通过以下部分代码,我们可以了解清楚Activity页面在横,竖屏切换时,生命周期的变化:
public class AndroidLifecycle extends Activity { public void onCreate(Bundle savedInstanceState) { System.out.println("First Activity =======onCreate()========"); super.onCreate(savedInstanceState); setContentView(R.layout.main); } @Override protected void onSaveInstanceState(Bundle outState) { System.out .println("First Activity =======onSaveInstanceState()========"); super.onSaveInstanceState(outState); } @Override protected void onRestoreInstanceState(Bundle outState) { System.out .println("First Activity =======onRestoreInstanceState()========"); super.onRestoreInstanceState(outState); } @Override public void onConfigurationChanged(Configuration newConfig) { System.out .println("First Activity =======onConfigurationChanged()========"); super.onConfigurationChanged(newConfig); } // Called after onCreate — or after onRestart when the activity had been // stopped, but is now again being displayed to the user. It will be // followed by onResume protected void onStart() { System.out.println("First Activity =======onStart()========"); super.onStart(); } // Called after onRestoreInstanceState, onRestart, or onPause, for your // activity to start interacting with the user protected void onResume() { System.out.println("First Activity =======onResume()========"); super.onResume(); } // Called as part of the activity lifecycle when an activity is going into // the background, but has not (yet) been killed protected void onPause() { System.out.println("First Activity =======onPause()========"); super.onPause(); } // Called when you are no longer visible to the user. You will next receive // either onRestart, onDestroy, or nothing, depending on later user // activity. protected void onStop() { System.out.println("First Activity =======onStop()========"); super.onStop(); } // Perform any final cleanup before an activity is destroyed protected void onDestroy() { System.out.println("First Activity =======onDestroy()========"); super.onDestroy(); } // Called after onStop when the current activity is being re-displayed to // the user (the user has navigated back to it). It will be followed by // onStart and then onResume protected void onRestart() { System.out.println("First Activity =======onRestart()========"); super.onRestart(); } }
<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="cn.d" android:versionCode="1" android:versionName="1.0"> <!-- android:configChanges="orientation" --> <application android:icon="@drawable/icon" android:label="@string/app_name"> <activity android:name=".AndroidLifecycle" android:label="@string/app_name" android:configChanges="orientation|keyboardHidden"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest>
1、新建一个Activity,并把各个生命周期打印出来
2、运行Activity,得到如下信息
10-23 02:35:54.261: INFO/chenys(4385): onCreate-->
10-23 02:35:54.271: INFO/chenys(4385): onStart-->
10-23 02:35:54.286: INFO/chenys(4385): onResume-->
3、按crtl+f12切换成横屏时
10-23 02:36:58.331: INFO/chenys(4385): onSaveInstanceState-->
10-23 02:36:58.411: INFO/chenys(4385): onPause-->
10-23 02:36:58.462: INFO/chenys(4385): onStop-->
10-23 02:36:58.481: INFO/chenys(4385): onDestroy-->
10-23 02:36:58.572: INFO/chenys(4385): onCreate-->
10-23 02:36:58.622: INFO/chenys(4385): onStart-->
10-23 02:36:58.632: INFO/chenys(4385): onRestoreInstanceState-->
10-23 02:36:58.642: INFO/chenys(4385): onResume-->
4、再按crtl+f12切换成竖屏时,发现打印了两次相同的log
10-23 02:38:14.172: INFO/chenys(4385): onSaveInstanceState-->
10-23 02:38:14.172: INFO/chenys(4385): onPause-->
10-23 02:38:14.172: INFO/chenys(4385): onStop-->
10-23 02:38:14.172: INFO/chenys(4385): onDestroy-->
10-23 02:38:14.281: INFO/chenys(4385): onCreate-->
10-23 02:38:14.301: INFO/chenys(4385): onStart-->
10-23 02:38:14.312: INFO/chenys(4385): onRestoreInstanceState-->
10-23 02:38:14.331: INFO/chenys(4385): onResume-->
10-23 02:38:14.812: INFO/chenys(4385): onSaveInstanceState-->
10-23 02:38:14.852: INFO/chenys(4385): onPause-->
10-23 02:38:14.861: INFO/chenys(4385): onStop-->
10-23 02:38:14.892: INFO/chenys(4385): onDestroy-->
10-23 02:38:14.921: INFO/chenys(4385): onCreate-->
10-23 02:38:15.021: INFO/chenys(4385): onStart-->
10-23 02:38:15.031: INFO/chenys(4385): onRestoreInstanceState-->
10-23 02:38:15.111: INFO/chenys(4385): onResume-->
5、修改AndroidManifest.xml,把该Activity添加 android:configChanges="orientation",执行步骤3
10-23 02:42:32.201: INFO/chenys(4875): onSaveInstanceState-->
10-23 02:42:32.232: INFO/chenys(4875): onPause-->
10-23 02:42:32.301: INFO/chenys(4875): onStop-->
10-23 02:42:32.311: INFO/chenys(4875): onDestroy-->
10-23 02:42:32.402: INFO/chenys(4875): onCreate-->
10-23 02:42:32.471: INFO/chenys(4875): onStart-->
10-23 02:42:32.471: INFO/chenys(4875): onRestoreInstanceState-->
10-23 02:42:32.481: INFO/chenys(4875): onResume-->
6、再执行步骤4,发现不会再打印相同信息,但多打印了一行onConfigChanged
10-23 02:44:41.151: INFO/chenys(4875): onSaveInstanceState-->
10-23 02:44:41.151: INFO/chenys(4875): onPause-->
10-23 02:44:41.151: INFO/chenys(4875): onStop-->
10-23 02:44:41.151: INFO/chenys(4875): onDestroy-->
10-23 02:44:41.371: INFO/chenys(4875): onCreate-->
10-23 02:44:41.421: INFO/chenys(4875): onStart-->
10-23 02:44:41.521: INFO/chenys(4875): onRestoreInstanceState-->
10-23 02:44:41.541: INFO/chenys(4875): onResume-->
10-23 02:44:42.002: INFO/chenys(4875): onConfigurationChanged-->1
7、把步骤5的android:configChanges="orientation" 改成 android:configChanges="orientation|keyboardHidden",执行步骤3,就只打印onConfigChanged
10-23 02:46:43.762: INFO/chenys(5193): onConfigurationChanged-->2
8、执行步骤4
10-23 02:47:27.652: INFO/chenys(5193): onConfigurationChanged-->2
10-23 02:47:27.902: INFO/chenys(5193): onConfigurationChanged-->1
总结:
1、不设置Activity的android:configChanges时,切屏会重新调用各个生命周期,切横屏时会执行一次,切竖屏时会执行两次
2、设置Activity的android:configChanges="orientation"时,切屏还是会重新调用各个生命周期,切横、竖屏时只会执行一次
3、设置Activity的android:configChanges="orientation|keyboardHidden"时,切屏不会重新调用各个生命周期,只会执行onConfigurationChanged方法