Android 你知道界面布局嵌套多少层之后会Crash吗

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。