Canvas显示黑色位图的透明部分 - Android

Question

在我的Android应用程序中,我想绘制两个图像 - img1和img2.首先,我将绘制img2 Canvas.之后,我将绘制Canvas与img2重叠的img1 .Img1包含透明部分.问题是,img1的透明部分以黑色显示,但我希望通过img1的透明部分可以看到img2.我无法做到这一点.请帮我解决这个问题.谢谢.

码:

protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        Bitmap b = BitmapFactory.decodeResource(getResources(),
                R.drawable.white_bg);    //img2
        canvas.drawBitmap(b, 0, 0, null);
        canvas.save();

        canvas.drawBitmap(realImage, 0, 0, null);  //img1
    }

Answer 1

对代码进行一些修改后，我得到了输出。这是我使用的代码。

  public class FrameView extends View{

    Bitmap bitmap = null;

    public FrameView(Context context) {
            super(context);
            this.context = context;

        }

        public FrameView(Context context, AttributeSet attrs) {
            super(context, attrs);
            bitmap = Bitmap.createBitmap(this.screenWidth, this.screenHeight,
                    Bitmap.Config.ARGB_8888);

        }

        public FrameView(Context context, AttributeSet attrs, int defStyle) {
            super(context, attrs, defStyle);
            this.context = context;
        }

    @Override
        protected void onDraw(Canvas canvas) {
            super.onDraw(canvas);
            if (isTouchGestures) {
                invalidate();
                mImgDrawables.get(0).draw(canvas);
                canvas.drawBitmap(bitmap, 0, 0, null);
            }

        }

    //this function is invoked from my activity which is using this view
    public void setFrame(int frame) {

            bitmap = BitmapFactory.decodeStream(getResources().openRawResource(
                    frame));

            bitmap = Bitmap.createScaledBitmap(bitmap, this.screenWidth,
                    this.screenHeight, true);

        }
    }