How to detect when an Android app goes to the background and come back to the foreground?

This example demonstrate about How to detect when an Android app goes to the background and come back to the foreground

Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.

Step 2 − Add the following code to res/layout/activity_main.xml.

<?xml version = "1.0" encoding = "utf-8"?>
<LinearLayout xmlns:android = "http://schemas.android.com/apk/res/android"
   android:orientation = "vertical"
   android:layout_width = "match_parent"
   android:layout_height = "match_parent">ss
   <TextView
      android:id = "@+id/text"
      android:layout_width = "match_parent"
      android:layout_height = "wrap_content"
      android:textSize = "30sp" />
</LinearLayout>

In the above code, we have taken text view to show an application status.

Step 3 − Add the following code to src/MainActivity.java

package com.example.myapplication;
import android.app.ActivityManager;
import android.content.ComponentName;
import android.content.Context;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.widget.TextView;
import java.util.List;

public class MainActivity extends FragmentActivity {
   TextView textView;
   @Override
   public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      textView = findViewById(R.id.text);
      if (!isApplicationBroughtToBackground()) {
         textView.setText("Application is foreground");
      }
   }
   private boolean isApplicationBroughtToBackground() {
      ActivityManager am = (ActivityManager) this.getSystemService(Context.ACTIVITY_SERVICE);
      List<ActivityManager.RunningTaskInfo> tasks = am.getRunningTasks(1);
      if (!tasks.isEmpty()) {
         ComponentName topActivity = tasks.get(0).topActivity;
         if (!topActivity.getPackageName().equals(this.getPackageName())) {
            return true;
         }
      }
      return false;
   }
}

Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click Run  icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen –

Click here to download the project code