android - 如何使用 RecyclerView 的焦点项目做某事？

Question

我有一个简单的 RecyclerView，每个项目只有一个 TextView。通过在 MainActivity 中使用 recyclerView.smoothScrollToPosition(myPosition);，我可以滚动到自定义项目。我需要的是在滚动之后更改滚动到的当前项目的 textColor。

例如，如果 myPosition 是 3 并且 RecyclerView 的第 3 项是“current”或“focused”，我想更改第 3 项的 textColor。

我该怎么做？

MainActivity.java:

public class MainActivity extends AppCompatActivity implements MyAdapter.ItemClickListener {

    MyAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        ArrayList<String> itemTitle_List = new ArrayList<>();
        itemTitle_List.add("facebook");
        itemTitle_List.add("flickr");
        itemTitle_List.add("google_plus");
        itemTitle_List.add("instagram");
        itemTitle_List.add("linkedin");
        itemTitle_List.add("pinterest");
        itemTitle_List.add("soundcloud");
        itemTitle_List.add("swarm");
        itemTitle_List.add("tumblr");
        itemTitle_List.add("twitter");

        // set up the RecyclerView
        RecyclerView recyclerView = findViewById(R.id.recycler_view);
        RecyclerView.LayoutManager layoutManager=new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);
        adapter = new MyAdapter(this, itemTitle_List);
        adapter.setClickListener(this);
        recyclerView.setAdapter(adapter);

        recyclerView.smoothScrollToPosition(3);
    }

    @Override
    public void onItemClick(View view, int position) {
        //Toast.makeText(this, "You clicked " + adapter.getItem(position) + " on row number " + position, Toast.LENGTH_SHORT).show();
    }
}

MyAdapter.java:

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

    private List<String> itemTitle_List;
    private LayoutInflater layoutInflater;
    private ItemClickListener itemClickListener;

    // data is passed into the constructor
    MyAdapter(Context context, List<String> itemTitle_List) {
        this.layoutInflater = LayoutInflater.from(context);
        this.itemTitle_List = itemTitle_List;
    }

    // inflates the row layout from xml when needed
    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = layoutInflater.inflate(R.layout.recyclerview_row, parent, false);
        return new ViewHolder(view);
    }


    // total number of rows
    @Override
    public int getItemCount() {
        return itemTitle_List.size();
    }


    // binds the title to the TextView, and image to the ImageView in each row
    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        String title = itemTitle_List.get(position);
        holder.textView.setText(title);
    }



    // stores and recycles views as they are scrolled off screen
    public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
        TextView textView;

        ViewHolder(View itemView) {
            super(itemView);
            textView = itemView.findViewById(R.id.text_view);
            itemView.setOnClickListener(this);
        }

        @Override
        public void onClick(View view) {
            if (itemClickListener != null) itemClickListener.onItemClick(view, getAdapterPosition());
        }
    }

    // convenience method for getting data at click position
    String getItem(int id) {
        return itemTitle_List.get(id);
    }

    // allows clicks events to be caught
    void setClickListener(ItemClickListener itemClickListener) {
        this.itemClickListener = itemClickListener;
    }

    // parent activity will implement this method to respond to click events
    public interface ItemClickListener {
        void onItemClick(View view, int position);
    }
}

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.v7.widget.RecyclerView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/recycler_view">
    </android.support.v7.widget.RecyclerView>

</RelativeLayout>

recyclerview_row.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="80dp"
    android:orientation="horizontal"
    android:padding="10dp">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/text_view"
        android:layout_gravity="center_vertical"
        android:layout_margin="10dp"/>

</LinearLayout>

Answer 1

我找到了一个简单的解决方案，但我不确定这是否是标准的。

在 MyAdapter.java 中添加一个名为 row_index=0 的公共(public)整数和一个公共(public)函数，如下所示:

public void selectRow(int index){
    row_index=index;
    notifyDataSetChanged();
}

然后在 MyAdapter.java 的 onBindViewHolder 函数中，添加以下代码:

if(position==row_index){
    holder.textView.setTextColor(Color.RED);
}
else{
    holder.textView.setTextColor(Color.BLACK);
}

然后，在 MainActivity.java 中的 recyclerView.smoothScrollToPosition(3) 之后，使用:

MyAdapter.selectRow(3);
MyAdapter.notifyDataSetChanged();

这样，当 RecyclerView 滚动到第 3 个项目时，该项目的 textColor 变为红色。