在廣播接收機中的上下文android

Question

我想在我的應用程序中偵聽傳入呼叫，所以我創建了一個相同的廣播接收器，但是當我在傳遞中傳遞上下文時，它顯示一個錯誤。任何人都可以判斷我做錯了什麼？ 這裏是我的代碼：

public class MainActivity extends BroadcastReceiver { 

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

     TelephonyManager tmngr= (TelephonyManager)context.getSystemService(Context.TELEPHONY_SERVICE); 
     MyPhoneStateListener PhoneListener = new MyPhoneStateListener(); 
     tmngr.listen(PhoneListener,PhoneStateListener.LISTEN_CALL_STATE); 
    } 

    private class MyPhoneStateListener extends PhoneStateListener { 
     public void onCallStateChanged(int state,String incoming) 
     { 
      if (state == 1) { 

       String msg = "New Phone Call Event. Incomming Number : "+incoming; 
       int duration = Toast.LENGTH_LONG; 
       //i am getting error here(context) 
       Toast toast = Toast.makeText(context, msg, duration); 
       toast.show(); 
     } 
    }}} 

Answer 1

這是我做了什麼（以及感謝@egor）雖然花了一些時間來了解。這裏是代碼：

public class MainActivity extends BroadcastReceiver { 

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

     TelephonyManager tmngr= (TelephonyManager)context.getSystemService(Context.TELEPHONY_SERVICE); 
     //referencing the context   
     pcontext=context; 
     //passing it to phonelistener   
     MyPhoneStateListener PhoneListener = new 
     MyPhoneStateListener(pcontext); 
      tmngr.listen(PhoneListener,PhoneStateListener.LISTEN_CALL_STATE); 


     } 

     private class MyPhoneStateListener extends PhoneStateListener { 


      public MyPhoneStateListener(Context pcontext) { 

      } 

      public void onCallStateChanged(int state,String incoming) 
      { 
       if (state == 1) { 

        String msg = "New Phone Call Event. Incomming Number : "+incoming; 
        int duration = Toast.LENGTH_LONG; 
        // Context pcontext; 
        Toast toast; 
        toast = Toast.makeText(pcontext, msg, duration); 
        toast.show(); 
      } 
     } 
    } 
    } 

Answer 2

您可以使用MainActivityContext實例。因爲Activity類延伸（間接）Context。這種替換您Toast行：

Toast toast = Toast.makeText(MainActivity.this, msg, duration);