设置Android设备在睡眠期间始终保持WLAN开启的代码实现

package cc.ab;

import android.os.Bundle;
import android.provider.Settings;
import android.app.Activity;
/**
 * Demo描述:
 * 设置设备在睡眠期间始终保持WLAN开启.
 * 
 * 参考资料:
 * 1 http://stackoverflow.com/questions/8652031/how-to-modify-wi-fi-sleep-policy-programmatically/8655070#8655070
 * 2 http://blog.csdn.net/mrlixirong/article/details/24938637
 *   Thank you very much
 *   
 *  注意事项:
 *  1 这里使用的是android.provider.Settings.System.WIFI_SLEEP_POLICY
 *    而不是Settings.System.WIFI_SLEEP_POLICY!!!!!!!!!!!!!!!!!!!!!!!
 *    
 *  2 权限<uses-permission android:name="android.permission.WRITE_SETTINGS"/>
 *  
 *  3 在实际项目中,这么强制性地设置WIFI在休眠时永不断开有些粗鲁了.
 *    可以先记录下WIFI原本的策略,待我们的逻辑完成后再还原回去为好.
 */
public class MainActivity extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		setWifiNeverSleep();
	}

	private void setWifiNeverSleep(){
		int wifiSleepPolicy=0;
		wifiSleepPolicy=Settings.System.getInt(getContentResolver(),
				                               android.provider.Settings.System.WIFI_SLEEP_POLICY,
				                               Settings.System.WIFI_SLEEP_POLICY_DEFAULT);
		System.out.println("---> 修改前的Wifi休眠策略值 WIFI_SLEEP_POLICY="+wifiSleepPolicy);
		
		
		Settings.System.putInt(getContentResolver(),
				               android.provider.Settings.System.WIFI_SLEEP_POLICY,
				               Settings.System.WIFI_SLEEP_POLICY_NEVER);
		
		
		wifiSleepPolicy=Settings.System.getInt(getContentResolver(),
                android.provider.Settings.System.WIFI_SLEEP_POLICY,
                Settings.System.WIFI_SLEEP_POLICY_DEFAULT);
        System.out.println("---> 修改后的Wifi休眠策略值 WIFI_SLEEP_POLICY="+wifiSleepPolicy);
	}
	
}

main.xml如下:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

</RelativeLayout>