MyActivityLifecycleCallbacks.java

package com.github.fmtprintlnmko.util;

import android.app.Activity;
import android.app.Application.ActivityLifecycleCallbacks;
import android.os.Bundle;

public static final class MyActivityLifecycleCallbacks implements ActivityLifecycleCallbacks {

  private AtomicInteger count = new AtomicInteger(0) ;

  public void onActivityCreated(Activity activity, Bundle bundle) {
   
  }

  public void onActivityDestroyed(Activity activity) {
   
  }

  public void onActivityPaused(Activity activity) {
   count.incrementAndGet();
  }

  public void onActivityResumed(Activity activity) {
   count.decrementAndGet();
  }

  public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
   
  }

  public void onActivityStarted(Activity activity) {
   count.decrementAndGet();
  }

  public void onActivityStopped(Activity activity) {
   count.incrementAndGet();
  }
  
  public boolean isAppResumed() {
    return count.get() == 2;
  }
}

MyApplication.java

package com.github.fmtprintlnmko.util;

import android.content.res.Configuration;

public class MyApplication extends Application {

  @Override
  public void onCreate (){
    super.onCreate();
    registerActivityLifecycleCallbacks(new MyActivityLifecycleCallbacks());
  }
  
}