Android RecyclerView的Item点击事件实现整理

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：

1. 在创建 itemview时添加点击监听
2. 当 itemview attach recyclerview时实现
3. 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：

1. boolean onsingletapup(motionevent e)：单击事件回调
2. void onlongpress(motionevent e)：长按事件回调
3. boolean ondoubletapevent(motionevent e)：双击事件回调
   

      如果我们只需要监听单击事件，而不需要监听长按事件和双击事件，构造simplerecycleviewitemclicklistener时只需要传入simpleonitemclicklistener即可，如果需要处理其它的手势监听，也可以覆写对应的手势回调方法。

4.三种方法对比

以上三种方式分别是：

1. 在创建itemview时添加点击监听
2. 当itemview attach recyclerview时实现
3. 通过recyclerview已有的方法addonitemtouchlistener()实现
   

从以上三种方式的实现过程可知:

三种均可实现itemview的点击事件和长按事件的监听。

第一种和第二种方式可以很方便对itemview中的子view进行监听。

第三种方式可以很方便获取用户点击的坐标。

第二种方式和第三种方式可以写在单独的类中，相对于第一种写在adapter的方式可使代码更独立整洁。

综上所述:

      如果你只想监听itemview的点击事件或长按事件，三种方式均可。

      如果你想监听itemview中每个子view的点击事件，采用第一种或者第二种比较方便。

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