package com.example.services;

import java.util.List;
import java.util.Timer;
import java.util.TimerTask;

import android.app.ActivityManager;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.os.IBinder;
import android.widget.Toast;

 public class ServiceTest extends Service {
Timer timer;

@Override
public void onCreate() {
    // TODO Auto-generated method stub
    super.onCreate();
    Toast.makeText(ServiceTest.this, "Service Start", Toast.LENGTH_SHORT)
            .show();

}

@Override
public IBinder onBind(Intent intent) {
    // TODO Auto-generated method stub
    return null;
}

@Override
public void onStart(Intent intent, int startId) {
    // TODO Auto-generated method stub
    Timer timer = new Timer();
    timer.scheduleAtFixedRate(new TimerTask() {
        public void run() {
            ActivityManager mActivityManager = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);
            List<ActivityManager.RunningTaskInfo> RunningTask = mActivityManager
                    .getRunningTasks(1);
            ActivityManager.RunningTaskInfo ar = RunningTask.get(0);
            String ActivityPackageName = ar.topActivity.getPackageName()
                    .toString();
            String ActivityAppName = ar.topActivity.getClassName()
                    .toString();
            if (ActivityPackageName.equals("org.wikipedia")
                    && ActivityAppName.equals("Wikipedia")) {
                Intent lockIntent = new Intent(getBaseContext(),
                        lockscreen.class);
                lockIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                getBaseContext().startActivity(lockIntent);
            }
        }
    }, 0, 1000);
}

}

<uses-sdk
    android:minSdkVersion="8"
    android:targetSdkVersion="14" />

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

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name="com.example.services.MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

    <service
        android:name="com.example.services.ServiceTest"
        android:enabled="true" >
    </service>

    <activity
        android:name="com.example.services.lockscreen"
        android:label="@string/app_name" >
    </activity>
</application>

</manifest>