android - 将 RecyclerView 可见性从 Gone 更改为 Visible，在显示新添加的项目之前暂时错误地显示先前删除的项目

Question

背景/背景:

在我的主要 Activity 中，我有一个选项卡布局，有两个选项卡。每个选项卡包含两个 fragment ，SearchVehicleFragment 和 VehicleListFragment。

以下是 VehicleListFragment 的布局文件。

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:tools="http://schemas.android.com/tools"
    tools:context=".ui.fragments.VehicleListFragment"
    android:orientation="vertical">


    <com.boulevardclan.vvp.ui.recyclerviews.VehicleRecyclerView
        android:id="@+id/rvVehicleList"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <TextView
        android:id="@+id/tvNoSearchedVehicles"
        style="?android:attr/textAppearanceMedium"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_gravity="center"
        android:gravity="center"
        android:text="You haven't searched for any vehicles yet." />
</LinearLayout>

我的 VehicleRecyclerView 的创建方式与可用的 AttractionsRecyclerView 完全相同 here .这是因为我想为我的 VehicleRecyclerView 实现空状态机制。此外，在初始化期间，我的 VehicleRecyclerView 有 setHasFixedSize(true)

public class VehicleRecyclerView extends RecyclerView {
    private View mEmptyView;

    public VehicleRecyclerView(Context context) {
        super(context);
    }

    private AdapterDataObserver mDataObserver = new AdapterDataObserver() {
        @Override
        public void onChanged() {
            super.onChanged();
            updateEmptyView();
        }

        @Override
        public void onItemRangeRemoved(int positionStart, int itemCount) {
            super.onItemRangeRemoved(positionStart, itemCount);
            try{
                updateEmptyView();
            }catch(Exception e){
            //                TODO
            }
        }

        @Override
        public void onItemRangeInserted(int positionStart, int itemCount) {
            super.onItemRangeInserted(positionStart, itemCount);
            updateEmptyView();
        }

        @Override
        public void onItemRangeChanged(int positionStart, int itemCount) {
            super.onItemRangeChanged(positionStart, itemCount);
            updateEmptyView();
        }

        @Override
        public void onItemRangeMoved(int fromPosition, int toPosition, int itemCount) {
            super.onItemRangeMoved(fromPosition, toPosition, itemCount);
            updateEmptyView();
        }
    };

    public VehicleRecyclerView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public VehicleRecyclerView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    /**
     * Designate a view as the empty view. When the backing adapter has no
     * data this view will be made visible and the recycler view hidden.
     *
     */
    public void setEmptyView(View emptyView) {
        mEmptyView = emptyView;
    }

    @Override
    public void setAdapter(RecyclerView.Adapter adapter) {
        if (getAdapter() != null) {
            getAdapter().unregisterAdapterDataObserver(mDataObserver);
        }
        if (adapter != null) {
            adapter.registerAdapterDataObserver(mDataObserver);
        }
        super.setAdapter(adapter);
        updateEmptyView();
    }

    private void updateEmptyView() {
        if (mEmptyView != null && getAdapter() != null) {
            boolean showEmptyView = getAdapter().getItemCount() == 0;
            if(showEmptyView){
                mEmptyView.setVisibility(VISIBLE);
                setVisibility(GONE);
            }else {
                mEmptyView.setVisibility(GONE);
                setVisibility(VISIBLE);
            }
        }
    }
}

我的 VehicleAdapter 有 setHasStableIds(true)以及覆盖 getItemId(position) .

public class VehicleAdapter extends RecyclerView.Adapter<VehicleAdapter.VehicleViewHolder> {

    private List<Vehicle> vehicleList = new ArrayList<>();
    private Context mContext;

    public VehicleAdapter(Context context, List<Vehicle> vehicles) {
        vehicleList.addAll(vehicles);
        setHasStableIds(true);
        mContext = context;
    }

    @Override
    public VehicleViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        return new VehicleViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.vehicle_list_item_card_view, parent, false));
    }

    @Override
    public void onBindViewHolder(VehicleViewHolder holder, int position) {
        holder.bind(vehicleList.get(position));
    }

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

    @Override
    public long getItemId(int position) {
        return vehicleList.get(position).getId();
    }

    public void addVehicle(Vehicle vehicle){
        if(vehicleList != null){
            vehicleList.add(0, vehicle);
            notifyItemInserted(0);
        }
    }

    public void removeVehicle(int position){
        if(vehicleList.get(position).delete()){
            vehicleList.remove(position);
            notifyItemRemoved(position);
        }else {
//            TODO
        }
    }

    public void updateVehicle(Vehicle vehicle, int position){
        vehicleList.set(position, vehicle);
        notifyItemChanged(position);
    }

    class VehicleViewHolder extends RecyclerView.ViewHolder{

        TextView tvRegistrationNumber;
        TextView tvOwnerName;
        TextView tvColor;
        TextView tvOwnerCity;
        TextView tvLookupDate;
        TextView tvManufacturer;
        TextView tvModel;
        TextView tvMakeYear;

        ImageView ivDetail;
        ImageView ivBookmark;
        ImageView ivDelete;

        public VehicleViewHolder(View itemView) {
            super(itemView);

            tvRegistrationNumber = (TextView) itemView.findViewById(R.id.tvRegistrationNumber);
            tvOwnerName = (TextView) itemView.findViewById(R.id.tvOwnerName);
            tvColor = (TextView) itemView.findViewById(R.id.tvColor);
            tvOwnerCity = (TextView) itemView.findViewById(R.id.tvOwnerCity);
            tvLookupDate = (TextView) itemView.findViewById(R.id.tvLookupDate);
            tvManufacturer = (TextView) itemView.findViewById(R.id.tvManufacturer);
            tvModel = (TextView) itemView.findViewById(R.id.tvModel);
            tvMakeYear = (TextView) itemView.findViewById(R.id.tvMakeYear);

            ivDetail = (ImageView) itemView.findViewById(R.id.ivDetail);
            ivBookmark = (ImageView) itemView.findViewById(R.id.ivBookmark);
            ivDelete = (ImageView) itemView.findViewById(R.id.ivDelete);
        }

        void setOwnerName(String ownerName){
            tvOwnerName.setText(ownerName);
        }
        void setColor(String color){
            tvColor.setText(color);
        }
        void setOwnerCity(String ownerCity){
            tvOwnerCity.setText(ownerCity);
        }
        void setLookupDate(String lookupDate){
            tvLookupDate.setText(lookupDate);
        }
        void setManufacturer(String manufacturer){
            tvManufacturer.setText(manufacturer);
        }
        void setMakeYear(int makeYear){
            tvMakeYear.setText(String.format(Locale.getDefault(),"%s",makeYear));
        }
        void setModel(String model){
            tvModel.setText(model);
        }
        void setBookmarked(boolean isBookmarked){
            ivBookmark.setImageDrawable(ViewUtils.getDrawable(mContext, (isBookmarked ? R.drawable.ic_favorite_black_24dp: R.drawable.ic_favorite_border_black_24dp)));
        }

        void bind(final Vehicle vehicle){
            tvRegistrationNumber.setText(vehicle.getRegistrationNumber());
            setOwnerName(vehicle.getOwnerName());
            setColor(vehicle.getColor());
            setOwnerCity(vehicle.getOwnerCity());
            setLookupDate(DateTimeUtils.getPKTDateTime(vehicle.getModifiedAt()));
            setManufacturer(vehicle.getManufacturer());
            setModel(vehicle.getMakeType());
            setMakeYear(vehicle.getMakeYear());
            setBookmarked(vehicle.isBookmarked());
            setupClickListeners(vehicle);
        }

        private void setupClickListeners(final Vehicle vehicle) {
            ivDelete.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    new MaterialDialog.Builder(mContext)
                            .title(R.string.confirm_delete_vehicle_heading)
                            .content(R.string.confirm_delete_vehicle_label)
                            .positiveText(R.string.confirm_response_yes)
                            .negativeText(R.string.confirm_response_cancel)
                            .stackingBehavior(StackingBehavior.ALWAYS)
                            .onPositive(new MaterialDialog.SingleButtonCallback() {
                                @Override
                                public void onClick(@NonNull MaterialDialog dialog, @NonNull DialogAction which) {
                                    if(getAdapterPosition() != RecyclerView.NO_POSITION){
                                        removeVehicle(getAdapterPosition());
                                    }
                                }
                            })
                            .show();
                }
            });
        }
    }
}

问题:

当 recyclerview 中没有项目并且我通过 notifyItemInserted(0) 添加一个或多个新项目到 recyclerview 时，一切正常。
但是当recyclerview中只有一项时，我通过 notifyItemRemoved(position)删除该项现在通过 notifyItemInserted(0) 向 recyclerview 添加一个新项目，有一个类似过渡/动画的效果，在隐藏空 View 后，recyclerview 会显示先前删除的项目，持续几分之一秒，然后新添加的项目淡入视口(viewport)。

因此，这是应该遵循的“理想”事件序列:

[工作正常] 我删除了recyclerview中的最后一项。 recyclerview 的可见性更改为 GONE，emptyView (TextView) 的可见性更改为 VISIBLE。

[工作正常] 然后，我在 recyclerview 中添加了一个新项目。 emptyView 的可见性更改为 GONE。

[未按预期工作] recyclerview 的可见性应更改为 VISIBLE，它应仅包含一项，即新添加的项 [未按预期工作]
相反，有一个 flickr/blink，其中包含先前存在的唯一项目的 recyclerview 显示了几分之一秒，然后该项目通过淡入(？)转换被新添加的项目替换。

更新:您可以在这里查看问题: https://media.giphy.com/media/l0IydcuJDAqPNlmla/giphy.gif

我期待有一种方法可以摆脱这种 flickr/blink 效果，该效果会在很短的时间内显示旧的 item/recyclerview 状态。

我试过的:

RecyclerView.ItemAnimator animator = mVehicleListRV.getItemAnimator();
if (animator instanceof SimpleItemAnimator) {
    ((SimpleItemAnimator) animator).setSupportsChangeAnimations(false);
}

免责声明:

我是 Android 开发的新手，并且在这个问题上停留了好几个小时。在 SO 寻求大神们的帮助/指点畅通无阻。请忍受我有限的知识。

Answer 1

我遇到了这个问题 - 事实上，当 Android 系统认为 RecyclerView 不可见时，它不会重新布局它的 child 。这将在重新显示 RecyclerView 时产生闪烁，因为旧的子项仍会在短时间内可见，然后才能为新数据更新 View 。
我尝试了几种不同的方法来欺骗 RecyclerView 使其对用户不可见，同时仍更新其子项。
的一些方法没有工作:

将 RecyclerView 可见性设置为 GONE

将 RecyclerView 可见性设置为 INVISIBLE

将 RecyclerView alpha 设置为 0

所有这些方法都会导致 RecyclerView 消失，但也不会重新布局其子项，从而导致闪烁。
的方法做了工作:

将 RecyclerView 高度设置为 1

我在 ConstraintLayout 中有我的 RecyclerView ，所以我写了一个小实用函数。它看起来像这样:

/**
 * Toggle whether [recyclerView] is visible.
 * It does not use [View.setVisibility] or [View.setAlpha],
 * because doing so will prevent recyclerView children from being updated,
 * and this creates a flicker.
 *
 * Instead, this workaround makes the recyclerView too small to be seen,
 * while 'tricking' the Android system into thinking the view is still visible,
 * so allows View updates to continue as necessary.
 */
fun toggleRecyclerView(shouldShow: Boolean) {
    recyclerView.updateLayoutParams {
        // Use 1 as the 'invisible' height - it's the smallest height available to us
        height = if(shouldShow) MATCH_CONSTRAINT else 1
    }
}

我将它与 submitList 结合使用 ListAdapter 提供的回调- 这只会在新旧数据之间的异步差异计算后重新显示 RecyclerView，然后是 View.post - 等到 RecyclerView 子级更新:

if (items.isEmpty()) {
    toggleRecyclerView(false)
    emptyItemsText.visibility = View.VISIBLE
    adapter.submitList(emptyList())
    return
}

// Only show recyclerview after items are updated, to prevent flicker
adapter.submitList(items) {
    recyclerView.post {
        toggleRecyclerView(true)
        emptyItemsText.visibility = View.GONE
    }
}