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View分析

时间:2014-08-08 15:38:26      阅读:270      评论:0      收藏:0      [点我收藏+]

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在Android的布局体系中,父View负责刷新、布局显示子View;而当子View需要刷新时,则是通知父View来完成。这种处理逻辑在View的代码中明确的表现出来: 

 1 public void invalidate() {
 2     final ViewParent p = mParent;
 3     final AttachInfo ai = mAttachInfo;
 4     if (p != null && ai != null) {
 5         final Rect r = ai.mTmpInvalRect;
 6 
 7         // 设置刷新区域为自己的尺寸 
 8         r.set(0, 0, mRight - mLeft, mBottom - mTop);
 9         p.invalidateChild(this, r);
10     }
11 }

 子View调用invalidate时,首先找到自己父View(View的成员变量mParent记录自己的父View),然后将AttachInfo中保存的信息告诉父View刷新自己。 

View的父子关系的建立分为两种情况:

1) View加入ViewGroup中

 1 private void addViewInner(View child, int index, LayoutParams params, boolean preventRequestLayout) {
 2 
 3         .....
 4 
 5             // tell our children
 6         if (preventRequestLayout) {
 7             child.assignParent(this);
 8         } else {
 9             child.mParent = this;
10         }
11 
12        .....
13 
14 } 

 

2)DecorView注册给WindowManagerImpl时,产生一个ViewRoot作为其父View。

1 public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView){
2 
3     .....
4 
5     view.assignParent(this);
6 
7     ....
8 
9 }

  AttachInfo是在View第一次attach到Window时,ViewRoot传给自己的子View的。这个AttachInfo之后,会顺着布局体系一直传递到最底层的View。

View.java 

1 void dispatchAttachedToWindow(AttachInfo info, int visibility) {
2     mAttachInfo = info;
3 
4     .....
5 }

 

 ViewGroup.java

1 void dispatchAttachedToWindow(AttachInfo info, int visibility) {
2     super.dispatchAttachedToWindow(info, visibility);
3 
4     for (int i = 0; i < count; i++) {
5         children[i].dispatchAttachedToWindow(info, visibility);
6     }
7 }

 

 并且在新的View被加入ViewGroup时,也会将该AttachInfo传给加入的View

ViewGroup.java

1 private void addViewInner(View child, int index, LayoutParams params, boolean preventRequestLayout) {
2 
3     child.dispatchAttachedToWindow(mAttachInfo, (mViewFlags&VISIBILITY_MASK));
4 
5 }

 

 到这里明白了mParent与AttachInfo代表的意义,可以继续刷新过程的分析。

 在invalidate中,调用父View的invalidateChild,这是一个从第向上回溯的过程,每一层的父View都将自己的显示区域与传入的刷新Rect做交集。 

 1 public final void invalidateChild(View child, final Rect dirty) {
 2     ViewParent parent = this;
 3 
 4     final AttachInfo attachInfo = mAttachInfo;
 5     if (attachInfo != null) {
 6         final int[] location = attachInfo.mInvalidateChildLocation;
 7 
 8         // 需要刷新的子View的位置 
 9         location[CHILD_LEFT_INDEX] = child.mLeft;
10         location[CHILD_TOP_INDEX] = child.mTop;
11 
12         // If the child is drawing an animation, we want to copy this flag onto
13         // ourselves and the parent to make sure the invalidate request goes through
14         final boolean drawAnimation = (child.mPrivateFlags & DRAW_ANIMATION) == DRAW_ANIMATION;
15 
16         // Check whether the child that requests the invalidate is fully opaque
17         final boolean isOpaque = child.isOpaque() && !drawAnimation && child.getAnimation() != null;
18 
19         // Mark the child as dirty, using the appropriate flag
20         // Make sure we do not set both flags at the same time
21         final int opaqueFlag = isOpaque ? DIRTY_OPAQUE : DIRTY;
22 
23         do {
24             View view = null;
25             if (parent instanceof View) {
26                 view = (View) parent;
27             }
28 
29             if (drawAnimation) {
30                 if (view != null) {
31                         view.mPrivateFlags |= DRAW_ANIMATION;
32                 } else if (parent instanceof ViewRoot) {
33                         ((ViewRoot) parent).mIsAnimating = true;
34                 }
35             }
36 
37                 // If the parent is dirty opaque or not dirty, mark it dirty with the opaque
38                 // flag coming from the child that initiated the invalidate
39             if (view != null && (view.mPrivateFlags & DIRTY_MASK) != DIRTY) {
40                 view.mPrivateFlags = (view.mPrivateFlags & ~DIRTY_MASK) | opaqueFlag;
41             }
42 
43             parent = parent.invalidateChildInParent(location, dirty);
44         } while (parent != null);
45     }
46 }
47 
48  
49 
50 public ViewParent invalidateChildInParent(final int[] location, final Rect dirty) {
51     if ((mPrivateFlags & DRAWN) == DRAWN) {
52         if ((mGroupFlags & (FLAG_OPTIMIZE_INVALIDATE | FLAG_ANIMATION_DONE)) !=
53                         FLAG_OPTIMIZE_INVALIDATE) {
54 
55             // 根据父View的位置,偏移刷新区域 
56             dirty.offset(location[CHILD_LEFT_INDEX] - mScrollX, location[CHILD_TOP_INDEX] - mScrollY);
57 
58             final int left = mLeft;
59             final int top = mTop;
60 
61             //计算实际可刷新区域 
62             if (dirty.intersect(0, 0, mRight - left, mBottom - top) ||
63                         (mPrivateFlags & DRAW_ANIMATION) == DRAW_ANIMATION) {
64                 mPrivateFlags &= ~DRAWING_CACHE_VALID;
65 
66                 location[CHILD_LEFT_INDEX] = left;
67                 location[CHILD_TOP_INDEX] = top;
68                 return mParent;
69             }
70         } else {
71             mPrivateFlags &= ~DRAWN & ~DRAWING_CACHE_VALID;
72 
73             location[CHILD_LEFT_INDEX] = mLeft;
74             location[CHILD_TOP_INDEX] = mTop;
75 
76            dirty.set(0, 0, mRight - location[CHILD_LEFT_INDEX],
77                         mBottom - location[CHILD_TOP_INDEX]);
78 
79                 return mParent;
80             }
81         }
82 
83         return null;
84 }

 

这个向上回溯的过程直到ViewRoot那里结束,由ViewRoot对这个最终的刷新区域做刷新。

ViewRoot.java

1 public void invalidateChild(View child, Rect dirty) {
2 
3     scheduleTraversals();
4 
5 }

 

View分析,布布扣,bubuko.com

View分析

标签:android   style   blog   color   java   io   for   ar   

原文地址:http://www.cnblogs.com/mjblogs/p/3899365.html

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