简介
不知道什么缘故起因,不知道从什么时间开始,口试八股文是Android开发挥之不去的噩梦,一次又一次的去看去学,然后一样平常开发中容易牵涉不到,导致逢口试就是八股文走一遍,恶心且头秃.
再一次看一下变乱分发的处理处罚,追着源码看一下(有些代码不能Debug,恶心+1)
团体流程
点击屏幕--->WindowCallbackWrapper 吸取到点击-->分发给Activity-->调用PhoneWindow 举行向下转达-->DecorView调用父结构的变乱分发-->ViewGroup dispatchTouchEvent()
然后ViewGroup,View的点击变乱的分发就开始了
关键点类
- Activity
- WindowCallbackWrapper
- PhoneWindow(Window)
- DecorView
- ViewGroup
- View
关键方法
- dispatchTouchEvent() 变乱分发
- onTouchEvent() 变乱处理处罚
- onInterceptTouchEvent() 是否拦截
执行流程
1.WindowCallbackWrapper Activity ,PhoneWindow,DecorView拦截点击变乱
// 窗口回调变乱@RestrictTo(LIBRARY_GROUP_PREFIX)public class WindowCallbackWrapper implements Window.Callback {// Called to process touch screen events. At the very least your implementation must call//调用以处理处罚触摸屏变乱。至少你的实行必须调用 @Override public boolean dispatchTouchEvent(MotionEvent event) { return mWrapped.dispatchTouchEvent(event); }}//页面ublic class Activity extends ContextThemeWrapper implements LayoutInflater.Factory2, Window.Callback, KeyEvent.Callback, OnCreateContextMenuListener, ComponentCallbacks2, Window.OnWindowDismissedCallback, WindowControllerCallback, AutofillManager.AutofillClient { ....public boolean dispatchTouchEvent(MotionEvent ev) { if (ev.getAction() == MotionEvent.ACTION_DOWN) { onUserInteraction(); } if (getWindow().superDispatchTouchEvent(ev)) { return true; } return onTouchEvent(ev); }}}// PhoneWindow Window窗口实现public class PhoneWindow extends Window implements MenuBuilder.Callback { @Override public boolean superDispatchTouchEvent(MotionEvent event) { return mDecor.superDispatchTouchEvent(event); }}//This is the top-level view of the window, containing the window decor. 页面最顶层控件public class DecorView extends implements RootViewSurfaceTaker, WindowCallbacks {... public boolean superDispatchTouchEvent(MotionEvent event) {//调用到了FrameLayout 的父类ViewGroup return super.dispatchTouchEvent(event); }}2. 执行到DecorView的 superDispatchTouchEvent方法就调用到了ViewGroup的dispatchTouchEvent() 方法举行变乱的分发
2.1ViewGroup dispatchTouchEvent() 代码执行
@Override public boolean dispatchTouchEvent(MotionEvent ev) { .... boolean handled = false; //一些安全战略的过滤这里不消思量 过滤触摸变乱以应用安全战略。 if (onFilterTouchEventForSecurity(ev)) { 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. 监测是否拦截变乱(关键点属性) //判断ViewGroup 是否拦截的变乱 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. 校验取消状态 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; //viewgroup 不拦截点击变乱 ViewGroup 下发变乱 if (!canceled && !intercepted) { // If the event is targeting accessibility 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; //有子结构向下转达(关键) 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 = buildTouchDispatchChildList(); final boolean customOrder = preorderedList == null && isChildrenDrawingOrderEnabled(); final View[] children = mChildren; for (int i = childrenCount - 1; i >= 0; i--) { final int childIndex = getAndVerifyPreorderedIndex( childrenCount, i, customOrder); final View child = getAndVerifyPreorderedView( preorderedList, children, 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); // 将变乱转达给子结构(关键) if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) { // 假如子结构处理处罚了就执行一下操纵 // 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. //假如拦截了上边代码不走 mFirstTouchTarget==null if (mFirstTouchTarget == null) { // No touch targets so treat this as an ordinary view. //拦截的时间mFirstTouchTarget 是null 调用了 dispatchTransformedTouchEvent()中的 handled = super.dispatchTouchEvent(event); //意思是回调用父结构的dispatchTouchEvent 的分配也就是View的 dispatchTouchEvent handled = dispatchTransformedTouchEvent(ev, canceled, null, TouchTarget.ALL_POINTER_IDS); } else { //假如拦截了 mFirstTouchTarget!=null // handled 赋值 就竣事了 // 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; }2.2 ViewGroup dispatchTransformedTouchEvent()
private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel, View child, int desiredPointerIdBits) { //核心代码就这一个判断 final boolean handled; if (child == null) {//向上返回//子结构为空调用父结构的变乱分发 handled = super.dispatchTouchEvent(event); } else { //向下执行 //子结构不为空调用子结构的的变乱分发 handled = child.dispatchTouchEvent(event); } return handled; }3.View 变乱分发处理处罚
3.1 View dispatchTouchEvent()变乱分发
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)) { if ((mViewFlags & ENABLED_MASK) == ENABLED && handleScrollBarDragging(event)) { result = true; } //noinspection SimplifiableIfStatement //点击变乱的的对象 ListenerInfo li = mListenerInfo; //没有触摸变乱监听 了onTouch()然后返回True 体现消化了 if (li != null && li.mOnTouchListener != null && (mViewFlags & ENABLED_MASK) == ENABLED && li.mOnTouchListener.onTouch(this, event)) {//直接返回了 消化了变乱 result = true; } // 没有触摸变乱监听 继续变乱分发onTouchEvent()消化触摸变乱 onTouchEvent(event)假如返回True 就直接返回True体现消化了触摸变乱 返回false 就向下走返回默认的result 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; }3.2 View onTouchEvent()是否消化触摸变乱 返回true 体现消化了 返回false 体现不消化 上层结构处理处罚
/** * Implement this method to handle touch screen motion events. * <p> * 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: * <ul> * <li>obeying click sound preferences * <li>dispatching OnClickListener calls * <li>handling {@link AccessibilityNodeInfo#ACTION_CLICK ACTION_CLICK} when * accessibility features are enabled * </ul> * * @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; final int action = event.getAction(); // clickable View 点击变乱的标识 梳理点击变乱和触摸变乱逻辑有效 final boolean clickable = ((viewFlags & CLICKABLE) == CLICKABLE || (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE) || (viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE; if ((viewFlags & ENABLED_MASK) == DISABLED) { if (action == MotionEvent.ACTION_UP && (mPrivateFlags & PFLAG_PRESSED) != 0) { setPressed(false); } mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN; // A disabled view that is clickable still consumes the touch // events, it just doesn't respond to them. return clickable; } if (mTouchDelegate != null) { if (mTouchDelegate.onTouchEvent(event)) { return true; } } if (clickable || (viewFlags & TOOLTIP) == TOOLTIP) { switch (action) { case MotionEvent.ACTION_UP: mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN; if ((viewFlags & TOOLTIP) == TOOLTIP) { handleTooltipUp(); } if (!clickable) { //移除 点击变乱 长按变乱,Button按压的一些状态的回调 removeTapCallback(); removeLongPressCallback(); mInContextButtonPress = false; mHasPerformedLongPress = false; mIgnoreNextUpEvent = false; break; } boolean prepressed = (mPrivateFlags & PFLAG_PREPRESSED) != 0; if ((mPrivateFlags & PFLAG_PRESSED) != 0 || prepressed) { // take focus if we don't have it already and we should in // touch mode. boolean focusTaken = false; if (isFocusable() && isFocusableInTouchMode() && !isFocused()) { focusTaken = requestFocus(); } 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. //处理处罚Button的一些按压状态 setPressed(true, x, y); } if (!mHasPerformedLongPress && !mIgnoreNextUpEvent) { // This is a tap, so remove the longpress check removeLongPressCallback(); // Only perform take click actions if we were in the pressed state if (!focusTaken) { // 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)) { performClickInternal(); } } } if (mUnsetPressedState == null) { mUnsetPressedState = new UnsetPressedState(); } if (prepressed) { postDelayed(mUnsetPressedState, ViewConfiguration.getPressedStateDuration()); } else if (!post(mUnsetPressedState)) { // If the post failed, unpress right now mUnsetPressedState.run(); } removeTapCallback(); } mIgnoreNextUpEvent = false; break; case MotionEvent.ACTION_DOWN: if (event.getSource() == InputDevice.SOURCE_TOUCHSCREEN) { mPrivateFlags3 |= PFLAG3_FINGER_DOWN; } mHasPerformedLongPress = false; if (!clickable) { //校验长安点击的逻辑处理处罚 checkForLongClick(0, x, y); break; } if (performButtonActionOnTouchDown(event)) { break; } // Walk up the hierarchy to determine if we're inside a scrolling container. boolean isInScrollingContainer = isInScrollingContainer(); // For views inside a scrolling container, delay the pressed feedback for // a short period in case this is a scroll. if (isInScrollingContainer) { mPrivateFlags |= PFLAG_PREPRESSED; if (mPendingCheckForTap == null) { mPendingCheckForTap = new CheckForTap(); } mPendingCheckForTap.x = event.getX(); mPendingCheckForTap.y = event.getY(); postDelayed(mPendingCheckForTap, ViewConfiguration.getTapTimeout()); } else { // Not inside a scrolling container, so show the feedback right away setPressed(true, x, y); checkForLongClick(0, x, y); } break; case MotionEvent.ACTION_CANCEL: if (clickable) { setPressed(false); } removeTapCallback(); removeLongPressCallback(); mInContextButtonPress = false; mHasPerformedLongPress = false; mIgnoreNextUpEvent = false; mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN; break; case MotionEvent.ACTION_MOVE: if (clickable) { drawableHotspotChanged(x, y); } // Be lenient about moving outside of buttons if (!pointInView(x, y, mTouchSlop)) { // Outside button // Remove any future long press/tap checks removeTapCallback(); removeLongPressCallback(); if ((mPrivateFlags & PFLAG_PRESSED) != 0) { setPressed(false); } mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN; } break; } return true; } 默认返回 false 标识不消化触摸变乱 return false; }总结
简朴的跟着源熟悉了一遍 变乱分发逻辑,大概思绪是 Activity PhoneWindow DecorView 将点击变乱分发到了ViewGroup .ViewGroup 判断本身要不要拦截处理处罚 不拦截处理处罚下发到View View判断本身是否消化,消化就自身处理处罚 不消化 返回到ViewGroup 处理处罚
末了还有几个点击变乱 和长按变乱 和变乱分发的关系以及逻辑梳理不到位 转头找时间再看看 |
