1）在显示登录对话框/活动只是检查你的preferences特殊标志presence：

1) Before displaying login dialog/activity just check in your preferences presence of special flag:

Context context=this.getApplicationContext();
SharedPreferences settings=context.getSharedPreferences(PREFERENCES, 0);
boolean isLogged=settings.getBoolean("isLogged", false);

根据 isLogged 值，可以重定向至登录或其他页

Depending on isLogged value you can redirect either to login or other page

2）在某处登录后保存您的登录页面 isLogged 状态，如：

2) Somewhere in your login page after logging save isLogged status, like:

Context context=this.getApplicationContext();
SharedPreferences settings=context.getSharedPreferences(PREFERENCES, 0);
SharedPreferences.Editor editor = settings.edit();
editor.putBoolean("isLogged", true);
editor.commit();

这是所有乡亲！