Communication between BroadcastReceiver and Activity – android-ThrowExceptions

Exception or error:

I have a broadcast receiver in my app which is fired every time the user gets an incoming call. Now, when it happens, I need the broadcast receiver to invoke a specific method in a specific activity. Now, I tried to make this method static and therefore available, but something tells me it is a very bad idea.

Accordingly, I tried to instantiate the broadcast receiver inside my activity without declaring it in my manifest but the problem is – when the app is off, the activity is not exist and therefore I can’t invoke my method.

So my question is – How can I invoke this method when the broadcast receiver is fired up, without making it “public static”?

Here is my activity code(I have deleted the irrelevant parts)

package com.silverfix.ringo.activities;

import com.silverfix.ringo.R;
import com.silverfix.ringo.activities.fragments.DataManagerFragment;

import android.app.ActionBar;
import android.app.Activity;
import android.app.FragmentTransaction;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;

public class RingtonesActivity extends Activity{

    private DataManagerFragment dataManagerFragment;
    private IntentFilter filter;
    private BroadcastReceiver phoneCall;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_ringtones);
        ActionBar ab = getActionBar();
        ab.setDisplayShowTitleEnabled(false);
        ab.setDisplayHomeAsUpEnabled(true);
        dataManagerFragment = new DataManagerFragment();
        FragmentTransaction ft = getFragmentManager().beginTransaction();
        ft.add(dataManagerFragment, "DataManagerFragment");
        ft.commit();
        filter = new IntentFilter();
        filter.addAction("android.intent.action.PHONE_STATE");
        phoneCall = new BroadcastReceiver() {

            @Override
            public void onReceive(Context context, Intent intent) {
                dataManagerFragment.act();
            }
        };
        registerReceiver(phoneCall, filter);
    }
}
How to solve:

You can use observers , like

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

    @Override
    public void onReceive(Context context, Intent intent) {
        ObservableObject.getInstance().updateValue(intent);
    }
}

public class MainActivity extends Activity implements Observer {
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ObservableObject.getInstance().addObserver(this);
    }

    @Override
    public void update(Observable observable, Object data) {            
        Toast.makeText(this, String.valueOf("activity observer " + data), Toast.LENGTH_SHORT).show();
    }
}

public class ObservableObject extends Observable {
    private static ObservableObject instance = new ObservableObject();

    public static ObservableObject getInstance() {
        return instance;
    }

    private ObservableObject() {
    }

    public void updateValue(Object data) {
        synchronized (this) {
            setChanged();
            notifyObservers(data);
        }
    }
}

Receiver can be used via manifest.
ObservableObject – must be singleton.

###

This might help: how can I notify a running activity from a broadcast receiver?

Also, you can try using Observers

Something like:

public class BroadcastObserver extends Observable {
    private void triggerObservers() {
        setChanged();
        notifyObservers();
    }

    public void change() {
        triggerObservers();
    }
}

In your broadcast receiver:

@Override
public void onReceive(Context context, Intent intent) {
    BroadcastObserver bco = new BroadcastObserver();
    bco.change();
}

and the Activity:

public class YourActivity extends Activity implements
        Observer {
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        BroadcastObserver bco = new BroadcastObserver();
        bco.addObserver(this);
    }

    @Override
    public void update() {
        //TODO: call your desired function
    }
}

###

If anyone needs two-way communication between a BroadcastReceiver and a Activity, I wrote this utility class which simplifies invoking Methods on each other while still being memory-safe.

https://gist.github.com/Jenjen1324/4a0c03beff827082cb641fc8fe2c4e71

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