just a short question: Is it possible to add a background color to a JComponent when it is added directly onto a JFrame using null layout? The size and position of the component are set by setBounds() and i know that the background color will not be displayed using this setup. (I know you should always use layout managers, but in this case i want to prevent this).
JComponent
is transparent by default, you'd either need to change its opaque
state or use a JPanel
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.LineBorder;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
TestPane pane = new TestPane();
pane.setBounds(10, 10, 100, 100);
JFrame frame = new JFrame("Testing");
frame.setLayout(null); // This is bad, but it proofs my point
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(pane);
frame.setSize(200, 200);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JComponent {
public TestPane() {
addMouseListener(new MouseAdapter() {
@Override
public void mouseClicked(MouseEvent e) {
setOpaque(!isOpaque());
repaint();
}
});
setBackground(Color.BLUE);
setBorder(new LineBorder(Color.RED));
}
}
}
null
layouts are bad news, I don't condone them and you should avoid using them, the example above simply proves the point that it's the JComponent
s opaque
state which needs to be changed
Why is it frowned upon to use a null layout in SWING? is a nice read about why you should avoid using null
layouts.
If you want more control, write your own.
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