

    }

    /**
     * 绘制圆形图片
     *
     * @author caizhiming
     */
    @Override
    protected void onDraw(Canvas canvas) {

        Drawable drawable = getDrawable();
        if (null != drawable) {
//            Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap();//此方法报错
            Bitmap bitmap = drawableToBitmap(drawable);//使用此方法将drawable转换成bitmap
            Bitmap b = getCircleBitmap(bitmap, 14);
            final Rect rectSrc = new Rect(0, 0, b.getWidth(), b.getHeight());
            final Rect rectDest = new Rect(0, 0, getWidth(), getHeight());
            paint.reset();
            canvas.drawBitmap(b, rectSrc, rectDest, paint);

        } else {
            super.onDraw(canvas);
        }
    }

    /**
     * 将Drawable转换成bitmap
     *
     * @param drawable
     * @return
     */
    public static Bitmap drawableToBitmap(Drawable drawable) {

        int w = drawable.getIntrinsicWidth();
        int h = drawable.getIntrinsicHeight();
        Bitmap.Config config =
                drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888
                        : Bitmap.Config.RGB_565;
        Bitmap bitmap = Bitmap.createBitmap(w, h, config);
        //注意，下面三行代码要用到，否则在View或者SurfaceView里的canvas.drawBitmap会看不到图
        Canvas canvas = new Canvas(bitmap);
        drawable.setBounds(0, 0, w, h);
        drawable.draw(canvas);

        return bitmap;
    }

    /**
     * 获取圆形图片方法
     *
     * @param bitmap
     * @param pixels
     * @return Bitmap
     * @author caizhiming
     */
    private Bitmap getCircleBitmap(Bitmap bitmap, int pixels) {
        Bitmap output = Bitmap.createBitmap(bitmap.getWidth(),
                bitmap.getHeight(), Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(output);

        final int color = 0xff424242;

        final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
        paint.setAntiAlias(true);
        canvas.drawARGB(0, 0, 0, 0);
        paint.setColor(color);
        int x = bitmap.getWidth();

        canvas.drawCircle(x / 2, x / 2, x / 2, paint);
        paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
        canvas.drawBitmap(bitmap, rect, rect, paint);
        return output;

    }
}