一、RecyclerView的焦点记忆封装的学习

https://www.jianshu.com/p/75465a7fdd0f

二、整体代码压缩包

CustomRecyclerView.zip

三、实现步骤：

1.将聚焦封装，继承Recyclerview即可

image.png

2.将原有的适配器的recyclerview改成FocusKeepRecyclerView

  1.    （1）在activity_main.xml中将RecyclerView改成FocusKeepRecyclerView<br />![image.png](https://cdn.nlark.com/yuque/0/2021/png/1574587/1616572125057-9b20b5eb-a55f-455a-b05f-c236f1b18372.png#align=left&display=inline&height=246&margin=%5Bobject%20Object%5D&name=image.png&originHeight=246&originWidth=623&size=30950&status=done&style=none&width=623)<br />       （2）在RecyclerViewAdapterDemo中将RecyclerView改成FocusKeepRecyclerView<br />![image.png](https://cdn.nlark.com/yuque/0/2021/png/1574587/1616572180807-58fccbbf-9750-4ed9-9e4d-e9e15c1ff8bd.png#align=left&display=inline&height=190&margin=%5Bobject%20Object%5D&name=image.png&originHeight=190&originWidth=590&size=19998&status=done&style=none&width=590)<br />![image.png](https://cdn.nlark.com/yuque/0/2021/png/1574587/1616572239772-86c91ccc-19ae-494a-b524-486c583699a4.png#align=left&display=inline&height=175&margin=%5Bobject%20Object%5D&name=image.png&originHeight=175&originWidth=613&size=19829&status=done&style=none&width=613)<br />       （3）在MainActivity中将RecyclerView改成FocusKeepRecyclerView<br />![image.png](https://cdn.nlark.com/yuque/0/2021/png/1574587/1616572305098-ea4b3c5a-c02c-4939-93d8-36e2d59ccf8e.png#align=left&display=inline&height=131&margin=%5Bobject%20Object%5D&name=image.png&originHeight=131&originWidth=471&size=15106&status=done&style=none&width=471)

3.添加item点击，以获取焦点

  1.    （1）定义一个接口，创建item点击方法<br />![image.png](https://cdn.nlark.com/yuque/0/2021/png/1574587/1616572492609-037272d7-0054-4314-a437-b55a240021f8.png#align=left&display=inline&height=151&margin=%5Bobject%20Object%5D&name=image.png&originHeight=151&originWidth=546&size=13421&status=done&style=none&width=546)<br />       （2）创建点击事件，当它不为空的时候，获取点击的位置<br />![image.png](https://cdn.nlark.com/yuque/0/2021/png/1574587/1616572545145-543416de-48b7-4081-a09e-ad7756b3a6d8.png#align=left&display=inline&height=251&margin=%5Bobject%20Object%5D&name=image.png&originHeight=251&originWidth=619&size=22499&status=done&style=none&width=619)<br />       （3）获取到的点击位置，按确定时，弹窗显示当前获取的位置数<br />![image.png](https://cdn.nlark.com/yuque/0/2021/png/1574587/1616572607640-7dfdc562-b21c-496d-a5a2-d2abe05217f9.png#align=left&display=inline&height=140&margin=%5Bobject%20Object%5D&name=image.png&originHeight=140&originWidth=644&size=13599&status=done&style=none&width=644)

4.创建item_seletor.xml布局文件，选中和未选中的背景颜色的变化

image.png

四、整体代码

  1. 1.activity_main.xml布局文件
  1. <?xml version="1.0" encoding="utf-8"?>
  2. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  3.     xmlns:app="http://schemas.android.com/apk/res-auto"
  4.     xmlns:tools="http://schemas.android.com/tools"
  5.     android:layout_width="match_parent"
  6.     android:layout_height="match_parent"
  7.     tools:context=".MainActivity">
  8.     <com.example.customrecyclerview.FocusKeepRecyclerView
  9.         android:id="@+id/rv_demo"
  10.         android:layout_width="match_parent"
  11.         android:focusable="true"
  12.         android:layout_height="match_parent"/>
  13. </LinearLayout>
  1. 2.item_recycler_view.xml布局文件
  1. <?xml version="1.0" encoding="utf-8"?>
  2. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  3.     xmlns:app="http://schemas.android.com/apk/res-auto"
  4.     xmlns:tools="http://schemas.android.com/tools"
  5.     android:layout_width="wrap_content"
  6.     android:layout_height="wrap_content"
  7.     android:layout_margin="8dp"
  8.     android:background="@drawable/item_seletor"
  9.     tools:context=".MainActivity">
  10.   <TextView
  11.       android:id="@+id/tv_view"
  12.       android:layout_width="100dp"
  13.       android:layout_height="100dp"
  14.       android:gravity="center"
  15.       android:text="测试"
  16.       android:textSize="20sp"
  17.       android:textColor="#E2583F"
  18.       android:focusable="true"/>
  19. </LinearLayout>
  1. 3.item_seletor.xml布局文件
  1. <?xml version="1.0" encoding="utf-8"?>
  2. <selector xmlns:android="http://schemas.android.com/apk/res/android">
  3.     <item android:state_focused="true" android:drawable="@color/teal_200"/>
  4.     <item android:state_focused="false" android:drawable="@color/teal_700"/>
  5. </selector>
  1. 4.FocusKeepRecyclerView文件代码
  1. package com.example.customrecyclerview;
  2. import android.content.Context;
  3. import android.util.AttributeSet;
  4. import android.util.Log;
  5. import android.view.View;
  6. import android.view.ViewGroup;
  7. import androidx.annotation.NonNull;
  8. import androidx.annotation.Nullable;
  9. import androidx.recyclerview.widget.RecyclerView;
  10. import java.util.ArrayList;
  11. public class FocusKeepRecyclerView extends RecyclerView {
  12.     private static final String TAG = FocusKeepRecyclerView.class.getSimpleName();
  13.     //是否可以纵向移出
  14.     private boolean mCanFocusOutVertical = true;
  15.     //是否可以横向移出
  16.     private boolean mCanFocusOutHorizontal = true;
  17.     //焦点移出recyclerview的事件监听
  18.     private FocusLostListener mFocusLostListener;
  19.     //焦点移入recyclerview的事件监听
  20.     private FocusGainListener mFocusGainListener;
  21.     //默认第一次选中第一个位置
  22.     private int mCurrentFocusPosition;
  23.     public FocusKeepRecyclerView(@NonNull Context context) {
  24.         super(context, null);
  25.     }
  26.     public FocusKeepRecyclerView(@NonNull Context context, @Nullable AttributeSet attrs) {
  27.         super(context, attrs, 0);
  28.     }
  29.     public FocusKeepRecyclerView(@NonNull Context context, 
  30.                                  @Nullable AttributeSet attrs, int defStyleAttr) {
  31.         super(context, attrs, defStyleAttr);
  32.         setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);
  33.         setChildrenDrawingOrderEnabled(true);
  34.         setItemAnimator(null);
  35.         this.setFocusable(true);
  36.     }
  37.     public boolean isCanFocusOutVertical() {
  38.         return mCanFocusOutVertical;
  39.     }
  40.     public void setCanFocusOutVertical(boolean canFocusOutVertical) {
  41.         mCanFocusOutVertical = canFocusOutVertical;
  42.     }
  43.     public boolean isCanFocusOutHorizontal() {
  44.         return mCanFocusOutHorizontal;
  45.     }
  46.     public void setCanFocusOutHorizontal(boolean canFocusOutHorizontal) {
  47.         this.mCanFocusOutHorizontal = canFocusOutHorizontal;
  48.     }
  49.     public View focusSearch(View focused, int direction) {
  50.         Log.i(TAG, "focusSearch" + focused + ",direction=" + direction);
  51.         View view = super.focusSearch(focused, direction);
  52.         if (focused == null) {
  53.             return view;
  54.         }
  55.         if (view != null) {
  56.             View nextFocusItemView = findContainingItemView(view);
  57.             if (nextFocusItemView == null) {
  58.                 if (!mCanFocusOutVertical && (direction == View.FOCUS_DOWN || direction == View.FOCUS_UP)) {
  59.                     //屏蔽焦点纵向移出recyclerview
  60.                     return focused;
  61.                 }
  62.                 if (!mCanFocusOutHorizontal && (direction == View.FOCUS_LEFT || direction == View.FOCUS_RIGHT)) {
  63.                     //屏蔽焦点横向移出recyclerview
  64.                     return focused;
  65.                 }
  66.                 //调用移出的监听
  67.                 if (mFocusLostListener != null) {
  68.                     mFocusLostListener.onFocusLost(focused, direction);
  69.                 }
  70.                 return view;
  71.             }
  72.         }
  73.         return view;
  74.     }
  75.     public void setFocusLostListener(FocusLostListener focusLostListener) {
  76.         this.mFocusLostListener = focusLostListener;
  77.     }
  78.     public interface FocusLostListener {
  79.         void onFocusLost(View lastFocusChild, int direction);
  80.     }
  81.     public void setFocusGainListener(FocusGainListener focusGainListener) {
  82.         this.mFocusGainListener = focusGainListener;
  83.     }
  84.     public interface FocusGainListener {
  85.         void onFocusGain(View child, View focused);
  86.     }
  87.     @Override
  88.     public void requestChildFocus(View child, View focused) {
  89.         mCurrentFocusPosition = getChildViewHolder(child).getAdapterPosition();
  90.         Log.i(TAG, "focusPos=" + focused);
  91.         if (!hasFocus()) {
  92.             //recyclerview 子view重新获取焦点，调用移入焦点的事件监听
  93.             if (mFocusGainListener != null) {
  94.                 mFocusGainListener.onFocusGain(child, focused);
  95.             }
  96.         }
  97.         //执行过super.requestChildFocus之后hasFocus会变成true
  98.         super.requestChildFocus(child, focused);
  99.         mCurrentFocusPosition = getChildViewHolder(child).getAdapterPosition();
  100.         Log.i(TAG, "focusPos=" + mCurrentFocusPosition);
  101.     }
  102.     //实现焦点记忆的关键代码
  103.     @Override
  104.     public void addFocusables(ArrayList<View> views, int direction, int focusableMode) {
  105.         View view = null;
  106.         if (this.hasFocus() || mCurrentFocusPosition < 0 || (view = getLayoutManager().findViewByPosition(mCurrentFocusPosition)) == null) {
  107.             super.addFocusables(views, direction, focusableMode);
  108.         } else if (view.isFocusable()) {
  109.             //将当前的view放到Focusable views列表中，再次移入焦点是会取到该view，实现焦点记忆功能
  110.             views.add(view);
  111.         } else {
  112.             super.addFocusables(views, direction, focusableMode);
  113.         }
  114.     }
  115.     //控制当前焦点最后绘制，防止焦点放大后被遮挡
  116.     //原顺序123456789，当4是focus时，绘制顺序变为123567894
  117.     @Override
  118.     protected int getChildDrawingOrder(int childCount, int i) {
  119.         View focusedChild = getFocusedChild();
  120.         Log.i(TAG, "focusedChild=" + focusedChild);
  121.         if (focusedChild == null) {
  122.             return super.getChildDrawingOrder(childCount, i);
  123.         } else {
  124.             int index = indexOfChild(focusedChild);
  125.             Log.i(TAG, "index=" + index + ",i=" + i + "count=" + childCount);
  126.             if (i == childCount - 1) {
  127.                 return index;
  128.             }
  129.             if (i < index) {
  130.                 return i;
  131.             }
  132.             return i + 1;
  133.         }
  134.     }
  135. }
  1. 5.RecyclerViewAdapterDemo文件代码
  1. package com.example.customrecyclerview;
  2. import android.content.Context;
  3. import android.view.LayoutInflater;
  4. import android.view.View;
  5. import android.view.ViewGroup;
  6. import android.widget.TextView;
  7. import androidx.annotation.NonNull;
  8. //import androidx.recyclerview.widget.RecyclerView;
  9. import java.util.List;
  10. // 1.创建适配器类继承自RecyclerView.Adapter，泛型传入RecyclerView.ViewHolder类。
  11. public class RecyclerViewAdapterDemo extends 
  12.     FocusKeepRecyclerView.Adapter<RecyclerViewAdapterDemo.MyViewHolder> {
  13.     private Context context;
  14.     private List<String> list;
  15.     private View inflater;
  16.     public RecyclerViewAdapterDemo(Context context, List<String> list){
  17.         this.context=context;
  18.         this.list=list;
  19.     }
  20.     private OnItemClickListener onItemClickListener;
  21.     public interface OnItemClickListener{
  22.         void onClick(int position);
  23.     }
  24.     public void setOnItemClickListener(OnItemClickListener listener){
  25.         this.onItemClickListener = listener;
  26.     }
  27.     //3.重写RecyclerView.Adapter类的相关方法。
  28.     @NonNull
  29.     @Override
  30.     public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
  31.         inflater= LayoutInflater.from(context).inflate(R.layout.item_recycler_view,parent,false);
  32.         MyViewHolder viewHolder=new MyViewHolder(inflater);
  33.         return viewHolder;
  34.     }
  35.     @Override
  36.     public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
  37.         holder.tv_view.setText(list.get(position));
  38.         holder.itemView.setOnClickListener(new View.OnClickListener() {
  39.             @Override
  40.             public void onClick(View v) {
  41.                 if(onItemClickListener!=null){
  42.                     onItemClickListener.onClick(position);
  43.                 }
  44.             }
  45.         });
  46.     }
  47.     @Override
  48.     public int getItemCount() {
  49.         return list.size();
  50.     }
  51.     // 2.创建内部类即RecyclerView.ViewHolder类的子类MyViewHolder，并初始化item的控件。
  52.     class MyViewHolder extends FocusKeepRecyclerView.ViewHolder{
  53.         private TextView tv_view;
  54.         public MyViewHolder(@NonNull View itemView) {
  55.             super(itemView);
  56.             tv_view=itemView.findViewById(R.id.tv_view);
  57.         }
  58.     }
  59. }
  1. 6.MainActivity文件代码
  1. package com.example.customrecyclerview;
  2. import androidx.appcompat.app.AppCompatActivity;
  3. import androidx.recyclerview.widget.GridLayoutManager;
  4. import androidx.recyclerview.widget.LinearLayoutManager;
  5. import androidx.recyclerview.widget.RecyclerView;
  6. import android.content.Context;
  7. import android.os.Bundle;
  8. import android.widget.Toast;
  9. import java.util.ArrayList;
  10. import java.util.List;
  11. public class MainActivity extends AppCompatActivity {
  12.     // 1.获取RecyclerView对象
  13.     private FocusKeepRecyclerView recyclerView;
  14.     private RecyclerViewAdapterDemo adapterDemo;
  15.     private Context context;
  16.     private List<String> list;
  17.     @Override
  18.     protected void onCreate(Bundle savedInstanceState) {
  19.         super.onCreate(savedInstanceState);
  20.         setContentView(R.layout.activity_main);
  21.         context=this;
  22.         // 2.初始化数据
  23.         recyclerView=findViewById(R.id.rv_demo);
  24.         //3.适配器实例化
  25.         list=new ArrayList<>();
  26.         for (int i=0;i<9;i++){
  27.             list.add("第"+i+"个测试");
  28.         }
  29.         adapterDemo=new RecyclerViewAdapterDemo(context,list);
  30.         // 4.设置LayoutManager
  31.         GridLayoutManager manager=new GridLayoutManager(context,3);
  32.         manager.setOrientation(GridLayoutManager.VERTICAL);
  33.         // LinearLayoutManager manager=new LinearLayoutManager(context);
  34.         // manager.setOrientation(LinearLayoutManager.VERTICAL);
  35.         recyclerView.setLayoutManager(manager);
  36.         // 5. 设置Adapter
  37.         recyclerView.setAdapter(adapterDemo);
  38.         adapterDemo.setOnItemClickListener(new RecyclerViewAdapterDemo.OnItemClickListener() {
  39.             @Override
  40.             public void onClick(int position) {
  41.                 Toast.makeText(MainActivity.this,""+position,Toast.LENGTH_SHORT).show();
  42.             }
  43.         });
  44.     }
  45. }
  1. 7.结果图：<br />![image.png](https://cdn.nlark.com/yuque/0/2021/png/1574587/1616572868577-fd5a756b-a88f-4099-ab99-6547f2c27c69.png#align=left&display=inline&height=887&margin=%5Bobject%20Object%5D&name=image.png&originHeight=887&originWidth=1845&size=230901&status=done&style=none&width=1845)