我有一個綁定的服務類Timer
。其中我想發起一個新的更新通知的CountDownTimer
。調用getSystemService();在CountDownTimer構造函數中給出NPE
如果我嘗試將Intent
,PendingIntent
和NotificationManager
的聲明移至onTick()
方法主體之外,則會發生異常。如果它們在onTick()
方法中聲明和實例化,則它工作正常。 任何人都可以幫助我理解爲什麼會出現這種情況,以及我如何解決它?在每個蜱工作過程中創建這些對象似乎是浪費資源。
private CountDownTimer newDownTimer() {
return new CountDownTimer(millisInFuture, countDownInterval) {
NotificationManager mNotificationManager =
(NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
Intent notificationIntent = new Intent(getApplicationContext(), com.kush.app.stayput.MainActivity.class);
PendingIntent pendingIntent = PendingIntent.getActivity(getApplicationContext(), 0, notificationIntent, PendingIntent.FLAG_UPDATE_CURRENT);
public void onTick(long millisUntilFinished) {
//Do something in every tick
if (isPaused || isCanceled) {
//If user requested to pause or cancel the count down timer
cancel();
} else {
tView.setText("TEXT");
//Put count down timer remaining time in a variable
timeRemaining = millisUntilFinished;
//Update notification
NotificationCompat.Builder mNotifyBuilder = new NotificationCompat.Builder(MainActivity.getContext())
.setContentTitle(getText(R.string.notification_title))
.setContentIntent(pendingIntent)
.setContentText("TEXT")
.setSmallIcon(R.drawable.ic_stat_name);
mNotificationManager.notify(NOTIFICATION_ID, mNotifyBuilder.build());
}
}
public void onFinish() {
//Do something when count down finished
timer = newUpTimer();
}
}.start();
}
FATAL EXCEPTION: main
Process: com.example.kush.com.kush.app.stayput, PID: 16993
java.lang.RuntimeException: Unable to instantiate service com.kush.app.stayput.countdown.Timer: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object android.content.Context.getSystemService(java.lang.String)' on a null object reference
at android.app.ActivityThread.handleCreateService(ActivityThread.java:2862)
at android.app.ActivityThread.-wrap4(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1427)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object android.content.Context.getSystemService(java.lang.String)' on a null object reference
at android.content.ContextWrapper.getSystemService(ContextWrapper.java:627)
at com.kush.app.stayput.countdown.Timer$1.<init>(Timer.java:156)
at com.kush.app.stayput.countdown.Timer.newDownTimer(Timer.java:153)
at com.kush.app.stayput.countdown.Timer.reset(Timer.java:147)
at com.kush.app.stayput.countdown.Timer.<init>(Timer.java:85)
at java.lang.Class.newInstance(Native Method)
at android.app.ActivityThread.handleCreateService(ActivityThread.java:2859)
at android.app.ActivityThread.-wrap4(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1427)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
這看起來像一個lifecylce bug.Context尚不存在。你有可能在一個構造函數中創建CountDownTimer?或者在調用Activty.onCreate()之前的其他地方? – muetzenflo
只有一個活動存在,MainActivity.class。它存在,因爲它是從服務啓動相同的上下文。在返回CountDownTimer中也沒有代碼;無論如何,調用該設置環境。 – KUSH42
嘗試使用:'this.getSystemService' – rafsanahmad007