View.java源码: /frameworks/base/core/java/android/view/View.java

View.java的 dispatchTouchEvent 方法: 经过一系列的处理后,将TouchEvent传递给 onTouch 或 onTouchEvent

/**     * Pass the touch screen motion event down to the target view, or this     * view if it is the target.     *     * @param event The motion event to be dispatched.     * @return True if the event was handled by the view, false otherwise.     */    public boolean dispatchTouchEvent(MotionEvent event) {        // If the event should be handled by accessibility focus first.是否应该被有焦点的控件先处理        if (event.isTargetAccessibilityFocus()) {            // We don't have focus or no virtual descendant has it, do not handle the event. 没有焦点, 不处理这个事件            if (!isAccessibilityFocusedViewOrHost()) {                return false;            }            // We have focus and got the event, then use normal event dispatch.目标View已经处理过了来, 接着用正常逻辑分发            event.setTargetAccessibilityFocus(false);        }        boolean result = false;        if (mInputEventConsistencyVerifier != null) { //只对eng版有效, 用来调试 一致性验证: "eng".equals(Build.TYPE);            mInputEventConsistencyVerifier.onTouchEvent(event, 0);        }        final int actionMasked = event.getActionMasked();  // 调用native方法        if (actionMasked == MotionEvent.ACTION_DOWN) {            // Defensive cleanup for new gesture            stopNestedScroll();    // 停止嵌套滚动. 如果调用这个方法时,嵌套滚动不是正在进行的,那么就是无害的        }        if (onFilterTouchEventForSecurity(event)) {  //如果窗口被遮挡了, 那么drop掉这个事件, 这是安全策略            //noinspection SimplifiableIfStatement            ListenerInfo li = mListenerInfo;            if (li != null && li.mOnTouchListener != null                    && (mViewFlags & ENABLED_MASK) == ENABLED                    && li.mOnTouchListener.onTouch(this, event)) {  // mOnTouchListener.onTouch()处理过以后, 就不再往下传递了                result = true;            }            if (!result && onTouchEvent(event)) {  //如果事件没有被处理过, 并且 将它传给onTouchEvent方法后, 由函数的返回值决定是否继续往下传递                result = true;            }        }        if (!result && mInputEventConsistencyVerifier != null) { // 如果这时候时间还没有被处理, 并且是eng模式, 则            mInputEventConsistencyVerifier.onUnhandledEvent(event, 0);        }        // Clean up after nested scrolls if this is the end of a gesture;        // also cancel it if we tried an ACTION_DOWN but we didn't want the rest        // of the gesture.        if (actionMasked == MotionEvent.ACTION_UP ||                actionMasked == MotionEvent.ACTION_CANCEL ||                (actionMasked == MotionEvent.ACTION_DOWN && !result)) {            stopNestedScroll(); // 如果是按下且没被处理, 或者取消, 或者UP事件, 停止滚动        }        return result;    }

 

View.java的 onTouchEvent 方法

/**     * Implement this method to handle touch screen motion events.     * 
     * If this method is used to detect click actions, it is recommended that     * the actions be performed by implementing and calling     * {
    @link #performClick()}. This will ensure consistent system behavior,     * including:     * 
     
           * 
      
obeying click sound preferences     * 
      
dispatching OnClickListener calls     * 
      
handling {
    @link AccessibilityNodeInfo#ACTION_CLICK ACTION_CLICK} when     * accessibility features are enabled     * 
     
     *     * @param event The motion event.     * @return True if the event was handled, false otherwise.     */    public boolean onTouchEvent(MotionEvent event) {        final float x = event.getX();        final float y = event.getY();        final int viewFlags = mViewFlags;        if ((viewFlags & ENABLED_MASK) == DISABLED) {            if (event.getAction() == MotionEvent.ACTION_UP && (mPrivateFlags & PFLAG_PRESSED) != 0) {                setPressed(false); // 如果一个View是被按下的状态, 但是现在事件是ACTION_UP的话, 而且是disable状态, 将状态设为非按下状态            }            // A disabled view that is clickable still consumes the touch            // events, it just doesn't respond to them. 一个被disable,但是clickable的View仍然可以消费触摸事件, 它仅仅是不做出反应            return (((viewFlags & CLICKABLE) == CLICKABLE ||                    (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE));  // true        }        if (mTouchDelegate != null) {            if (mTouchDelegate.onTouchEvent(event)) {  // 这个物理上可触摸的View 的触摸事件, 应该被另一个View处理                return true;            }        }        if (((viewFlags & CLICKABLE) == CLICKABLE ||                (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)) {    //如果View是可点击的, 那么就处理, 如果是不可点击的返回false, 让其他View继续处理            switch (event.getAction()) {                case MotionEvent.ACTION_UP:                    boolean prepressed = (mPrivateFlags & PFLAG_PREPRESSED) != 0;                    if ((mPrivateFlags & PFLAG_PRESSED) != 0 || prepressed) {    // 处于按下状态                        // take focus if we don't have it already and we should in                        // touch mode.                        boolean focusTaken = false;                        if (isFocusable() && isFocusableInTouchMode() && !isFocused()) {                            focusTaken = requestFocus();                        }  // 如果可以获取焦点, 那么请求获取焦点                        if (prepressed) {                            // The button is being released before we actually                            // showed it as pressed.  Make it show the pressed                            // state now (before scheduling the click) to ensure                            // the user sees it.                            setPressed(true, x, y);  //还没有识别为按下状态就释放了, 设置为按下状态, 保证用户看到了                       }                        if (!mHasPerformedLongPress) {                              // This is a tap, so remove the longpress check                            removeLongPressCallback();   // 如果还没有被识别为长按, 移除下一步判断                            // Only perform take click actions if we were in the pressed state                            if (!focusTaken) {  // 如果还没有表现为按下状态, 呈现一次click                                // Use a Runnable and post this rather than calling                                // performClick directly. This lets other visual state                                // of the view update before click actions start.                                if (mPerformClick == null) {                                    mPerformClick = new PerformClick();                                }                                if (!post(mPerformClick)) {                                    performClick();                                }                            }                        }                        if (mUnsetPressedState == null) {                            mUnsetPressedState = new UnsetPressedState();                        }                        if (prepressed) { // 如果是未按下的状态, 延迟一段时间 再处理                            postDelayed(mUnsetPressedState,                                    ViewConfiguration.getPressedStateDuration());                        } else if (!post(mUnsetPressedState)) { // 直接处理                            // If the post failed, unpress right now                            mUnsetPressedState.run();                        }                        removeTapCallback();  //移除点击检测计时器                    }                    break;                case MotionEvent.ACTION_DOWN:                    mHasPerformedLongPress = false;                    if (performButtonActionOnTouchDown(event)) {  // 已经 被处理了                        break;                    }                    // Walk up the hierarchy to determine if we're inside a scrolling container.                    boolean isInScrollingContainer = isInScrollingContainer();  // 判断是否在可滚动的容器里                    // For views inside a scrolling container, delay the pressed feedback for                    // a short period in case this is a scroll.                    if (isInScrollingContainer) {  // 如果在滚动容器里, 延迟一小会,防止是一个滚动事件                        mPrivateFlags |= PFLAG_PREPRESSED;                        if (mPendingCheckForTap == null) {                            mPendingCheckForTap = new CheckForTap();                        }                        mPendingCheckForTap.x = event.getX();                        mPendingCheckForTap.y = event.getY();                        postDelayed(mPendingCheckForTap, ViewConfiguration.getTapTimeout());                    } else {  // 不再滚动容器里的话, 就能直接表现为 点击事件, 顺便开启检测是否为长按事件                        // Not inside a scrolling container, so show the feedback right away                        setPressed(true, x, y);                        checkForLongClick(0);                    }                    break;                case MotionEvent.ACTION_CANCEL:                    setPressed(false);  取消按下                    removeTapCallback();                    removeLongPressCallback(); 取消长按反馈                    break;                case MotionEvent.ACTION_MOVE:                    drawableHotspotChanged(x, y);  //画出点的移动                    // Be lenient about moving outside of buttons                    if (!pointInView(x, y, mTouchSlop)) {    // 如果点已经出了View的外面, 设置为非按下状态                        // Outside button                        removeTapCallback();                        if ((mPrivateFlags & PFLAG_PRESSED) != 0) {                            // Remove any future long press/tap checks                            removeLongPressCallback();                            setPressed(false);                        }                    }                    break;            }            return true;   // 如果View是 CLICKABLE 或者 LONG_CLICKABLE状态, 返回事件已经被消费        }        return false;    }

 

 

延迟post加入MessageQueue:

public boolean postDelayed(Runnable action, long delayMillis) {        final AttachInfo attachInfo = mAttachInfo;        if (attachInfo != null) {            return attachInfo.mHandler.postDelayed(action, delayMillis);        }        // Assume that post will succeed later        ViewRootImpl.getRunQueue().postDelayed(action, delayMillis);        return true;    }

 

直接post, 加入MessageQueue:

public boolean post(Runnable action) {        final AttachInfo attachInfo = mAttachInfo;        if (attachInfo != null) {            return attachInfo.mHandler.post(action);        }        // Assume that post will succeed later        ViewRootImpl.getRunQueue().post(action);        return true;    }

 

 

 

ViewGroup.java源码 :  /frameworks/base/core/java/android/view/ViewGroup.java

public abstract class ViewGroup extends View implements ViewParent, ViewManager  

public interface ViewManager{    /**     * Assign the passed LayoutParams to the passed View and add the view to the window.     * 
Throws {
    @link android.view.WindowManager.BadTokenException} for certain programming     * errors, such as adding a second view to a window without removing the first view.     * 
Throws {
    @link android.view.WindowManager.InvalidDisplayException} if the window is on a     * secondary {
    @link Display} and the specified display can't be found     * (see {
    @link android.app.Presentation}).     * @param view The view to be added to this window.     * @param params The LayoutParams to assign to view.     */    public void addView(View view, ViewGroup.LayoutParams params);    public void updateViewLayout(View view, ViewGroup.LayoutParams params);    public void removeView(View view);}

 ViewGroup 的 onInterceptTouchEvent 方法

/**     * Implement this method to intercept all touch screen motion events.  This     * allows you to watch events as they are dispatched to your children, and     * take ownership of the current gesture at any point.     *     * 
Using this function takes some care, as it has a fairly complicated     * interaction with {
    @link View#onTouchEvent(MotionEvent)     * View.onTouchEvent(MotionEvent)}, and using it requires implementing     * that method as well as this one in the correct way.  Events will be     * received in the following order:     *     * 
     
           * 
      
 You will receive the down event here.     * 
      
 The down event will be handled either by a child of this view     * group, or given to your own onTouchEvent() method to handle; this means     * you should implement onTouchEvent() to return true, so you will     * continue to see the rest of the gesture (instead of looking for     * a parent view to handle it).  Also, by returning true from     * onTouchEvent(), you will not receive any following     * events in onInterceptTouchEvent() and all touch processing must     * happen in onTouchEvent() like normal.     * 
      
 For as long as you return false from this function, each following     * event (up to and including the final up) will be delivered first here     * and then to the target's onTouchEvent().     * 
      
 If you return true from here, you will not receive any     * following events: the target view will receive the same event but     * with the action {
    @link MotionEvent#ACTION_CANCEL}, and all further     * events will be delivered to your onTouchEvent() method and no longer     * appear here.     * 
     
     *     * @param ev The motion event being dispatched down the hierarchy.     * @return Return true to steal motion events from the children and have     * them dispatched to this ViewGroup through onTouchEvent().     * The current target will receive an ACTION_CANCEL event, and no further     * messages will be delivered here.     */    public boolean onInterceptTouchEvent(MotionEvent ev) {        return false;    }

 

 ViewGroup 的 dispatchTouchEvent 方法, 重写View的dispatch方法

/**     * {
    @inheritDoc}     */    @Override    public boolean dispatchTouchEvent(MotionEvent ev) {        if (mInputEventConsistencyVerifier != null) {  // 对eng版本的 一致性校验            mInputEventConsistencyVerifier.onTouchEvent(ev, 1);        }        // If the event targets the accessibility focused view and this is it, start        // normal event dispatch. Maybe a descendant is what will handle the click.        if (ev.isTargetAccessibilityFocus() && isAccessibilityFocusedViewOrHost()) {            ev.setTargetAccessibilityFocus(false);        }        boolean handled = false;        if (onFilterTouchEventForSecurity(ev)) {  //如果View被遮挡了, 那么drop掉这个事件, 这是安全策略            final int action = ev.getAction();            final int actionMasked = action & MotionEvent.ACTION_MASK;            // Handle an initial down.            if (actionMasked == MotionEvent.ACTION_DOWN) {                // Throw away all previous state when starting a new touch gesture.                // The framework may have dropped the up or cancel event for the previous gesture                // due to an app switch, ANR, or some other state change.                cancelAndClearTouchTargets(ev);                resetTouchState();            }            // Check for interception.            final boolean intercepted;            if (actionMasked == MotionEvent.ACTION_DOWN                    || mFirstTouchTarget != null) {                final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;                if (!disallowIntercept) {                    intercepted = onInterceptTouchEvent(ev);                    ev.setAction(action); // restore action in case it was changed                } else {                    intercepted = false;                }            } else {                // There are no touch targets and this action is not an initial down                // so this view group continues to intercept touches.                intercepted = true;            }            // If intercepted, start normal event dispatch. Also if there is already            // a view that is handling the gesture, do normal event dispatch.            if (intercepted || mFirstTouchTarget != null) {                ev.setTargetAccessibilityFocus(false);            }            // Check for cancelation.            final boolean canceled = resetCancelNextUpFlag(this)                    || actionMasked == MotionEvent.ACTION_CANCEL;            // Update list of touch targets for pointer down, if needed.            final boolean split = (mGroupFlags & FLAG_SPLIT_MOTION_EVENTS) != 0;            TouchTarget newTouchTarget = null;            boolean alreadyDispatchedToNewTouchTarget = false;            if (!canceled && !intercepted) {                // If the event is targeting accessiiblity focus we give it to the                // view that has accessibility focus and if it does not handle it                // we clear the flag and dispatch the event to all children as usual.                // We are looking up the accessibility focused host to avoid keeping                // state since these events are very rare.                View childWithAccessibilityFocus = ev.isTargetAccessibilityFocus()                        ? findChildWithAccessibilityFocus() : null;                if (actionMasked == MotionEvent.ACTION_DOWN                        || (split && actionMasked == MotionEvent.ACTION_POINTER_DOWN)                        || actionMasked == MotionEvent.ACTION_HOVER_MOVE) {                    final int actionIndex = ev.getActionIndex(); // always 0 for down                    final int idBitsToAssign = split ? 1 << ev.getPointerId(actionIndex)                            : TouchTarget.ALL_POINTER_IDS;                    // Clean up earlier touch targets for this pointer id in case they                    // have become out of sync.                    removePointersFromTouchTargets(idBitsToAssign);                    final int childrenCount = mChildrenCount;                    if (newTouchTarget == null && childrenCount != 0) {                        final float x = ev.getX(actionIndex);                        final float y = ev.getY(actionIndex);                        // Find a child that can receive the event.                        // Scan children from front to back.                        final ArrayList
     
       preorderedList = buildOrderedChildList();                        final boolean customOrder = preorderedList == null                                && isChildrenDrawingOrderEnabled();                        final View[] children = mChildren;                        for (int i = childrenCount - 1; i >= 0; i--) {                            final int childIndex = customOrder                                    ? getChildDrawingOrder(childrenCount, i) : i;                            final View child = (preorderedList == null)                                    ? children[childIndex] : preorderedList.get(childIndex);                            // If there is a view that has accessibility focus we want it                            // to get the event first and if not handled we will perform a                            // normal dispatch. We may do a double iteration but this is                            // safer given the timeframe.                            if (childWithAccessibilityFocus != null) {                                if (childWithAccessibilityFocus != child) {                                    continue;                                }                                childWithAccessibilityFocus = null;                                i = childrenCount - 1;                            }                            if (!canViewReceivePointerEvents(child)                                    || !isTransformedTouchPointInView(x, y, child, null)) {                                ev.setTargetAccessibilityFocus(false);                                continue;                            }                            newTouchTarget = getTouchTarget(child);                            if (newTouchTarget != null) {                                // Child is already receiving touch within its bounds.                                // Give it the new pointer in addition to the ones it is handling.                                newTouchTarget.pointerIdBits |= idBitsToAssign;                                break;                            }                            resetCancelNextUpFlag(child);                            if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) {                                // Child wants to receive touch within its bounds.                                mLastTouchDownTime = ev.getDownTime();                                if (preorderedList != null) {                                    // childIndex points into presorted list, find original index                                    for (int j = 0; j < childrenCount; j++) {                                        if (children[childIndex] == mChildren[j]) {                                            mLastTouchDownIndex = j;                                            break;                                        }                                    }                                } else {                                    mLastTouchDownIndex = childIndex;                                }                                mLastTouchDownX = ev.getX();                                mLastTouchDownY = ev.getY();                                newTouchTarget = addTouchTarget(child, idBitsToAssign);                                alreadyDispatchedToNewTouchTarget = true;                                break;                            }                            // The accessibility focus didn't handle the event, so clear                            // the flag and do a normal dispatch to all children.                            ev.setTargetAccessibilityFocus(false);                        }                        if (preorderedList != null) preorderedList.clear();                    }                    if (newTouchTarget == null && mFirstTouchTarget != null) {                        // Did not find a child to receive the event.                        // Assign the pointer to the least recently added target.                        newTouchTarget = mFirstTouchTarget;                        while (newTouchTarget.next != null) {                            newTouchTarget = newTouchTarget.next;                        }                        newTouchTarget.pointerIdBits |= idBitsToAssign;                    }                }            }            // Dispatch to touch targets.            if (mFirstTouchTarget == null) {                // No touch targets so treat this as an ordinary view.                handled = dispatchTransformedTouchEvent(ev, canceled, null,                        TouchTarget.ALL_POINTER_IDS);            } else {                // Dispatch to touch targets, excluding the new touch target if we already                // dispatched to it.  Cancel touch targets if necessary.                TouchTarget predecessor = null;                TouchTarget target = mFirstTouchTarget;                while (target != null) {                    final TouchTarget next = target.next;                    if (alreadyDispatchedToNewTouchTarget && target == newTouchTarget) {                        handled = true;                    } else {                        final boolean cancelChild = resetCancelNextUpFlag(target.child)                                || intercepted;                        if (dispatchTransformedTouchEvent(ev, cancelChild,                                target.child, target.pointerIdBits)) {                            handled = true;                        }                        if (cancelChild) {                            if (predecessor == null) {                                mFirstTouchTarget = next;                            } else {                                predecessor.next = next;                            }                            target.recycle();                            target = next;                            continue;                        }                    }                    predecessor = target;                    target = next;                }            }            // Update list of touch targets for pointer up or cancel, if needed.            if (canceled                    || actionMasked == MotionEvent.ACTION_UP                    || actionMasked == MotionEvent.ACTION_HOVER_MOVE) {                resetTouchState();            } else if (split && actionMasked == MotionEvent.ACTION_POINTER_UP) {                final int actionIndex = ev.getActionIndex();                final int idBitsToRemove = 1 << ev.getPointerId(actionIndex);                removePointersFromTouchTargets(idBitsToRemove);            }        }        if (!handled && mInputEventConsistencyVerifier != null) {            mInputEventConsistencyVerifier.onUnhandledEvent(ev, 1);        }        return handled;    }
     

 ViewGroup 的 onTouchEvent 来自与View    public boolean onTouchEvent(MotionEvent event),  没有重写View的方法

 

 

 

 

 

可参考链接

http://zhidao.baidu.com/question/540838549.html