Android中DrawerLayout+ViewPager滑动冲突的解决方法

DrawerLayout 是 Android 官方的侧滑菜单控件，而 ViewPager 相信大家都很熟悉了。今天这里就讲一下当在 DrawerLayout 中嵌套 ViewPager 时，要如何解决滑动冲突的问题，效果如下：

首先，让我们先来解决 DrawerLayout 和 ViewPager 的侧滑事件冲突。当 DrawerLayout 中嵌套 ViewPager 时，侧滑默认是执行 DrawerLayout 的侧滑事件，因为 Android 的事件分发是从 外层 ViewGroup 向里逐级传递到 View 的。
所以会先执行 DrawerLayout 的 onTouchEvent 方法：

@Overridepublic boolean onTouchEvent(MotionEvent ev) {  mLeftDragger.processTouchEvent(ev);   mRightDragger.processTouchEvent(ev);   final int action = ev.getAction(); boolean wantTouchEvents = true;   switch (action & MotionEventCompat.ACTION_MASK) {     case MotionEvent.ACTION_DOWN: {       final float x = ev.getX();       final float y = ev.getY();       mInitialMotionX = x;       mInitialMotionY = y;       mDisallowInterceptRequested = false;       mChildrenCanceledTouch = false;       break;     }     case MotionEvent.ACTION_UP: {       final float x = ev.getX();       final float y = ev.getY();       boolean peekinGonly = true;      final View touchedView = mLeftDragger.findTopChildUnder((int) x, (int) y);       if (touchedView != null && isContentView(touchedView)) {         final float dx = x - mInitialMotionX;         final float dy = y - mInitialMotionY;         final int slop = mLeftDragger.getTouchSlop();         if (dx * dx + dy * dy < slop * slop) {           // Taps close a dimmed open drawer but only if it isn't locked open.           final View openDrawer = findOpenDrawer();           if (openDrawer != null) {             peekingOnly = getDrawerLockMode(openDrawer) == LOCK_MODE_LOCKED_OPEN;           }         }        }       closeDrawers(peekingOnly);       mDisallowInterceptRequested = false;       break;     }     case MotionEvent.ACTION_CANCEL: {       closeDrawers(true);       mDisallowInterceptRequested = false;      mChildrenCanceledTouch = false; break;     }   }   return wantTouchEvents;}