view中事件ontouch与ontouchEvent源码分析

看过一些书籍，也简单做了些，总结，有时候就会忘记，今天将它记录下来。

废话不多说，进入正题：

关于viewGroup的事件分发：

先贴一端源码，

@Overridepublic boolean dispatchTouchEvent(MotionEvent ev) {

    //关于下面这一段代码，我个人认为应该跟输入法相关的触摸事件

    if (mInputEventConsistencyVerifier != null) {        mInputEventConsistencyVerifier.onTouchEvent(ev, 1);    }    //这段代码，也就是给有焦点的触摸设置标识。好分发事件    // 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);    }    //最后返回的也是这个handled，    boolean handled = false;

     //过滤事件，    if (onFilterTouchEventForSecurity(ev)) {        final int action = ev.getAction();        final int actionMasked = action & MotionEvent.ACTION_MASK;

      //这里首先对down进行咯处理

        // 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.

//关闭和清理的触摸对象集合            cancelAndClearTouchTargets(ev);

        //重设触摸状态            resetTouchState();        }        //是否进行事件拦截的标识符        // Check for interception.        final boolean intercepted;        if (actionMasked == MotionEvent.ACTION_DOWN                || mFirstTouchTarget != null) {            final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;            if (!disallowIntercept) {

          //这里调用的是自身的方法返回false，当然也可以重写                intercepted = onInterceptTouchEvent(ev);                ev.setAction(action); // restore action in case it was changed            } else {                intercepted = false;            }        } else {//如果不是down就拦截，此时触摸的对象都没有了            // There are no touch targets and this action is not an initial down            // so this view group continues to intercept touches.            intercepted = true;        }         //如果拦截，做正常的事件调度.估计就是事件的一些逻辑处理        // 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<View> preorderedList = buildOrderedChildList();                    final boolean customOrder = preorderedList == null                            && isChildrenDrawingOrderEnabled();                    final View[] children = mChildren;

//给每个子控件分发事件

                    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;                        }

这个
dispatchTransformedTouchEvent重点说一下，它里面调用咯surper. dispathtoucher方法，如果父类是view则调用view的dispachtouch事件,后面会介绍view的dispachtouch事件,也是在这里调用ontouchEvent事件的。

                        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;

给控件分发事件

                    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;}

从上面可以看出来 是对down进行事件拦截，然后touch分发处理,所以在这里，应该注意在处理事件的时候，返回类型咯。，

那么接下来看view的dispachtouch事件

public boolean dispatchTouchEvent(MotionEvent event) {    // If the event should be handled by accessibility focus first.    if (event.isTargetAccessibilityFocus()) {        // We don't have focus or no virtual descendant has it, do not handle the event.        if (!isAccessibilityFocusedViewOrHost()) {            return false;        }        // We have focus and got the event, then use normal event dispatch.        event.setTargetAccessibilityFocus(false);    }    boolean result = false;    if (mInputEventConsistencyVerifier != null) {        mInputEventConsistencyVerifier.onTouchEvent(event, 0);    }    final int actionMasked = event.getActionMasked();    if (actionMasked == MotionEvent.ACTION_DOWN) {        // Defensive cleanup for new gesture        stopNestedScroll();    }    if (onFilterTouchEventForSecurity(event)) {        //noinspection SimplifiableIfStatement        ListenerInfo li = mListenerInfo;

在这里是先执行咯ontouch事件,这里有个条件就是监听器不能为空。

        if (li != null && li.mOnTouchListener != null                && (mViewFlags & ENABLED_MASK) == ENABLED                && li.mOnTouchListener.onTouch(this, event)) {            result = true;        }

然后在执行
onTouchEvent事件,如果ontouch返回的是true，那么将不会执行onTouchEvent事件.

        if (!result && onTouchEvent(event)) {            result = true;        }    }    if (!result && mInputEventConsistencyVerifier != null) {        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();    }    return result;}

因为在为重写的ontouchEvent里面都是调用父类的ontoucheEvent事件，所以 事件也是dispachTouch到拦截 

onInterceptTouchEvent在到 一步一步往下传，然后ontouch是一步一步往上传。