Android 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

1. 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;
    }