Universal-Image-Loader的一个BUG

使用UIL的内置圆角图片的功能时，发现一个BUG，就是它会拉伸图片，造成图片失真。费了一下午的功夫，重写了RoundedBitmapDisplayer，总算解决这个问题。

代码如下：

public class RoundedBitmapDisplayer implements BitmapDisplayer {
    protected final int cornerRadius;
    protected final int margin;

    public RoundedBitmapDisplayer(int cornerRadiusPixels) {
        this(cornerRadiusPixels, 0);
    }

    public RoundedBitmapDisplayer(int cornerRadiusPixels, int marginPixels) {
        this.cornerRadius = cornerRadiusPixels;
        this.margin = marginPixels;
    }

    @Override
    public void display(Bitmap bitmap, ImageAware imageAware, LoadedFrom loadedFrom) {
        if (!(imageAware instanceof ImageViewAware)) {
            throw new IllegalArgumentException("ImageAware should wrap ImageView. ImageViewAware is expected.");
        }

        imageAware.setImageDrawable(new RoundedDrawable(bitmap, cornerRadius, margin));
    }

    public static class RoundedDrawable extends Drawable {
        protected final float cornerRadius;
        protected final int margin;
        protected final RectF mBorderRect = new RectF(), mBitmapRect;
        protected final BitmapShader mBitmapShader;
        protected final Paint paint;

        private final Matrix mShaderMatrix = new Matrix();
        private float scale = 1.0f, dx, dy; 
        private int mBitmapWidth, mBitmapHeight;
        private int mBorderWidth = 0;

        public RoundedDrawable(Bitmap bitmap, int cornerRadius, int margin) {
            this.cornerRadius = cornerRadius;
            this.margin = margin;
            mBitmapWidth = bitmap.getWidth();
            mBitmapHeight = bitmap.getHeight();

            mBitmapShader = new BitmapShader(bitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
            mBitmapRect = new RectF (margin, margin, bitmap.getWidth() - margin, bitmap.getHeight() - margin);
            
            paint = new Paint();
            paint.setAntiAlias(true);
            paint.setShader(mBitmapShader);
            paint.setFilterBitmap(true);
            paint.setDither(true);
        }

        @Override
        protected void onBoundsChange(Rect bounds) {
            super.onBoundsChange(bounds);
            mBorderRect.set(margin, margin, bounds.width() - margin, bounds.height() - margin);    
            
            mBorderRect.inset(mBorderWidth / 2, mBorderWidth / 2);
            mShaderMatrix.reset();
            dx = 0;
            dy = 0;
            if (mBitmapWidth * mBorderRect.height() > mBorderRect.width() * mBitmapHeight) {
                scale = mBorderRect.height() / (float) mBitmapHeight;
                dx = (mBorderRect.width() - mBitmapWidth * scale) * 0.5f;
            } else {
                scale = mBorderRect.width() / (float) mBitmapWidth;
                dy = (mBorderRect.height() - mBitmapHeight * scale) * 0.5f;
            }

            mShaderMatrix.setScale(scale, scale);
            mShaderMatrix.postTranslate((int) (dx + 0.5f) + mBorderWidth / 2, (int) (dy + 0.5f) + mBorderWidth / 2);
            // 设置shader
            mBitmapShader.setLocalMatrix(mShaderMatrix);
        }

        @Override
        public void draw(Canvas canvas) {
            canvas.drawRoundRect(mBorderRect, cornerRadius, cornerRadius, paint);
        }

        @Override
        public int getOpacity() {
            return PixelFormat.TRANSLUCENT;
        }

        @Override
        public void setAlpha(int alpha) {
            paint.setAlpha(alpha);
        }

        @Override
        public void setColorFilter(ColorFilter cf) {
            paint.setColorFilter(cf);
        }
    }
}