調用BroadcastReceiver中的主要活動方法

Question

我想在新的特定短信出現時顯示從我的應用生成的通知。 所以通知生成方法是我的主要活動。當新的收入消息到來時，我必須生成通知。 這是我的BroadcastReceiver類。

public class BroadCastReceiver extends BroadcastReceiver {//私有AudioManager myAudioManager;

public MainActivity mainactivity = null;

public BroadCastReceiver() { 
} 

public void setMainactivityHandler(MainActivity mainn){ 
    this.mainactivity = mainn; 
} 



@Override 
public void onReceive(Context context, Intent intent) { 



    if(intent.getAction().equals("android.provider.Telephony.SMS_RECEIVED")) 
    { 
     Toast.makeText(context, "SMS_RECEIVED", Toast.LENGTH_LONG).show(); 
     System.out.println("received sms"); 

     Bundle bundle = intent.getExtras(); 
     if (bundle != null) { 
      Log.i("cs.fsu", "smsReceiver : Reading Bundle"); 

      Object[] pdus = (Object[])bundle.get("pdus"); 
      SmsMessage sms = SmsMessage.createFromPdu((byte[])pdus[0]); 

      if(sms.getMessageBody().contains("aa")) { 
       abortBroadcast(); 
       System.out.println("received correct"); 
       Log.e("tag", "corecttttttttttttttttttttttttttttttttttttttttttt"); 
       Toast toast = Toast.makeText(context, "BLOCKED Received SMS: ", Toast.LENGTH_LONG); 
       toast.show(); 
       mainactivity.showNotification(); 
       abortBroadcast(); 






      }} 
    } 


} 

}

這是我的主要活動

public class MainActivity extends Activity { 

public BroadCastReceiver Br = null; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 

    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    Br = new BroadCastReceiver(); 
    Br.setMainactivityHandler(this); 
    IntentFilter callInterceptorIntentFilter = new IntentFilter("android.provider.Telephony.SMS_RECEIVED"); 
    registerReceiver(Br, callInterceptorIntentFilter); 


    // listener handler 
    View.OnClickListener handler = new View.OnClickListener(){ 
     public void onClick(View v) { 

      switch (v.getId()) { 

       case R.id.btnShowNotification: 
        showNotification(); 
        break; 

       case R.id.btnCancelNotification: 
        cancelNotification(0); 
        break; 
      } 
     } 
    }; 

    // we will set the listeners 
    findViewById(R.id.btnShowNotification).setOnClickListener(handler); 
    findViewById(R.id.btnCancelNotification).setOnClickListener(handler); 

} 


public void showNotification(){ 

    Log.e("","show notification"); 
    // define sound URI, the sound to be played when there's a notification 
    Uri soundUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION); 

    // intent triggered, you can add other intent for other actions 
    Intent intent = new Intent(MainActivity.this, NotificationReceiver.class); 
    PendingIntent pIntent = PendingIntent.getActivity(MainActivity.this, 0, intent, 0); 

    // this is it, we'll build the notification! 
    // in the addAction method, if you don't want any icon, just set the first param to 0 
    Notification mNotification = new Notification.Builder(this) 

      .setContentTitle("New Post!") 
      .setContentText("Here's an awesome update for you!") 
      .setSmallIcon(R.drawable.ic_launcher) 
      .setContentIntent(pIntent) 
      .setSound(soundUri) 

      .addAction(R.drawable.ic_launcher, "View", pIntent) 
      .addAction(0, "Remind", pIntent) 

      .build(); 

    NotificationManager notificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE); 

    // If you want to hide the notification after it was selected, do the code below 
    // myNotification.flags |= Notification.FLAG_AUTO_CANCEL; 

    notificationManager.notify(0, mNotification); 
} 

public void cancelNotification(int notificationId){ 

    if (Context.NOTIFICATION_SERVICE!=null) { 
     String ns = Context.NOTIFICATION_SERVICE; 
     NotificationManager nMgr = (NotificationManager) getApplicationContext().getSystemService(ns); 
     nMgr.cancel(notificationId); 
    } 
} 

}

當新的消息來它給這個錯誤

07-29 22:06:59.227 23021-23021/com.example.siluni.myapplication E/tag﹕ corecttttttttttttttttttttttttttttttttttttttttttt 

07-29 22：06：59.267 23021-23021/com.example.siluni.myapplication d/AndroidRuntime：關閉VM 07-29 22：06：59.277 23021-23021/com。示例。 siluni.myapplication E/AndroidRuntime：致命例外：main 進程：com.example.siluni.myapplication，PID：23021 java.lang.RuntimeException：無法啓動接收方com.example.siluni.myapplication.BroadCastReceiver：java.lang。 NullPointerException：嘗試調用空對象的虛方法'void com.example.siluni.myapplication.MainActivity.showNotification（）'參考

Answer 1

這是因爲當您的廣播接收機執行您的MainAc tivity的方法，那麼你的活動可能不會運行或甚至沒有開始，所以會出現這種問題。

如何解決：

1. 創建一個全局類。
2. 使您的showNotification方法公共靜態那裏，如果你想然後傳遞上下文。 3.從廣播接收機的主要活動中調用它。

如果您無法創建靜態方法，那麼只需創建該全局類的對象，然後使用object調用該方法。

告訴我，如果您在實施時遇到任何問題。