撤消后，Recycleview项不可见

Question

我是一个android编程新手，在我的应用程序中，我使用recycleview来显示SQLite数据库的内容，我将数据库读入一个Arraylist，我在recycleview中显示它。我已经成功实现了向左滑动(删除项目)和向右滑动(编辑项目)功能。我在向左滑动时遇到了一个问题，这意味着在删除功能中，我实现了一个撤销功能:

    void restoreItem( SequenceItem sequenceItem, int position) {
    sequenceItemList.add(position, sequenceItem);
    notifyItemInserted(position);
    notifyItemRangeChanged(position, getItemCount());
    }

（SequenceItem 是我的自定义项类，sequenceItemList 是我的 arraylist）

如果我删除了第一个或最后一个项目之间的列表项目并撤消它们，这个函数工作得很好。如果我在撤销后删除了recycleview中的第一个或最后一个项目，我会在那个位置看到一个空格，列表项目布局完全不可见，它只是白色的。然后，我在调用restore方法后添加了一个“recycleview.scrollToPosition ”:

    recycleAdapter.restoreItem(deletedItem, deletedIndex);
    recyclerView.scrollToPosition(deletedIndex);

在此更改之后，如果我从recycleview中删除第一个项目，而不是单击“撤消”，则先前删除的项目将正确还原，但如果我从“recycleview”中删除最后一个项目并单击“撤消”（undo），我仍然会看到一个空白（白色）项目。

你能帮我一下吗？可能是什么问题？如果你需要进一步的细节，我可以张贴更多的代码或告诉更多的应用程序。

编辑于2018年10月6日，我附加了RecyclerItemTouchHelper类，因为在我看来，这导致了问题：

public class RecyclerItemTouchHelper extends ItemTouchHelper.SimpleCallback {
    private RecyclerItemTouchHelperListener listener;
    private Context mContext;

    public RecyclerItemTouchHelper(Context mContext, int dragDirs, int swipeDirs, RecyclerItemTouchHelperListener listener) {
        super(dragDirs, swipeDirs);
        this.listener = listener;
        this.mContext = mContext;
    }

    //This is not used
    @Override
    public boolean onMove(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, @NonNull RecyclerView.ViewHolder viewHolder1) {
        return false;
    }

    @Override
    public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder, int direction) {
        if (listener != null) {
            listener.onSwiped(viewHolder, direction, viewHolder.getAdapterPosition());
        }
    }

    @Override
    public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
        View list_foreground = ((RecycleAdapter.mViewHolder)viewHolder).list_foreground;
        getDefaultUIUtil().clearView(list_foreground);
    }

    @Override
    public int convertToAbsoluteDirection(int flags, int layoutDirection) {
        return super.convertToAbsoluteDirection(flags, layoutDirection);
    }

    @Override
    public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {
        if (viewHolder != null) {
            View list_foreground = ((RecycleAdapter.mViewHolder)viewHolder).list_foreground;
            getDefaultUIUtil().onSelected(list_foreground);
        }
    }

    @Override
    public void onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {

        float mdX = dX / 1;

        if(actionState == ItemTouchHelper.ACTION_STATE_SWIPE){

            Bitmap icon;
            Paint p = new Paint();

            Resources resources = mContext.getResources();

            View itemView = viewHolder.itemView;
            float height = (float) itemView.getBottom() - (float) itemView.getTop();
            float width = height / 3;

            if(dX > 0){ //Swipe right
                p.setColor(Color.parseColor("#D32F2F"));
                RectF background = new RectF((float) itemView.getLeft() , (float) itemView.getTop(), mdX, (float) itemView.getBottom());
                c.drawRect(background,p);
                icon = BitmapFactory.decodeResource(resources, R.drawable.ic_delete_white);
                RectF icon_dest = new RectF((float) itemView.getLeft() + width ,(float) itemView.getTop() + width,(float) itemView.getLeft()+ 2*width,(float)itemView.getBottom() - width);
                c.drawBitmap(icon,null,icon_dest,p);
            } else { //Swipe left
                p.setColor(Color.parseColor("#388E3C"));
                RectF background = new RectF((float) itemView.getRight() + mdX, (float) itemView.getTop(), (float) itemView.getRight(), (float) itemView.getBottom());
                c.drawRect(background,p);
                icon = BitmapFactory.decodeResource(resources, R.drawable.ic_edit_white);
                RectF icon_dest = new RectF((float) itemView.getRight() - 2*width ,(float) itemView.getTop() + width,(float) itemView.getRight() - width,(float)itemView.getBottom() - width);
                c.drawBitmap(icon,null,icon_dest,p);
            }
        }
        super.onChildDraw(c, recyclerView, viewHolder, mdX, dY, actionState, isCurrentlyActive);
    }

    @Override
    public void onChildDrawOver(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
        View list_foreground = ((RecycleAdapter.mViewHolder)viewHolder).list_foreground;
        getDefaultUIUtil().onDrawOver(c, recyclerView, list_foreground, dX, dY, actionState, isCurrentlyActive);
    }
}

下面是滑动的活动实现：

    @Override
public void onSwiped(final RecyclerView.ViewHolder viewHolder, int direction, final int position) {
    //Swipe LEFT to DELETE
    if (direction == ItemTouchHelper.RIGHT) {
        Snackbar snackbar = Snackbar.make(rootLayout, "Phase " + (position + 1) + " is removed!", Snackbar.LENGTH_LONG);

        //Backup of removed item dor UNDO purpose
        final SequenceItem deletedItem = sequenceItemList.get(viewHolder.getAdapterPosition());
        final int deletedIndex = viewHolder.getAdapterPosition();

        //Remove the item from recyclerview
        recycleAdapter.removeItem(viewHolder.getAdapterPosition());

        snackbar.setAction(R.string.undo, new OnClickListener() {
            @Override
            public void onClick(View v) {
                //Restore deleted item
                recycleAdapter.restoreItem(deletedItem, deletedIndex);
                recyclerView.scrollToPosition(deletedIndex);

            }
        }).addCallback(new Snackbar.Callback() {
            @Override
            public void onDismissed(Snackbar snackbar, int dismissType) {
                super.onDismissed(snackbar, dismissType);

                if (dismissType != DISMISS_EVENT_ACTION) {
                    //Delete the item from the database
                    databaseHelper.removePhase(deletedItem);
                    Toast.makeText(getApplicationContext(), R.string.phase_successfully_deleted, Toast.LENGTH_LONG).show();
                }
            }
        });
        snackbar.setActionTextColor(getResources().getColor(R.color.warningColor));
        snackbar.show();
    }
    //Swipe RIGHT to EDIT
    else {
        Intent intent = new Intent(this, AddPhaseActivity.class);
        intent.putExtra("dbPosition", (long) viewHolder.itemView.getTag());
        intent.putExtra("rvPosition", position);
        recycleAdapter.notifyItemChanged(position);
        this.startActivity(intent);
    }
}

Answer 1

您的代码没问题。这种奇怪的性能的唯一可能的地方是下面的功能。

@Override public void clearView（RecyclerView recyclerView， RecyclerView.ViewHolder viewHolder） { View list_foreground = （（RecycleAdapter.mViewHolder）viewHolder）.list_foreground; getDefaultUIUtil（）.clearView（list_foreground）; }

你清除了错误的视图。尝试清除项目的根视图，例如

@覆盖公共无效clearView（RecyclerView，RecyclerView.ViewHolderviewHolder）{View itemView=（（RecycleAdapter.mViewHolder）viewHolder）. itemView； getDefaultUIUtil（）. clearView（itemView）；}

或

将公共void更改为onchildraw（Canvas c、RecyclerView和RecyclerView、recycerView.ViewHolder和viewholders、float dX、float dY、int actionState、boolean isCurrentlyActive）方法。

放

View list_foreground=（（recycledapter.mViewHolder）viewHolder）。列表_前景；getDefaultUIUtil（）。onDraw（c，recyclerView，list_foreground，dX，dY，actionState，isCurrentlyActive）

而不是

super.onChildDraw（c， recyclerView， viewHolder， mdX， dY， actionState， isCurrentlyActive）;

它会解决你的问题。

解释：

问题的根源在于onchildraw方法调用

super.onChildDraw（c， recyclerView， viewHolder， mdX， dY， actionState， isCurrentlyActive）;

它在内部调用< code>onDraw(Canvas c，RecyclerView recyclerView，View view，float dX，float dY，int actionState，boolean isCurrentlyActive)函数，传递< code>viewHolder.itemView作为< code>view的参数，并实现对它的转换，如

< code > view . settranslationx(dX)；view . settranslationy(dY)；

但是清晰的视野就像

    @Override
    public void clearView(View view) {
        view.setTranslationX(0f);
        view.setTranslationY(0f);
    }

因此，在您的情况下，ChildDraw和clearView上的功能适用于不同的视图。