Android拖放图像：ACTION_DROP从未调用

Posted 2023-05-08

【中文标题】Android拖放图像：ACTION_DROP从未调用

【英文标题】：Android drag and drop image: ACTION_DROP never called

【发布时间】：2014-04-29 12:03:45

【问题描述】：

我在这里按照教程进行操作：http://www.tutorialspoint.com/android/android_drag_and_drop.htm 我想让图像在屏幕上可拖动。我在我的 xml 文件中添加了 FrameLayout 并在其中添加了图像。问题是 DragEvent.ACTION_DROP 永远不会被调用。我确保在我的容器框架布局上实现 onDrag 并返回 true，但它仍然没有被调用。

//MainActivity.java
public class MainActivity extends Activity 
ImageView ima;
private static final String IMAGEVIEW_TAG = "Android Logo";
private android.widget.FrameLayout.LayoutParams layoutParams;
String msg;
int x_cord = 0;
int y_cord = 0;

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

    FrameLayout container = (FrameLayout) findViewById(R.id.container);

    container.setOnDragListener(new OnDragListener() 

        @Override
        public boolean onDrag(View arg0, DragEvent arg1) 
            return true;
        

    );

    ima = (ImageView) findViewById(R.id.iv_logo);
    ima.bringToFront();
    ima.setTag(IMAGEVIEW_TAG);

    ima.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);

            // Instantiates the drag shadow builder.
            View.DragShadowBuilder myShadow = new DragShadowBuilder(ima);

            // Starts the drag
            v.startDrag(dragData, // the data to be dragged
                    myShadow, // the drag shadow builder
                    null, // no need to use local data
                    0 // flags (not currently used, set to 0)
            );
            return true;
        
    );

    // Create and set the drag event listener for the View
    ima.setOnDragListener(new OnDragListener() 
        @Override
        public boolean onDrag(View v, DragEvent event) 
            layoutParams = (FrameLayout.LayoutParams) v.getLayoutParams();

            switch (event.getAction()) 
            case DragEvent.ACTION_DRAG_STARTED:
                Log.d(msg, "Action is DragEvent.ACTION_DRAG_STARTED");
                // Do nothing
                break;
            case DragEvent.ACTION_DRAG_ENTERED:
                Log.d(msg, "Action is DragEvent.ACTION_DRAG_ENTERED");
                x_cord = (int) event.getX();
                y_cord = (int) event.getY();
                break;
            case DragEvent.ACTION_DRAG_EXITED:
                Log.d(msg, "Action is DragEvent.ACTION_DRAG_EXITED");
                x_cord = (int) event.getX();
                y_cord = (int) event.getY();
                // layoutParams.leftMargin = x_cord;
                // layoutParams.topMargin = y_cord;
                Log.e("y cord", String.valueOf(y_cord));
                // v.setLayoutParams(layoutParams);
                break;
            case DragEvent.ACTION_DRAG_LOCATION:
                Log.d(msg, "Action is DragEvent.ACTION_DRAG_LOCATION");
                x_cord = (int) event.getX();
                y_cord = (int) event.getY();
                break;
            case DragEvent.ACTION_DRAG_ENDED:
                Log.d(msg, "Action is DragEvent.ACTION_DRAG_ENDED");
                // y_cord = (int) event.getY();
                // layoutParams.leftMargin = x_cord;
                Log.e("y cord action drag ended", String.valueOf(y_cord));

                layoutParams.topMargin = y_cord;
                // Log.e("y cord", String.valueOf(y_cord));
                v.setLayoutParams(layoutParams);

                // Do nothing
                break;

            case DragEvent.ACTION_DROP:
                Log.d(msg, "ACTION_DROP event");

                y_cord = (int) event.getY();
                Log.e("y cord action drop", String.valueOf(y_cord));

                // layoutParams.leftMargin = x_cord;
                layoutParams.topMargin = y_cord;
                v.setLayoutParams(layoutParams);

                // Do nothing
                break;
            default:
                break;
            
            return true;
        
    );

//activity_main.xml
<?xml version="1.0" encoding="utf-8"?>

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/container"
    android:layout_
    android:layout_
    android:layout_weight="0.70"
    android:orientation="vertical" >

    <ImageView
        android:id="@+id/iv_logo"
        android:layout_
        android:layout_
        android:src="@drawable/butterfly" />

</FrameLayout>

【参考方案1】：

在容器的拖动侦听器上调用 ACTION_DROP，而不是在被拖动的图像上。