我有列表视图，其中我将图像作为项目列表。现在我想在列表视图中执行项目的拖放。因此，我创建了一个“DragNDropListView”类，它扩展了ListView，并覆盖了该类中列表视图的onTouch（）方法，并执行拖放操作，并且工作正常。
但是我的要求是在我的列表视图中存在的长按图像上拖放项目。那怎么可以做到。我应该在列表视图的onTouch（）方法中执行相同的操作，还是应该修改此方法。
请帮我解决这个问题。
我的代码onTouch方法
@Override
public boolean onTouchEvent(MotionEvent ev)
{
final int action = ev.getAction();
final int x = (int) ev.getX();
final int y = (int) ev.getY();
if (action == MotionEvent.ACTION_DOWN)
{
mDragMode = true;
}
if (!mDragMode)
return super.onTouchEvent(ev);
switch (action)
{
case MotionEvent.ACTION_DOWN:
mStartPosition = pointToPosition(x,y);
if (mStartPosition != INVALID_POSITION)
{
int mItemPosition = mStartPosition - getFirstVisiblePosition();
mDragPointOffset = y - getChildAt(mItemPosition).getTop();
mDragPointOffset -= ((int)ev.getRawY()) - y;
startDrag(mItemPosition,y);
drag(0,y);// replace 0 with x if desired
}
break;
case MotionEvent.ACTION_MOVE:
{
drag(0,y);// replace 0 with x if desired
}
break;
case MotionEvent.ACTION_CANCEL:
case MotionEvent.ACTION_UP:
default:
mDragMode = false;
mEndPosition = pointToPosition(x,y);
stopDrag(mStartPosition - getFirstVisiblePosition());
if (mDropListener != null && mStartPosition != INVALID_POSITION && mEndPosition != INVALID_POSITION)
mDropListener.onDrop(mStartPosition, mEndPosition);
break;
}
return true;
}
// move the drag view
private void drag(int x, int y)
{
if (mDragView != null)
{
WindowManager.LayoutParams layoutParams = (WindowManager.LayoutParams) mDragView.getLayoutParams();
layoutParams.x = x;
layoutParams.y = y - mDragPointOffset;
WindowManager mWindowManager = (WindowManager) getContext()
.getSystemService(Context.WINDOW_SERVICE);
mWindowManager.updateViewLayout(mDragView, layoutParams);
if (mDragListener != null)
mDragListener.onDrag(x, y, null);// change null to "this" when ready to use
}
}
// enable the drag view for dragging
private void startDrag(int itemIndex, int y)
{
stopDrag(itemIndex);
View item = getChildAt(itemIndex);
if (item == null) return;
item.setDrawingCacheEnabled(true);
if (mDragListener != null)
mDragListener.onStartDrag(item);
// Create a copy of the drawing cache so that it does not get recycled
// by the framework when the list tries to clean up memory
Bitmap bitmap = Bitmap.createBitmap(item.getDrawingCache());
WindowManager.LayoutParams mWindowParams = new WindowManager.LayoutParams();
mWindowParams.gravity = Gravity.TOP;
mWindowParams.x = 0;
mWindowParams.y = y - mDragPointOffset;
mWindowParams.height = WindowManager.LayoutParams.WRAP_CONTENT;
mWindowParams.width = WindowManager.LayoutParams.WRAP_CONTENT;
mWindowParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
| WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE
| WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
| WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN
| WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS;
mWindowParams.format = PixelFormat.TRANSLUCENT;
mWindowParams.windowAnimations = 0;
Context context = getContext();
ImageView v = new ImageView(context);
v.setImageBitmap(bitmap);
WindowManager mWindowManager = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);
mWindowManager.addView(v, mWindowParams);
mDragView = v;
}
// destroy drag view
private void stopDrag(int itemIndex)
{
if (mDragView != null) {
if (mDragListener != null)
mDragListener.onStopDrag(getChildAt(itemIndex));
mDragView.setVisibility(GONE);
WindowManager wm = (WindowManager)getContext().getSystemService(Context.WINDOW_SERVICE);
wm.removeView(mDragView);
mDragView.setImageDrawable(null);
mDragView = null;
}
}
使用听众
ListView listView = getListView();
if (listView instanceof DragNDropListView)
{
((DragNDropListView) listView).setDropListener(mDropListener);
((DragNDropListView) listView).setRemoveListener(mRemoveListener);
((DragNDropListView) listView).setDragListener(mDragListener);
}
private DropListener mDropListener = new DropListener()
{
public void onDrop(int from, int to)
{
ListAdapter adapter = getListAdapter();
if (adapter instanceof ListViewAdapter)
{
((ListViewAdapter)adapter).onDrop(from, to);
getListView().invalidateViews();
}
}
};
private RemoveListener mRemoveListener = new RemoveListener()
{
public void onRemove(int which)
{
ListAdapter adapter = getListAdapter();
if (adapter instanceof ListViewAdapter) {
((ListViewAdapter)adapter).onRemove(which);
getListView().invalidateViews();
}
}
};
private DragListener mDragListener = new DragListener()
{
public void onDrag(int x, int y, ListView listView)
{
}
public void onStartDrag(View itemView)
{
itemView.setVisibility(View.INVISIBLE);
ImageView iv = (ImageView)itemView.findViewById(R.id.image);
if (iv != null) iv.setVisibility(View.VISIBLE);
}
public void onStopDrag(View itemView)
{
itemView.setVisibility(View.VISIBLE);
ImageView iv = (ImageView)itemView.findViewById(R.id.image);
if (iv != null) iv.setVisibility(View.VISIBLE);
}
};
答案 0 :(得分：2)
是的，你可以简单地使用一些监听器到你的列表视图 -
public interface DropListener {
/**
* Called when an item is to be dropped.
* @param from - index item started at.
* @param to - index to place item at.
*/
void onDrop(int from, int to);
}
尝试查看此Example.
答案 1 :(得分：0)
@Override
public boolean onTouchEvent(MotionEvent event) {
return touchHandler(event);
}
private boolean touchHandler(final MotionEvent event) {
final int action = event.getAction();
final int x = (int) event.getX();
final int y = (int) event.getY();
if (prevY < 0) {
prevY = y;
}
Log.d(TAG, "Motion event " + event.getAction());
int flatPosition = pointToPosition(x, y);
dragRatio = getHeight() / screenHeight;
long packagedPosition = getExpandableListPosition(flatPosition);
if (action == MotionEvent.ACTION_DOWN
&& getPackedPositionType(packagedPosition) == 1) {
if (dragOnLongPress) {
if (pressedItem) {
mDragMode = true;
pressedItem = false;
} else {
pressedItem = true;
Runnable r = new Runnable() {
@Override
public void run() {
// y coordinate is changing for no reason ??
event.setLocation(x, y);
touchHandler(event);
}
};
handler.postDelayed(r, 200);
return true;
}
} else if (x < dragOffset) {
mDragMode = true;
}
}
if (!mDragMode) {
/** when user action on other areas */
if ((pressedItem && Math.abs(prevY - y) > 30)
|| event.getAction() != MotionEvent.ACTION_MOVE) {
pressedItem = false;
handler.removeCallbacksAndMessages(null);
}
return super.onTouchEvent(event);
}
switch (action) {
case MotionEvent.ACTION_DOWN:
mStartFlatPosition = flatPosition;
mStartPosition[0] = getPackedPositionGroup(packagedPosition);
mStartPosition[1] = getPackedPositionChild(packagedPosition);
if (packagedPosition != PACKED_POSITION_VALUE_NULL) {
int mItemPosition = flatPosition - getFirstVisiblePosition();
mDragPointOffset = y - getChildAt(mItemPosition).getTop();
mDragPointOffset -= ((int) event.getRawY()) - y;
startDrag(mItemPosition, y);
if (listeners != null) {
listeners.onPick(mStartPosition);
}
drag(x, y);
}
break;
case MotionEvent.ACTION_MOVE:
int speed = (int) ((y - prevY) * dragRatio);
if (getLastVisiblePosition() < getCount() && speed > 0) {
smoothScrollBy(speed, 1);
}
if (getFirstVisiblePosition() > 0 && speed < 0) {
smoothScrollBy(speed, 1);
}
drag(x, y);// replace 0 with x if desired
if (listeners != null) {
listeners.onDrag(x, y);
}
break;
case MotionEvent.ACTION_CANCEL:
case MotionEvent.ACTION_UP:
default:
mDragMode = false;
if (getPackedPositionType(packagedPosition) == 0) {
mEndPosition[0] = getPackedPositionGroup(packagedPosition);
mEndPosition[1] = 0;
} else {
mEndPosition[0] = getPackedPositionGroup(packagedPosition);
mEndPosition[1] = getPackedPositionChild(packagedPosition);
}
stopDrag(mStartFlatPosition);
if (packagedPosition != PACKED_POSITION_VALUE_NULL) {
if (adapter != null) {
adapter.onDrop(mStartPosition, mEndPosition);
}
if (listeners != null) {
listeners.onDrop(mStartPosition, mEndPosition);
}
}
break;
}
prevY = y;
return true;
}
长按here检查拖放可扩展列表视图，您可以对其进行修改并将其实现为列表视图