Android RecyclerView的Item点击事件实现整理

2019-12-12 03:59:24

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自从开始使用RecyclerView代替ListView，会发现有很多地方需要学习。前一段时间的学习记录有：

RecyclerView的滚动事件研究 - DevWiki
RecyclerView的ViewHolder和Adapter的封装优化 - DevWiki
RecyclerView问题记录 - DevWiki

实现 RecyclerView的Item的点击事件有三种方式：

在创建 ItemView时添加点击监听
当 ItemView attach RecyclerView时实现
通过RecyclerView已有的方法addOnItemTouchListener()实现

1.在创建ItemView时添加点击监听

思路是：因为ViewHolder我们可以拿到每个Item的根布局，所以如果我们为根布局设置单独的OnClick监听并将其开放给Adapter，那不就可以在组装RecyclerView时就能够设置ItemClickListener，只不过这个Listener不是设置到RecyclerView上而是设置到Adapter。具体实现代码如下：

public class SampleAdapter extends RecyclerView.Adapter<SampleAdapter.SampleViewHolder> {    private List<DataBean> mDatas;   private OnItemClickListener mListener; // Item点击事件    public DataBean getItem(int position) {     return mDatas == null ? null : mDatas.get(position);   }    @Override   public SampleViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {     View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item, parent,false);     return new SampleViewHolder(itemView);   }    @Override   public void onBindViewHolder(SampleViewHolder holder, int position) {    }    @Override   public int getItemCount() {     return mDatas == null ? 0 : mDatas.size();   }    class SampleViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener, View.OnLongClickListener {      public SampleViewHolder(View itemView) {       super(itemView);       // TODO:初始化View       ...        itemView.setOnClickListener(this);       itemView.setOnLongClickListener(this);     }      @Override     public void onClick(View v) {       if (mListener != null) {         mListener.onItemClick(SampleAdapter.this, v, getLayoutPosition());       }     }      @Override     public boolean onLongClick(View v) {       if (mListener != null) {         mListener.onItemLongClick(SampleAdapter.this, v, getLayoutPosition());         return true;       }       return false;     }   } }

2.当ItemView attach RecyclerView时实现

该实现方法是在阅读国外的一篇博客时发现的,原文链接如下：Getting your clicks on RecyclerView
实现的代码如下：

public class ItemClickSupport {    private static final int KEY = 0x99999999;   private final RecyclerView mRecyclerView;   private OnItemClickListener mOnItemClickListener;   private OnItemLongClickListener mOnItemLongClickListener;    private View.OnClickListener mOnClickListener = new View.OnClickListener() {     @Override     public void onClick(View v) {       if (mOnItemClickListener != null) {         RecyclerView.ViewHolder holder = mRecyclerView.getChildViewHolder(v);         mOnItemClickListener.onItemClicked(mRecyclerView, v, holder.getAdapterPosition());       }     }   };    private View.OnLongClickListener mOnLongClickListener = new View.OnLongClickListener() {     @Override     public boolean onLongClick(View v) {       if (mOnItemLongClickListener != null) {         RecyclerView.ViewHolder holder = mRecyclerView.getChildViewHolder(v);         return mOnItemLongClickListener.onItemLongClicked(mRecyclerView, v, holder.getAdapterPosition());       }       return false;     }   };    private RecyclerView.OnChildAttachStateChangeListener mAttachListener = new RecyclerView.OnChildAttachStateChangeListener() {      @Override     public void onChildViewAttachedToWindow(View view) {       if (mOnItemClickListener != null) {         view.setOnClickListener(mOnClickListener);       }       if (mOnItemLongClickListener != null) {         view.setOnLongClickListener(mOnLongClickListener);       }     }      @Override     public void onChildViewDetachedFromWindow(View view) {     }   };    /**    * ItemClickSupport的私有构造方法    */   private ItemClickSupport(RecyclerView recyclerView) {     mRecyclerView = recyclerView;     mRecyclerView.setTag(KEY, this);     // 为RecyclerView设置OnChildAttachStateChangeListener事件监听     mRecyclerView.addOnChildAttachStateChangeListener(mAttachListener);   }    /**    * 为RecyclerView设置ItemClickSupport    */   public static ItemClickSupport addTo(RecyclerView view) {     ItemClickSupport support = (ItemClickSupport) view.getTag(KEY);     if (support == null) {       support = new ItemClickSupport(view);     }     return support;   }    /**    * 为RecyclerView移除ItemClickSupport    */   public static ItemClickSupport removeFrom(RecyclerView view) {     ItemClickSupport support = (ItemClickSupport) view.getTag(KEY);     if (support != null) {       support.detach(view);     }     return support;   }    /**    * 为RecyclerView设置点击事件监听    */   public ItemClickSupport setOnItemClickListener(OnItemClickListener listener) {     mOnItemClickListener = listener;     return this;   }    /**    * 为RecyclerView设置长按事件监听    */   public ItemClickSupport setOnItemLongClickListener(OnItemLongClickListener listener) {     mOnItemLongClickListener = listener;     return this;   }    /**    * 为RecyclerView移除OnChildAttachStateChangeListener事件监听    */   private void detach(RecyclerView view) {     view.removeOnChildAttachStateChangeListener(mAttachListener);     view.setTag(KEY, null);   }    /**    * RecyclerView的点击事件监听接口    */   public interface OnItemClickListener {     void onItemClicked(RecyclerView recyclerView, View itemView, int position);   }    /**    * RecyclerView的长按事件监听接口    */   public interface OnItemLongClickListener {     boolean onItemLongClicked(RecyclerView recyclerView, View itemView, int position);   } }

上面的代码中给RecyclerView设置了OnChildAttachStateChangeListener事件监听，当子View attach RecyclerView时设置事件监听。

private RecyclerView.OnChildAttachStateChangeListener mAttachListener = new RecyclerView.OnChildAttachStateChangeListener() {   @Override   public void onChildViewAttachedToWindow(View view) {     if (mOnItemClickListener != null) {       view.setOnClickListener(mOnClickListener);     }     if (mOnItemLongClickListener != null) {       view.setOnLongClickListener(mOnLongClickListener);     }   }     @Override   public void onChildViewDetachedFromWindow(View view) {} };

使用时只需要调用addTo(RecycleView view)方法得到ItemClickSupport对象，然后调用setOnItemClickListener()方法和setOnItemLongClickListener()方法设置ItemView的点击事件和长按事件监听即可。

3.通过RecyclerView已有的方法addOnItemTouchListener()实现

3.1、查看源码

查看RecyclerView源码可以看到,RecyclerView预留了一个Item的触摸事件方法：

/**  * Add an {@link OnItemTouchListener} to intercept touch events before they are dispatched  * to child views or this view's standard scrolling behavior.  *  * <p>Client code may use listeners to implement item manipulation behavior. Once a listener  * returns true from  * {@link OnItemTouchListener#onInterceptTouchEvent(RecyclerView, MotionEvent)} its  * {@link OnItemTouchListener#onTouchEvent(RecyclerView, MotionEvent)} method will be called  * for each incoming MotionEvent until the end of the gesture.</p>  *  * @param listener Listener to add  * @see SimpleOnItemTouchListener  */ public void addOnItemTouchListener(OnItemTouchListener listener) {   mOnItemTouchListeners.add(listener); }

通过注释我们可知,此方法是在滚动事件之前调用，需要传入一个OnItemTouchListener对象。OnItemTouchListener的代码如下：

public static interface OnItemTouchListener {      public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent e);     public void onTouchEvent(RecyclerView rv, MotionEvent e);     public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept); }

此接口还提供了一个实现类，且官方推荐使用该实现类SimpleOnItemTouchListener：

/**  * An implementation of {@link RecyclerView.OnItemTouchListener} that has empty method bodies and  * default return values.  *  * You may prefer to extend this class if you don't need to override all methods. Another  * benefit of using this class is future compatibility. As the interface may change, we'll  * always provide a default implementation on this class so that your code won't break when  * you update to a new version of the support library.  */ public static class SimpleOnItemTouchListener implements RecyclerView.OnItemTouchListener {   <span style="font-family:'Microsoft YaHei';">  </span>  @Override   public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent e) {     return false;   }     @Override   public void onTouchEvent(RecyclerView rv, MotionEvent e) {   }     @Override   public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {   } }

在触摸接口中，当触摸时会回调一个MotionEvent对象，通过使用GestureDetectorCompat来解析用户的操作。

3.2、了解GestureDetector的工作原理

对于触摸屏，其原生的消息无非按下、抬起、移动这几种，我们只需要简单重载onTouch或者设置触摸侦听器setOnTouchListener即可进行处理。不过，为了提高我们的APP的用户体验，有时候我们需要识别用户的手势，Android给我们提供的手势识别工具GestureDetector就可以帮上大忙了。

GestureDetector的工作原理是，当我们接收到用户触摸消息时，将这个消息交给GestureDetector去加工，我们通过设置侦听器获得GestureDetector处理后的手势。

GestureDetector提供了两个侦听器接口，OnGestureListener处理单击类消息，OnDoubleTapListener处理双击类消息。
OnGestureListener的接口有这几个：

// 单击，触摸屏按下时立刻触发  abstract boolean onDown(MotionEvent e);  // 抬起，手指离开触摸屏时触发(长按、滚动、滑动时，不会触发这个手势)  abstract boolean onSingleTapUp(MotionEvent e);  // 短按，触摸屏按下后片刻后抬起，会触发这个手势，如果迅速抬起则不会  abstract void onShowPress(MotionEvent e);  // 长按，触摸屏按下后既不抬起也不移动，过一段时间后触发  abstract void onLongPress(MotionEvent e);  // 滚动，触摸屏按下后移动  abstract boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY);  // 滑动，触摸屏按下后快速移动并抬起，会先触发滚动手势，跟着触发一个滑动手势  abstract boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY);  OnDoubleTapListener的接口有这几个：

// 双击，手指在触摸屏上迅速点击第二下时触发  abstract boolean onDoubleTap(MotionEvent e);  // 双击的按下跟抬起各触发一次  abstract boolean onDoubleTapEvent(MotionEvent e);  // 单击确认，即很快的按下并抬起，但并不连续点击第二下  abstract boolean onSingleTapConfirmed(MotionEvent e);

有时候我们并不需要处理上面所有手势，方便起见，Android提供了另外一个类SimpleOnGestureListener实现了如上接口，我们只需要继承SimpleOnGestureListener然后重载需要的手势即可。

3.3、实现点击事件监听

了解了GestureDetector的工作原理之后，便开始实现RecycleView的Item的点击事件。首先写一个SimpleRecycleViewItemClickListener类继承SimpleOnItemTouchListener，构造时传入Item点击回调OnItemClickListener，并覆写父类的boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent e)方法，具体代码如下：

/**  * RecyclerView的Item点击事件监听  *  * @author liyunlong  * @date 2016/11/21 9:42  */ public class SimpleRecycleViewItemClickListener extends RecyclerView.SimpleOnItemTouchListener {    private OnItemClickListener mListener;   private GestureDetectorCompat mGestureDetector;    public SimpleRecycleViewItemClickListener(OnItemClickListener listener) {     this.mListener = listener;   }    @Override   public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent e) {     if (mGestureDetector == null) {       initGestureDetector(rv);     }     if (mGestureDetector.onTouchEvent(e)) { // 把事件交给GestureDetector处理       return true;     } else {       return false;     }   }    /**    * 初始化GestureDetector    */   private void initGestureDetector(final RecyclerView recyclerView) {     mGestureDetector = new GestureDetectorCompat(recyclerView.getContext(), new GestureDetector.SimpleOnGestureListener() { // 这里选择SimpleOnGestureListener实现类，可以根据需要选择重写的方法        /**        * 单击事件        */       @Override       public boolean onSingleTapUp(MotionEvent e) {         View childView = recyclerView.findChildViewUnder(e.getX(), e.getY());         if (childView != null && mListener != null) {           mListener.onItemClick(childView, recyclerView.getChildLayoutPosition(childView));           return true;         }         return false;       }        /**        * 长按事件        */       @Override       public void onLongPress(MotionEvent e) {         View childView = recyclerView.findChildViewUnder(e.getX(), e.getY());         if (childView != null && mListener != null) {           mListener.onItemLongClick(childView, recyclerView.getChildLayoutPosition(childView));         }       }        /**        * 双击事件        */       @Override       public boolean onDoubleTapEvent(MotionEvent e) {         int action = e.getAction();         if (action == MotionEvent.ACTION_UP) {           View childView = recyclerView.findChildViewUnder(e.getX(), e.getY());           if (childView != null && mListener != null) {             mListener.onItemDoubleClick(childView, recyclerView.getChildLayoutPosition(childView));             return true;           }         }         return false;       }      });    }    /**    * RecyclerView的Item点击事件监听接口    *    * @author liyunlong    * @date 2016/11/21 9:43    */   public interface OnItemClickListener {      /**      * 当ItemView的单击事件触发时调用      */     void onItemClick(View view, int position);      /**      * 当ItemView的长按事件触发时调用      */     void onItemLongClick(View view, int position);      /**      * 当ItemView的双击事件触发时调用      */     void onItemDoubleClick(View view, int position);   }     /**    * RecyclerView的Item点击事件监听实现    *    * @author liyunlong    * @date 2016/11/21 10:05    */   public class SimpleOnItemClickListener implements OnItemClickListener {      @Override     public void onItemClick(View view, int position) {      }      @Override     public void onItemLongClick(View view, int position) {      }      @Override     public void onItemDoubleClick(View view, int position) {      }   } }

在GestureDetectorCompat的手势回调中我们覆写：