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:

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

今天来学习一下如何实现RecyclerView的Item的点击事件.实现Item的点击事件有三种方式:

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

1. 通过RecyclerView的addOnItemTouchListener()实现

1.1 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.
 * <p>
 * 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.

1.2 实现点击事件监听

写一个ItemClickListener类继承SimpleOnItemTouchListener,构造时传入RecyclerView对象和Item点击回调,并覆写父类的boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent e)方法,具体代码如下:

/**
 * 点击事件
 * Created by DevWiki on 2016/7/16.
 */

public class ItemClickListener extends RecyclerView.SimpleOnItemTouchListener {

    private OnItemClickListener clickListener;
    private GestureDetectorCompat gestureDetector;

    public interface OnItemClickListener {

        void onItemClick(View view, int position);

        void onItemLongClick(View view, int position);
    }

    public ItemClickListener(final RecyclerView recyclerView,
                             OnItemClickListener listener) {
        this.clickListener = listener;
        gestureDetector = new GestureDetectorCompat(recyclerView.getContext(),
                new GestureDetector.SimpleOnGestureListener() {
                    @Override
                    public boolean onSingleTapUp(MotionEvent e) {
                        View childView = recyclerView.findChildViewUnder(e.getX(), e.getY());
                        if (childView != null && clickListener != null && gestureDetector.onTouchEvent(e)) {
                            clickListener.onItemClick(childView, recyclerView.getChildAdapterPosition(childView));
                        }
                        return true;
                    }

                    @Override
                    public void onLongPress(MotionEvent e) {
                        View childView = recyclerView.findChildViewUnder(e.getX(), e.getY());
                        if (childView != null && clickListener != null) {
                            clickListener.onItemLongClick(childView,
                                    recyclerView.getChildAdapterPosition(childView));
                        }
                    }
                });
    }

    @Override
    public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent e) {
        gestureDetector.onTouchEvent(e);
        return false;
    }
}

在GestureDetectorCompat的手势回调中我们覆写:

  1. boolean onSingleTapUp(MotionEvent e)单击抬起回调
  2. void onLongPress(MotionEvent e)长按回调

1.3 使用事件监听

在RecyclerView的对象中添加addOnItemTouchListener()方法,然后在回调中处理你需要的事件:

recyclerView.addOnItemTouchListener(new SingleItemClickListener(recyclerView,
        new SingleItemClickListener.OnItemClickListener() {

            @Override
            public void onItemClick(View view, int position) {
                DevLog.i("touch click name:" + position);
                Toast.makeText(SingleActivity.this, "touch click:" + position, Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onItemLongClick(View view, int position) {
                DevLog.i("touch long click:" + position);
                Toast.makeText(SingleActivity.this, "touch long click:" + position, Toast.LENGTH_SHORT).show();
            }
        }));

2. 在创建ItemView时添加点击监听

这种方法和ListView一样,在Adapter里面创建View时添加点击事件.比如:

@Override
public void bindCustomViewHolder(SingleHolder holder, final int position) {
    Person person = getItem(position);
    holder.nameView.setText(person.getName());
    holder.ageView.setText(String.valueOf(person.getAge()));

    if (clickListener != null) {
        holder.nameView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                clickListener.onNameClick(position);
            }
        });
        holder.ageView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                clickListener.onAgeClick(position);
            }
        });
    }
}

然后在Adapter对象上添加监听回调:

singleAdapter.setClickListener(new SingleAdapter.OnSingleItemClickListener() {
    @Override
    public void onNameClick(int position) {
        DevLog.i("adapter click name:" + position);
        Toast.makeText(SingleActivity.this, "adapter click name:" + position, Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onAgeClick(int position) {
        DevLog.i("adapter click age:" + position);
        Toast.makeText(SingleActivity.this, "adapter click name:" + position, Toast.LENGTH_SHORT).show();
    }
});

3. 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 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, holder.getAdapterPosition(), v);
            }
        }
    };
    
    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, holder.getAdapterPosition(), v);
            }
            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(R.id.item_click_support, this);
        mRecyclerView.addOnChildAttachStateChangeListener(mAttachListener);
    }

    public static ItemClickSupport addTo(RecyclerView view) {
        ItemClickSupport support = (ItemClickSupport) view.getTag(R.id.item_click_support);
        if (support == null) {
            support = new ItemClickSupport(view);
        }
        return support;
    }

    public static ItemClickSupport removeFrom(RecyclerView view) {
        ItemClickSupport support = (ItemClickSupport) view.getTag(R.id.item_click_support);
        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(R.id.item_click_support, null);
    }

    public interface OnItemClickListener {
        void onItemClicked(RecyclerView recyclerView, int position, View v);
    }

    public interface OnItemLongClickListener {
        boolean onItemLongClicked(RecyclerView recyclerView, int position, View v);
    }
}

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) {}
    };

4. 三种方式对比

以上三种方式分别是:

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

从以上三种方式的实现过程可知:

  1. 三种均可实现ItemView的点击事件和长按事件的监听.
  2. 第一种方式可以很方便获取用户点击的坐标.
  3. 第二种和第三种方式可以很方便对ItemView中的子View进行监听.
  4. 第一种方式和第三种方式可以写在单独的类中,相对于第二种写在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,采用第二种或者第三种比较方面.

5. 后记

以上三种方式均为在学习RecyclerView过程中学到的,项目地址如下:Dev-Wiki/RecyclerView

如果有错误请指正,如果你有更好的方式实现,请留言或者联系我,谢谢!

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