虽然在onCreate()
中传递了null
,即super.onCreate(null);
,但在屏幕旋转后,我仍然遇到LinearLayout
对象返回的空指针异常。
我知道Activity必须被销毁并重新创建,在旋转时,我传递了null
,这意味着Activity应该像第一次启动时一样开始。为什么我在旋转后会遇到此异常?
在onCreate()
中调用LinearLayout
对象historyText的片段
LinearLayout historyText ; // this return exception if it used after rotation .
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(null);
setContentView(R.layout.activity_main);
historyText = (LinearLayout) findViewById(R.id.historyLayoutText);
Log.e("HISTORYVISIBILITY", "VISIBILITY = "+historyText.getVisibility());
getWindow().getDecorView().setSystemUiVisibility(
View.SYSTEM_UI_FLAG_LAYOUT_STABLE
| View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN);
database = new Database(this);
Bundle extras = getIntent().getExtras();
intent = extras.getInt("activity");
p = new Progress();
getSupportFragmentManager().beginTransaction()
.add(R.id.group, p)
.commit();
orientation = getRotation();
switch (orientation){
case "p" :
addPlus();
}
}
Logcat
10-07 22:21:24.365: E/AndroidRuntime(7768): FATAL EXCEPTION: main
10-07 22:21:24.365: E/AndroidRuntime(7768): Process: developer.mohab.gymee, PID: 7768
10-07 22:21:24.365: E/AndroidRuntime(7768): java.lang.RuntimeException: Unable to start activity ComponentInfo{developer.mohab.gymee/developer.mohab.gymee.Cardio.Cardio}: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.widget.LinearLayout.getVisibility()' on a null object reference
10-07 22:21:24.365: E/AndroidRuntime(7768): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2379)
10-07 22:21:24.365: E/AndroidRuntime(7768): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2442)
10-07 22:21:24.365: E/AndroidRuntime(7768): at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:4053)
10-07 22:21:24.365: E/AndroidRuntime(7768): at android.app.ActivityThread.access$900(ActivityThread.java:156)
10-07 22:21:24.365: E/AndroidRuntime(7768): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1357)
10-07 22:21:24.365: E/AndroidRuntime(7768): at android.os.Handler.dispatchMessage(Handler.java:102)
10-07 22:21:24.365: E/AndroidRuntime(7768): at android.os.Looper.loop(Looper.java:211)
10-07 22:21:24.365: E/AndroidRuntime(7768): at android.app.ActivityThread.main(ActivityThread.java:5389)
10-07 22:21:24.365: E/AndroidRuntime(7768): at java.lang.reflect.Method.invoke(Native Method)
10-07 22:21:24.365: E/AndroidRuntime(7768): at java.lang.reflect.Method.invoke(Method.java:372)
10-07 22:21:24.365: E/AndroidRuntime(7768): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1020)
10-07 22:21:24.365: E/AndroidRuntime(7768): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:815)
10-07 22:21:24.365: E/AndroidRuntime(7768): Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.widget.LinearLayout.getVisibility()' on a null object reference
10-07 22:21:24.365: E/AndroidRuntime(7768): at developer.mohab.gymee.Cardio.Cardio.onCreate(Cardio.java:76)
10-07 22:21:24.365: E/AndroidRuntime(7768): at android.app.Activity.performCreate(Activity.java:5990)
10-07 22:21:24.365: E/AndroidRuntime(7768): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
10-07 22:21:24.365: E/AndroidRuntime(7768): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2332)
10-07 22:21:24.365: E/AndroidRuntime(7768): ... 11 more
10-07 22:21:24.633: E/SurfaceFlinger(319): rejecting buffer: bufWidth=1358, bufHeight=624, front.active.{w=193, h=193}
at developer.mohab.gymee.Cardio.Cardio.onCreate(Cardio.java:76)
这可能是日志行... 到目前为止,这看起来是"正确的",但也请展示一下您的 onpause/onresume。此外,您在哪里运行此代码?请检查 onDestroy 是否正在收集变量,或者它是否仍然存在。 - BonattionDestroy
、onStop
和最有可能发生这种情况的onPause
……此外,尽可能多地添加有关您问题的信息。编辑它,并写下:设备(品牌,操作系统版本,构建版本),集成开发环境(我猜是Android Studio),任何可能帮助我们帮助您的东西。 - Bonatti