Android ImageView在拖动时消失了

Question

我想将我的ImageView 拖到我的RelativeLayout 中的任何位置。当我尝试拖动 ImageView 时它可以工作，但是当我从屏幕上松开手指时它消失了。我找不到错误在哪里。

这是我的代码结构：

OnLongClickListener 对于 ImageView

imageView.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(imageView);

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

DragListener方法

        imageView.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(); //layoutParams is defined on Top.
                    Log.d(msg, "Action is DragEvent.ACTION_DRAG_STARTED");

                   break;

                case DragEvent.ACTION_DRAG_ENTERED:
                    Log.d(msg, "Action is DragEvent.ACTION_DRAG_ENTERED");
                    int x_cord = (int) event.getX();
                    int y_cord = (int) event.getY();
                    Log.d(msg,"Drag Location Entered "+x_cord+" Ycord "+y_cord);

                    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();
                    Log.d(msg, "Drag Exited xcord " + x_cord + " Ycord " + y_cord);


                    layoutParams.leftMargin = x_cord;
                    layoutParams.topMargin = y_cord;

                    v.setLayoutParams(layoutParams);
                    Log.d(msg, "layoutparams set success.");
                        v.setVisibility(View.VISIBLE);
                        Log.d(msg,"Made View Visible");

                    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();
                    Log.d(msg,"Drag Location xcord "+x_cord+" Ycord "+y_cord);
                    break;


                case DragEvent.ACTION_DRAG_ENDED:
                    Log.d(msg, "Action is DragEvent.ACTION_DRAG_ENDED");
                    break;

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


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

OnTouchListener方法

        imageView.setOnTouchListener(new View.OnTouchListener() {
        @Override
        public boolean onTouch(View v, MotionEvent event) {
            if (event.getAction() == MotionEvent.ACTION_DOWN) {
                ClipData data = ClipData.newPlainText("", "");
                View.DragShadowBuilder shadowBuilder = new View.DragShadowBuilder(imageView);
                imageView.startDrag(data, shadowBuilder, imageView, 0);
                return true;
            }
            else
            {
                return false;
            }
        }
    });

Answer 1

我怀疑你搞错了。在底线你看不到ImageView，因为你打电话：

v.setVisibility(View.GONE);

在您的 OnCLickListener 中，您永远不会将其更改回来。

问题是您将DragListener 分配给布局中您希望收到有关DragEvents 的通知的任何View，但无论如何都会发生拖动，即使您不会将任何侦听器分配给任何View 只需调用startDrag() 系统即可开始使用ShadowBuilder 进行拖动。

总而言之，如果您拖动一个View，那么通常您会将DragListener 分配给布局中的其他Views，您将鼠标悬停在它们上方。您似乎认为通过调用：

v.setLayoutParams(layoutParams);

这是导致View 跟随您的手指而实际上是呼叫的原因：

v.startDrag()

对它负责。

无论如何，如果你打电话：

 case DragEvent.ACTION_DRAG_ENDED:
        case DragEvent.ACTION_DRAG_ENDED:
        v.setVisibility(View.VISIBLE);
        break;

你应该看到ImageView回来了。