RecyclerView的Item點選事件實現總結
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:
實現 RecyclerView
的Item的點選事件有三種方式:
-
在建立
ItemView
時新增點選監聽 -
當
ItemView attach RecyclerView
時實現 -
通過
RecyclerView
已有的方法addOnItemTouchListener()
實現
1.在建立ItemView
時新增點選監聽
思路是:因為ViewHolder我們可以拿到每個Item的根佈局,所以如果我們為根佈局設定單獨的OnClick監聽並將其開放給Adapter,那不就可以在組裝RecyclerView時就能夠設定ItemClickListener,只不過這個Listener不是設定到RecyclerView上而是設定到Adapter。具體實現程式碼如下:
public class SampleAdapter extends RecyclerView.Adapter<SampleAdapter.SampleViewHolder> { private List<DataBean> mDatas; private OnItemClickListener mListener; // Item點選事件 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
實現的程式碼如下:
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設定OnChildAttachStateChangeListener事件監聽 mRecyclerView.addOnChildAttachStateChangeListener(mAttachListener); } /** * 為RecyclerView設定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設定點選事件監聽 */ public ItemClickSupport setOnItemClickListener(OnItemClickListener listener) { mOnItemClickListener = listener; return this; } /** * 為RecyclerView設定長按事件監聽 */ 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的點選事件監聽介面 */ public interface OnItemClickListener { void onItemClicked(RecyclerView recyclerView, View itemView, int position); } /** * RecyclerView的長按事件監聽介面 */ public interface OnItemLongClickListener { boolean onItemLongClicked(RecyclerView recyclerView, View itemView, int position); } }
上面的程式碼中給RecyclerView
設定了OnChildAttachStateChangeListener
事件監聽,當子View
attach RecyclerView
時設定事件監聽。
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) {}
};
使用時只需要呼叫addTo(RecycleView view)方法得到ItemClickSupport物件,然後呼叫setOnItemClickListener()方法和setOnItemLongClickListener()方法設定ItemView的點選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、檢視原始碼
檢視RecyclerView
原始碼可以看到,RecyclerView
預留了一個Item的觸控事件方法:
/**
* 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);
}
通過註釋我們可知,此方法是在滾動事件之前呼叫,需要傳入一個OnItemTouchListener
物件。OnItemTouchListener
的程式碼如下:public static interface OnItemTouchListener {
public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent e);
public void onTouchEvent(RecyclerView rv, MotionEvent e);
public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept);
}
此介面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 {
@Override
public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent e) {
return false;
}
@Override
public void onTouchEvent(RecyclerView rv, MotionEvent e) {
}
@Override
public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {
}
}
在觸控介面中,當觸控時會回撥一個MotionEvent物件,通過使用GestureDetectorCompat來解析使用者的操作。
3.2、瞭解GestureDetector的工作原理
對於觸控式螢幕,其原生的訊息無非按下、擡起、移動這幾種,我們只需要簡單過載onTouch或者設定觸控偵聽器setOnTouchListener即可進行處理。不過,為了提高我們的APP的使用者體驗,有時候我們需要識別使用者的手勢,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,當我們接收到使用者觸控訊息時,將這個訊息交給GestureDetector去加工,我們通過設定偵聽器獲得GestureDetector處理後的手勢。
GestureDetector提供了兩個偵聽器介面,OnGestureListener處理單擊類訊息,OnDoubleTapListener處理雙擊類訊息。
OnGestureListener的介面有這幾個:
// 單擊,觸控式螢幕按下時立刻觸發
abstract boolean onDown(MotionEvent e);
// 擡起,手指離開觸控式螢幕時觸發(長按、滾動、滑動時,不會觸發這個手勢)
abstract boolean onSingleTapUp(MotionEvent e);
// 短按,觸控式螢幕按下後片刻後擡起,會觸發這個手勢,如果迅速擡起則不會
abstract void onShowPress(MotionEvent e);
// 長按,觸控式螢幕按下後既不擡起也不移動,過一段時間後觸發
abstract void onLongPress(MotionEvent e);
// 滾動,觸控式螢幕按下後移動
abstract boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY);
// 滑動,觸控式螢幕按下後快速移動並擡起,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的介面有這幾個: // 雙擊,手指在觸控式螢幕上迅速點選第二下時觸發
abstract boolean onDoubleTap(MotionEvent e);
// 雙擊的按下跟擡起各觸發一次
abstract boolean onDoubleTapEvent(MotionEvent e);
// 單擊確認,即很快的按下並擡起,但並不連續點選第二下
abstract boolean onSingleTapConfirmed(MotionEvent e);
有時候我們並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實現瞭如上介面,我們只需要繼承SimpleOnGestureListener然後過載需要的手勢即可。
3.3、實現點選事件監聽
瞭解了GestureDetector的工作原理之後,便開始實現RecycleView的Item的點選事件。首先寫一個SimpleRecycleViewItemClickListener類繼承SimpleOnItemTouchListener,構造時傳入Item點選回撥OnItemClickListener,並覆寫父類的boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent e)方法,具體程式碼如下:
/**
* RecyclerView的Item點選事件監聽
*
* @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() { // 這裡選擇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點選事件監聽介面
*
* @author liyunlong
* @date 2016/11/21 9:43
*/
public interface OnItemClickListener {
/**
* 當ItemView的單擊事件觸發時呼叫
*/
void onItemClick(View view, int position);
/**
* 當ItemView的長按事件觸發時呼叫
*/
void onItemLongClick(View view, int position);
/**
* 當ItemView的雙擊事件觸發時呼叫
*/
void onItemDoubleClick(View view, int position);
}
/**
* RecyclerView的Item點選事件監聽實現
*
* @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的手勢回撥中我們覆寫:
-
boolean onSingleTapUp(MotionEvent e):單擊事件回撥
-
void onLongPress(MotionEvent e):長按事件回撥
-
boolean onDoubleTapEvent(MotionEvent e):雙擊事件回撥
如果我們只需要監聽單擊事件,而不需要監聽長按事件和雙擊事件,構造
SimpleRecycleViewItemClickListener
時只需要傳入SimpleOnItemClickListener即可,如果需要處理其它的手勢監聽,也可以覆寫對應的手勢回撥方法。
4.三種方法對比
以上三種方式分別是:
-
在建立
ItemView
時新增點選監聽 -
當
ItemView
attachRecyclerView
時實現 -
通過
RecyclerView
已有的方法addOnItemTouchListener()
實現
從以上三種方式的實現過程可知:
-
三種均可實現
ItemView
的點選事件和長按事件的監聽。 -
第一種和第二種方式可以很方便對
ItemView
中的子View
進行監聽。 -
第三種方式可以很方便獲取使用者點選的座標。
-
第二種方式和第三種方式可以寫在單獨的類中,相對於第一種寫在
Adapter
的方式可使程式碼更獨立整潔。
綜上所述:
如果你只想監聽ItemView
的點選事件或長按事件,三種方式均可。
如果你想監聽ItemView
中每個子View
的點選事件,採用第一種或者第二種比較方便。