BroadcastReceiver not called when WiFi changes

Question

I've implemented a BroadcastReceiver according to https://developer.android.com/guide/components/broadcasts but it does not seem to work.

The receiver part of my Manifest.xml looks like this (I use android.permission.ACCESS_NETWORK_STATE and android.permission.ACCESS_WIFI_STATE):

...
<receiver android:name=".BackgroundTask">
    <intent-filter>
        <action android:name="android.net.wifi.WIFI_STATE_CHANGED"/>
        <action android:name="android.net.wifi.STATE_CHANGE" />
    </intent-filter>
</receiver>
...

and it's declared within my application.

My BroadcastReceiver class looks like this:

public class BackgroundTask extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        System.out.println("Connection changed!");
        Toast.makeText(context, "Network state changed", Toast.LENGTH_LONG).show();
    }
}

Neither the toast is displayed nor I receive the println-ed output on my logcat. I also read the note which recommends me to use scheduled jobs instead of receivers, but I could not find an example how to use this for listening to network changes.

The reason I want to use this is because I want my (background)-app only to run while my phone is connected to my WiFi - if you have any different suggestions on how to implement this, I'm also very thankful.

Btw. I'm using Android 8.0.0.

Cheers, Nikolar

Update:

Somehow it still does not work. Am I forgetting anything?

Manifest:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="mypackagename">
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <receiver android:name=".BootReceiver">
            <intent-filter>
                <action android:name="android.intent.action.ACTION_BOOT_COMPLETED"></action>
            </intent-filter>
        </receiver>
        <receiver android:name=".BackgroundPoller">
        </receiver>
    </application>
</manifest>

Just for clearence I renamed my BackgroundTask-Class to BootReceiver:

public class BootReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        Log.d("INFO", "BootReceiver started");
        Intent newIntent = new Intent(context, BackgroundPoller.class);
        context.sendBroadcast(newIntent);
        Log.d("INFO", "BackgroundPoller activated");
    }
}

When I successfully send my broadcast

adb.exe shell am broadcast -a android.intent.action.ACTION_BOOT_COMPLETED

I still don't get a log output.

Answer 1

To get around Oreo's broadcast receiver restrictions, you have to register your receivers using Context.registerReceiver(). You could do this by subclassing Application and registering receivers in onCreate(). The only downside to doing this is your app would have to be launched to have Application.onCreate() get called. To get around this, you could register an ACTION_BOOT_COMPLETED receiver in your manifest as this action is exempt from the restriction. Your ACTION_BOOT_COMPLETED receiver doesn't have to do anything, but it will force your app to start running on boot and therefore Application.onCreate() will get called. Then the only challenge is keeping your app running because the system will kill it if the user doesn't go into it. There's a couple options to solve this. You could write a foreground service whose only purpose is to keep the app alive. Or perhaps use AlarmManager to schedule some intent that will wake your app back up, which will register your receivers again.