Android拖放图片:从未调用过ACTION_DROP

Question

我按照这里的教程:http://www.tutorialspoint.com/android/android_drag_and_drop.htm 我想在屏幕上绘制一个可拖动的图像.我在我的xml文件中添加了一个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framelayout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_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_weight="0.70"
    android:orientation="vertical" >

    <ImageView
        android:id="@+id/iv_logo"
        android:layout_width="167dp"
        android:layout_height="117dp"
        android:src="@drawable/butterfly" />

</FrameLayout>

Answer 1

在容器的拖动侦听器上调用ACTION_DROP而不是被拖动的图像.