[英]RecyclerView - Drag and Drop - move item over another item. (placeholder)
[英]how to create RecyclerView drag and drop (swap 2 item positions version)
我有 ItemTouchHelper class,它使用滑動和拖放來執行操作。 但我想改變拖放行為。 它應該交換 2 個元素的位置,我拖動的第一個元素和放置它的另一個元素的位置。 我想交換拖放位置的項目。 不要改變它們之間所有項目的位置。
怎么做
這是我的 class 用於拖放
public class ItemTouchHelper extends
androidx.recyclerview.widget.ItemTouchHelper.Callback {
private Drawable icon;
private Context context;
private ColorDrawable background;
private final ItemTouchHelperListener dragDropListener;
public ItemTouchHelper(Context context, Drawable icon,
ItemTouchHelperListener dragDropListener) {
this.icon = icon;
this.dragDropListener = dragDropListener;
this.context = context;
this.background = new ColorDrawable(context.getResources().getColor(R.color.deleteItem));
}
@Override
public void onChildDraw(@NonNull Canvas c, @NonNull RecyclerView recyclerView,
@NonNull RecyclerView.ViewHolder viewHolder,
float dX, float dY,
int actionState, boolean isCurrentlyActive) {
super.onChildDraw(c, recyclerView, viewHolder, dX,
dY, actionState, isCurrentlyActive);
View itemView = viewHolder.itemView;
int iconMargin = (itemView.getHeight() - icon.getIntrinsicHeight()) / 2;
int iconTop = itemView.getTop() + (itemView.getHeight() - icon.getIntrinsicHeight()) / 2;
int iconBottom = iconTop + icon.getIntrinsicHeight();
if (dX > 0) {
background = new ColorDrawable(context.getResources().getColor(R.color.deleteItem));
iconMargin = (itemView.getHeight() - icon.getIntrinsicHeight()) / 2;
iconTop = itemView.getTop() + (itemView.getHeight() - icon.getIntrinsicHeight()) / 2;
iconBottom = iconTop + icon.getIntrinsicHeight();
int iconRight = itemView.getLeft() + iconMargin + icon.getIntrinsicWidth();
int iconLeft = itemView.getLeft() + iconMargin;
icon.setBounds(iconLeft, iconTop, iconRight, iconBottom);
background.setBounds(itemView.getLeft(), itemView.getTop(),
itemView.getLeft() + ((int) dX),
itemView.getBottom());
} else if (dX < 0) {
int iconRight = itemView.getRight() - iconMargin;
int iconLeft = itemView.getRight() - iconMargin - icon.getIntrinsicWidth();
icon.setBounds(iconLeft, iconTop, iconRight, iconBottom);
background.setBounds(itemView.getRight(), itemView.getTop(),
itemView.getRight() + ((int) dX),
itemView.getBottom());
} else {
background.setBounds(0, 0, 0, 0);
icon.setBounds(0, 0, 0, 0);
}
background.draw(c);
icon.draw(c);
}
@Override
public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder,
int direction) {
dragDropListener.deleteElementDialog(viewHolder.getAdapterPosition());
}
@Override
public int getMovementFlags(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder) {
int dragFlags = UP | DOWN;
int swipeFlags = START | END;
return makeMovementFlags(dragFlags, swipeFlags);
}
@Override
public boolean onMove(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder,
@NonNull RecyclerView.ViewHolder target) {
dragDropListener.onRowMoved(viewHolder.getAdapterPosition(), target.getAdapterPosition());
return true;
}
@Override
public void onSelectedChanged(RecyclerView.ViewHolder viewHolder,
int actionState) {
if (actionState != ACTION_STATE_IDLE && actionState != ACTION_STATE_SWIPE) {
dragDropListener.onRowSelected(viewHolder);
}
super.onSelectedChanged(viewHolder, actionState);
}
@Override
public void clearView(@NonNull RecyclerView recyclerView,
@NonNull RecyclerView.ViewHolder viewHolder) {
super.clearView(recyclerView, Objects.requireNonNull(viewHolder));
dragDropListener.onRowClear(Objects.requireNonNull(viewHolder));
}
@Override
public boolean isLongPressDragEnabled() {
return true;
}
}
這是我的 ItemTouchHelperListener:
public void setItemTouchHelperListener() {
ItemTouchHelperListener itemTouchHelperListener = new
ItemTouchHelperListener() {
@Override
public void onRowMoved(int fromPosition, int toPosition) {
presenter.rowMoved(fromPosition, toPosition);
}
@Override
public void onRowSelected(RecyclerView.ViewHolder myViewHolder) {
if (myViewHolder instanceof ElementsAdapter.ElementsViewHolder) {
elementsAdapter.rowSelected((ElementsAdapter.ElementsViewHolder) myViewHolder);
presenter.rowSelected(myViewHolder.getAdapterPosition());
}
}
@Override
public void onRowClear(RecyclerView.ViewHolder myViewHolder) {
if (myViewHolder instanceof ElementsAdapter.ElementsViewHolder) {
elementsAdapter.rowClear((ElementsAdapter.ElementsViewHolder) myViewHolder);
presenter.rowClear(myViewHolder.getAdapterPosition());
}
}
@Override
public void deleteElementDialog(int adapterPosition) {
createDeleteDialog(adapterPosition);
}
};
您可以通過使用 onMove() 方法注冊拖動的項目和使用 clearView() 方法注冊拖放的項目來實現這一點; 然后修改你的RecyclerView
適配器的數據源; 因此您可以使用存儲拖動項目的臨時項目; 然后將拖放的項目設置為拖動的項目; 最后將臨時項目放在掉落的項目上。
然后對這兩個項目使用RecyclerView
適配器notifyItemChanged()
以使用此更改更新布局
注意:這里我禁用了滑動,因為您的問題主要是拖放
final int[] oldPos = new int[1];
final int[] newPos = new int[1];
ItemTouchHelper itemTouchHelper = new ItemTouchHelper(new ItemTouchHelper.SimpleCallback(
ItemTouchHelper.UP |
ItemTouchHelper.DOWN |
ItemTouchHelper.LEFT |
ItemTouchHelper.RIGHT,
0) {
@Override
public boolean onMove(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, @NonNull RecyclerView.ViewHolder target) {
oldPos[0] = viewHolder.getAdapterPosition();
newPos[0] = target.getAdapterPosition();
return false;
}
@Override
public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder, int direction) {
}
@Override
public void clearView(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder) {
super.clearView(recyclerView, viewHolder);
moveItem(oldPos[0], newPos[0]);
}
});
private void moveItem(int oldPos, int newPos) {
Item temp = mItems.get(oldPos);
mItems.set(oldPos, mItems.get(newPos));
mItems.set(newPos, temp);
mAdapter.notifyItemChanged(oldPos);
mAdapter.notifyItemChanged(newPos);
}
結果
我完全同意@Zain 的回答,但有一個問題,即假設您想用第 3 項替換第 1 項,然后您將單擊並按住第 3 項並將其拖到第 1 項上。 放下后,您會注意到第三個項目將再次轉移到其原始 position 之后,這兩個項目將得到正確更新。 看起來不太好。
我剛剛稍微修改了@Zain 的答案。
private int fromPos = -1;
private int toPos = -1;
ItemTouchHelper itemTouchHelper = new ItemTouchHelper(new
ItemTouchHelper.SimpleCallback(
ItemTouchHelper.UP | ItemTouchHelper.DOWN |
ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT, 0) {
@Override
public boolean onMove(@NonNull RecyclerView recyclerView,
@NonNull RecyclerView.ViewHolder viewHolder,
@NonNull RecyclerView.ViewHolder target) {
toPos = target.getAdapterPosition();
return false;
}
@Override
public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder,
int direction) {}
@Override
public void onSelectedChange(@NonNull RecyclerView.ViewHolder
viewHolder, int actionState) {
switch(actionState){
case ItemTouchHelper.ACTION_STATE_DRAG:{
fromPos = viewHolder.getAdapterPosition();
break;
}
case ItemTouchHelper.ACTION_STATE_IDLE: {
//Execute when the user dropped the item after dragging.
if(fromPos != -1 && toPos != -1
&& fromPos != toPos) {
moveItem(fromPos, toPos);
fromPos = -1;
toPos = -1;
}
break;
}
}
private void moveItem(int oldPos, int newPos) {
Item temp = mItems.get(oldPos);
mItems.set(oldPos, mItems.get(newPos));
mItems.set(newPos, temp);
mAdapter.notifyItemChanged(oldPos);
mAdapter.notifyItemChanged(newPos);
}
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