突出显示 RecyclerView 中的选定项目

Question

我在 RecyclerView 中突出显示项目时遇到问题，类似于在 ListView 中设置选定项目。

目前，我已经设置了 RecyclerView，有一个默认的 LayoutManager，并有一个显示所有数据的适配器。我最近刚刚让onClickListener() 工作（虽然我不确定它是否应该进入onCreateViewHolder() 或onBindViewHolder*( - 不确定何时调用onBindViewHolder()）。

我试过四处搜索，最接近的是question here。但是，我完全迷失在这个问题上。 onClick() 方法在哪里（在适配器内部，在包含的活动/片段内部等？）。那是什么viewHolderListener？ getPosition() 是什么，它到底是做什么的？从本质上讲，我没有从那个问题中得到任何结果，这是迄今为止我能找到的最好的资源。

这是我当前设置 RecyclerView 的代码：

// Sets up the main navigation
private void setupMainNav() {
    // use this setting to improve performance if you know that changes
    // in content do not change the layout size of the RecyclerView
    mMainRecyclerNav.setHasFixedSize(true);

    // use a linear layout manager
    LinearLayoutManager layoutManager = new LinearLayoutManager(getActivity());
    mMainRecyclerNav.setLayoutManager(layoutManager);

    // Create and set the adapter for this recyclerView
    MainNavAdapter adapter = new MainNavAdapter(getActivity());
    mMainRecyclerNav.setAdapter(adapter);
}

这是我当前的适配器代码：

class MainNavAdapter extends RecyclerView.Adapter<MainNavAdapter.ViewHolder> {
    Context mContext;

    // Holds the titles of every row
    String[] rowTitles;

    // Default constructor
    MainNavAdapter(Context context) {
        this.mContext = context;

        // Get the rowTitles - the necessary data for now - from resources
        rowTitles = context.getResources().getStringArray(R.array.nav_items);
    }

    // Simple class that holds all the views that need to be reused
    class ViewHolder extends RecyclerView.ViewHolder{
        View parentView; // The view which holds all the other views
        TextView rowTitle; // The title of this item

        // Default constructor, itemView holds all the views that need to be saved
        public ViewHolder(View itemView) {
            super(itemView);

            // Save the entire itemView, for setting listeners and usch later
            this.parentView = itemView;

            // Save the TextView- all that's supported at the moment
            this.rowTitle = (TextView) itemView.findViewById(R.id.row_title);
        }
    }

    // Create new views (invoked by the layout manager)
    @Override
    public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
        // Create the view for this row
        View row = LayoutInflater.from(mContext)
                .inflate(R.layout.list_navmain_row, viewGroup, false);

        // Create a new viewHolder which caches all the views that needs to be saved
        ViewHolder viewHolder = new ViewHolder(row);

        return viewHolder;
    }

    // Replace the contents of a view (invoked by the layout manager)
    @Override
    public void onBindViewHolder(ViewHolder viewHolder, int i) {
        // - get element from your dataset at this position
        // - replace the contents of the view with that element
        viewHolder.rowTitle.setText(rowTitles[i]);

        // TODO: Make a better workaround for passing in the position to the listener
        final int position = i;



        // Set a listener for this entire view
        viewHolder.parentView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(getActivity(), "Clicked on row: " + position, Toast.LENGTH_SHORT).show();
            }
        });
    }

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

如果有任何帮助，我将不胜感激。谢谢。

Answer 1

RecyclerView 不像ListView 那样处理项目选择或状态。相反，您必须在视图持有者中手动处理此问题。

您可以做的第一件事是在 `ViewHolder 构造函数中将您的项目视图声明为可点击：

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

        // Make this view clickable
        itemView.setClickable(true);

        // ...
    } 

然后，如果您想突出显示选择，则必须跟踪适配器中的选定行（例如使用索引列表）和 onBindViewHolder 方法：

@Override 
public void onBindViewHolder(ViewHolder viewHolder, int i) {
    // mark  the view as selected:
    viewHolder.parentview.setSelected(mSelectedRows.contains(i));
} 

作为旁注，您应该在 onCreateViewHolder 而不是 onBindViewHolder 中的父视图上设置 onClickListener。 onBindViewHolder 方法会为同一个视图持有者调用多次，并且您将执行不必要的操作

Answer 2

有一个简单的方法：

  int row_index=0;
    @Override
    public void onBindViewHolder(MyViewHolder holder, final int position) {
        Movie movie = moviesList.get(position);
        holder.title.setText(movie.getTitle());
        holder.genre.setText(movie.getGenre());
        holder.year.setText(movie.getYear());

        holder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                row_index=position;
                notifyDataSetChanged();
            }
        });

        if(row_index==position){
            holder.itemView.setBackgroundColor(Color.parseColor("#567845"));
        }
        else
        {
            holder.itemView.setBackgroundColor(Color.parseColor("#ffffff"));
        }

    }

Answer 3

我正在扩展@XGouchet 的答案，因为即使它让我走上了正确的道路，我仍然需要做额外的工作来支持选择和取消选择行（如切换）。 @ScottBiggs 和我都需要这种类型的支持。

代码保留mSelectedPosition，允许在onBindViewHolder 和mSelectedView 中正确设置选择，从而允许在单击时正确切换选择（打开和关闭）。

private class AsanaAdapter extends RecyclerView.Adapter<AsanaViewHolder> {
    private RecyclerView mRecyclerView;

    private final List<Asana> mAsanas;
    private int mSelectedPosition;
    private View mSelectedView;

    public AsanaAdapter(RecyclerView recyclerView, List<Asana> items) {
        mRecyclerView = recyclerView;
        mAsanas = items;
        setHasStableIds(true);
        setSelected(0);
    }

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

    @Override
    public AsanaViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View newView = getLayoutInflater().inflate(
                R.layout.performance_builder_list_content, parent, false);
        newView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (!v.isSelected()) {
                    // We are selecting the view clicked
                    if (mSelectedView != null) {
                        // deselect the previously selected view
                        mSelectedView.setSelected(false);
                    }
                    mSelectedPosition = mRecyclerView.getChildAdapterPosition(v);
                    mSelectedView = v;
                    setTitle(mAsanas.get(mSelectedPosition).getName());
                } else {
                    // We are deselecting the view clicked
                    setTitle("");
                    mSelectedPosition = -1;
                    mSelectedView = null;
                }

                // toggle the item clicked
                v.setSelected(!v.isSelected());
            }
        });
        return new AsanaViewHolder(newView);
    }

    @Override
    public void onBindViewHolder(AsanaViewHolder holder, int position) {
        if (position == mSelectedPosition) {
            holder.itemView.setSelected(true);

            // keep track of the currently selected view when recycled
            mSelectedView = holder.itemView;
        } else {
            holder.itemView.setSelected(false);
        }
    }
}

Answer 4

如果您只想在单击后突出显示选定的项目，请尝试此解决方案。我使用 retrolambda，但你也可以使用普通的 Runnable 对象。

1.

class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{
    @BindView(R.id.appIcon)
    ImageView appIcon;
    @BindView(R.id.appName)
    TextView appName;

    public ViewHolder(View itemView) {
        super(itemView);
        itemView.setOnClickListener(this);
        ButterKnife.bind(this, itemView);
    }

    @Override
    public void onClick(View v) {
        v.setSelected(true);
        new Handler().postDelayed(() -> v.setSelected(false), 100);
        //or new Handler().postDelayed(new Runnable...

        //your onClick action
    }
}

1. 在你的 Drawable 目录中创建 list_item_selector.xml

   <?xml version="1.0" encoding="utf-8"?>
   <selector xmlns:android="http://schemas.android.com/apk/res/android">
       <item android:state_selected="true" android:drawable="@color/colorPrimary" />
       <item android:drawable="@android:color/transparent" />
   </selector>
   

2. 在单个项目的根布局中设置选择器

   android:background="@drawable/list_item_selector"