如何检测Android中可拖动视图外部的丢弃

Question

我正在开发Android应用程序,我正在使用拖放视图.

我在我的视图上实现了onLongClick(实际上使用带有1.5秒长点击阈值的onTouch)(屏幕截图中的圆圈).当检测到长按时,我会显示两个拖放区域(图像视图的onDragListener分别附加,绿色框位于屏幕截图中).

当我的视图被拖放到任一个拖放区域(调用ACTION_DROP)时,我的代码工作正常,但问题是,我还需要能够告诉我的圆圈何时掉落到拖放区域之外,这样我就可以重置了国家.在这种情况下,我没有从两个丢弃区域中的任何一个触发任何回调.我不认为我从使用startDrag方法的视图中看到了任何调用方法.

只有在将视图放到任何拖放区域之外后才能从logcat获取的是:

I/ViewRootImpl:报告丢弃结果:false

有没有办法从我的代码中检测到"drop result:false"？帮助将不胜感激!

截图链接如下:

----------更新11/21 ----------

在我第一次发布这个问题时,我仍然试图掌握高级概念,但现在我意识到我应该包含更多细节.

以下是我的应用中目前使用的一些代码段.顺便说一下,我在服务中使用那些视图 - 圆(锚)和绿框(dropRegions) - 而不是Activity,所以我使用WindowManager添加视图.

我仍然有同样的问题,而我没有得到的主要内容是,从未调用过ACTION_DRAG_ENTERED和ACTION_DRAG_EXITED.到目前为止,只有ACTION_DROP为我工作.我还缺少什么吗？

以下是代码的相关部分.

在长按圆圈时调用(在sandrstar的响应后稍微修改):

private void anchorOnLongClick(View view) {
    Log.d("####", "LONG CLICK");
    showAnchorDropRegion();

    ClipData.Item item = new ClipData.Item((String) view.getTag());
    ClipData data = new ClipData((String) view.getTag(),
            new String[]{ClipDescription.MIMETYPE_TEXT_PLAIN}, item);

    View.DragShadowBuilder shadowBuilder = new View.DragShadowBuilder(view);
    view.startDrag(data, shadowBuilder, null, 0);
    setupAnchorDropRegion();
    showAnchorDropRegion();
}

将拖动侦听器附加到绿色框:

/* set up the region where anchor can be drag-and-dropped */
private void setupAnchorDropRegion() {
    ivDropRight = new ImageView(this);
    ivDropRight.setImageDrawable(getResources().getDrawable(R.drawable.dropregion_normal));
    ivDropRight.setOnDragListener(new View.OnDragListener() {
        @Override
        public boolean onDrag(View v, DragEvent event) {
            Log.d("####", "onDrag");
            switch (event.getAction()) {

                case DragEvent.ACTION_DRAG_STARTED:
                    // do nothing
                    return true;

                case DragEvent.ACTION_DRAG_ENTERED:
                    Log.d("####", "DRAG_ENTERED");
                    break;

                case DragEvent.ACTION_DRAG_EXITED:
                    Log.d("####", "DRAG_EXITED");
                    break;

                case DragEvent.ACTION_DROP:
                    Log.d("####", "DROP ON: " + event.getX() + ", " + event.getY());
                    hideDropRegion();
                    // initialize anchor locations to the right
                    break;

                case DragEvent.ACTION_DRAG_ENDED:
                    Log.d("####", "DRAG ENDED");
                    break;

                default:
                    break;
            }
            return true;
        }
    });

// repeat for ivDropLeft

显示绿色框(下拉区域):

/* display anchor drop region left and right */
private void showAnchorDropRegion() {
    WindowManager.LayoutParams dropRegionParmas = new WindowManager.LayoutParams(
            app.dropRegionSize, app.dropRegionSize, 0, 0,
            WindowManager.LayoutParams.TYPE_PHONE,
            WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
            PixelFormat.TRANSLUCENT);
    dropRegionParmas.gravity = Gravity.BOTTOM | Gravity.LEFT;
    mWindowManager.addView(ivDropLeft, dropRegionParmas);

    dropRegionParmas.gravity = Gravity.BOTTOM | Gravity.RIGHT;
    mWindowManager.addView(ivDropRight, dropRegionParmas);
}

Answer 1

主要思想来自DragEvent.getResult()的这个文档:

返回拖放操作结果的指示.如果操作类型为ACTION_DRAG_ENDED,则此方法仅返回有效数据.返回值取决于用户释放拖动阴影后发生的情况.

因此,在删除之后,您可以通过getResult()以下方式获取结果:如果它返回,true那么它已被删除,在某些视图中接受了drop.请注意,它接受降回报的观点true来ACTION_DROP:

View应该从onDragEvent(DragEvent)处理程序或OnDragListener.onDrag()侦听器返回true(如果它接受了drop),如果它忽略了drop,则返回false.

下面是一些小例子,类似于你的布局,显示了这种方法:

public class MainActivity extends Activity {
    private static final String TAG = "MainActivity";

    private View mCircleView = null;
    private Boolean mDroppedIn = null;

    private View.OnDragListener mLeftDragListener = new View.OnDragListener() {
        private boolean mInView = false;

        @Override
        public boolean onDrag(final View v, final DragEvent event) {
            final int action = event.getAction();

            switch (action) {
                case DragEvent.ACTION_DRAG_STARTED:
                    mDroppedIn = null;
                    mCircleView.setVisibility(View.INVISIBLE);
                    v.setBackgroundResource(android.R.color.holo_green_dark);
                    break;

                case DragEvent.ACTION_DRAG_ENTERED:
                    mInView = true;
                    v.setBackgroundResource(android.R.color.holo_green_light);
                    break;

                case DragEvent.ACTION_DRAG_EXITED:
                    mInView = false;
                    v.setBackgroundResource(android.R.color.holo_green_dark);
                    break;

                case DragEvent.ACTION_DRAG_ENDED:
                    mCircleView.post(new Runnable() {
                        @Override
                        public void run() {
                            if (mCircleView.getVisibility() != View.VISIBLE) {
                                mCircleView.setVisibility(View.VISIBLE);
                            }
                        }
                    });
                    reportResult(R.id.leftView, event.getResult());
                    break;

                case DragEvent.ACTION_DROP:
                    return mInView;
            }

            return true;
        }
    };

    private View.OnDragListener mRightDragListener = new View.OnDragListener() {
        private boolean mInView = false;

        @Override
        public boolean onDrag(final View v, final DragEvent event) {
            final int action = event.getAction();

            switch (action) {
                case DragEvent.ACTION_DRAG_STARTED:
                    mDroppedIn = null;
                    mCircleView.setVisibility(View.INVISIBLE);
                    v.setBackgroundResource(android.R.color.holo_green_dark);
                    break;

                case DragEvent.ACTION_DRAG_ENTERED:
                    mInView = true;
                    v.setBackgroundResource(android.R.color.holo_green_light);
                    break;

                case DragEvent.ACTION_DRAG_EXITED:
                    mInView = false;
                    v.setBackgroundResource(android.R.color.holo_green_dark);
                    break;

                case DragEvent.ACTION_DRAG_ENDED:
                    mCircleView.post(new Runnable() {
                        @Override
                        public void run() {
                            if (mCircleView.getVisibility() != View.VISIBLE) {
                                mCircleView.setVisibility(View.VISIBLE);
                            }
                        }
                    });
                    reportResult(R.id.rightView, event.getResult());
                    break;

                case DragEvent.ACTION_DROP:
                    return mInView;
            }

            return true;
        }
    };

    private void reportResult(final int viewId, final boolean result) {
        if (mDroppedIn == null) {
            mDroppedIn = result;
            Toast.makeText(this, "Dropped in: " + result, Toast.LENGTH_SHORT).show();
        }
    }

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

        mCircleView = findViewById(R.id.circleView);

        mCircleView.setOnLongClickListener(new View.OnLongClickListener() {
            @Override
            public boolean onLongClick(final View v) {
                final ClipData.Item item = new ClipData.Item((String)v.getTag());
                final ClipData dragData = new ClipData((String)v.getTag(),
                        new String[] {ClipDescription.MIMETYPE_TEXT_PLAIN}, item);

                mCircleView.startDrag(dragData, new CircleShadowBuilder(v), null, 0);
                findViewById(R.id.leftView).setOnDragListener(mLeftDragListener);
                findViewById(R.id.rightView).setOnDragListener(mRightDragListener);
                return true;
            }
        });
    }

    private class CircleShadowBuilder extends View.DragShadowBuilder {

        private final Drawable mShadow;

        CircleShadowBuilder(final View v) {
            super(v);
            mShadow = v.getResources().getDrawable(R.drawable.circle);
        }

        @Override
        public void onProvideShadowMetrics(final Point shadowSize, final Point shadowTouchPoint) {
            int width = getView().getWidth();
            int height = getView().getHeight();

            mShadow.setBounds(0, 0, width, height);
            shadowSize.set(width, height);
            shadowTouchPoint.set(width, height);
        }

        @Override
        public void onDrawShadow(final Canvas canvas) {
            mShadow.draw(canvas);
        }
    }
}