| A configuration change | An activity restart | A process restart | |
|---|---|---|---|
| Dialog | reset | reset | reset |
| Activity, View, Fragment | save/restore | save/restore | save/restore |
| Fragment with setRetainInstance(true) | no change | save/restore | save/restore |
| Static variables and threads | no change | no change | reset |
当设置变化时，例如横竖屏切换，Activity会被销毁并立即被重建，而View、Fragment、Dialog也自然如此，除了Fragment被设置为setRetainInstance(true)状态时不会被销毁重建，不影响静态变量和线程状态
Some device configurations can change during runtime (such as screen orientation, keyboard availability, and language). When such a change occurs, Android recreates the running activity (the system calls onDestroy(), then immediately calls onCreate()).
当用户开启了“Don’t keep activities”选项或者内存不足时，Activity、Dialog、View、Fragment（包括设置为setRetainInstance(true)状态的）都会被销毁重建，不影响静态变量和线程状态
当系统内存不足，且程序不在前台运行时，当再次回到程序时，程序的进程有可能会被重启，这会导致静态变量和线程状态都会被重置