的Android在拖放，降不工作

在这里，我把我的代码，当我将我的观点（ImageView的），它是无形的，请帮我的Android在拖放，降不工作

public class MainActivity extends ActionBarActivity { 

    ImageView ivfirst; 
    private android.widget.RelativeLayout.LayoutParams layoutParams; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 

     ivfirst = (ImageView) findViewById(R.id.imgView); 

     ivfirst.setOnLongClickListener(new View.OnLongClickListener() { 
      @Override 
      public boolean onLongClick(View v) { 
       ClipData.Item item = new ClipData.Item((CharSequence) v 
         .getTag()); 
       String[] mimeTypes = { ClipDescription.MIMETYPE_TEXT_PLAIN }; 

       ClipData dragData = new ClipData(v.getTag().toString(), 
         mimeTypes, item); 
       View.DragShadowBuilder myShadow = new View.DragShadowBuilder(
         ivfirst); 

       v.startDrag(dragData, myShadow, null, 0); 
       return true; 
      } 
     }); 


      ivfirst.setOnDragListener(new View.OnDragListener() { 
      @Override 
      public boolean onDrag(View v, DragEvent event) { 
       switch(event.getAction()) 
       { 
        case DragEvent.ACTION_DRAG_STARTED: 
        layoutParams = (RelativeLayout.LayoutParams)v.getLayoutParams(); 

        // Do nothing 
        break; 

        case DragEvent.ACTION_DRAG_ENTERED: 
        int x_cord = (int) event.getX(); 
        int y_cord = (int) event.getY(); 
        break; 

        case DragEvent.ACTION_DRAG_EXITED : 
        x_cord = (int) event.getX(); 
        y_cord = (int) event.getY(); 
        layoutParams.leftMargin = x_cord; 
        layoutParams.topMargin = y_cord; 
        v.setLayoutParams(layoutParams); 
        break; 

        case DragEvent.ACTION_DRAG_LOCATION : 
        x_cord = (int) event.getX(); 
        y_cord = (int) event.getY(); 
        break; 

        case DragEvent.ACTION_DRAG_ENDED : 

        // Do nothing 
        break; 

        case DragEvent.ACTION_DROP: 

        // Do nothing 
        break; 
        default: break; 
       } 
       return true; 
      } 
      }); 
     ivfirst.setOnTouchListener(new View.OnTouchListener() { 
      @SuppressLint("ClickableViewAccessibility") 
      @Override 
      public boolean onTouch(View v, MotionEvent event) { 
       if (event.getAction() == MotionEvent.ACTION_DOWN) { 
        ClipData data = ClipData.newPlainText("", ""); 
        View.DragShadowBuilder shadowBuilder = new View.DragShadowBuilder(
          ivfirst); 

        ivfirst.startDrag(data, shadowBuilder, ivfirst, 0); 
        ivfirst.setVisibility(View.INVISIBLE); 

        return true; 
       } else { 
        return false; 
       } 
      } 
     }); 

    } 

}

当我运行该程序的正常工作，但降不行，请指点我，我错了

来源

2016-02-29 Pipariya Himanshu