我有两个活动(MainActivity和Player)。在MainActivity中,我创建了两种方法:如何在android中获取getSharedPreferences?
private final long DEFAULTLONG = 0;
public long getTotalPlayTime(){
SharedPreferences sp = getApplicationContext().getSharedPreferences("TotalPlaybackTime", MODE_PRIVATE);
long tempTotalTime = sp.getLong("totalPlayTime", DEFAULTLONG);
return tempTotalTime;
}
public void updateTotalPlayTime(){
SharedPreferences sp = getSharedPreferences("TotalPlaybackTime", Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sp.edit();
editor.putLong("totalPlayTime", totalPlayTime);
editor.commit();
}
当我从Player活动调用这两种方法时,我的应用程序崩溃。 我已经实例化球员在MainActivity并呼吁通过这条线的方法:
if (preferenceScheduler++ == 10) {
f.updateTotalPlayTime();
seconds2 = (f.getTotalPlayTime()) % 60;
minutes2 = ((f.getTotalPlayTime() - seconds2))/60;
}
我不知道为什么,它给我的NullPointerException。
以下是完整的错误日志:
java.lang.NullPointerException
at android.content.ContextWrapper.getSharedPreferences(ContextWrapper.java:161)
at tushar.prime.primeplayer.MainActivity.updateTotalPlayTime(MainActivity.java:329)
at tushar.prime.primeplayer.player.update(player.java:506)
at tushar.prime.primeplayer.player.access$000(player.java:40)
at tushar.prime.primeplayer.player$1.run(player.java:133)
at android.os.Handler.handleCallback(Handler.java:725)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:153)
at android.app.ActivityThread.main(ActivityThread.java:5297)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
at dalvik.system.NativeStart.main(Native Method)
发布调用'updateTotalPlayTime()'的代码 - 你可能在那里实例化了一个有'new'的活动(你不应该)。 – laalto 2015-02-09 12:39:36
是的你是对的。我已经在Player中实例化了MainActivity:'private static MainActivity f = new MainActivity();' – Tushar 2015-02-09 12:43:49
也许你在super.onCreate()方法之前调用updateTotalPlayTime,在super.onCreate()之后调用,否则你可以使用application context.getSharedPreferences () – 2015-02-09 12:50:10