交通大学资讯工学系.ppt

Programming in Java More about GUI 蔡文能 交通大學資訊工程學系 tsaiwn@.tw Agenda GUI (Graphical User Interface) AWT Component (package java.awt ) Graphics and Events Event Model Listener interfaces and Adaptors Events and Listeners for standard AWT events Layout Manager? Swing Library Java UI functionality Presenting a Graphical User Interface (GUI) Playing sounds Applications can play sounds as well as Applets since JDK1.2. Getting configuration information Users can specify configuration information to a program using command-line arguments (applications only) and parameters (applets only). Saving user preferences using properties For information that applications need to save even when theyre not running, you can use properties. (not for Applets due to security problem.) Getting/displaying text using the standard input/output/error streams Standard input, output, and error are the old-fashioned way of presenting a user interface. Theyre still useful for testing and debugging programs. The AWT Components Example using AWT Component The following figure shows the Graphical UI (GUI) components that the AWT provides. The Basic Controls Buttons, Checkboxes, Choices, Lists, Menus, and Text Fields When a user activates one of these controls, it posts an event. An object that contains the control can react to the event by implementing the action() method. Clicking a button. Pressing Return in a text field. Swing Library Other Ways of Getting User Input Sliders, Scrollbars, and Text Areas The Scrollbar class is used for both slider and scrollbar functionality. The TextArea class simply provides an area to display or allow editing of several lines of text. Text areas automatically include scrollbars. More AWT Components Creating Custom Components: Canvases The Canvas class lets you write custom Components. With your Canvas subclass, you can draw custom graphics to the screen. Labels A Label simply displays an unselectable line of text. Containers: Windows, Panel