android 中 FLAG_SHOW_WHEN_LOCKED 的用法及解释

如何让一个activity 浮在锁屏界面的上方，返回即进入解锁界面。
譬如在锁屏界面，来电时是不需要先解锁才能接听电话的。这样能带来快捷。
如果你想在android 上实现 iphone 4s 上面在锁屏界面就能进照相机的话也可以按此方式来进行。
只需要在 Camera 的 activity 的 onResume 函数中添加如下 flag 即可实现。

import android.view.Window;
import android.view.WindowManager;

final Window win = activity.getWindow();
final WindowManager.LayoutParams params = win.getAttributes();
params.flags |= WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED;

        /** Window flag: special flag to let windows be shown when the screen
         * is locked. This will let application windows take precedence over
         * key guard or any other lock screens. Can be used with
         * {@link #FLAG_KEEP_SCREEN_ON} to turn screen on and display windows
         * directly before showing the key guard window. Can be used with
         * {@link #FLAG_DISMISS_KEYGUARD} to automatically fully dismisss
         * non-secure keyguards. This flag only applies to the top-most
         * full-screen window.
         */
        public static final int FLAG_SHOW_WHEN_LOCKED = 0x00080000

补充：移动开发 , Android ,