android 屏幕保持唤醒 不锁屏 android.permission.WAKE_LOCK

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.
Flag Value	CPU	Screen	Keyboard
PARTIAL_WAKE_LOCK	On*	Off	Off
SCREEN_DIM_WAKE_LOCK	On	Dim	Off
SCREEN_BRIGHT_WAKE_LOCK	On	Bright	Off
FULL_WAKE_LOCK	On	Bright	Bright
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.
Flag Value	Description
ACQUIRE_CAUSES_WAKEUP	Normal wake locks don't actually turn on the illumination. Instead, they cause the illumination to remain on once it turns on (e.g. from user activity). This flag will force the screen and/or keyboard to turn on immediately, when the WakeLock is acquired. A typical use would be for notifications which are important for the user to see immediately.
ON_AFTER_RELEASE	If this flag is set, the user activity timer will be reset when the WakeLock is released, causing the illumination to remain on a bit longer. This can be used to reduce flicker if you are cycling between wake lock conditions.