爲什麼dragShadowBuilder不顯示圖像視圖？

Question

我想使用dragShadowBuilder（視圖視圖）構造函數發送給它ImageView沒有與我開始拖動的那個分離。 ImageView img = new ImageView（this）; img.setbackgroundresource（R.drawable.icon）; 爲什麼dragShadowBuilder在拖動過程中不顯示它？

Answer 1

我認爲這個問題是，ImageView不會被繪製直到它被添加到佈局。 我通過使用擴展的ShadowBuilder繪製位圖來解決此問題：

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; 
    } 
}