[英]Android onRestoreInstanceState(Bundle savedInstanceState)
[英]Bundle null in onRestoreInstanceState?
我最近在我的程序中遇到了崩潰。 使用logCat我確定崩潰是由於我的應用程序恢復時主活動中的onRestoreInstanceState()
中的代碼所致。 Logcat文件:
07-23 16:27:01.927 I/ActivityManager( 390): START u0 {act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10200000 cmp=com.myapp/.MainActivity bnds=[1184,809][1376,1001]} from pid 30666
07-23 16:27:01.997 I/ActivityManager( 390): Start proc com.myapp for activity com.myapp/.MainActivity: pid=31007 uid=10070 gids={50070, 1028}
07-23 16:27:02.137 E/AndroidRuntime(31007): FATAL EXCEPTION: main
07-23 16:27:02.137 E/AndroidRuntime(31007): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.myapp/com.myapp.MainActivity}: java.lang.ClassCastException: android.os.Parcelable[] cannot be cast to com.myapp.Panel[]
07-23 16:27:02.137 E/AndroidRuntime(31007): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
07-23 16:27:02.137 E/AndroidRuntime(31007): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
07-23 16:27:02.137 E/AndroidRuntime(31007): at android.app.ActivityThread.access$600(ActivityThread.java:141)
07-23 16:27:02.137 E/AndroidRuntime(31007): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
07-23 16:27:02.137 E/AndroidRuntime(31007): at android.os.Handler.dispatchMessage(Handler.java:99)
07-23 16:27:02.137 E/AndroidRuntime(31007): at android.os.Looper.loop(Looper.java:137)
07-23 16:27:02.137 E/AndroidRuntime(31007): at android.app.ActivityThread.main(ActivityThread.java:5041)
07-23 16:27:02.137 E/AndroidRuntime(31007): at java.lang.reflect.Method.invokeNative(Native Method)
07-23 16:27:02.137 E/AndroidRuntime(31007): at java.lang.reflect.Method.invoke(Method.java:511)
07-23 16:27:02.137 E/AndroidRuntime(31007): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
07-23 16:27:02.137 E/AndroidRuntime(31007): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
07-23 16:27:02.137 E/AndroidRuntime(31007): at dalvik.system.NativeStart.main(Native Method)
07-23 16:27:02.137 E/AndroidRuntime(31007): Caused by: java.lang.ClassCastException: android.os.Parcelable[] cannot be cast to com.myapp.Panel[]
07-23 16:27:02.137 E/AndroidRuntime(31007): at com.myapp.MainActivity.onRestoreInstanceState(MainActivity.java:177)
07-23 16:27:02.137 E/AndroidRuntime(31007): at android.app.Activity.performRestoreInstanceState(Activity.java:910)
07-23 16:27:02.137 E/AndroidRuntime(31007): at android.app.Instrumentation.callActivityOnRestoreInstanceState(Instrumentation.java:1131)
07-23 16:27:02.137 E/AndroidRuntime(31007): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2158)
07-23 16:27:02.137 E/AndroidRuntime(31007): ... 11 more
07-23 16:27:02.167 W/ActivityManager( 390): Force finishing activity com.myapp/.MainActivity
崩潰發生在mPanels = (Panel[]) inState.getParcelableArray("panelParcel");
在下面的onRestoreInstanceState方法中。
這種方法對我來說非常有效,直到這次崩潰,我想弄清楚為什么inState似乎沒有我保存在其中的對象數組(Panels)。 我很困惑,因為看起來inState並沒有包含我保存到它的panelParcel。
我從這個問題看,我通常應該使用onCreate
而不是onRestoreInstanceState
,但是我很想知道為什么這種情況在極少數情況下不起作用,也許我對活動生命周期沒有完全理解?
保存和還原實例狀態的代碼:
@Override
public void onSaveInstanceState(@NotNull Bundle outState)
{
Log.d("panelCreation", "onSaveInstanceState Called");
super.onSaveInstanceState(outState);
// save the current panel state
outState.putParcelableArray("panelParcel", mPanels);
}
@Override
public void onRestoreInstanceState(Bundle inState)
{
Log.d("panelCreation", "onsState Called");
super.onRestoreInstanceState(inState);
// Note getParcelable returns a *new* array, so we must setup the drawer listener after this
mPanels = (Panel[]) inState.getParcelableArray("panelParcel");
// set up the drawer's list view with items and click listener
mDrawerList.setAdapter(new PanelArrayAdapter(this,
R.layout.drawer_list_item, mPanels));
refreshDrawerListChecked();
// Forces the Adapter to redraw the view to ensure color stylings are applied
((PanelArrayAdapter)mDrawerList.getAdapter()).notifyDataSetChanged();
}
你不能將Parcelable
數組轉換為Panel
數組。
有關theSaveInstanceState()和onRestoreInstanceState()的更多信息,請查看這篇文章。
“onRestoreInstanceState()僅在被OS殺死后重新創建活動時被調用”
並從文件:
大多數實現只是使用onCreate(Bundle)來恢復它們的狀態,但有時在完成所有初始化之后在此處執行它或者允許子類決定是否使用默認實現。 此方法的默認實現執行先前已被onSaveInstanceState(Bundle)凍結的任何視圖狀態的恢復。
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