Android亮屏、熄屏的时候会发出广播，通常在熄屏广播中启动屏保

注册屏幕广播

/**

* 注册广播

*

* @param mContext 上下文环境

* @param receiver 将要注册的广播

*/

public void registerScreenSaverReceiver(Context mContext, ScreenReceiver receiver) {

IntentFilter filter = new IntentFilter();

filter.addAction(Intent.ACTION_SCREEN_OFF);

filter.addAction(Intent.ACTION_SCREEN_ON);

mContext.registerReceiver(receiver, filter);

}

在该广播的Action中有着这样的注释：

/**

* Broadcast Action: Sent when the device wakes up and becomes interactive.

*

* For historical reasons, the name of this broadcast action refers to the power

* state of the screen but it is actually sent in response to changes in the

* overall interactive state of the device.

*

* This broadcast is sent when the device becomes interactive which may have

* nothing to do with the screen turning on. To determine the

* actual state of the screen, use {@link android.view.Display#getState}.

*

* See {@link android.os.PowerManager#isInteractive} for details.

*

* You cannot receive this through components declared in

* manifests, only by explicitly registering for it with

* {@link Context#registerReceiver(BroadcastReceiver, IntentFilter)

* Context.registerReceiver()}.

*

*

This is a protected intent that can only be sent

* by the system.

*/

这就是说，由于历史原因，该广播Action表示屏幕的电信号状态，但是实际上该广播是在屏幕不可进行交互时发出

注：不能通过在Manifest.xml文件注册的方式接收该广播，仅仅支持通过代码registerReceiver(Broadcast ，IntentFilter)的方式进行注册

在 onReceive(Context context, Intent intent) 方法中进行开启自定义屏保：

public class ScreenReceiver extends BroadcastReceiver {

@Override

public void onReceive(Context context, Intent intent) {

//拿到屏幕锁，亮屏，随即释放，否则屏幕就会保持常量

WakeUtil.getInstance().wakeScreenLock();

WakeUtil.getInstance().releaseScreenLock();

//屏蔽系统的屏保

mKeyguardManager = (KeyguardManager) MyApplication.getInstance().getSystemService(Context.KEYGUARD_SERVICE);

mKeyguardLock = mKeyguardManager.newKeyguardLock("ScreenLockService");

mKeyguardLock.disableKeyguard();

//TODO 开启自定义的屏保；例如：跳转一个Activity，显示屏保图片

}

}

保持屏幕常量

通常，保持屏幕常量有如下方法：

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

官方注释：

/** Window flag: as long as this window is visible to the user, keep the device's screen turned on and bright. */

public static final int FLAG_KEEP_SCREEN_ON = 0x00000080;

即当window对用户可见时，保持屏幕常量。

通过PowerManager.WakeLock

mScreenWakeLock = powerManager.newWakeLock(PowerManager.ACQUIRE_CAUSES_WAKEUP | PowerManager.SCREEN_DIM_WAKE_LOCK,

this.getClass().getCanonicalName());

if (!mScreenWakeLock.isHeld()) {

mScreenWakeLock.acquire();

}

对于方法newWakeLock(int levelAndFlags, String tag),下面看看该flag和level分别代表什么意义。

PowerManager.ACQUIRE_CAUSES_WAKEUP|PowerManager.SCREEN_DIM_WAKE_LOCK

/**

* 获得唤醒锁时亮屏

*

* 正常情况下，唤醒锁并不能真正唤醒设备，一旦屏幕已经打开，它们就只能继续工作。

* 正如视频软件正常工作一样。

*

*/

public static final int ACQUIRE_CAUSES_WAKEUP = 0x10000000;

/**

* 保证亮屏状态 (可能会变暗);

* 允许关闭背光

* @deprecated Most applications should use

* {@link android.view.WindowManager.LayoutParams#FLAG_KEEP_SCREEN_ON} instead

* of this type of wake lock, as it will be correctly managed by the platform

* as the user moves between applications and doesn't require a special permission.

*/

@Deprecated

public static final int SCREEN_DIM_WAKE_LOCK = 0x00000006;

可以看出该方法已经过时，系统更推荐使用方法1.

3.通过设置系统进入屏保的时间

try {

Settings.System.putInt(mContext.getContentResolver(), Settings.System.SCREEN_OFF_TIMEOUT, paramInt);

} catch (Exception localException) {

localException.printStackTrace();

}

paramInt代表进入屏保或锁屏的时间，单位毫秒ms。这里可设置为Integer.MAX_VALUE。

同样可以通过这种方式进行屏幕亮度(0-255)等的设置：

try {

Settings.System.putInt(mContext.getContentResolver(), Settings.System.SCREEN_BRIGHTNESS, paramInt);

} catch (Exception localException) {

localException.printStackTrace();

}

进入浅休眠(熄屏状态下CPU仍在运行)

mCpuWakeLock = powerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, this.getClass().getCanonicalName());

synchronized (WakeUtil.class) {

if (!mCpuWakeLock.isHeld()) {

mCpuWakeLock.acquire();

}

}