In AndroidManifest.xml 加上权限:

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

方法一：

public class UnLockActivity2 extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
} 
}

方法二：

public class UnLockActivity extends Activity {
/** Called when the activity is first created. */

WakeLock m_wklk;

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

PowerManager pm = (PowerManager)getSystemService(POWER_SERVICE);
m_wklk = pm.newWakeLock(PowerManager.SCREEN_DIM_WAKE_LOCK, "cn");

m_wklk.acquire(); //设置保持唤醒
}

@Override
protected void onDestroy() {
// TODO Auto-generated method stub
super.onDestroy();
m_wklk.release(); //解除保持唤醒
}

@Override
protected void onPause() {
// TODO Auto-generated method stub
super.onPause();

m_wklk.release();//解除保持唤醒

}

@Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();


m_wklk.acquire(); //设置保持唤醒
}


}

解释：

用到的类

PowerManager

主要是这两个参数：PowerManager.SCREEN_BRIGHT_WAKE_LOCK | PowerManager.ON_AFTER_RELEASE

下面是 android 官方API 解释：

he following flags are defined, with varying effects on system power.These flags are mutually exclusive - you may only specify one of them.

一般要使程序运行过程中背景保持常亮，使用

SCREEN_BRIGHT_WAKE_LOCK 就可以，

SCREEN_BRIGHT_WAKE_LOCK CPU：唤醒 屏幕背光：唤醒 键盘灯：关闭

第二个参数：

In addition, you can add two more flags, which affect behavior of the screen only.These flags have no effect when combined with aPARTIAL_WAKE_LOCK.

http://www.cnblogs.com/chengning/archive/2012/04/26/2472789.html

http://mysuperbaby.iteye.com/blog/1454178

http://wenku.baidu.com/view/a9c0fa01de80d4d8d15a4f96.html

http://blog.csdn.net/xieying15170814609/article/details/7723928

文章来源: blog.csdn.net，作者：悟空胆好小，版权归原作者所有，如需转载，请联系作者。

原文链接：blog.csdn.net/xushx_bigbear/article/details/45061327