Here I am creating an online application that depends only on Internet.

So whenever there is a network error it must notify user. For that, I have created a BroadcastReciver that receives call when network connection gets lost(Internet).

All this works perfectly. Now what I need is that I have to call a method of Activity from this Broadcast Receiver, where I have created an Alert Dialogue.

I have read many answers on stack-overflow.com that I can declare that method static and call by using only Activity name,

e.g MyActivityName.myMethod()

But I can't declare my method static, because I am using Alert Dialogue there and it shows me error on line,

AlertDialog.Builder alertDialog = new AlertDialog.Builder(this);

that Cannot use this in a static context.

So, how can I call a method of Activity(must not static and without starting that activity) from a Broadcast Receiver ?

And can I get Activity(or fragment) name from Broadcast Receiver which is currently running?

Vijju

try this code :

your broadcastreceiver class for internet lost class :

public class InternetLostReceiver extends BroadcastReceiver{
@Override
public void onReceive(Context context, Intent intent) {
    context.sendBroadcast(new Intent("INTERNET_LOST"));
}
}

in your activity add this for calling broadcast:

public class TestActivity  extends Activity{

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    registerReceiver(broadcastReceiver, new IntentFilter("INTERNET_LOST"));
}

BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        // internet lost alert dialog method call from here...
    }
};

@Override
protected void onDestroy() {
    super.onDestroy();
    unregisterReceiver(broadcastReceiver);
}
}

Add a boolean variable in you activity from where you are open alertdialog

boolean isDialogOpened = false;

// in broadcast recever check 
if(isDialogOpened) {
    alertDialog();
}

And replace your code for alertdialog with this one

public void alertDialog() {
    AlertDialog.Builder alertDialog = new AlertDialog.Builder(this);

    alertDialog.setMessage("Network not found.");
    alertDialog.setPositiveButton("Check Setting",
            new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int which) {
                }
            });
    alertDialog.setNegativeButton("Cancel",
            new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int which) {
                }
            });

    alertDialog.setOnDismissListener(new OnDismissListener() {
        @Override
        public void onDismiss(DialogInterface dialog) {
            isDialogOpened = false;
        }
    });

    alertDialog.setOnCancelListener(new OnCancelListener() {
        @Override
        public void onCancel(DialogInterface dialog) {
            isDialogOpened = false;
        }
    });

    alertDialog.show();
}

INTERFACE: Keep BroadCastReceiver and Activity code separate!

You can make a CallBackListener interface. The interface will work as a bridge between BroadcastReceiver and Activity.

1) Create a CallbackListener

interface ConnectionLostCallback{

      public void connectionLost();

}

2) Provide ConnectionLostCallback in your BroadcastReceiver

public class MyBroadcastReceiver extends BroadcastReceiver{

     private ConnectionLostCallback listener;

     public MyBroadcastReceiver(ConnectionLostCallback listener ){

           this.listener = listener     //<-- Initialze it

     }

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

           listener.connectionLost();

     }
}

3) Implement the ConnectionLostCallback in your Activity and override the method

YourActvity extends AppcompatActivity implements ConnectionLostCallback{

    // Your Activity related code //
      //    new MyBroadcastReceiver(this);  <-- create instance

    private void showAlertMessage(){
       AlertDialog.Builder alertDialog = new AlertDialog.Builder(this);
    } 


    @Override 
    public void connectionLost(){

         showAlertMessage();          //<--- Call the method to shoe alert dialog

    }


}

Relevant link:

If you want to know how to make a BroadcastReceiver independent of any activity ie How can you reuse the same BroadCastReceiver with different Activities? Then READ THIS

Pass your Activity's context to BroadcastReceiver's contructor.

public class ResponseReceiver extends BroadcastReceiver{

    MainActivity ma; //a reference to activity's context

    public ResponseReceiver(MainActivity maContext){
        ma=maContext;
    }

    @Override
    public void onReceive(Context context, Intent intent) {
        ma.brCallback("your string"); //calling activity method
    }

}

and in your MainActivity

public class MainActivity extends AppCompatActivity {
    ...
    public void onStart(){
        ...        
    ResponseReceiver responseReceiver = new ResponseReceiver(this); //passing context
    LocalBroadcastManager.getInstance(this).registerReceiver(responseReceiver,null);
        ...
    }

    public void brCallback(String param){
        Log.d("BroadcastReceiver",param);
    }
}

hope it helps

Same as Vijju' s answer but using Local Broadcasts instead

public class SampleReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        Intent intentToBroadcast =  new Intent("YOUR_ACTION_HERE");
        LocalBroadcastManager.getInstance(context).sendBroadcast(intentToBroadcast);
    }
}

In your activity add this

public class SampleActivity extends Activity {

    @Override
    protected void onResume() {
        super.onResume();
        LocalBroadcastManager.getInstance(this).registerReceiver(mSampleReceiver, new IntentFilter(YOUR_ACTION_HERE));
    }

    @Override
    protected void onPause() {
        LocalBroadcastManager.getInstance(this).unregisterReceiver(mSampleReceiver);
        super.onPause();
    }

    private SampleReceiver mSampleReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            // your code here
        }
    };
}

Note Move the register/unregister calls to onCreate/onDestroy is you want to be notified even when your activity is in the background.

来源：https://stackoverflow.com/questions/22241705/calling-a-activity-method-from-broadcastreceiver-in-android

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