Android 如何通过动态编码设置背景

我曾经画过背景，但我想把它画成可画的/图片背景，而且背景是错误的，我该怎么做

public void surfaceCreated(SurfaceHolder arg0) {
        Bitmap background = BitmapFactory.decodeResource(context.getResources(), R.drawable.download);
        float scale = (float)background.getHeight()/(float)GetHeight();
        int newWidth = Math.round(background.getWidth()/scale);
        int newHeight = Math.round(background.getHeight()/scale);
        scaled = Bitmap.createScaledBitmap(background, newWidth, newHeight, true);

    }
public void onDraw(Canvas canvas) {
    canvas.drawPicture(mbgdDrawable);// draw the background
}
public void DrawBackground(Canvas canvas) {
    canvas.drawBitmap(scaled, mScreenHeight, mScreenWidth,null);
}

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那么你到底想做什么？他给了我错误的方法，它给了你什么？你想不想得到答案？