Java: Summary - Basic GUI Elements

In this tutorial we will learn about Basic GUI elements in Java program.

Following table summarizes the variable declarations.

String s; // Any string.
String t; // A string.
//Interpreted as HTML if starts with "<html>" and ends with "</html>".
Font f; // A Font object.
Icon img; // An image.
Container cont; // Container is the superclass of JPanel.

Now let's see the Top-level Container in Swing. JFrame is top level container in Swing.

Following table summarizes the useful methods of JFrame.

Top-level Containers (JFrame)
JFrame - window, typically subclassed
w =	new JFrame();	Constructor
	w.setTitle(t);	Sets titlebar text to t
	w.setDefaultCloseOperation(opt);	Use opt `JFrame.EXIT_ON_CLOSE` to terminate program when close box clicked.
	w.setResizable(false);	Prevent user from resizing window.
	w.show~~();~~	Use `w.setVisible(true)` instead.
	w.~~hide~~();	Use `w.setVisible(false)` instead.
	w.setVisible(true/false);	Same as `w.show()` or `w.hide()`
	w.setContentPane(cont);	Sets the content pane - common to pass a JPanel here.
cont =	w.getContentPane();	Returns the window's content pane.
	w.setJMenuBar(mb);	Adds JMenuBar (contains `Jmenu`s, which contain `JMenuItem`s) to window.
Low-level Containers (JPanel)
JPanel - Set layout and add components to JPanel.
p =	new JPanel();	Creates new JPanel
	p.setLayout(layout);	Sets the panel's layout.
	p.add(widget);	Adds the widget to next position in Layout (eg, Flow, Grid, or Box layouts).
	p.add(widget, constraint);	Adds the widget to position defined by constraint (eg, Border or Gridbag layouts).
Components (JLabel, JTextField, JButton) and their common methods
	cmp.requestFocus();	Puts focus (eg, blinking cursor) in the field, selection of a button, etc.
	tf.setFont(f);	Sets font.
JLabel - For fixed text.
lbl =	new JLabel(t);	Creates JLabel with text (can be HTML). Typically created in `add()` call.
JTextField - Box containing one line of text.
tf =	new JTextField(n);	Creates textfield about n columns wide.
s =	tf.getText();	Returns string in textfield.
	tf.setText(s);	Sets text to s.
	tf.addActionListener(lst);	Action listener lst will be called if enter typed.
	tf.setEditable(true/false);	Don't allow user to edit text field used for output.
	tf.setHorizontalAlignment(align);	`JTextField.LEFT` (default), `JTextField.CENTER`, or `JTextField.RIGHT`
JButton - Standard clickable button.
btn =	new JButton(t);	Creates button with text t.
btn =	new JButton(act);	Creates button from Action act for text, icon, listener, etc.
btn =	new JButton(img);	Creates button with icon img.
btn =	new JButton(t, img);	Creates button with both text and icon.
	btn.addActionListener(lst);	Action listener lst called when button clicked.
	btn.setEnabled(true/false);	Used to enable/disable button.
Layouts (FlowLayout, BorderLayout, GridLayout, BoxLayout)
FlowLayout - Arranges widgets left-to-right, top-to-bottom.
	p.setLayout(new FlowLayout());	Sets layout of the panel to FlowLayout.
BorderLayout - Lays out components in BorderLayout.NORTH, EAST, SOUTH, WEST, and CENTER sections.
	p.setLayout(new BorderLayout());	Sets layout of the panel to BorderLayout. Widgets added with constraint.
GridLayout - Lays out components in equal sized rectangular grid, added r-t-l, top-to-bottom.
	p.setLayout(new GridLayout(r, c));	Sets layout to GridLayout with specified rows and columns.
	p.setLayout(new GridLayout(r, c, h, v));	As above but also specifies horizontal and vertical space between cells.
BoxLayout - Lays out components in a single row or column. Can add "glue" and rigid areas to control spacing.
	p.setLayout(new BoxLayout(p, dir));	Layout is horizontal (dir is `BoxLayout.X_AXIS`) or vertical (`BoxLayout.X_AXIS`).

Copyleft 2004 Fred Swartz

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Java: Summary - Basic GUI Elements

Top-level Containers (JFrame)

Low-level Containers (JPanel)

Components (JLabel, JTextField, JButton) and their common methods

Layouts (FlowLayout, BorderLayout, GridLayout, BoxLayout)