使用 contentproviders 时如何在 recyclerview 中滑动项目

Question

我想从 recyclerview 中滑动项目，当项目被滑动时，底部的项目应该向上移动。

在我的 Fragment 的 onCreateView 中

 new ItemTouchHelper(new ItemTouchHelper.SimpleCallback(0,
                ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT) {
            @Override
            public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
                return false;
            }

            @Override
            public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
                //Toast.makeText(getActivity(),"ByBy",Toast.LENGTH_LONG).show();

                myListCursorAdapter.onItemRemove(viewHolder, recyclerView);
            }
        }).attachToRecyclerView(recyclerView);

在适配器中

public class TaskCursorAdapter extends RecyclerCursorAdapter<TaskCursorAdapter.ViewHolder> {
    Context context;
    Cursor cursor;


    public TaskCursorAdapter(Context context, Cursor cursor) {
        super(context, cursor);
        this.cursor = cursor;
        this.context = context;
        setHasStableIds(true);

    }

    public static class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
        public TextView taskname;
        public TextView dateDetails;
        Context context;
        Cursor cursor;

        public ViewHolder(View view, Context context, Cursor cursor) {
            super(view);
            this.context = context;
            this.cursor = cursor;
            taskname = (TextView) view.findViewById(R.id.listitemtaskname);
            dateDetails = (TextView) view.findViewById(R.id.listitemdatedetails);
            view.setOnClickListener(this);
        }


        @Override
        public void onClick(View v) {

            // Form the content URI that represents the specific pet that was clicked on,
            // by appending the "id" (passed as input to this method) onto the
            // {@link PetEntry#CONTENT_URI}.
            // For example, the URI would be "content://com.example.android.pets/pets/2"
            // if the pet with ID 2 was clicked on.
            Intent intent = new Intent(context, EditorActivity.class);
            Uri currentPetUri = ContentUris.withAppendedId(TaskContract.TaskEntry.CONTENT_URI, this.getAdapterPosition() + 1);

            intent.setData(currentPetUri);
            context.startActivity(intent);


        }
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        LayoutInflater layoutInflater = LayoutInflater.from(parent.getContext());
        View view = layoutInflater.inflate(R.layout.list_item, parent, false);
        return new ViewHolder(view, context, cursor);
    }

    @Override
    public void onBindViewHolder(ViewHolder viewHolder, Cursor cursor) {

        int taskColumnIndex = cursor.getColumnIndex(TaskContract.TaskEntry.NAME);
        int dateColumnIndex = cursor.getColumnIndex(TaskContract.TaskEntry.DUEDATE);
        int timeColumnIndex = cursor.getColumnIndex(TaskContract.TaskEntry.DUETIME);

        String task = cursor.getString(taskColumnIndex);
        String dateString = cursor.getString(dateColumnIndex);
        String timeString = cursor.getString(timeColumnIndex);

        viewHolder.cursor = cursor;
        viewHolder.taskname.setText(task);

        if (timeString == null && dateString == null) {
            viewHolder.dateDetails.setVisibility(View.GONE);

        } else {
            viewHolder.dateDetails.setText(dateString + "\t\t" + timeString);
        }

    }

    public void onItemRemove(final RecyclerView.ViewHolder viewHolder, final RecyclerView recyclerView) {
        int adapterPosition = viewHolder.getAdapterPosition()+1;
         Uri currentPetUri = ContentUris.withAppendedId(TaskContract.TaskEntry.CONTENT_URI, viewHolder.getAdapterPosition());


        Snackbar snackbar = Snackbar
                .make(recyclerView, "PHOTO REMOVED", Snackbar.LENGTH_LONG)
                .setAction("UNDO", new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        int mAdapterPosition = viewHolder.getAdapterPosition() + 1;
                        Toast.makeText(context,"Hi",Toast.LENGTH_LONG).show();

                        recyclerView.scrollToPosition(mAdapterPosition);

                    }
                });
        snackbar.show();
        context.getContentResolver().insert(TaskContract.TaskEntry.CONTENT_URI_FINISHED, values);
       // Toast.makeText(context,"Hi2",Toast.LENGTH_LONG).show();
        //notifyItemChanged(adapterPosition);
        recyclerView.scrollToPosition(adapterPosition);


    }

}

我尝试了所有方法，但它很难从 recyclerview 中滑动项目，当按下小吃栏的撤消时，我希望该项目重新出现。我想从 recyclerview 中滑动项目，当项目被滑动时，底部项目应该向上移动。

Answer 1

1) 您需要重写 onSwiped() 方法，如下所示。

ItemTouchHelper.SimpleCallback simpleItemTouchCallback = new ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT | ItemTouchHelper.DOWN | ItemTouchHelper.UP) {

            @Override
            public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
               //do something
                return false;
            }

            @Override
            public void onSwiped(RecyclerView.ViewHolder viewHolder, int swipeDir) {      
                int position = viewHolder.getAdapterPosition();
                arrayList.remove(position);//remove swiped item
                adapter.notifyDataSetChanged();//notify the recyclerview changes in the dataset

            }
     };

ItemTouchHelper itemTouchHelper = new ItemTouchHelper(simpleItemTouchCallback);
itemTouchHelper.attachToRecyclerView(rv);//attach to your recyclerview

2) 不要忘记导入 RecyclerView 库的 v22.2.+。

3) 要使底部项目向上移动（更新），您需要在“adapter.notifyDataSetChanged()”首先更新数据库后进行刷新，然后从数据库中提取新数据（有更改）。这将更新数据库和recyclerview。

4) 要撤消，您需要保留一堆已删除的元素（LIFO 顺序），并在单击撤消时将它们插入回去。

Answer 2

如果您使用的是 Content Provider，您必须在 onSwiped 方法中调用您的光标，如下所示：

 ItemTouchHelper.SimpleCallback simpleItemTouchCallback = new ItemTouchHelper.SimpleCallback(
            0, ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT) {

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

        @Override
        public void onSwiped(RecyclerView.ViewHolder viewHolder, int swipeDir) {      
            final int position = viewHolder.getLayoutPosition();
            Cursor cursor = myListCursorAdapter.getCursor();
            cursor.moveToPosition(x);
                final long id = cursor.getLong(cursor.getColumnIndex(Your_Column_ID));
                getActivity().getContentResolver().delete(Uri.withAppendedPath(YourContract.YOUR_URI, String.valueOf(id)), null, null);
            }
 };
ItemTouchHelper itemTouchHelper = new ItemTouchHelper(simpleItemTouchCallback);
itemTouchHelper.attachToRecyclerView(yourRecyclerView);          //attach to your recyclerview

在您的适配器中，您必须设置 getCursor()：

   public Cursor getCursor(){
    return yourCursor;
  }