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我正在尝试使用带有垂直 LinearLayoutManager 的 RecyclerView 来显示列表项。此列表可以包含几种不同的项目类型（不同的布局），并且可以由用户使用拖放重新排序。

对于项目类型，如 Android 文档中所述，我重写了getItemType方法，以便在回收器中处理不同类型的视图，并在 onCreateViewHolder 和 onBindViewHolder 中处理它。这就像一个魅力。

对于拖放重新排序，我使用了ItemTouchHelper.Callback （受此示例项目的启发）。这也很有效。

当我尝试使用不同的项目类型和拖放行为时，就会出现问题。只要拖动发生在相同类型的项目之间，这效果很好，但是当我将 A 类型的视图拖动到 B 类型的视图上时，拖动停止并且视图返回到它的原始位置。

这是我的代码：

MyFragment.java

public class MyFragment extends Fragment implements MyAdapter.Listener {

private MyViewModel mViewModel;
private RecyclerView mRecyclerView;
private MyAdapter mAdapter;
private ItemTouchHelper mItemTouchHelper;

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    View root = inflater.inflate(R.layout.fragment, container, false);
    mRecyclerView = root.findViewById(R.id.recyclerView);

    mAdapter = new MyAdapter(this);
    mRecyclerView.setAdapter(mAdapter);
    mItemTouchHelper = new ItemTouchHelper(new MyDragHelperCallback(mAdapter));
    mItemTouchHelper.attachToRecyclerView(mRecyclerView);


    mViewModel = ViewModelProviders.of(getActivity()).get(MyViewModel.class);
    mViewModel.addObserver(this, new Observer<List<Item>>() {
        @Override
        public void onChanged(@Nullable List<Item> items) {
            mAdapter.updateList(items);
        }
    });
    mAdapter.updateList(mViewModel.getList());

    return root;
}

@Override
public void onStartDragRequest(@NonNull RecyclerView.ViewHolder viewHolder) {
    mItemTouchHelper.startDrag(viewHolder);
}
}

MyDragHelperCallback.java

public class MyDragHelperCallback extends ItemTouchHelper.Callback {

private static final int DRAG_MOVEMENT_FLAGS = ItemTouchHelper.UP | ItemTouchHelper.DOWN;

@NonNull
private MyDragListener mListener;

public MyDragHelperCallback(@NonNull MyDragListener listener) {
    mListener = listener;
}

@Override
public boolean isLongPressDragEnabled() {
    return true;
}

@Override
public boolean isItemViewSwipeEnabled() {
    return false;
}

@Override
public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
    if (!(recyclerView.getLayoutManager() instanceof LinearLayoutManager)) {
        throw new IllegalArgumentException("Should only be used with a LinearLayoutManager");
    }

    return makeMovementFlags(DRAG_MOVEMENT_FLAGS, 0);
}

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

@Override
public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
    // Nothing to do
}

}

MyDragListener.java

public interface MyDragListener {
    void onItemMoved(int from, int to);
}

我的适配器.java

public class MyAdapter extends RecyclerView.Adapter<MyHolder> implements MyDragListener {

    @Nullable
    private List<Item> mList;

    public void updateList(@Nullable List<Item> list) {
        mList = list;
        notifyDataSetChanged();
    }

    @Override
    public MyHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        if (viewType == 0) {
            return new MyHolderBis(LayoutInflater.from(parent.getContext()).inflate(R.layout.item_bis, parent, false));
        }
        return new MyHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.item, parent, false));
    }

    @Override
    public void onBindViewHolder(final MyHolder holder, int position) {
        holder.itemView.setOnLongClickListener(new View.OnLongClickListener() {
            @Override
            public boolean onLongClick(View view) {
                mListener.onStartDragRequest(holder);
                return true;
            }
        });
        // bind views to data
    }

    @Override
    public int getItemCount() {
        return mList != null ? mList.size() : 0;
    }

    @Override
    public int getItemViewType(int position) {
        return mList.get(position).getType();
    }

    @Override
    public void onItemMoved(int from, int to) {
        notifyItemMoved(from, to);
    }
}

有什么我想念的吗？或者这仅仅是可能实现的？

感谢您的所有回答！

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0 回答 0