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Android中触摸事件传递过程中最重要的是dispatchTouchEvent()、onInterceptTouchEvent()和onTouchEvent()方法。这个是困扰初学者的问题之一,我开始也是。这里记录一下dispatchTouchEvent()、onInterceptTouchEvent()和onTouchEvent()的处理过程,以供记忆。
dispatchTouchEvent是处理触摸事件分发,事件(多数情况)是从Activity的dispatchTouchEvent开始的。执行
super.dispatchTouchEvent(ev),事件向下分发。
onInterceptTouchEvent是ViewGroup提供的方法,默认返回false,返回true表示拦截。
onTouchEvent是View中提供的方法,ViewGroup也有这个方法,view中不提供onInterceptTouchEvent。view中默认返回true,表示消费了这个事件。
View里,有两个回调函数 :
public boolean dispatchTouchEvent(MotionEvent ev); public boolean onTouchEvent(MotionEvent ev);
ViewGroup里,有三个回调函数 :
public boolean dispatchTouchEvent(MotionEvent ev); public boolean onInterceptTouchEvent(MotionEvent ev); public boolean onTouchEvent(MotionEvent ev);
在Activity里,有两个回调函数 :
public boolean dispatchTouchEvent(MotionEvent ev); public boolean onTouchEvent(MotionEvent ev);
Android中默认情况下事件传递是由最终的view的接收到,传递过程是从父布局到子布局,也就是从Activity到ViewGroup到View的过程,默认情况,ViewGroup起到的是透传作用。Android中事件传递过程(按箭头方向)如下图,图片来自[qiushuiqifei],谢谢[qiushuiqifei]整理。
触摸事件是一连串ACTION_DOWN,ACTION_MOVE..MOVE…MOVE、最后ACTION_UP,触摸事件还有ACTION_CANCEL事件。事件都是从ACTION_DOWN开始的,Activity的dispatchTouchEvent()首先接收到ACTION_DOWN,执行super.dispatchTouchEvent(ev),事件向下分发。
dispatchTouchEvent()返回true,后续事件(ACTION_MOVE、ACTION_UP)会再传递,如果返回false,dispatchTouchEvent()就接收不到ACTION_UP、ACTION_MOVE。
下面的几张图参考自[eoe]
图1.ACTION_DOWN都没被消费
图2-1.ACTION_DOWN被View消费了
图2-2.后续ACTION_MOVE和UP在不被拦截的情况下都会去找VIEW
图3.后续的被拦截了
图4ACTION_DOWN一开始就被拦截
android中的Touch事件都是从ACTION_DOWN开始的:
单手指操作:ACTION_DOWN---ACTION_MOVE----ACTION_UP
多手指操作:ACTION_DOWN---ACTION_POINTER_DOWN---ACTION_MOVE--ACTION_POINTER_UP---ACTION_UP.
public class StickyNavLayout extends LinearLayout { private View mTop; private View mNav; private ViewPager mViewPager; private int mTopViewHeight; private ViewGroup mInnerScrollView; private boolean isTopHidden = false; private OverScroller mScroller; private VelocityTracker mVelocityTracker; private int mTouchSlop; private int mMaximumVelocity, mMinimumVelocity; private float mLastY; private boolean mDragging; private boolean isInControl = false; public StickyNavLayout(Context context, AttributeSet attrs) { super(context, attrs); setOrientation(LinearLayout.VERTICAL); mScroller = new OverScroller(context); // getScaledTouchSlop是一个距离,表示滑动的时候,手的移动要大于这个距离才开始移动控件。 // 如果小于这个距离就不触发移动控件,如viewpager就是用这个距离来判断用户是否翻页 mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop(); mMaximumVelocity = ViewConfiguration.get(context) .getScaledMaximumFlingVelocity(); mMinimumVelocity = ViewConfiguration.get(context) .getScaledMinimumFlingVelocity(); } @Override protected void onFinishInflate() { super.onFinishInflate(); mTop = findViewById(R.id.id_stickynavlayout_topview); mNav = findViewById(R.id.id_stickynavlayout_indicator); View view = findViewById(R.id.id_stickynavlayout_viewpager); if (!(view instanceof ViewPager)) { throw new RuntimeException( "id_stickynavlayout_viewpager show used by ViewPager !"); } mViewPager = (ViewPager) view; } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); ViewGroup.LayoutParams params = mViewPager.getLayoutParams(); params.height = getMeasuredHeight() - mNav.getMeasuredHeight(); } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); mTopViewHeight = mTop.getMeasuredHeight(); } /* @Override public boolean dispatchTouchEvent(MotionEvent ev) { int action = ev.getAction(); float y = ev.getY(); switch (action) { case MotionEvent.ACTION_DOWN: mLastY = y; break; case MotionEvent.ACTION_MOVE: float dy = y - mLastY; getCurrentScrollView(); if (mInnerScrollView instanceof ScrollView) { // 如果topView没有隐藏 // 或sc的scrollY = 0 && topView隐藏 && 下拉,则拦截 if (mInnerScrollView.getScrollY() == 0 && isTopHidden && dy > 0 && !isInControl) { isInControl = true; // 将触摸事件修改为取消 ev.setAction(MotionEvent.ACTION_CANCEL); MotionEvent ev2 = MotionEvent.obtain(ev); dispatchTouchEvent(ev); // 再将触摸事件修改为点下 ev2.setAction(MotionEvent.ACTION_DOWN); return dispatchTouchEvent(ev2); } } else if (mInnerScrollView instanceof ListView) { ListView lv = (ListView) mInnerScrollView; View c = lv.getChildAt(lv.getFirstVisiblePosition()); if (!isInControl && c != null && c.getTop() == 0 && isTopHidden && dy > 0) { isInControl = true; ev.setAction(MotionEvent.ACTION_CANCEL); MotionEvent ev2 = MotionEvent.obtain(ev); dispatchTouchEvent(ev); ev2.setAction(MotionEvent.ACTION_DOWN); return dispatchTouchEvent(ev2); } } break; } return super.dispatchTouchEvent(ev); } */ @Override public boolean onInterceptTouchEvent(MotionEvent ev) { final int action = ev.getAction(); float y = ev.getY(); switch (action) { case MotionEvent.ACTION_DOWN: mLastY = y; break; case MotionEvent.ACTION_MOVE: float dy = y - mLastY; getCurrentScrollView(); if (Math.abs(dy) > mTouchSlop) { mDragging = true; if (mInnerScrollView instanceof ScrollView) { // 如果topView没有隐藏 // 或sc的scrollY = 0 && topView隐藏 && 下拉,则拦截 if (!isTopHidden || (mInnerScrollView.getScrollY() == 0 && isTopHidden && dy > 0)) { initVelocityTrackerIfNotExists(); mVelocityTracker.addMovement(ev); mLastY = y; return true; } } else if (mInnerScrollView instanceof ListView) { ListView lv = (ListView) mInnerScrollView; View c = lv.getChildAt(lv.getFirstVisiblePosition()); // 如果topView没有隐藏 // 或sc的listView在顶部 && topView隐藏 && 下拉,则拦截 if (!isTopHidden || // (c != null // && c.getTop() == 0// && isTopHidden && dy > 0)) { initVelocityTrackerIfNotExists(); mVelocityTracker.addMovement(ev); mLastY = y; return true; } } } break; case MotionEvent.ACTION_CANCEL: case MotionEvent.ACTION_UP: mDragging = false; recycleVelocityTracker(); break; } return super.onInterceptTouchEvent(ev); } /* */ // 获取ViewPager里面Fragment里面的ScrollView private void getCurrentScrollView() { int currentItem = mViewPager.getCurrentItem(); PagerAdapter a = mViewPager.getAdapter(); if (a instanceof FragmentPagerAdapter) { FragmentPagerAdapter fadapter = (FragmentPagerAdapter) a; Fragment item = (Fragment) fadapter.instantiateItem(mViewPager, currentItem); mInnerScrollView = (ViewGroup) (item.getView() .findViewById(R.id.id_stickynavlayout_innerscrollview)); } else if (a instanceof FragmentStatePagerAdapter) { FragmentStatePagerAdapter fsAdapter = (FragmentStatePagerAdapter) a; Fragment item = (Fragment) fsAdapter.instantiateItem(mViewPager, currentItem); mInnerScrollView = (ViewGroup) (item.getView() .findViewById(R.id.id_stickynavlayout_innerscrollview)); } } @Override public boolean onTouchEvent(MotionEvent event) { initVelocityTrackerIfNotExists(); mVelocityTracker.addMovement(event); int action = event.getAction(); float y = event.getY(); switch (action) { case MotionEvent.ACTION_DOWN: if (!mScroller.isFinished()) mScroller.abortAnimation(); mLastY = y; return true; case MotionEvent.ACTION_MOVE: float dy = y - mLastY; Log.e("TAG", "dy = " + dy + " , y = " + y + " , mLastY = " + mLastY); if (!mDragging && Math.abs(dy) > mTouchSlop) { mDragging = true; } if (mDragging) { scrollBy(0, (int) -dy); // 如果topView隐藏,且上滑动时,则改变当前事件为ACTION_DOWN if (getScrollY() == mTopViewHeight && dy < 0) { event.setAction(MotionEvent.ACTION_DOWN); dispatchTouchEvent(event); isInControl = false; } } mLastY = y; break; case MotionEvent.ACTION_CANCEL: mDragging = false; recycleVelocityTracker(); if (!mScroller.isFinished()) { mScroller.abortAnimation(); } break; case MotionEvent.ACTION_UP: mDragging = false; mVelocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); int velocityY = (int) mVelocityTracker.getYVelocity(); if (Math.abs(velocityY) > mMinimumVelocity) { fling(-velocityY); } recycleVelocityTracker(); break; } return super.onTouchEvent(event); } public void fling(int velocityY) { mScroller.fling(0, getScrollY(), 0, velocityY, 0, 0, 0, mTopViewHeight); invalidate(); } @Override public void scrollTo(int x, int y) { if (y < 0) { y = 0; } if (y > mTopViewHeight) { y = mTopViewHeight; } if (y != getScrollY()) { super.scrollTo(x, y); } isTopHidden = getScrollY() == mTopViewHeight; } @Override public void computeScroll() { if (mScroller.computeScrollOffset()) { scrollTo(0, mScroller.getCurrY()); invalidate(); } } private void initVelocityTrackerIfNotExists() { if (mVelocityTracker == null) { mVelocityTracker = VelocityTracker.obtain(); } } private void recycleVelocityTracker() { if (mVelocityTracker != null) { mVelocityTracker.recycle(); mVelocityTracker = null; } } }
http://blog.csdn.net/xyz_lmn/article/details/12517911
http://blog.csdn.net/lmj623565791/article/details/43649913
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原文地址:http://www.cnblogs.com/xbx2015/p/4711200.html