powerManager weaklock的用法
- PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE); 通过
Context.getSystemService().方法获取PowerManager实例。 - 然后通过PowerManager的newWakeLock((int flags, String tag)来生成WakeLock实例。int Flags指示要获取哪种WakeLock，不同的Lock对cpu 、屏幕、键盘灯有不同影响。
- 获取WakeLock实例后通过acquire()获取相应的锁，然后进行其他业务逻辑的操作，最后使用release()释放（释放是必须的）。
Demo
public class WakeLockDemo extends Activity {
private PowerManager.WakeLock wakeLock = null;
//获取锁
public void acquireWakeLock(Context context) {
if (wakeLock == null) {
PowerManager powerManager = (PowerManager)(context.getSystemService(Context.POWER_SERVICE)); wakeLock = powerManager.newWakeLock(PowerManager.SCREEN_DIM_WAKE_LOCK, "My Tag");
wakeLock.acquire();
}
}
//释放锁
public void releaseWakeLock() {
if(wakeLock != null && wakeLock.isHeld()){
wakeLock.release();
wakeLock = null;
}
}
@Override
public void onCreate() {
super.onCreate();
//初始化
}
@Override
public void onResume() {
acquireWakeLock(this);
super.onResume();
}
@Override
public void onPause() {
//获取和释放一一对应
releaseWakeLock();
super.onPause();
}
}
关于int flags
各种锁的类型对CPU 、屏幕、键盘的影响：
PARTIAL_WAKE_LOCK:保持CPU 运转，屏幕和键盘灯有可能是关闭的。
SCREEN_DIM_WAKE_LOCK：保持CPU 运转，允许保持屏幕显示但有可能是灰的，允许关闭键盘灯
SCREEN_BRIGHT_WAKE_LOCK：保持CPU 运转，允许保持屏幕高亮显示，允许关闭键盘灯
FULL_WAKE_LOCK：保持CPU 运转，保持屏幕高亮显示，键盘灯也保持亮度
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.
获取锁ACQUIRE_CAUSES_WAKEUP之后，立即亮屏，常用于即时通知。
ON_AFTER_RELEASE：f 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.
设置了这个标志，在释放锁后，屏幕仍然会亮一会。
权限获取
要进行电源的操作需要在AndroidManifest.xml中声明该应用有设置电源管理的权限。
<uses-permission android:name="android.permission.WAKE_LOCK" />
你可能还需要
<uses-permission android:name="android.permission.DEVICE_POWER" />
另外WakeLock的设置是 Activiy 级别的，不是针对整个Application应用的。
可以在activity的onResume方法里面操作WakeLock, 在onPause方法里面释放。