为什么在覆盖getItemViewType()之后，带有ItemTouchHelper的RecyclerView只停止拖动一个项目? [英] Why does my RecyclerView with ItemTouchHelper stop dragging after only one item, after overriding getItemViewType()?

问题描述

我有一个简单的RecyclerView，它使用ItemTouchHelper来滑动和拖动项目.在我需要对第一个和最后一个项目进行不同样式设置之前，一切工作正常，因此我需要重写适配器中的getItemViewType(int p)函数.完成后，拖动功能不再流畅，只能在上/下移动一个位置后才放下物品.这是我的RecyclerView适配器:

I have a simple RecyclerView that uses ItemTouchHelper to both swipe and drag items. Everything worked fine until I needed to style the first and last items differently, so I needed to override the getItemViewType(int p) function in the adapter. After I did, the drag functionality stopped being fluent and always dropped the items after moving only one position up/down. This is my RecyclerView Adapter:

public class CurrentStopsAdapter extends RecyclerView.Adapter<CurrentStopsAdapter.ViewHolder> {
private RemoveFromTripListener removeFromTripListener = null;
private SwapPlacesTripListener swapPlacesTripListener = null;
private Context context;
private List<PlaceLink> stops;

public CurrentStopsAdapter(Context context, List<PlaceLink> stops,
                           RemoveFromTripListener removeListener, SwapPlacesTripListener swapListener) {
    this.context = context;
    this.stops = stops;
    removeFromTripListener = removeListener;
    swapPlacesTripListener = swapListener;
}

public interface RemoveFromTripListener {
    void onRemoveTripButtonClick(String id);
}

public interface SwapPlacesTripListener {
    void onSwapPlacesButtonClick(int first, int second);
}

@Override
public int getItemViewType(int position) {
    if (position == (getItemCount()-1)) {
        return -1;
    }
    return position;
}

@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    switch (viewType) {
        case -1:
            return new ViewHolder(LayoutInflater.from(context).inflate(R.layout.list_item_destination, parent, false));
        case 0:
            return new ViewHolder(LayoutInflater.from(context).inflate(R.layout.list_item_origin, parent, false));
        default:
            return new ViewHolder(LayoutInflater.from(context).inflate(R.layout.list_item_stop, parent, false));
    }
}

@Override
public void onBindViewHolder(ViewHolder holder, int position) {
    holder.bindStop(stops.get(position));
}

@Override
public int getItemCount() {
    return stops.size();
}

public void remove(int position) {
    if (removeFromTripListener != null) {
        removeFromTripListener.onRemoveTripButtonClick(stops.get(position).getId());
    }
    notifyItemRemoved(position);
}

public void swap(int firstPosition, int secondPosition) {
    if (swapPlacesTripListener != null) {
       swapPlacesTripListener.onSwapPlacesButtonClick(firstPosition, secondPosition);
    }
    notifyItemMoved(firstPosition, secondPosition);
}

public class ViewHolder extends RecyclerView.ViewHolder {
    public final TextView placeTitle;

    public ViewHolder(View view){
        super(view);
        placeTitle = (TextView) view.findViewById(R.id.stops_list_item_title);
    }

    public void bindStop(PlaceLink place){
        this.placeTitle.setText(place.getTitle());

    }
}
}

和我的ItemTouchHelper:

And My ItemTouchHelper:

public class TripTouchHelper extends ItemTouchHelper.SimpleCallback {
    private CurrentStopsAdapter currentStopsAdapter;

    public TripTouchHelper(CurrentStopsAdapter currentStopsAdapter){
        super(ItemTouchHelper.UP | ItemTouchHelper.DOWN, ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT);
        this.currentStopsAdapter = currentStopsAdapter;
    }

    @Override
    public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
        currentStopsAdapter.swap(viewHolder.getAdapterPosition(), target.getAdapterPosition());
        return true;
    }

    @Override
    public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
        currentStopsAdapter.remove(viewHolder.getAdapterPosition());
    }

}

如果我跳过getItemViewType上的Override并为所有项目使用相同的布局，则一切正常，但是我非常想找到解决此问题的方法.任何帮助将不胜感激:)

If I skip the Override on getItemViewType and use the same layout for all items, everything works fine but I would very much like to find a solutions to this problem. Any help would be really appreciated :)

推荐答案

适配器认为您移动的两个ViewHolder被视为不同类型，因为getItemViewType()返回的是唯一类型.因此，它应该重新渲染.

Adapter thinks that the both ViewHolder you moved is considered different type because getItemViewType() returned the type unique. So it should re-render.

例如，您可以按照我的步骤返回类型:

For example, you can return the type by following my procedure:

return 0表示r.layout.foo

return 0 for r.layout.foo

return 1用于r.layout.bar

return 1 for r.layout.bar

然后，您可以编写自己的方法/对，以在想要按类型排列布局时检查布局.如果您仍然需要该职位，则可以在创建ViewHolder之后获取该职位:AdapterPosition.

Then you can write own method/pair to check layout when you wanted the layout by type. If you still need the position, you can get it after ViewHolder is created:AdapterPosition.

如果您需要在OnCreateViewHolder()中的职位，则您有问题，可能无法达到ViewHolder的目的.在处理数据时或在onBindViewHolder()不太昂贵的情况下，考虑进行此工作.

If you needed position in OnCreateViewHolder(), you have something wrong and might defeated the purpose of ViewHolder. Considered doing that work when manipulating data or when onBindViewHolder() if not so expensive.

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