滚动期间回收器空间 ItemDecoration 不断增加

Question

这是我的第一个堆栈溢出问题。在过去的几个小时里，我一直试图找到解决堆栈溢出问题的方法，但我什么也没找到。

我在这里创建的应用程序（或特定活动）非常简单，基本上是一个包含 TextView 和 RecyclerView 的垂直回收器，例如：

立式 RecyclerView

--- TextView（标题）

--- Horizo​​ntal RecyclerView（卡片视图）

--- TextView（标题）

--- Horizo​​ntal RecyclerView（卡片视图）

......（更多在这里）

--- TextView（标题）

--- Horizo​​ntal RecyclerView（卡片视图）

（Vertical RecyclerView 结束）

一切正常，除了当我开始滚动垂直回收器（向上和向下）时，第一个和最后两个水平 RecyclerView 的空间项装饰（如下所示）不断增加。我猜测问题可能出在哪里，但我不确定如何解决它。

水平回收器适配器（这是非常标准的）

 public class HorizontalRecyclerViewAdapter extends RecyclerView.Adapter<HorizontalRecyclerViewAdapter.ViewHolder> {
private ArrayList<String> mDataset;
private Context mContext;

// Provide a reference to the views for each data item
// Complex data items may need more than one view per item, and
// you provide access to all the views for a data item in a view holder
public class ViewHolder extends RecyclerView.ViewHolder {
    // each data item is just a string in this case
    public TextView txtViewTitle;
    public ImageView imgViewIcon;

    public ViewHolder(View itemLayoutView) {
        super(itemLayoutView);
        txtViewTitle = (TextView) itemLayoutView.findViewById(R.id.text_view);
        imgViewIcon = (ImageView) itemLayoutView.findViewById(R.id.image_view);
    }
}

// Provide a suitable constructor (depends on the kind of mDataset)
public HorizontalRecyclerViewAdapter(Context myContext, ArrayList myDataset) {
    this.mContext = myContext;
    this.mDataset = myDataset;
}

// Create new views (invoked by the layout manager)
@Override
public HorizontalRecyclerViewAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
                                                                   int viewType) {
    // create a new view
    View v = LayoutInflater.from(parent.getContext())
            .inflate(R.layout.view_image, parent, false);
    // Goes here: set the view's size, margins, paddings and layout parameters

    ViewHolder viewHolder = new ViewHolder(v);
    return viewHolder;
}

// Replace the contents of a view (invoked by the layout manager)
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
    // - get element from your mDataset at this position
    // - replace the contents of the view with that element

    String mDrawableName = mDataset.get(position);
    int resID = mContext.getResources().getIdentifier(mDrawableName , "drawable", mContext.getPackageName());
    holder.imgViewIcon.setImageResource(resID);
}

// Return the size of your mDataset (invoked by the layout manager)
@Override
public int getItemCount() {
    return mDataset.size();
}

空间物品装饰

class HorizantalSpaceItemDecoration extends RecyclerView.ItemDecoration {

private final int mHorizantalSpaceWidth;

public HorizantalSpaceItemDecoration(int horizantalItemSpace) {
    mHorizantalSpaceWidth = horizantalItemSpace;
}

@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent,
                           RecyclerView.State state) {
    outRect.right = mHorizantalSpaceWidth;
}

立式回收器适配器：

public class VerticalRecyclerViewAdapter extends RecyclerView.Adapter<VerticalRecyclerViewAdapter.ViewHolder> {

private ArrayList<String> mHeaderList;
private ArrayList<String> mSportList;
private ArrayList<Boolean> mSpaceItemDecorationFlagList;
private Context context;

public static final int HORIZANTAL_ITEM_SPACE = 30;

// Provide a reference to the views for each data item
// Complex data items may need more than one view per item, and
// you provide access to all the views for a data item in a view holder
public class ViewHolder extends RecyclerView.ViewHolder {
    // each data item is just a string in this case
    public TextView textView;
    public CardView cardView;
    public RecyclerView recyclerView;

    public ViewHolder(View itemLayoutView) {
        super(itemLayoutView);
        cardView = (CardView) itemLayoutView.findViewById(R.id.card_view);
        textView = (TextView) itemLayoutView.findViewById(R.id.text_view);
        recyclerView = (RecyclerView) itemLayoutView.findViewById(R.id.recycler_view);
    }
}

// Provide a suitable constructor (depends on the kind of mHeaderList)
public VerticalRecyclerViewAdapter(Context context) {
    Resources res = context.getResources();
    String[] headers = res.getStringArray(R.array.header_home);
    mHeaderList = new ArrayList<String>(Arrays.asList(headers));
    String[] sports = res.getStringArray(R.array.sports);
    mSportList = new ArrayList<String>(Arrays.asList(sports));
    mSpaceItemDecorationFlagList = new ArrayList<Boolean>();
    for(int i = 0; i < mHeaderList.size(); i++){
        mSpaceItemDecorationFlagList.add(false);
    }
    this.context = context;
}

@Override
public int getItemViewType(int position) {
    // Just as an example, return 0 or 2 depending on position
    // Note that unlike in ListView adapters, types don't have to be contiguous
    return position % 2 * 2;
}

// Create new views (invoked by the layout manager)
@Override
public VerticalRecyclerViewAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
                                                                 int viewType) {
    // Create a new view depends on view type
    // 0: Text View (Header)
    // 1: Recycler View (Category Explorer)
    View newView;

    if(viewType == 0) {
        newView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.view_text, parent, false);
    }else{
        newView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.view_recycler, parent, false);
    }
    // Goes here: set the view's size, margins, paddings and layout parameters

    ViewHolder viewHolder = new ViewHolder(newView);
    return viewHolder;
}

// Replace the contents of a view (invoked by the layout manager)
@Override
public void onBindViewHolder(ViewHolder holder, int position) {

    // - get element from your mHeaderList at this position
    // - replace the contents of the view with that element
    if(position % 2 == 0)
    {
        String header = mHeaderList.get(position);
        holder.textView.setText(header);
    }else{
        // ??????????????
        // Problem might be holder.recyclerView not reset properly?

        RecyclerView.LayoutManager popularLayoutManager= new LinearLayoutManager(context, LinearLayoutManager.HORIZONTAL, false);
        RecyclerView.Adapter adapter = new HorizontalRecyclerViewAdapter(context, mSportList);
        holder.recyclerView.setLayoutManager(popularLayoutManager);
        holder.recyclerView.setAdapter(adapter);

        //add Space ItemDecoration
        holder.recyclerView.addItemDecoration(new HorizantalSpaceItemDecoration(HORIZANTAL_ITEM_SPACE));
        holder.recyclerView.setHasFixedSize(true);

    }
}

// Return the size of your mHeaderList (invoked by the layout manager)
@Override
public int getItemCount() {
    return mHeaderList.size();
}

在每个水平回收器中，我试图在每个图像/项目之间添加 30 dp 空间，但在滚动期间，第一个水平回收器视图和最后两个水平回收器视图不断增加。（我猜是 30，然后是 60 然后是 90？）

我的猜测是在 onBindViewHolder() 中，我的持有者的回收者视图没有正确重置，并且其 rect.right 不断更新为新值（旧 + 30）。但这纯粹是我的猜测。可以请其他人吗？

提前致谢。

Answer 1

对于那些面临此问题的人，可能是因为每次数据更新时您都会添加项目装饰视图（这很糟糕）。但作为快速修复，您可以检查回收器视图是否添加了任何项目装饰器，如果没有，您可以添加您的项目装饰器。将其添加到初始化适配器的 Activity 或片段文件中

if (your_recycler_view.itemDecorationCount < 1) {
    your_recycler_view.addItemDecoration(HorizantalSpaceItemDecoration())
}

Answer 2

这里的问题是每次将数据绑定到视图时都会添加项目装饰器。而之前添加的那些永远不会被删除。

可以进行检查以防止这种情况发生，或者我们可以删除现有的。但是最好只声明和添加一次装饰器，也就是在创建视图时。

所以要解决这个问题：

在课堂上VerticalRecyclerViewAdapter：

• 目前您正在方法中添加项目装饰onBindViewHolder。每次重新渲染持有者时都会调用它（滚动时发生），因此我们需要从这里删除它。

• 然后转到onCreateViewHolder方法并将装饰添加到那里的视图中。

• 请注意，您需要检查是否符合viewType == 1您的情况，否则将导致 NullPointer。

因此，您生成的onCreateViewHolder方法可能如下所示：

// Create new views (invoked by the layout manager)
@Override
public VerticalRecyclerViewAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
                                                                 int viewType) {
    // Create a new view depends on view type
    // 0: Text View (Header)
    // 1: Recycler View (Category Explorer)
    View newView;

    if (viewType == 0) {
        newView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.view_text, parent, false);
    } else {
        newView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.view_recycler, parent, false);
    }
    // Goes here: set the view's size, margins, paddings and layout parameters

    ViewHolder viewHolder = new ViewHolder(newView);
    if (viewType == 1) {
        // Adding the itemDecorator here
        viewHolder.recyclerView.addItemDecoration(new HorizantalSpaceItemDecoration(HORIZANTAL_ITEM_SPACE));
    }
    return viewHolder;
}