JCheckBox

Create Software Components

Using Java Level 2

Course Info

Scheme

Resources

Tutorials

Java Demos

Utilities

Links

Swing

JCheckBox

This tutorial describes the Swing JCheckBox class.

The JCheckBox Class

Plain JCheckBox

Image JCheckBox

Other JCheckBox Methods

The JCheckBox Class

A checkbox exists to allow the user to select or deselect an option. You can use the JCheckBox class to implement checkboxes. You should not that you can also put check boxes in menus using the JCheckBoxMenuItem class.

There are no less than seven constructors that can be used to create a JCheckBox because you have the choice of creating a checkbox with a plain box area or a checkbox where the boxed area is replaced by an image. Here are the constructors:-

`JCheckBox()`	Creates a checkbox with no text, no icon, unselected
`JCheckBox(String s)`	Creates a checkbox with the specified text, no icon, unselected
`JCheckBox(String s, boolean b)`	Creates a checkbox with the specified text, no icon, and selected if b is true
`JCheckBox(Icon m)`	Creates a checkbox with no text, the specified image, unselected
`JCheckBox(Icon m, boolean b)`	Creates a checkbox with no text, the specified image, and selected if b is true
`JCheckBox(String s, Icon m)`	Creates a checkbox with the specified text, the specified image, unselected
`JCheckBox(String s, Icon m, boolean b)`	Creates a checkbox with the specified text, the specified image, and selected if b is true

Plain JCheckBox

To create a plain unselected checkbox, use a line of code such as:-

JCheckBox cloudCheckBox = new JCheckBox("Cloud");

If you want to create a selected checkbox you can create it like this:-

JCheckBox cloudCheckBox = new JCheckBox("Cloud", true);

Alternatively, you can set the selected status using :-

//Set box to be selected

cloudCheckBox.setSelected (true);

//Set box to be unselected

cloudCheckBox.setSelected (false);

The applet below shows two checkboxes. The first one was created with the selected status set to true. The second was created with the selected status set to false.

~~~Applet~~~

Image JCheckBox

We can specify images to be used in place of the standard selected and unselected box. To do this we need to create an Icon. We can use the ImageIcon class for this:-

ImageIcon imgUnselected = new ImageIcon (getImage

(getCodeBase(),"unselected.gif"));

then we can use the variable that references the ImageIcon object in the argument for the checkbox's constructor:-

JCheckBox cloudCheckBox = new JCheckBox("Cloud",imgUnselected);

The image specified at checkbox creation time is the image that will be used for the unselected state. This means we have to specify another image to be used when the checkbox is in the selected state. To do this use code such as:-

ImageIcon imgSelected = new ImageIcon (getImage

(getCodeBase(),"selected .gif"));

cloudCheckBox.setSelectedIcon(imgSelected);

Don't forget to place your image file in the same folder as you class file.

The applet below shows two checkboxes. I have specified an image of a tick and an image of a cross to be used in place of the standard selected and unselected box.

~~~Applet~~~

Important: -- Using images in applets? Then read this to understand the lines of code like:-

ImageIcon imgUnselected = new ImageIcon (getImage

(getCodeBase(),"unselected.gif"));

Don't forget to import the package java.net.*

Other JCheckBox Methods

Here are some methods we can use with the JCheckBox class. You should note that this is not a full list, there are lots of other methods.

JCheckBoc inherits a lot of these methods from JComponent and AbstractButton. You should check out the inherited JComponent and JAbstractButton class methods.

`setText(String s)`	Set the text displayed by the checkbox.
`setHorizontalTextPosition(int i)`	Set the horizontal position of the checkbox text relative to the checkbox image using as the argument: `JCheckBox.LEFT, JCheckBox.CENTER or JCheckBox.RIGHT`.
`setVerticalTextPosition(int i)`	Set the vertical position of the checkbox's text relative to the checkbox's image using as the argument: `JCheckBox.TOP, JCheckBox.CENTER or JCheckBox.BOTTOM`.
`setSelected(boolean b)`	Sets the checkbox to selected if b is true else set it to unselected .
`boolean isSelected()`	Returns true if the checkbox is selected and false if is unselected .
`setSelectedIcon(Icon m)`	Sets the image to be used when the checkbox is in the selected state.
`setRolloverIcon(Icon m)` `setRolloverEnabled(boolean b)`	Use `setRolloverIcon(Icon m)` with `setRolloverEnabled(true)`to make the checkbox display the specified icon when the cursor passes over it.

~Now try the activity~

Activity A

Using appropriate methods from the JCheckBox, JAbstractButton and JComponent class, create an applet with ...

at least one panel to contain some checkboxes

two checkboxes similar to the first applet shown on this page

set the font color of the checkbox labels to any color of your choice, (apart from black).

set the font of the checkbox labels to Times, italic and 10 points in size. The Font class is explained in the Graphics tutorial.

set the panel background color to any color of your choice