Lab 12: Graphical User Interfaces (GUI's) in Java
For most of the relevant Information on how to build GUIs in Java, see the following reference: Java GUI Programming Primer
The content below discusses material not explicitly covered in the above reference.
Few people code GUI's by hand these days--it's just too complicated. Typically, one would use a "GUI builder" to drag-and-drop GUI components onto a design canvas, greatly simplifying and speeding up the GUI creation process. But it is very helpful to know the basics of how to build a GUI by hand because one often needs to go in an manually tweak the GUI code even when using a sophisticated GUI builder tool.
Basic structure of a simple GUI application:
import java.awt.*;
import javax.swing.*
import java.awt.event.*;
class MyGUIApp extends JFrame {
// Use fields for GUI components that need to be referenced outside of the GUI initialization process (initGUI)
/**
* Constructor for the GUI.
*/
public MyGUIApp() {
// initialize fields here.
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // Causes the application to end if the GUI frame is closed.
initGUI(); // initialize the GUI components
}
/**
* Actually start the GUI
*/
public void start() {
// Do any last second initializations, if needed.
setVisible(true); // Make the GUI visible
}
/**
* Initialize the GUI components
*/
private void initGUI() {
Container contentPane = getContentPane(); // all GUI components are added to the frame's ContentPane.
// You can also just call the accessor each time as well and not use a local variable.
// instantiate, initialize and connect all the GUI's components here.
// Don't forget to add them to the container that holds them, e.g. the ContentPane.
}
/**
* Main method that starts the app.
* In general, this would not be in this class but rather in a separate "controller" class
* with slightly different coding (as required for a true Model-View-Controller system).
* We put it here for now, for simplicity's sake only.
*/
public static void main(String[] args) {
MyGUIApp view = new MyGUIApp(); // instantiate the GUI but don't show it yet.
// Model classes would be instantiated here plus any other required objects.
view.start(); // Start the application by making the GUI visible.
}
}
Some typical GUI initializations: