Java Swing - GUIs
TOPIC 03 – MORE ON COMPONENTS

LESSON NOTE - JTEXTAREA

JTEXTAREA CONSTRUCTOR

We create a JTextArea by specifying the number of rows and columns. In the following statement, the JTextArea will have 5 rows and 20 columns:

JTextArea ta = new JTextArea(5,20);

EDITABILITY

We can set whether a JTextArea can be edited or not by using the setEditable(Boolean) method. Here is an example to set it to be uneditable:

ta.setEditable(false);

CHANGING TEXT

We can set the text inside a JTextArea by using the setText(String) method. This will replace any existing text.

ta.setText("hello");

We can add text to the end of the current text in a JTextArea by using the append(String) method.

ta.append(" there");

We can get the text in a JTextArea by using the getText() method.

String s = ta.getText();

We can add new text to the beginning of a JTextArea by using the following:

ta.setText("Put me at the start\n" + ta.getText());

FULL CODE EXAMPLE

Here is an example that displays some of the functionality of a JTextArea shown above:

public class MyGUI extends JFrame implements ActionListener

{

Public JTextArea ta;

public MyGUI()

{

Container cp = this.getContentPane();

cp.setLayout(new FlowLayout());

ta = new JTextArea(5,20);

cp.add(ta);

ta.setText("Hello");

ta.append(" there");

this.setTitle("JTextArea");

this.setSize(500,500);

this.setVisible(true);

}

public void actionPerformed(ActionEvent e)

{

}

public static void main(String[] args)

{

MyGUI sg = new MyGUI();

}

}

JTEXTAREA WITH SCROLLING

To make a JTextArea have scrollbars, we use the JScrollPane object. The code looks like this:

Container cp = this.getContentPane();

cp.setLayout(new FlowLayout());

JTextArea ta = new JTextArea(5,20);

JScrollPane sp = new JScrollPane(ta);

cp.add(sp);

The result of the above code is

If we want to use code to add to a JTextArea inside a JScrollPane, then we still use the setText(String) method on the JTextArea.

ta.setText("hello");