Java Canvas or JPanel

Question

When making a graphics canvas in Java, which would be better to extend? Should you extend JPanel or Canvas? Are there any performance considerations?

Answer 1

Unless you need to position other components within the custom rendered area, sub-classing a JComponent is often all that is necessary (JPanel provides nothing more that is especially useful).

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Mixing Swing with AWT

BTW - be especially wary of mixing Swing with AWT. It generally causes rendering problems for Swing floating GUI elements. Java 7 promises to provide functionality to seamlessly mix Swing and AWT based components.

E.G.

import java.awt.*;
import javax.swing.*;

class MixSwingAwt {

    public static void main(String[] args) {
        JPanel p = new JPanel(new BorderLayout(10,10));

        String[] fruit = {"Apples", "Oranges", "Pears"};
        JComboBox fruitChoice = new JComboBox(fruit);
        p.add(fruitChoice, BorderLayout.NORTH);

        p.add(new TextArea(10,20));

        JOptionPane.showMessageDialog(null, p);
    }
}

Screenshot

Screenshot of the dialog using Java 6, when the JComboBox is expanded.

We can see the top of Apples, but the rest of the list is missing.