新的 nextfocus 和 prevfocus 属性允许控制焦点在屏幕元素间转移的顺序，该属性对于建立可导航的用户界面至关重要。
The new nextfocus and prevfocus attributes allow you to control the order in which focus moves among the screen elements; this can be a vital feature for creating navigable user interfaces.
使用登录界面建立一个新的用户然后登录，您也可以在控制台上以root登录，不需要密码。
Use the login screen to set up a new user and log in. You can also log in on the console as root, no password required.
然后解释事件处理，基本和先进的用户界面控制，设计和布局，建立对话，组件和扩展功能等。
It then explains event handling, basic and advanced user interface controls, designing and layout, creating dialogs, components and extending functionality, and so on.
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