fitsSystemWindows
Added in API level 1
int fitsSystemWindows
Boolean internal attribute to adjust view layout based on system windows such as the status bar. If true, adjusts the padding of this view to leave space for the system windows. Will only take effect if this view is in a non-embedded activity.
Must be a boolean value, either "true" or "false".This may also be a reference to a resource (in the form "@[package:]type:name") or theme attribute (in the form "?[package:][type:]name") containing a value of this type.
将该属性设置为true，可不再受actionbar(toolbar),statuebar,底部虚拟键等的限制，将contentView扩展到系统屏幕整个界面.
