Behavior对象是怎么被实例化的
CoordinatorLayout里面的子View是怎么拿到Behavior对象的。设置Bevior有两种方式
1. 代码里面直接设置(LayoutParams)child.getLayoutParams().setBehavior()这个就好说了。
2. XML里面去设置app:layout_behavior=”” 。
对应第二种情况Behavior是怎么实例化的。
CoordinatorLayout里面LayoutParams两个参数的构造函数。
LayoutParams(Context context, AttributeSet attrs) { super(context, attrs); final TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CoordinatorLayout_LayoutParams); this.gravity = a.getInteger( R.styleable.CoordinatorLayout_LayoutParams_android_layout_gravity, Gravity.NO_GRAVITY); mAnchorId = a.getResourceId(R.styleable.CoordinatorLayout_LayoutParams_layout_anchor, View.NO_ID); this.anchorGravity = a.getInteger( R.styleable.CoordinatorLayout_LayoutParams_layout_anchorGravity, Gravity.NO_GRAVITY); this.keyline = a.getInteger(R.styleable.CoordinatorLayout_LayoutParams_layout_keyline, -1); mBehaviorResolved = a.hasValue( R.styleable.CoordinatorLayout_LayoutParams_layout_behavior); if (mBehaviorResolved) { mBehavior = parseBehavior(context, attrs, a.getString( R.styleable.CoordinatorLayout_LayoutParams_layout_behavior)); } a.recycle(); }
第20行是否设置了app:layout_behavior=”” 如果设置了调用parseBehavior函数。利用反射去实例化出Behavior对象。
Behavior简单分析
Behavior都是配合CoordinatorLayout来使用的。
对于Behavior我们分三种情况来考虑。
1. Behavior的onInterceptTouchEvent + onTouchEvent。
2. Behavior的layoutDependsOn + onDependentViewChanged + onDependentViewRemoved。View引起的变化。
3. Behavior的onStartNestedScroll + onNestedScrollAccepted + onStopNestedScroll + onNestedScroll + onNestedPreScroll + onNestedFling + onNestedPreFling。嵌套滑动引起的变化。
大概的去知道每种情况里面每个函数的调用时机。和大概的作用。
Behavior的onInterceptTouchEvent + onTouchEvent
分两部分来考虑。
1. CoordinatorLayout里面是怎么调用到我们指定View的Behavior的onInterceptTouchEvent和onTouchEvent里面去的。
2. View的Behavior里面onInterceptTouchEvent和onTouchEvent里面干了什么事情。(这个一般是我们自定义Behavior的时候处理,这个先不管)。
CoordinatorLayout里面是怎么调用到我们指定View的Behavior的onInterceptTouchEvent和onTouchEvent里面去的。直接CoordinatorLayout的onInterceptTouchEvent函数和onTouchEvent函数里面了先CoordinatorLayout类的onInterceptTouchEvent函数。
@Override public boolean onInterceptTouchEvent(MotionEvent ev) { MotionEvent cancelEvent = null; final int action = MotionEventCompat.getActionMasked(ev); // Make sure we reset in case we had missed a previous important event. if (action == MotionEvent.ACTION_DOWN) { resetTouchBehaviors(); } final boolean intercepted = performIntercept(ev, TYPE_ON_INTERCEPT); if (cancelEvent != null) { cancelEvent.recycle(); } if (action == MotionEvent.ACTION_UP || action == MotionEvent.ACTION_CANCEL) { resetTouchBehaviors(); } return intercepted; }
第12行调用了performIntercept函数,参数type TYPE_ON_INTERCEPT表示从onInterceptTouchEvent函数进来的,TYPE_ON_TOUCH表示从onTouchEvent函数进来的。
private boolean performIntercept(MotionEvent ev, final int type) { boolean intercepted = false; boolean newBlock = false; MotionEvent cancelEvent = null; final int action = MotionEventCompat.getActionMasked(ev); final List<View> topmostChildList = mTempList1; getTopSortedChildren(topmostChildList); // Let topmost child views inspect first final int childCount = topmostChildList.size(); for (int i = 0; i < childCount; i++) { final View child = topmostChildList.get(i); final LayoutParams lp = (LayoutParams) child.getLayoutParams(); final Behavior b = lp.getBehavior(); if ((intercepted || newBlock) && action != MotionEvent.ACTION_DOWN) { // Cancel all behaviors beneath the one that intercepted. // If the event is "down" then we don't have anything to cancel yet. if (b != null) { if (cancelEvent != null) { final long now = SystemClock.uptimeMillis(); cancelEvent = MotionEvent.obtain(now, now, MotionEvent.ACTION_CANCEL, 0.0f, 0.0f, 0); } switch (type) { case TYPE_ON_INTERCEPT: b.onInterceptTouchEvent(this, child, cancelEvent); break; case TYPE_ON_TOUCH: b.onTouchEvent(this, child, cancelEvent); break; } } continue; } if (!intercepted && b != null) { switch (type) { case TYPE_ON_INTERCEPT: intercepted = b.onInterceptTouchEvent(this, child, ev); break; case TYPE_ON_TOUCH: intercepted = b.onTouchEvent(this, child, ev); break; } if (intercepted) { mBehaviorTouchView = child; } } // Don't keep going if we're not allowing interaction below this. // Setting newBlock will make sure we cancel the rest of the behaviors. final boolean wasBlocking = lp.didBlockInteraction(); final boolean isBlocking = lp.isBlockingInteractionBelow(this, child); newBlock = isBlocking && !wasBlocking; if (isBlocking && !newBlock) { // Stop here since we don't have anything more to cancel - we already did // when the behavior first started blocking things below this point. break; } } topmostChildList.clear(); return intercepted; }
第14行开始,遍历CoordinatorLayout所有的View,第19行第一个if做的事情是如果现在已经有View对应的Behavoir拦截了的,并且不是ACTION_DOWN的时候,其他View的Behavoir都会收到ACTION_CANCEL事件。
第40行第二个if如果没有被拦截并且有Behavoir则调用Behavoir对应的函数onInterceptTouchEvent或者onTouchEvent函数。
CoordinatorLayout的onTouchEvent函数
@Override public boolean onTouchEvent(MotionEvent ev) { boolean handled = false; boolean cancelSuper = false; MotionEvent cancelEvent = null; final int action = MotionEventCompat.getActionMasked(ev); if (mBehaviorTouchView != null || (cancelSuper = performIntercept(ev, TYPE_ON_TOUCH))) { // Safe since performIntercept guarantees that // mBehaviorTouchView != null if it returns true final LayoutParams lp = (LayoutParams) mBehaviorTouchView.getLayoutParams(); final Behavior b = lp.getBehavior(); if (b != null) { handled = b.onTouchEvent(this, mBehaviorTouchView, ev); } } // Keep the super implementation correct if (mBehaviorTouchView == null) { handled |= super.onTouchEvent(ev); } else if (cancelSuper) { if (cancelEvent != null) { final long now = SystemClock.uptimeMillis(); cancelEvent = MotionEvent.obtain(now, now, MotionEvent.ACTION_CANCEL, 0.0f, 0.0f, 0); } super.onTouchEvent(cancelEvent); } if (!handled && action == MotionEvent.ACTION_DOWN) { } if (cancelEvent != null) { cancelEvent.recycle(); } if (action == MotionEvent.ACTION_UP || action == MotionEvent.ACTION_CANCEL) { resetTouchBehaviors(); } return handled; }
CoordinatorLayout的onTouchEvent函数就是看下当前事件是不是有哪个View的Behavior感兴趣。如果感兴趣就给View的Behavior做处理,不敢兴趣就给CoordinatorLayout自己处理。
这样Behavior的onInterceptTouchEvent + onTouchEvent。两个函数的调用也引导进去了。
Behavior的layoutDependsOn + onDependentViewChanged + onDependentViewRemoved
/** * child是否要依赖dependency * @param parent CoordinatorLayout * @param child 该Behavior对应的那个View * @param dependency 要检查的View(child是否要依赖这个dependency) * @return true 依赖, false 不依赖 */ public boolean layoutDependsOn(CoordinatorLayout parent, V child, View dependency) { return false; } /** * 在layoutDependsOn返回true的基础上之后,及时报告dependency的状态变化 * @param parent CoordinatorLayout * @param child 该Behavior对应的那个View * @param dependency child依赖dependency * @return true 处理了, false 没处理 */ public boolean onDependentViewChanged(CoordinatorLayout parent, V child, View dependency) { return false; } /** * 在layoutDependsOn返回true的基础上之后,报告dependency被移除了 * @param parent CoordinatorLayout * @param child 该Behavior对应的那个View * @param dependency child依赖dependency */ public void onDependentViewRemoved(CoordinatorLayout parent, V child, View dependency) { }
所有的源头都在CoordinatorLayout类里面
CoordinatorLayout类里面onAttachedToWindow
@Override public void onAttachedToWindow() { super.onAttachedToWindow(); resetTouchBehaviors(); if (mNeedsPreDrawListener) { if (mOnPreDrawListener == null) { mOnPreDrawListener = new OnPreDrawListener(); } final ViewTreeObserver vto = getViewTreeObserver(); vto.addOnPreDrawListener(mOnPreDrawListener); } if (mLastInsets == null && ViewCompat.getFitsSystemWindows(this)) { // We're set to fitSystemWindows but we haven't had any insets yet... // We should request a new dispatch of window insets ViewCompat.requestApplyInsets(this); } mIsAttachedToWindow = true; }
第10行给ViewTreeObserver添加了一个OnPreDrawListener的监听。OnPreDrawListener代码如下
class OnPreDrawListener implements ViewTreeObserver.OnPreDrawListener { @Override public boolean onPreDraw() { dispatchOnDependentViewChanged(false); return true; } }
OnPreDrawListener实现了ViewTreeObserver.OnPreDrawListener接口重写了onPreDraw函数,onPreDraw在每次draw的时候都会调用。就是在CoordinatorLayout每次重绘的时候调用。View状态发生变化的时候调用。这样重点就到了dispatchOnDependentViewChanged函数了参数false表示不是嵌套滑动引起的变化是View状态改变引起的变化。
void dispatchOnDependentViewChanged(final boolean fromNestedScroll) { final int layoutDirection = ViewCompat.getLayoutDirection(this); final int childCount = mDependencySortedChildren.size(); for (int i = 0; i < childCount; i++) { final View child = mDependencySortedChildren.get(i); final LayoutParams lp = (LayoutParams) child.getLayoutParams(); // Check child views before for anchor for (int j = 0; j < i; j++) { final View checkChild = mDependencySortedChildren.get(j); if (lp.mAnchorDirectChild == checkChild) { offsetChildToAnchor(child, layoutDirection); } } // Did it change? if not continue final Rect oldRect = mTempRect1; final Rect newRect = mTempRect2; getLastChildRect(child, oldRect); getChildRect(child, true, newRect); if (oldRect.equals(newRect)) { continue; } recordLastChildRect(child, newRect); // Update any behavior-dependent views for the change for (int j = i + 1; j < childCount; j++) { final View checkChild = mDependencySortedChildren.get(j); final LayoutParams checkLp = (LayoutParams) checkChild.getLayoutParams(); final Behavior b = checkLp.getBehavior(); if (b != null && b.layoutDependsOn(this, checkChild, child)) { if (!fromNestedScroll && checkLp.getChangedAfterNestedScroll()) { // If this is not from a nested scroll and we have already been changed // from a nested scroll, skip the dispatch and reset the flag checkLp.resetChangedAfterNestedScroll(); continue; } final boolean handled = b.onDependentViewChanged(this, checkChild, child); if (fromNestedScroll) { // If this is from a nested scroll, set the flag so that we may skip // any resulting onPreDraw dispatch (if needed) checkLp.setChangedAfterNestedScroll(handled); } } } } }
第3行 mDependencySortedChildren里面放的是CoordinatorLayout所有的子View,只不过把相关连的View放到一起了(相关联有两种一种是直接xml里面设置了layout_anchor,一种是Behavior里面设置了关联layoutDependsOn函数)。接着遍历所有的View。
第9行到15行找到哪个View设置了layout_anchor也就是说设置显示坐标的锚点 哪个View的layout_anchor对应child。调整位置,这个应该好理解点layout_anchor设置的View和当前的View是相关会一起变化的。
第28行到49行找到哪个View的Behavior depend on child这个View。第0行调用了Behavior的layoutDependsOn判断是否依赖。如果依赖继续调用Behavior的onDependentViewChanged函数。
到这里Behavior的layoutDependsOn和onDependentViewChanged的调用的地方和调用的时机我们都知道了。还差一个onDependentViewRemoved函数。继续看CoordinatorLayout里面的HierarchyChangeListener里 在哪里用到了呢构造函数里面super.setOnHierarchyChangeListener(new HierarchyChangeListener());设置了去监听ViewGroup中的View的层次变化当View removed掉的时候这里能够监听到了会调用onChildViewRemoved。
final class HierarchyChangeListener implements OnHierarchyChangeListener { @Override public void onChildViewAdded(View parent, View child) { if (mOnHierarchyChangeListener != null) { mOnHierarchyChangeListener.onChildViewAdded(parent, child); } } @Override public void onChildViewRemoved(View parent, View child) { dispatchDependentViewRemoved(child); if (mOnHierarchyChangeListener != null) { mOnHierarchyChangeListener.onChildViewRemoved(parent, child); } } }
继续dispatchDependentViewRemoved函数。
void dispatchDependentViewRemoved(View removedChild) { final int childCount = getChildCount(); for (int i = 0; i < childCount; i++) { final View child = getChildAt(i); final LayoutParams lp = (LayoutParams) child.getLayoutParams(); final Behavior b = lp.getBehavior(); if (b != null && b.layoutDependsOn(this, child, removedChild)) { b.onDependentViewRemoved(this, child, removedChild); } } }
找到对应View的Behavior 如果是layoutDependsOn的就去调用Behavior的onDependentViewRemoved。
到此Behavior的layoutDependsOn + onDependentViewChanged + onDependentViewRemoved三个函数的调用时机和调用顺序都结束了。
Behavior的onStartNestedScroll + onNestedScrollAccepted + onStopNestedScroll + onNestedScroll + onNestedPreScroll + onNestedFling + onNestedPreFling
/** * 有嵌套滑动到来了,问下该Behavior是否接受嵌套滑动 * * @param coordinatorLayout CoordinatorLayout * @param child 该Behavior对应的View * @param directTargetChild 嵌套滑动对应的父类的子类(因为嵌套滑动对于的父View不一定是一级就能找到的,可能挑了两级父View的父View, directTargetChild>=target) * @param target 具体嵌套滑动的那个子类 * @param nestedScrollAxes 支持嵌套滚动轴。水平方向,垂直方向,或者不指定 * @return 是否接受该嵌套滑动 */ public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout, V child, View directTargetChild, View target, int nestedScrollAxes) { return false; } /** * Behavior接受了嵌套滑动的请求该函数调用。onStartNestedScroll返回true该函数会被调用。 参数和onStartNestedScroll一样 */ public void onNestedScrollAccepted(CoordinatorLayout coordinatorLayout, V child, View directTargetChild, View target, int nestedScrollAxes) { // Do nothing } /** * 停止嵌套滑动 * * @param coordinatorLayout CoordinatorLayout * @param child 该Behavior对应的View * @param target 具体嵌套滑动的那个子类 */ public void onStopNestedScroll(CoordinatorLayout coordinatorLayout, V child, View target) { // Do nothing } /** * 嵌套滑动的子View在滑动之后报告过来的滑动情况 * * @param coordinatorLayout CoordinatorLayout * @param child 该Behavior对应的View * @param target 具体嵌套滑动的那个子类 * @param dxConsumed 水平方向嵌套滑动的子View滑动的距离(消耗的距离) * @param dyConsumed 垂直方向嵌套滑动的子View滑动的距离(消耗的距离) * @param dxUnconsumed 水平方向嵌套滑动的子View未滑动的距离(未消耗的距离) * @param dyUnconsumed 垂直方向嵌套滑动的子View未滑动的距离(未消耗的距离) */ public void onNestedScroll(CoordinatorLayout coordinatorLayout, V child, View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) { // Do nothing } /** * 在嵌套滑动的子View未滑动之前告诉过来的准备滑动的情况 * * @param coordinatorLayout CoordinatorLayout * @param child 该Behavior对应的View * @param target 具体嵌套滑动的那个子类 * @param dx 水平方向嵌套滑动的子View想要变化的距离 * @param dy 垂直方向嵌套滑动的子View想要变化的距离 * @param consumed 这个参数要我们在实现这个函数的时候指定,回头告诉子View当前父View消耗的距离 consumed[0] 水平消耗的距离,consumed[1] 垂直消耗的距离 好让子view做出相应的调整 */ public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, V child, View target, int dx, int dy, int[] consumed) { // Do nothing } /** * 嵌套滑动的子View在fling之后报告过来的fling情况 * * @param coordinatorLayout CoordinatorLayout * @param child 该Behavior对应的View * @param target 具体嵌套滑动的那个子类 * @param velocityX 水平方向速度 * @param velocityY 垂直方向速度 * @param consumed 子view是否fling了 * @return true Behavior是否消耗了fling */ public boolean onNestedFling(CoordinatorLayout coordinatorLayout, V child, View target, float velocityX, float velocityY, boolean consumed) { return false; } /** * 在嵌套滑动的子View未fling之前告诉过来的准备fling的情况 * * @param coordinatorLayout CoordinatorLayout * @param child 该Behavior对应的View * @param target 具体嵌套滑动的那个子类 * @param velocityX 水平方向速度 * @param velocityY 垂直方向速度 * @return true Behavior是否消耗了fling */ public boolean onNestedPreFling(CoordinatorLayout coordinatorLayout, V child, View target, float velocityX, float velocityY) { return false; }
嵌套滑动引起的变化,根据前一篇文章Android 嵌套滑动分析的分析CoordinatorLayout 实现了 NestedScrollingParent,有嵌套滑动的时候会调用到CoordinatorLayout里面的onStartNestedScroll onNestedScrollAccepted onStopNestedScroll onNestedScroll onNestedPreScroll onNestedFling onNestedPreFling这些函数。至于是怎么调用到的这些函数可以看看Android 嵌套滑动分析的介绍。这些函数里面做的事情也都是大同小异的都是直接过度给了Behavior里面对应的函数。
这样我们就知道了Behavior的onStartNestedScroll + onNestedScrollAccepted + onStopNestedScroll + onNestedScroll + onNestedPreScroll + onNestedFling + onNestedPreFling。的调用时机是有嵌套滑动的时候会被调用到。