Android 你知道介面布局嵌套多少層之後會Crash嗎

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我們先放一張Hierarchy Viewer的圖：（模擬器Android4.4）

 

看到數字6了嗎，那個RelativeLayout是MainActivity的根ViewGroup, 而在RelativeLayout之前還有5層， 即系統預設的介面DecorView(FrameLayout) --> LinearLayout --> FramelLayout-- >ActionBarOverlayLayout --> ContentFrameLayout.

 直接說結果吧，用模擬器在API19  也就是Android4.4 上最大可以嵌套39層，包含系統預設的5層，也就說我們最大可以寫34層的嵌套。

當嵌套層數達到40層時報如下異常，

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

View Code

在API23 Android6.0上嵌套層數可以更多，實驗了四十多層還依舊沒有crash

至於具體低於4.4的版本是什麼樣的結果，我並沒有測試，且Android開源各大手機廠商可能會修改邏輯。不過考慮到向下相容的問題，還是不應該嵌套太多層數，

當自己寫的布局層級超過10層的時候就該考慮最佳化布局了，因為即使應用不因為嵌套的太多而crash，也會造成渲染時間過長等問題，影響UI流暢度。

 

Android 你知道介面布局嵌套多少層之後會Crash嗎