如何在 BroadcastReceiver 中访问 MainActivity 的对象或方法？

Question

I'm creating an android app that uses AlarmManager to create an alarm by playing a sound. To do this, I first create a PendingIntent, for which I have to create a class called AlarmReceiver , which extends BroadcastReceiver . In this new class, I override the onReceive method, in which I also start the sound. What I have right now works. However, as part of a bigger project, I will be later getting some data from a database. Regarding my question, this data is not important; what's important is that, after analyzing all the data, it will all come down to a boolean variable, which will be true or false. This variable will be in MainActivity and I want to access it in my BroadcastReceiver class to check it and if true, I would stop the music. I've checked many SO questions related to these, but I still haven't found a solution.

The code for the MainActivity is:

package com.example.alarmsound;

public class MainActivity extends AppCompatActivity {

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

    Calendar t = Calendar.getInstance();
    t.add(Calendar.SECOND, 5);

    Context context = this;
    AlarmManager alarmMgr;
    alarmMgr = (AlarmManager)getSystemService(Context.ALARM_SERVICE);
    Intent intent = new Intent(this, AlarmReceiver.class);
    PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
    alarmMgr.set(AlarmManager.RTC_WAKEUP, t.getTimeInMillis(), pendingIntent);
    boolean result; //the variable I want to access to BroadcastReceiver class
}
}

And the code for the BroadcastReceiver class is:

public class AlarmReceiver extends BroadcastReceiver{
public AlarmReceiver() {}

@Override
public void onReceive(Context context, Intent intent) {
    final MediaPlayer mp = MediaPlayer.create(context, R.raw.music);
    Log.d("Music", "It went here.");
    mp.start();

    //here, I want to access result
}
}

I would really appreciate any help.

Answer 1

In MainActivity:

Intent intent = new Intent(this, AlarmReceiver.class);
intent.putExtra("some_constant", result);

In your broadcast receiver:

boolean result = intent.getBooleanExtra("some_constant", false);

Answer 2

Create an instance of your MainActivity and get it using a method, add following code in your MainActivity :

private static MainActivity instance;

@Override
protected void onStart() { // onStart() of your activity
    super.onStart();
    instance = this;
}

public void yourMethod(){
    // Your code here
}

public static MainActivity getInstance(){
    return instance;
}

Now, in your BroadcastReceiver , you can get the instance using:

MainActivity obj = MainActivity.getInstance();

And you can call your method using:

obj.yourMethod();