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{ private List 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) { } }; private ItemClickSupport(RecyclerView recyclerView) { mRecyclerView = recyclerView; mRecyclerView.setTag(KEY, this); // 为RecyclerView设置OnChildAttachStateChangeListener事件监听 mRecyclerView.addonChildAttachStateChangeListener(mAttachListener); } public static ItemClickSupport addTo(RecyclerView view) { ItemClickSupport support = (ItemClickSupport) view.getTag(KEY); if (support == null) { support = new ItemClickSupport(view); } return support; } public static ItemClickSupport removeFrom(RecyclerView view) { ItemClickSupport support = (ItemClickSupport) view.getTag(KEY); if (support != null) { support.detach(view); } return support; } public ItemClickSupport setonItemClickListener(onItemClickListener listener) { monItemClickListener = listener; return this; } public ItemClickSupport setonItemLongClickListener(onItemLongClickListener listener) { monItemLongClickListener = listener; return this; } private void detach(RecyclerView view) { view.removeonChildAttachStateChangeListener(mAttachListener); view.setTag(KEY, null); } public interface onItemClickListener { void onItemClicked(RecyclerView recyclerView, View itemView, int position); } 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:
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:
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 onSingleTap/confirm/ied(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:
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; } } 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 @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; } @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)); } } @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; } }); } public interface onItemClickListener { void onItemClick(View view, int position); void onItemLongClick(View view, int position); void onItemDoubleClick(View view, int position); } 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:
- boolean onSingleTapUp(MotionEvent e):单击事件回调
- void onLongPress(MotionEvent e):长按事件回调
- 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:
- 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
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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