Android 如何通过长按项目在列表视图中拖放项目
我有一个Android 如何通过长按项目在列表视图中拖放项目,android,listview,Android,Listview,我有一个列表视图，其中有一个作为项目列表的图像。现在，我想在列表视图中执行项目的拖放操作。为此，我创建了一个类“DragNDropListView”，它扩展了ListView，并在这个类中重写列表视图的onTouch（）方法，执行拖放操作，效果很好 但我的要求是在长按列表视图中显示的图像时进行项目的拖放。那么如何做到这一点呢。我应该像在列表视图的onTouch（）方法中那样做，还是必须修改此方法 请帮我整理一下 My code onTouch方法 @Override public boolean
列表视图ListViewonTouch（）@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;
}
}
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);
}
};
是的，您可以简单地使用一些侦听器来访问您的listview-
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);
}
通过长按查看拖放可扩展列表视图您可以修改此内容并将其实现到列表视图yeh我使用了listener..u请检查代码，让我帮助在长按imageview时执行此操作..我仅使用该示例，因为您已经给了我链接..@Anshuman我还没有尝试过。根据自己的需要定制课程。
@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;
}