android - 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，还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()。

我尝试四处搜索，我得到的最接近的是 question here .但是，我完全迷失了那个问题。 onClick() 方法在哪里(在适配器内部、包含的 Activity/fragment 等内部？)。 viewHolderListener 是什么？ getPosition() 的来源是什么？它的具体作用是什么？从本质上讲，我对这个问题一无所知，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 View 持有者中手动处理它。

您可以做的第一件事是在 `ViewHolder 构造函数中将项目 View 声明为可点击:

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

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

        // ...
    } 

然后如果你想突出显示选择，你必须在你的适配器(例如使用索引列表)和你的 onBindViewHolder 方法中跟踪选定的行:

@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 的父 View 上设置 onClickListener。 onBindViewHolder 方法将针对同一 View 持有者多次调用，您将执行不必要的操作