Question

我想将ImageView拖到RelativeLayout内的任何位置。当我尝试拖动它ImageView时它可以工作，但是当我从屏幕上松开手指时它会消失。我无法找到错误的位置。

这是我的代码结构：

OnLongClickListener 适用于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

我怀疑你弄错了。在底线，您没有看到ImageView，因为您致电：

v.setVisibility(View.GONE);

在OnCLickListener内，你永远不会改回来。

问题是您要将DragListener分配给您希望收到有关View的通知的布局中的任何DragEvents，但无论如何拖动都会发生，即使您赢了＆＃ 39;只需通过调用View系统开始使用startDrag()进行拖动，将任何听众分配给任何ShadowBuilder。

总而言之，如果您拖动一个View，那么通常会将DragListener分配给布局中的其他Views，将其悬停在其上方。你似乎认为通过调用：

v.setLayoutParams(layoutParams);

这导致View跟随你的手指而实际上是通话的原因：

v.startDrag()

对此负责。

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;

您应该看到ImageView返回。

拖动时Android ImageView消失了

1 个答案: