killProcess can lead to restart application!

退出应用程序方法，暂列两种：

一种：

android.os.Process.killProcess(android.os.Process.myPid());

另一种：

System.exit(code);

see alse:

System.exit()

 does
not kill your app if you have more than one activity on the stack. What actually happens is that the
process is killed and immediately restarted with one fewer activity on the stack. This is also what happens when your app is killed
by the Force Close dialog, or even when you try to kill the process from DDMS.
This is a fact that is entirely undocumented, to my knowledge.

 if you want to exit your application,
you've got to keep track of all activities in your stack and 

finish().

there
is no way to iterate through the Activity stack, so you have to manage all of this yourself

killProcess方法我试过了，当activity1跳到activity2时，activity2执行强退，会出现先退出，然后立即重启应用。

单纯的System.exit(code);，也会立即重启。

所有还是用System.exit(code);吧

而且还应这样用：

public void exit(int code)
{
for (Activity activity : listActivities)
{
activity.finish();
}
System.exit(code);
}