To get the Recent Apps in Android

AndroidManifest.xml

// We should have this 2 permissions to get the recent app
<uses-permission android:name="android.permission.GET_TASKS" />
<uses-permission android:name="android.permission.PACKAGE_USAGE_STATS" />

// we should register our service in manifest file

AndroidUtils.java

public class AndroidUtils {
    private static final String RECENT_ACTIVITY;

    static {
        if (Build.VERSION.SDK_INT > Build.VERSION_CODES.LOLLIPOP) {
            RECENT_ACTIVITY = "com.android.systemui.recents.RecentsActivity";
        } else if (Build.VERSION.SDK_INT > Build.VERSION_CODES.JELLY_BEAN_MR1) {
            RECENT_ACTIVITY = "com.android.systemui.recent.RecentsActivity";
        } else {
            RECENT_ACTIVITY = "com.android.internal.policy.impl.RecentApplicationDialog";
        }
    }
  
    public static boolean isRecentActivity(String className) {
        if (RECENT_ACTIVITY.equalsIgnoreCase(className)) {
            return true;
        }

        return false;
    }
}

AppLockService.java

public class AppLockService extends Service {
  // Write code here to run the service contiuously, and call every 50 to 300 ms getRecentApps(Context context) method to get the current open application
   
    public String getRecentApps(Context context) {
        String topPackageName = "";

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            UsageStatsManager mUsageStatsManager = (UsageStatsManager) context.getSystemService(Context.USAGE_STATS_SERVICE);

            long time = System.currentTimeMillis();

            UsageEvents usageEvents = mUsageStatsManager.queryEvents(time - 1000 * 30, System.currentTimeMillis() + (10 * 1000));
            UsageEvents.Event event = new UsageEvents.Event();
            while (usageEvents.hasNextEvent()) {
                usageEvents.getNextEvent(event);
            }

            if (event != null && !TextUtils.isEmpty(event.getPackageName()) && event.getEventType() == UsageEvents.Event.MOVE_TO_FOREGROUND) {
                if (AndroidUtils.isRecentActivity(event.getClassName())) {
                    return event.getClassName();
                }
                return event.getPackageName();
            } else {
                topPackageName = "";
            }
        } else {
            ActivityManager am = (ActivityManager) context.getSystemService(context.ACTIVITY_SERVICE);
            List<ActivityManager.RunningTaskInfo> taskInfo = am.getRunningTasks(1);
            ComponentName componentInfo = taskInfo.get(0).topActivity;

            // If the current running activity it will return not the package name it will return the activity refernce.
            if (AndroidUtils.isRecentActivity(componentInfo.getClassName())) {
                return componentInfo.getClassName();
            }

            topPackageName = componentInfo.getPackageName();
        }


        return topPackageName;
    }
}

MainActivity.java

public class MainViewActivity extends AppCompatActivity {
  
  @Override
  public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
      
      // Do you stuff
      startServiceToGetRecentApps();
  }
  
  public void startServiceToGetRecentApps() {
    // And you should check first the user API level is 21 or more if yes you should get access for usage access settings
      if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.LOLLIPOP) {
         if (UStats.getUsageStatsList(this).isEmpty()) {

             Intent intent = new Intent(Settings.ACTION_USAGE_ACCESS_SETTINGS);
             startActivity(intent);
           
             retrun;
         }
     }
    
     // Start your service here
  }
}

UStats.java

import android.app.usage.UsageStats;
import android.app.usage.UsageStatsManager;
import android.content.Context;
import android.util.Log;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.List;

/**
 * Created by User on 3/2/15.
 */
public class UStats {
    public static final String TAG = UStats.class.getSimpleName();

    public static List<UsageStats> getUsageStatsList(Context context){
        UsageStatsManager usm = (UsageStatsManager) context.getSystemService("usagestats");
        Calendar calendar = Calendar.getInstance();
        long endTime = calendar.getTimeInMillis();
        calendar.add(Calendar.DATE, -1);
        long startTime = calendar.getTimeInMillis();

        List<UsageStats> usageStatsList = usm.queryUsageStats(UsageStatsManager.INTERVAL_DAILY,startTime,endTime);

        return usageStatsList;
    }
}