Android Studio - ¿How can i launch my app or an activity in background?

AdrianPalacios
June 17, 2022
56 views
0 votes
2 Answers

How can I start an activity when my app is in background? I mean, when it has not been destroyed? I have tried with IntentService and nothing, I just want to make a StartActivity to launch my MainActivity in the background.

Answers

Right-click on the project, Select New >> Service >> Service and add the following to MyServices.java

public class MyService extends Service {
   public MyService() {
   }
   @Override
   public int onStartCommand(Intent intent, int flags, int startId){
      onTaskRemoved(intent);
      Toast.makeText(getApplicationContext(),"This is a Service running in Background",
      Toast.LENGTH_SHORT).show();
      return START_STICKY;
   }
   @Override
   public IBinder onBind(Intent intent) {
      // TODO: Return the communication channel to the service.
      throw new UnsupportedOperationException("Not yet implemented");
   }
   @Override
   public void onTaskRemoved(Intent rootIntent) {
      Intent restartServiceIntent = new Intent(getApplicationContext(),this.getClass());
      restartServiceIntent.setPackage(getPackageName());
      startService(restartServiceIntent);
      super.onTaskRemoved(rootIntent);
   }
}

Add the following code to res/layout/activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
   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"
      android:text="Click here"
      android:textStyle="bold"
      android:textSize="16sp"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerInParent="true" />
</RelativeLayout>

Add the following code to src/MainActivity.java

public class MainActivity extends AppCompatActivity {
   Button button;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      button = findViewById(R.id.button);
      button.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View v) {
            startService(new Intent(getApplicationContext(),MyService.class));
         }
      });
   }
}

Add the following code to androidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="app.com.sample">
   <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">
      <service
         android:name=".MyService"
         android:enabled="true"
         android:exported="true"></service>
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>

Let’s try to run your application.
Click on the Click here button to start background services.

Your service needs to be a foreground service.
Here is how.

First in your Manifest.xml file.
Request for permission

<uses-permission android:name="android.permission.FOREGROUND_SERVICE"/>

......

<!-- Your Service-->
<service
  android:name=".MyService"
  android:enabled="true"
  android:exported="true"
  android:permission="android.permission.FOREGROUND_SERVICE"/>

Start your service with:
startForegroundService(Intent(this, MyService::class.java))

Then in your service display the foreground notification(usually in the onStartCommand):

override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
val ncCompat = NotificationChannelCompat.Builder("your.own.id.here", NotificationManagerCompat.IMPORTANCE_DEFAULT).setName("Important").build()

NotificationManagerCompat.from(baseContext).createNotificationChannel(ncCompat)
startForeground("your.notification.id.goes.here".hashCode(), NotificationCompat.Builder(baseContext, nmCompat.id).setContentTitle("My Foreground Service").setContentText("Running Service").build())


return super.onStartCommand(intent, flags, startId)
}

Then your can start an activity(for example: see below)

val intent = Intent(application, MainActivity2::class.java)
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_TASK_ON_HOME)
intent.addFlags(Intent.FLAG_FROM_BACKGROUND)
startActivity(intent)

Android may complain that your activity needs to inherit theme from Theme.AppCompat and you may also have difficulties loading an xml layout.

I believe your can work around those. Apart from that your are good to go.
And also note that i only tested it on Android 10 and below.

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Android Studio – ¿How can i launch my app or an activity in background?

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