MainActivity is as follows:

package cc.ab;

import android.os.Bundle;
import android.provider.Settings;
import android.app.Activity;
/**
 * Demo describe :
 *  Set the device to remain in place during sleep WLAN open .
 *
 *  The resources :
 * 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
 *
 *  Matters needing attention :
 * 1  This is the one that's used here android.provider.Settings.System.WIFI_SLEEP_POLICY
 *   Rather than Settings.System.WIFI_SLEEP_POLICY!!!!!!!!!!!!!!!!!!!!!!!
 *
 * 2  permissions <uses-permission android:name="android.permission.WRITE_SETTINGS"/>
 *
 * 3  In a real project , This is mandatory WIFI It's a little rude to never disconnect from sleep .
 *   You can write it down first WIFI Original strategy , It is better to revert back after our logic is complete .
 */
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("--->  Before the change Wifi Sleep strategy value  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("--->  The modified Wifi Sleep strategy value  WIFI_SLEEP_POLICY="+wifiSleepPolicy);
 }

}
<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>

The code is as above, but in a real project, it would be rude to force WIFI to never disconnect when sleeping. We can record the original strategy of WIFI and restore it after our logic is completed.