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The paintComponent()method
In order to display text in a content pane, you have to:
- Create a class that extends
JPanel
- Implement
paintComponent(Graphics g) in that class;
this is where all the drawing of text occurs
- The first thing this method should do is call
super.paintComponent(g)
-- if you don't, you will most likely find that strange things happen.
- The rest of the code in the method should cause graphic elements to
be displayed -- in this case, we'll be displaying text.
- Finally:
- Create an instance of this class and add it to the JFrame's content pane.
Note: In addition to the paintComponent(Graphics g) method, there is also a
paint(Graphics g) method. Don't get confused between the two methods:
- If you're programming in Swing, use
paintComponent
- If you're programming in AWT, use
paint
Here's an example:
package swingExamples;
import java.awt.Container;
import java.awt.Graphics;
import javax.swing.JFrame;
import javax.swing.JPanel;
class TextDisplayPanel extends JPanel
{
public void paintComponent(Graphics g)
{
// Don't forget to do this!
super.paintComponent(g);
// Display the text in the panel
g.drawString("Hello from a Java Swing application!", 50, 80);
}
}
class TextDisplayFrame extends JFrame
{
public TextDisplayFrame()
{
setTitle("Text Display Frame");
setSize(300, 200);
setDefaultCloseOperation(EXIT_ON_CLOSE);
// Find the JFrame's content pane
Container contentPane = getContentPane();
// Add the TextDisplayPanel to the content pane
contentPane.add( new TextDisplayPanel() );
}
}
public class TextDisplay
{
public static void main(String[] args)
{
TextDisplayFrame frame = new TextDisplayFrame();
frame.setVisible(true);
}
}
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Here's the result:
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