Question

我已经覆盖了onDraw（）方法，如下所示：

public void onDraw(Canvas canvas1){
Canvas canvas2 = new Canvas();

Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.graphic1);
Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.graphic2);

canvas1.drawBitmap(
          top,
          new Rect(0, 0, graphic1.getWidth(), graphic1.getHeight()),
          new Rect(0, 0, width, width),
          null);

canvas2.drawBitmap(
          top,
          new Rect(0, 0, graphic2.getWidth(), graphic2.getHeight()),
          new Rect(0, 0, width, width),
          null);

}

只显示canvas1上的graphic1，canvas2和graphic2不显示。如何在一个视图上显示多个画布？

Answer 1

正如评论所说，你没有将Canvas2附加到任何东西上。你在每一帧（这是坏的）创建它，绘制它，然后让它的范围被垃圾收集。您应该做什么创建Canvas2，在视图的构造函数中使用支持Bitmap并将其保留为成员。然后你可以绘制它，然后将它的Bitmap blit到Canvas1。例如：

public MyCustomView(Context context)
{
    super(context);
    _canvas2 = new Canvas(_backingBitmap);
}

public void onDraw(Canvas canvas1)
{
Bitmap graphic1 = BitmapFactory.decodeResource(getResources(), R.drawable.graphic1);
Bitmap graphic2 = BitmapFactory.decodeResource(getResources(), R.drawable.graphic2);

canvas1.drawBitmap(
          top,
          new Rect(0, 0, graphic1.getWidth(), graphic1.getHeight()),
          new Rect(0, 0, width, width),
          null);

_canvas2.drawBitmap(
          top,
          new Rect(0, 0, graphic2.getWidth(), graphic2.getHeight()),
          new Rect(0, 0, width, width),
          null);

canvas1.drawBitmap(
          top,
          new Rect(0, 0, _backingBitmap.getWidth(), _backingBitmap.getHeight()),
          new Rect(0, 0, width, width),
          null);
}

视图中的多个画布

1 个答案: