Lecture17 - Graphical User Interfaces (Input) Events and...

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Unformatted text preview: Graphical User Interfaces (Input) Events and Listeners Buttons Text Fields Reading for this lecture: L&L 4.5-4.8 Review for Exam 2 Graphical User Interfaces A Graphical User Interface (GUI) in Java is created with at least three kinds of objects: components events listeners We've previously discussed components , which are objects that represent screen elements labels, buttons, text fields, menus, etc. Some components are containers that hold and organize other components frames, panels, applets, dialog boxes Events An event is an object that represents some activity to which we may want to respond For example, we may want our program to perform some action when the following occurs: the mouse is moved the mouse is dragged a mouse button is clicked a graphical button is clicked a keyboard key is pressed a timer expires Events often correspond to user actions, but not always Events and Listeners The Java standard class library contains several classes that represent typical events Components, such as a graphical button, generate (or fire) an event when it occurs A listener object "waits" for an event to occur and responds accordingly...
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Lecture17 - Graphical User Interfaces (Input) Events and...

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