How to change TextView txtView in MainActivity from class FirebaseMessagingService

Question

I have made research but without success. Could anybody give me help how to change TextView txtView in MainActivity from class FirebaseMessagingService. The program seem to be without error, but after Firebase console the application is imidiatelly closed (destroyd) by txt.setText(a);

MainActivity.java :

package com.islk.gcmexample;

import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import com.google.firebase.iid.FirebaseInstanceId;
import java.util.ArrayList;
import java.util.Arrays;

public class MainActivity extends AppCompatActivity {
    ListView listView ;
    ArrayAdapter<String> adapter;
    ArrayList<String> arrayList;
    public static Context contextA;
    private static final String TAG = "MainActivity";

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

        TextView txtView = (TextView) findViewById(R.id.textView);
        txtView.setText("Hello i1");

        listView = (ListView) findViewById(R.id.list);
        String[] values = new String[] { "Android List View",
            "Adapter implementation",
            "Simple List View In Android",
            "Create List View Android",
            "Android Example",
            "List View Source Code",
            "List View Array Adapter",
            "Android Example List View"
        };

        arrayList = new ArrayList<>(Arrays.asList(values));
        adapter = new ArrayAdapter<String>(this,
            android.R.layout.simple_list_item_1, android.R.id.text1, arrayList);
        listView.setAdapter(adapter);
        arrayList.add("iSLK");
        adapter.notifyDataSetChanged();

        setNotificationData(getIntent().getExtras());

        Utils.showToast(MainActivity.this, "FB: hello");

        Button btnShowToken = (Button) findViewById(R.id.button_show_token);
        btnShowToken.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String token = FirebaseInstanceId.getInstance().getToken();
                Log.d(TAG, "Token: " + token);
                listView.setAdapter(null);
                Toast.makeText(MainActivity.this, token, Toast.LENGTH_SHORT).show();
                jano();
            }
        });

    }

    private void jano(){
        TextView txtView = (TextView) findViewById(R.id.textView);
        txtView.setText("Hello i2");
    }





}

FirebaseMessagingService.java :

package com.islk.gcmexample;

import android.app.Activity;
import android.util.Log;
import android.widget.TextView;
import com.google.firebase.messaging.RemoteMessage;
import static com.islk.gcmexample.MainActivity.contextA;

public class FirebaseMessagingService extends com.google.firebase.messaging.FirebaseMessagingService{
    private static final String TAG = "MyFirebaseMsgService";

    TextView txt = (TextView) ((Activity)contextA).findViewById(R.id.textView);

    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {

        Log.d(TAG, "FB: From: " + remoteMessage.getFrom());
        sendNotification(remoteMessage);

        if (remoteMessage.getData().size() > 0) {
            Log.d(TAG, "FB: Message data payload: " + remoteMessage.getData());

            if (/* Check if data needs to be processed by long running job */ true) {

            } else {

            }

        }

        // Check if message contains a notification payload.
        if (remoteMessage.getNotification() != null) {
            Log.d(TAG, "FB: Message Notification Body: " + remoteMessage.getNotification().getBody());
        }
    }

    private void sendNotification(RemoteMessage remoteMessage) {
        setTextViewToModify("Hello i3");
    }

    public void setTextViewToModify (String a){
        txt.setText(a);

    }
}

MyFirebaseInstanceIDService.java :

package com.islk.gcmexample;

import android.util.Log;

import com.google.firebase.iid.FirebaseInstanceId;
import com.google.firebase.iid.FirebaseInstanceIdService;

public class MyFirebaseInstanceIDService extends FirebaseInstanceIdService {

    private static final  String TAG = "MyFirebaseInsIDService";

    @Override
    public void onTokenRefresh() {
        //Get update token
        String refreshedToken = FirebaseInstanceId.getInstance().getToken();
        Log.d(TAG, "New Token :" + refreshedToken);

        //sendRegistrationToServer(refreshedToken);


        // You can save the token into third party server to do anything you want
    }
}

activity_main.xml :

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/button_show_token"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Token and Clear Alarms EVENTS"
        tools:layout_editor_absoluteX="16dp"
        tools:layout_editor_absoluteY="2dp" />

    <ListView
        android:id="@+id/list"
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        tools:layout_editor_absoluteX="16dp"
        tools:layout_editor_absoluteY="50dp" >
    </ListView>

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginRight="8dp"
        android:text="TextView"
        app:layout_constraintEnd_toEndOf="parent"
        tools:layout_editor_absoluteY="16dp" />


</android.support.constraint.ConstraintLayout>

Thank you in advance.

Answer 1

You can use LocalBroadcastManager for sending any value from service to the main activity.

Intent intent = new Intent("filter_string");
   intent.putExtra("key", "My Data");
   // put your all data using put extra 

   LocalBroadcastManager.getInstance(this).sendBroadcast(intent);

And in your MainActivity

@Override
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);

      LocalBroadcastManager lbm = LocalBroadcastManager.getInstance(this);
      lbm.registerReceiver(receiver, new IntentFilter("filter_string"));
  }

  public BroadcastReceiver receiver = new BroadcastReceiver() {
      @Override
      public void onReceive(Context context, Intent intent) {
          if (intent != null) {
              String str = intent.getStringExtra("key");

          }
      }
  };

Hopefully this will solve your problem.