View与ViewGroup layout 过程

1. public void layout ( int l , int t , int r , int b ) {
2. if ( DBG_SYSTRACE_LAYOUT ) {
3. Trace . traceBegin ( Trace . TRACE_TAG_VIEW , "layout : " + getClass (). getSimpleName ());
4. }
5. // !=0 表示在measure 的时候设置这个标志,也就是measure的时候根据measure cache 测量,而不是直接调用onMeasure(),所以这里要重新onMeasure一次
6. if (( mPrivateFlags3 & PFLAG3_MEASURE_NEEDED_BEFORE_LAYOUT ) != 0 ) {
8. /// M: Monitor onLayout time if longer than 3s print log.
9. if ( DBG_LAYOUT || DBG_MEASURE_LAYOUT ) {
10. Xlog . d ( VIEW_LOG_TAG , "view onMeasure start (measure cache), this =" + this
11. + ", widthMeasureSpec = " + MeasureSpec . toString ( mOldWidthMeasureSpec )
12. + ", heightMeasureSpec = " + MeasureSpec . toString ( mOldHeightMeasureSpec ));
13. }
14. long logTime = System . currentTimeMillis ();
15. onMeasure ( mOldWidthMeasureSpec , mOldHeightMeasureSpec );
16. long nowTime = System . currentTimeMillis ();
17. if ( nowTime - logTime > DBG_TIMEOUT_VALUE ) {
18. Xlog . d ( VIEW_LOG_TAG , "[ANR Warning]onMeasure time too long, this =" + this
19. + "time =" + ( nowTime - logTime ) + " ms" );
20. }
21. if ( DBG_LAYOUT || DBG_MEASURE_LAYOUT ) {
22. Xlog . d ( VIEW_LOG_TAG , "view onMeasure end (measure cache), this =" + this
23. + ", mMeasuredWidth = " + mMeasuredWidth + ", mMeasuredHeight = "
24. + mMeasuredHeight + ", time =" + ( nowTime - logTime ) + " ms" );
25. }
26. mPrivateFlags3 &= ~ PFLAG3_MEASURE_NEEDED_BEFORE_LAYOUT ; //将标志位恢复
27. }
29. int oldL = mLeft ;
30. int oldT = mTop ;
31. int oldB = mBottom ;
32. int oldR = mRight ;
34. //视觉/光学边界布局,一般是false
35. boolean changed = isLayoutModeOptical ( mParent ) ?
36. setOpticalFrame ( l , t , r , b ) : setFrame ( l , t , r , b );
37. if ( DBG_LAYOUT || DBG_MEASURE_LAYOUT ) {
38. Xlog . d ( VIEW_LOG_TAG , "view layout start, this = " + this + ", mLeft = " + mLeft
39. + ", mTop = " + mTop + ", mRight = " + mRight + ", mBottom = " + mBottom
40. + ", changed = " + changed );
41. }
42. //PFLAG_LAYOUT_REQUIRED这个标志也是在measure 的时候设置的.
43. if ( changed || ( mPrivateFlags & PFLAG_LAYOUT_REQUIRED ) == PFLAG_LAYOUT_REQUIRED ) {
44. /// M: Monitor onLayout time if longer than 3s print log.
45. long logTime = System . currentTimeMillis ();
46. onLayout ( changed , l , t , r , b ); //这个方法view和ViewGroup都没有实现,具体是有子类去实现
47. long nowTime = System . currentTimeMillis ();
48. if ( nowTime - logTime > DBG_TIMEOUT_VALUE ) {
49. Xlog . d ( VIEW_LOG_TAG , "[ANR Warning]onLayout time too long, this =" + this
50. + "time =" + ( nowTime - logTime ) + " ms" );
51. }
52. if ( DBG_LAYOUT || DBG_MEASURE_LAYOUT ) {
53. Xlog . d ( VIEW_LOG_TAG , "view layout end, this =" + this + ", mLeft = " + mLeft
54. + ", mTop = " + mTop + ", mRight = " + mRight + ", mBottom = " + mBottom
55. + ", time =" + ( nowTime - logTime ) + " ms" );
56. }
57. mPrivateFlags &= ~ PFLAG_LAYOUT_REQUIRED ; //将标志位恢复
59. ListenerInfo li = mListenerInfo ;
60. if ( li != null && li . mOnLayoutChangeListeners != null ) {
61. ArrayList < OnLayoutChangeListener > listenersCopy =
62. ( ArrayList < OnLayoutChangeListener >) li . mOnLayoutChangeListeners . clone ();
63. int numListeners = listenersCopy . size ();
64. for ( int i = 0 ; i < numListeners ; ++ i ) {
65. listenersCopy . get ( i ). onLayoutChange ( this , l , t , r , b , oldL , oldT , oldR , oldB ); //接口回调
66. }
67. }
68. } else {
69. if ( DBG_LAYOUT || DBG_MEASURE_LAYOUT ) {
70. Xlog . d ( VIEW_LOG_TAG , "view layout end 2 (use previous layout), this = " + this
71. + ", mLeft = " + mLeft + ", mTop = " + mTop
72. + ", mRight = " + mRight + ", mBottom = " + mBottom );
73. }
74. }
76. mPrivateFlags &= ~ PFLAG_FORCE_LAYOUT ;
77. mPrivateFlags3 |= PFLAG3_IS_LAID_OUT ;
78. if ( DBG_SYSTRACE_LAYOUT ) {
79. Trace . traceEnd ( Trace . TRACE_TAG_VIEW );
80. }
81. }