Android RecyclerView的Item點擊事件實現整理

2019-12-12 03:59:24

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自從開始使用RecyclerView代替ListView，會發現有很多地方需要學習。前一段時間的學習記錄有：

RecyclerView的滾動事件研究 - DevWiki
RecyclerView的ViewHolder和Adapter的封裝優化 - DevWiki
RecyclerView問題記錄 - DevWiki

實現 RecyclerView的Item的點擊事件有三種方式：

在創建 ItemView時添加點擊監聽
當 ItemView attach RecyclerView時實現
通過RecyclerView已有的方法addOnItemTouchListener()實現

1.在創建ItemView時添加點擊監聽

思路是：因為ViewHolder我們可以拿到每個Item的根布局，所以如果我們為根布局設置單獨的OnClick監聽并將其開放給Adapter，那不就可以在組裝RecyclerView時就能夠設置ItemClickListener，只不過這個Listener不是設置到RecyclerView上而是設置到Adapter。具體實現代碼如下：

public class SampleAdapter extends RecyclerView.Adapter<SampleAdapter.SampleViewHolder> {    private List<DataBean> mDatas;   private OnItemClickListener mListener; // Item點擊事件    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.當ItemView attach RecyclerView時實現

該實現方法是在閱讀國外的一篇博客時發現的,原文鏈接如下：Getting your clicks on RecyclerView
實現的代碼如下：

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的私有構造方法    */   private ItemClickSupport(RecyclerView recyclerView) {     mRecyclerView = recyclerView;     mRecyclerView.setTag(KEY, this);     // 為RecyclerView設置OnChildAttachStateChangeListener事件監聽     mRecyclerView.addOnChildAttachStateChangeListener(mAttachListener);   }    /**    * 為RecyclerView設置ItemClickSupport    */   public static ItemClickSupport addTo(RecyclerView view) {     ItemClickSupport support = (ItemClickSupport) view.getTag(KEY);     if (support == null) {       support = new ItemClickSupport(view);     }     return support;   }    /**    * 為RecyclerView移除ItemClickSupport    */   public static ItemClickSupport removeFrom(RecyclerView view) {     ItemClickSupport support = (ItemClickSupport) view.getTag(KEY);     if (support != null) {       support.detach(view);     }     return support;   }    /**    * 為RecyclerView設置點擊事件監聽    */   public ItemClickSupport setOnItemClickListener(OnItemClickListener listener) {     mOnItemClickListener = listener;     return this;   }    /**    * 為RecyclerView設置長按事件監聽    */   public ItemClickSupport setOnItemLongClickListener(OnItemLongClickListener listener) {     mOnItemLongClickListener = listener;     return this;   }    /**    * 為RecyclerView移除OnChildAttachStateChangeListener事件監聽    */   private void detach(RecyclerView view) {     view.removeOnChildAttachStateChangeListener(mAttachListener);     view.setTag(KEY, null);   }    /**    * RecyclerView的點擊事件監聽接口    */   public interface OnItemClickListener {     void onItemClicked(RecyclerView recyclerView, View itemView, int position);   }    /**    * RecyclerView的長按事件監聽接口    */   public interface OnItemLongClickListener {     boolean onItemLongClicked(RecyclerView recyclerView, View itemView, int position);   } }

上面的代碼中給RecyclerView設置了OnChildAttachStateChangeListener事件監聽，當子View attach RecyclerView時設置事件監聽。

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) {} };

使用時只需要調用addTo(RecycleView view)方法得到ItemClickSupport對象，然后調用setOnItemClickListener()方法和setOnItemLongClickListener()方法設置ItemView的點擊事件和長按事件監聽即可。

3.通過RecyclerView已有的方法addOnItemTouchListener()實現

3.1、查看源碼

查看RecyclerView源碼可以看到,RecyclerView預留了一個Item的觸摸事件方法：

/**  * 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); }

通過注釋我們可知,此方法是在滾動事件之前調用，需要傳入一個OnItemTouchListener對象。OnItemTouchListener的代碼如下：

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

此接口還提供了一個實現類，且官方推薦使用該實現類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) {   } }

在觸摸接口中，當觸摸時會回調一個MotionEvent對象，通過使用GestureDetectorCompat來解析用戶的操作。

3.2、了解GestureDetector的工作原理

對于觸摸屏，其原生的消息無非按下、抬起、移動這幾種，我們只需要簡單重載onTouch或者設置觸摸偵聽器setOnTouchListener即可進行處理。不過，為了提高我們的APP的用戶體驗，有時候我們需要識別用戶的手勢，Android給我們提供的手勢識別工具GestureDetector就可以幫上大忙了。

GestureDetector的工作原理是，當我們接收到用戶觸摸消息時，將這個消息交給GestureDetector去加工，我們通過設置偵聽器獲得GestureDetector處理后的手勢。

GestureDetector提供了兩個偵聽器接口，OnGestureListener處理單擊類消息，OnDoubleTapListener處理雙擊類消息。
OnGestureListener的接口有這幾個：

// 單擊，觸摸屏按下時立刻觸發  abstract boolean onDown(MotionEvent e);  // 抬起，手指離開觸摸屏時觸發(長按、滾動、滑動時，不會觸發這個手勢)  abstract boolean onSingleTapUp(MotionEvent e);  // 短按，觸摸屏按下后片刻后抬起，會觸發這個手勢，如果迅速抬起則不會  abstract void onShowPress(MotionEvent e);  // 長按，觸摸屏按下后既不抬起也不移動，過一段時間后觸發  abstract void onLongPress(MotionEvent e);  // 滾動，觸摸屏按下后移動  abstract boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY);  // 滑動，觸摸屏按下后快速移動并抬起，會先觸發滾動手勢，跟著觸發一個滑動手勢  abstract boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY);  OnDoubleTapListener的接口有這幾個：

// 雙擊，手指在觸摸屏上迅速點擊第二下時觸發  abstract boolean onDoubleTap(MotionEvent e);  // 雙擊的按下跟抬起各觸發一次  abstract boolean onDoubleTapEvent(MotionEvent e);  // 單擊確認，即很快的按下并抬起，但并不連續點擊第二下  abstract boolean onSingleTapConfirmed(MotionEvent e);

有時候我們并不需要處理上面所有手勢，方便起見，Android提供了另外一個類SimpleOnGestureListener實現了如上接口，我們只需要繼承SimpleOnGestureListener然后重載需要的手勢即可。

3.3、實現點擊事件監聽

了解了GestureDetector的工作原理之后，便開始實現RecycleView的Item的點擊事件。首先寫一個SimpleRecycleViewItemClickListener類繼承SimpleOnItemTouchListener，構造時傳入Item點擊回調OnItemClickListener，并覆寫父類的boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent e)方法，具體代碼如下：

/**  * RecyclerView的Item點擊事件監聽  *  * @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)) { // 把事件交給GestureDetector處理       return true;     } else {       return false;     }   }    /**    * 初始化GestureDetector    */   private void initGestureDetector(final RecyclerView recyclerView) {     mGestureDetector = new GestureDetectorCompat(recyclerView.getContext(), new GestureDetector.SimpleOnGestureListener() { // 這里選擇SimpleOnGestureListener實現類，可以根據需要選擇重寫的方法        /**        * 單擊事件        */       @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;       }        /**        * 長按事件        */       @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));         }       }        /**        * 雙擊事件        */       @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點擊事件監聽接口    *    * @author liyunlong    * @date 2016/11/21 9:43    */   public interface OnItemClickListener {      /**      * 當ItemView的單擊事件觸發時調用      */     void onItemClick(View view, int position);      /**      * 當ItemView的長按事件觸發時調用      */     void onItemLongClick(View view, int position);      /**      * 當ItemView的雙擊事件觸發時調用      */     void onItemDoubleClick(View view, int position);   }     /**    * RecyclerView的Item點擊事件監聽實現    *    * @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的手勢回調中我們覆寫：