android - 按钮扩展：onDraw 方法中的画布不会仅在 Gingerbread 上绘制位图

Question

方法：

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    if(icon!=null)
    canvas.drawBitmap(icon, iconBounds, buttonBounds, null);
}

public void setIcon(int res) {
    this.icon = BitmapFactory.decodeResource(getResources(), res);
    this.iconBounds = new Rect(0, 0, icon.getWidth(), icon.getHeight());
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    this.setTextScaleX(1.0f);
    bw = MeasureSpec.getSize(widthMeasureSpec)-6;
    if(tw>bw)
        setTextScaleX(bw/tw);
    bh = MeasureSpec.getSize(heightMeasureSpec)-6;
    if(icon!=null) {
        int centerX = (bw+6)/2;
        int centerY = (bh+6)/2;
        int mWidth = icon.getWidth()/2;
        int mHeight = icon.getHeight()/2;
        this.buttonBounds = new Rect(centerX-mWidth, centerY-mHeight, centerX+mWidth, centerY+mHeight);
    }

}

这适用于 Froyo 和冰淇淋三明治，但不适用于 Gingerbread。按钮背景是一个 TransitionDrawable。