Android(安卓)View，ViewGroup 事件分发

虽然一直原来也有看过相关方面的资料,并且用到的也不少了, 但是还是记一记吧, 希望大家都能明白理解
View 继承
Drawable.Callback,
KeyEvent.Callback，
AccessibilityEventSource

ViewRootImpl
frameworks/base/core/java/android/view/ViewRootImpl.java

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

事件的传递(是由最外层的view 最先获取到)

ViewGroup - ViewGroup - view

View中的方法
事件分发

public boolean dispatchTouchEvent(MotionEvent ev)

事件拦截（默认返回false）

public boolean onInterceptTouchEvent(MotionEvent ev)

事件处理（默认返回false）

public boolean onTouchEvent(MotionEvent ev)

* 默认的分发和处理结合起来，就类似是个闭环*
1
1.1 进入最顶层父View 的 dispatchTouchEvent 进行事件分发

true 交给本身处理（进入onTouchEvent）
false 进入（方法onInterceptTouchEvent）看是否拦截事件
如果拦截返回true - （进入本View onTouchEvent）
不拦截返回false - （传给子View）

1.2 子View相同判断

1.3 如果View发现自己没有子View 时，则自己处理。

2
2.1 如果子View的 onTouchEvent

返回false （既不做处理） onTouchEvent 事件会向父View传递，并由父View的onTouchEvent 接受
返回true （做处理）既交给自身的 onTouchEvent 处理

当某个view 拦截，并且处理onTouchEvent

1. 源码 View 是如何获得事件消息的
1.1 view 的初始化

public class View implements Drawable.Callback, KeyEvent.Callback, AccessibilityEventSource {// 初始化 public View(Context context, AttributeSet attrs, int defStyle) {// View() {        mResources = null;    }

1.2 attachInfo 的获取

  /** * @param info the {@link android.view.View.AttachInfo} to associated with * this view */    void dispatchAttachedToWindow(AttachInfo info, int visibility) {        //System.out.println("Attached! " + this);        mAttachInfo = info;        mWindowAttachCount++;        // We will need to evaluate the drawable state at least once.        mPrivateFlags |= PFLAG_DRAWABLE_STATE_DIRTY;        if (mFloatingTreeObserver != null) {            info.mTreeObserver.merge(mFloatingTreeObserver);            mFloatingTreeObserver = null;        }        if ((mPrivateFlags&PFLAG_SCROLL_CONTAINER) != 0) {            mAttachInfo.mScrollContainers.add(this);            mPrivateFlags |= PFLAG_SCROLL_CONTAINER_ADDED;        }        performCollectViewAttributes(mAttachInfo, visibility);        onAttachedToWindow();        ListenerInfo li = mListenerInfo;        final CopyOnWriteArrayList<OnAttachStateChangeListener> listeners =                li != null ? li.mOnAttachStateChangeListeners : null;        if (listeners != null && listeners.size() > 0) {            // NOTE: because of the use of CopyOnWriteArrayList, we *must* use an iterator to            // perform the dispatching. The iterator is a safe guard against listeners that            // could mutate the list by calling the various add/remove methods. This prevents            // the array from being modified while we iterate it.            for (OnAttachStateChangeListener listener : listeners) {                listener.onViewAttachedToWindow(this);            }        }        int vis = info.mWindowVisibility;        if (vis != GONE) {            onWindowVisibilityChanged(vis);        }        if ((mPrivateFlags&PFLAG_DRAWABLE_STATE_DIRTY) != 0) {            // If nobody has evaluated the drawable state yet, then do it now.            refreshDrawableState();        }        needGlobalAttributesUpdate(false);    }

1.3获得 ViewRootImpl

    /** * Gets the view root associated with the View. * @return The view root, or null if none. * @hide */    public ViewRootImpl getViewRootImpl() {        if (mAttachInfo != null) {            return mAttachInfo.mViewRootImpl;        }        return null;    }

1.4 View 的 dispatchPointerEvent （这个就是传进来的重点了），得到了 dispatchTouchEvent 获得 MotionEvent

  public final boolean dispatchPointerEvent(MotionEvent event) {        if (event.isTouchEvent()) {            return dispatchTouchEvent(event);        } else {            return dispatchGenericMotionEvent(event);        }    }

1.5接下来 dispatchTouchEvent ，会陆续传给其他

    public boolean dispatchTouchEvent(MotionEvent event) {        if (mInputEventConsistencyVerifier != null) {//======================================================= mInputEventConsistencyVerifier.onTouchEvent(event, 0);        }        if (onFilterTouchEventForSecurity(event)) {            //noinspection SimplifiableIfStatement            ListenerInfo li = mListenerInfo;            if (li != null && li.mOnTouchListener != null && (mViewFlags & ENABLED_MASK) == ENABLED                    && li.mOnTouchListener.onTouch(this, event)) {                return true;            }//=========================================            if (onTouchEvent(event)) {                return true;            }        }        if (mInputEventConsistencyVerifier != null) {            mInputEventConsistencyVerifier.onUnhandledEvent(event, 0);        }        return false;    }

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