Android : Can't receive NEW_OUTGOING_CALL when my application is not in background

when my application runs, I can get the receiver in OutcallReceiver , but when my application didn't run, I can't get the receiver, I want to know why I can not get the receiver when Application isn't in background.

However, when I use android.intent.action.BOOT_COMPLETED ,I can got the receiver,even though the application is not in background, so my question is : What 's the difference between android.intent.action.BOOT_COMPLETED And android.intent.action.NEW_OUTGOING_CALL ? they are both sent by android system. BOOT_COMPLETED can get the receiver even though my application is not in background.

1. AndroidManifest.xml
   <receiver android:name=".ui.guide.OutcallReceiver" android:exported="true" > 
            <intent-filter android:priority="2147483647" >
                <action android:name="android.intent.action.NEW_OUTGOING_CALL" />
            </intent-filter>
   </receiver>
<uses-permission android:name="android.permission.PROCESS_OUTGOING_CALLS"/>

2. 
   

   OutcallReceiver .java

   
   

   public class OutcallReceiver extends BroadcastReceiver {

   
   

   
   @Override
   public void onReceive(Context context, Intent intent) {
       String currentNumber = getResultData();
       if (currentNumber == null) {
           currentNumber = intent.getStringExtra(Intent.EXTRA_PHONE_NUMBER);
       }
       SharedPreferences preference = PreferenceManager.getDefaultSharedPreferences(context);
       String number = preference.getString(Constants.PRIVACY_DIAL_PHONE_NUMBER, "");
       if (currentNumber.equals(number)) {
           lockscreenApp(context);
           setResultData(null);
           abortBroadcast();
       }
   }
   
   

   
   

   }