HackService.java

package com.example.hackpolicy;

import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.os.IBinder;
import android.util.Log;
import android.view.Window;
import android.view.WindowManager;

import java.lang.reflect.Method;

/**
 * Created by Hirofumi Nakagawa on 13/08/17.
 */
public class HackService extends Service{
	private static final String TAG = HackService.class.getSimpleName();

	private static final String POLICY_IMPL_CLASS_NAME =
			"com.android.internal.policy.impl.Policy";

	private static final Object sPolicy;

	static {
		// Pull in the actual implementation of the policy at run-time
		try {
			Class policyClass = Class.forName(POLICY_IMPL_CLASS_NAME);
			sPolicy = policyClass.newInstance();
		} catch (ClassNotFoundException ex) {
			throw new RuntimeException(
					POLICY_IMPL_CLASS_NAME + " could not be loaded", ex);
		} catch (InstantiationException ex) {
			throw new RuntimeException(
					POLICY_IMPL_CLASS_NAME + " could not be instantiated", ex);
		} catch (IllegalAccessException ex) {
			throw new RuntimeException(
					POLICY_IMPL_CLASS_NAME + " could not be instantiated", ex);
		}
	}

	@Override
	public void onCreate() {
		super.onCreate();
		try {
			Method method = sPolicy.getClass().getMethod("makeNewWindow", Context.class);
			Window window = (Window)method.invoke(sPolicy, this);
			window.setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
					WindowManager.LayoutParams.FLAG_FULLSCREEN);
			//need additional hack...
		} catch (Exception exp) {
			Log.e(TAG, exp.getMessage() + "", exp);
		}
	}

	public int onStartCommand(Intent intent, int flags, int startId) {
		return START_STICKY;
	}

	@Override
	public IBinder onBind(Intent intent) {
		return null;
	}
}