Develop Reference

How to make the application run in the background, as soon as the device starts/restarts

So, I have an alarm application which works good and behaves normally as long as the device remains online until the alarm time.
Problem is, let's say I ran out of battery, or I just want to restart the device... the alarm won't fire upon its time.
I tried something like:
public class BootCompletedReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
if (intent.getAction().equals("android.intent.action.BOOT_COMPLETED")) {
Utils.set_alarms(context);
}
}
}
In my BroadcastReceiver... but doesn't seem to work. Oh, and it's registered in the AndroidManifest too...:
<receiver
android:name=".receivers.AlarmReceiver" // The receiver which starts the alarm activity.
android:enabled="true" />
<receiver
android:name=".receivers.BootCompletedReceiver" // The receiver which is supposed to set the alarms after the device is online again.
android:enabled="true">
<intent-filter>
<action android:name="android.intent.action.BOOT_COMPLETED" />
</intent-filter>
</receiver>
But doesn't work... help will be appreciated.

You probably need to add the permission to receive boot completed to your manifest. See Manifest Permission: RECEIVE_BOOT_COMPLETED

Add below permission and actions
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
<receiver
android:name=".receivers.BootCompletedReceiver" // The receiver which is supposed to set the alarms after the device is online again.
android:enabled="true">
<intent-filter>
<!-- used for restart or reboot -->
<action android:name="android.intent.action.QUICKBOOT_POWERON" />
<!-- Used for cold boot -->
<action android:name="android.intent.action.BOOT_COMPLETED" />//cold start
</intent-filter>
</receiver>

BroadcastReceiver not called when WiFi changes

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.

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.

Android tablet - modify OS so app launches on boot

I have written an Android application for a large store for the purposes of production inspection. I have a few Android tablets with the app installed on each that will be provided to the store.
As the only purpose of this tablet is to run a single app, is there a way to force this app to load upon switching on the tablet, and only allow this app to be used? The app does require an active 4G connection so it still needs to use a few of the core functions of Android as well as actually running the app.
I don't know much about this so apologies for naivety in advance, but could someone please shed some light on this for me?

First, you need the permission in your AndroidManifest.xml:
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
Also, in yourAndroidManifest.xml, define your service and listen for the BOOT_COMPLETED action:
<service android:name=".MyService" android:label="My Service">
<intent-filter>
<action android:name="com.myapp.MyService" />
</intent-filter>
</service>
<receiver
android:name=".receiver.StartMyServiceAtBootReceiver"
android:label="StartMyServiceAtBootReceiver">
<intent-filter>
<action android:name="android.intent.action.BOOT_COMPLETED" />
</intent-filter>
</receiver>
Then you need to define the receiver that will get the BOOT_COMPLETED action and start your service.
public class StartMyActivityeAtBootReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
if (Intent.ACTION_BOOT_COMPLETED.equals(intent.getAction())) {
Intent serviceIntent = new Intent(context, MyActivity.class);
context.startService(serviceIntent);
}
}
}

Google Glass - Autostart Application on Boot

I just received a new google-glass from a company which wants it to support their employees while picking and packing goods in their warehouse. For this reason they need a Server Client application which really isn't the problem.
I never did something with the Glass before and i want to know if it is possible to run a custom Application on boot and to jail the user into it.
Yesterday i rooted the device which gives me full access but i don't know how to go on.
Thank you!

Yes, it is possible.
As you have rooted the device, so you can create system app that can be recognised by the reboot event. Rest of the steps are totally similar to android mobile.
How to do it:
If you need to know the steps you can search on the web or you can try the following:
First, you need the permission in your AndroidManifest.xml:
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
Also, in yourAndroidManifest.xml, define your service and listen for the BOOT_COMPLETED action:
<service android:name=".MyService" android:label="My Service">
<intent-filter>
<action android:name="com.myapp.MyService" />
</intent-filter>
</service>
<receiver
android:name=".receiver.StartMyServiceAtBootReceiver"
android:label="StartMyServiceAtBootReceiver">
<intent-filter>
<action android:name="android.intent.action.BOOT_COMPLETED" />
</intent-filter>
</receiver>
Then you need to define the receiver that will get the BOOT_COMPLETED action and start your service.
public class StartMyServiceAtBootReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
if (Intent.ACTION_BOOT_COMPLETED.equals(intent.getAction())) {
Intent serviceIntent = new Intent(context, MySystemService.class);
context.startService(serviceIntent);
}
}
}
And now your service should be running when the phone starts up.

Application calling with screen lock

I want to launch an application immediately after the screen gets unlocked and at the time of booting. How is it possible? What changes do I need to make?

To launch your application when the screen locks, you need to register a BroadcastReceiver for the Intent.ACTION_SCREEN_OFF Intent for more information check the example http://thinkandroid.wordpress.com/2010/01/24/handling-screen-off-and-screen-on-intents/
To launch your application at the time of boot you need a broadcast receiver that listens for the BOOT_COMPLETED action, please refer How to start an Application on startup?
First, you need the permission in your manifest:
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
Also, in your manifest, define your service and listen for the boot-completed action:
<service android:name=".MyService" android:label="My Service">
<intent-filter>
<action android:name="com.myapp.MyService" />
</intent-filter>
</service>
<receiver
android:name=".receiver.StartMyServiceAtBootReceiver"
android:enabled="true"
android:exported="true"
android:label="StartMyServiceAtBootReceiver">
<intent-filter>
<action android:name="android.intent.action.BOOT_COMPLETED" />
</intent-filter>
</receiver>
Then you need to define the receiver that will get the BOOT_COMPLETED action and start your service.
public class StartMyServiceAtBootReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
if ("android.intent.action.BOOT_COMPLETED".equals(intent.getAction())) {
Intent serviceIntent = new Intent("com.myapp.MySystemService");
context.startService(serviceIntent);
}
}
}
And now your service should be running when the phone starts up.