标签：hdr pre flow open 界面 alt pen omv star
我们先放一张Hierarchy Viewer的图：（模拟器Android4.4）
看到数字6了吗，那个RelativeLayout是MainActivity的根ViewGroup, 而在RelativeLayout之前还有5层， 即系统默认的界面DecorView(FrameLayout) --> LinearLayout --> FramelLayout-- >ActionBarOverlayLayout --> ContentFrameLayout.
直接说结果吧，用模拟器在API19 也就是Android4.4 上最大可以嵌套39层，包含系统默认的5层，也就说我们最大可以写34层的嵌套。
当嵌套层数达到40层时报如下异常，
10-27 11:38:53.901 25582-25582/com.aquarius.customview E/AndroidRuntime: FATAL EXCEPTION: main Process: com.aquarius.customview, PID: 25582 java.lang.StackOverflowError at android.util.Pools$SynchronizedPool.acquire(Pools.java:154) at android.view.GLES20RecordingCanvas.obtain(GLES20RecordingCanvas.java:43) at android.view.GLES20DisplayList.start(GLES20DisplayList.java:61) at android.view.View.getDisplayList(View.java:13323) at android.view.View.getDisplayList(View.java:13404) at android.view.View.draw(View.java:14182) at android.view.ViewGroup.drawChild(ViewGroup.java:3103) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2940) at android.view.View.getDisplayList(View.java:13357) at android.view.View.getDisplayList(View.java:13404) at android.view.View.draw(View.java:14182) at android.view.ViewGroup.drawChild(ViewGroup.java:3103) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2940) at android.view.View.getDisplayList(View.java:13357) at android.view.View.getDisplayList(View.java:13404) at android.view.View.draw(View.java:14182) at android.view.ViewGroup.drawChild(ViewGroup.java:3103) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2940) at android.view.View.getDisplayList(View.java:13357) at android.view.View.getDisplayList(View.java:13404) at android.view.View.draw(View.java:14182) at android.view.ViewGroup.drawChild(ViewGroup.java:3103) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2940) at android.view.View.getDisplayList(View.java:13357) at android.view.View.getDisplayList(View.java:13404) at android.view.View.draw(View.java:14182) at android.view.ViewGroup.drawChild(ViewGroup.java:3103) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2940) at android.view.View.getDisplayList(View.java:13357) at android.view.View.getDisplayList(View.java:13404) at android.view.View.draw(View.java:14182) at android.view.ViewGroup.drawChild(ViewGroup.java:3103) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2940) at android.view.View.getDisplayList(View.java:13357) at android.view.View.getDisplayList(View.java:13404) at android.view.View.draw(View.java:14182) at android.view.ViewGroup.drawChild(ViewGroup.java:3103) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2940) at android.view.View.getDisplayList(View.java:13357) at android.view.View.getDisplayList(View.java:13404) at android.view.View.draw(View.java:14182) at android.view.ViewGroup.drawChild(ViewGroup.java:3103) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2940) at android.view.View.getDisplayList(View.java:13357) at android.view.View.getDisplayList(View.java:13404) at android.view.View.draw(View.java:14182) at android.view.ViewGroup.drawChild(ViewGroup.java:3103) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2940) at android.view.View.getDisplayList(View.java:13357) at android.view.View.getDisplayList(View.java:13404) at android.view.View.draw(View.java:14182) at android.view.ViewGroup.drawChild(ViewGroup.java:3103) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2940) at android.view.View.getDisplayList(View.java:13357) at android.view.View.getDisplayList(View.java:13404) at android.view.View.draw(View.java:14182) at android.view.ViewGroup.drawChild(ViewGroup.java:3103) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2940) at android.view.View.getDisplayList(View.java:13357) at android.view.View.getDisplayList(View.java:13404) at android.view.View.draw(View.java:14182) at android.view.ViewGroup.drawChild(ViewGroup.java:3103) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2940) at android.view.View.getDisplayList(View.java:13357) at android.view.View.getDisplayList(View.java:13404) at android.view.View.draw(View.java:14182) at android.view.ViewGroup.drawChild(ViewGroup.java:3103) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2940) at android.view.View.getDisplayList(View.java:13357) at android.view.View.getDisplayList(View.java:13404) at android.view.View.draw(View.java:14182) at android.view.ViewGroup.drawChild(ViewGroup.java:3103) at android.view.View
在API23 Android6.0上嵌套层数可以更多，实验了四十多层还依旧没有crash
至于具体低于4.4的版本是什么样的结果，我并没有测试，且Android开源各大手机厂商可能会修改逻辑。不过考虑到向下兼容的问题，还是不应该嵌套太多层数，
当自己写的布局层级超过10层的时候就该考虑优化布局了，因为即使应用不因为嵌套的太多而crash，也会造成渲染时间过长等问题，影响UI流畅度。
标签：hdr pre flow open 界面 alt pen omv star
原文地址：http://www.cnblogs.com/sphere/p/7745687.html
