android - 为什么 dragShadowBuilder 不显示 imageview？

Question

我正在尝试使用 dragShadowBuilder(View view) 构造函数发送给它的 ImageView 与我开始拖动的那个不相关。ImageView img=new ImageView(this); img.setbackgroundresource(R.drawable.icon); 为什么 dragShadowBuilder 在拖动过程中不显示它？

Answer 1

我认为问题在于 ImageView 在添加到布局之前不会被绘制。我通过使用扩展 ShadowBuilder 绘制位图解决了这个问题：

public class LJDragShadowBuilder extends View.DragShadowBuilder {

   private Bitmap image; // image to draw as a drag shadow

   public LJDragShadowBuilder(Bitmap _image) {
      super();
      image = _image;
   }

   public void onDrawShadow(Canvas canvas)
   {
      canvas.drawBitmap(image, 0, 0, null);
   }

   public void onProvideShadowMetrics(Point shadowSize, Point shadowTouchPoint)
   {
      shadowSize.x = image.getWidth();
      shadowSize.y = image.getHeight();
      shadowTouchPoint.x = shadowSize.x / 2;
      shadowTouchPoint.y = shadowSize.y / 2;
   }
}