http://www.cnblogs.com/android-blogs/p/5690725.html
http://www.jianshu.com/p/687010ccad66
http://blog.csdn.net/neoadrian/article/details/51446573
http://www.cnblogs.com/snake-hand/p/3186931.html
完全沉浸式，即状态栏完全不显示
@Override
public void onWindowFocusChanged(boolean hasFocus) {
super.onWindowFocusChanged(hasFocus);
if (hasFocus && Build.VERSION.SDK_INT >= 19) {
View decorView = getWindow().getDecorView();
decorView.setSystemUiVisibility(
View.SYSTEM_UI_FLAG_LAYOUT_STABLE
| View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
| View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_FULLSCREEN
| View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY);
}
}
Api19以上可以给theme设置
windowTranslucentStatus 为true ，即状态栏显示为半透明
windowTranslucentNavigation 为true ，即导航栏栏显示为半透明
这两个属性设置为true之后，DecorView会占据整个window(下图蓝色的框框)。
