无法显示JOptionPane-Java Swing

Question

I am new to Java. And I need your help.

My code is working well until it shows JDialog . I have a button to show a message dialog ( JOptionPane ). The problem exist when the button is clicked. Message dialog doesn't seems to appear. It more like stuck, can't be closed and it must be terminated from my Eclipse.

Please anyone tell me why JOptionPane can't show? And I don't know what the meaning of parentComponent on its parameter.

Here is my code.

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JDialog;
import javax.swing.JButton;
import javax.swing.JOptionPane;

@SuppressWarnings("serial")
public class Test extends JDialog implements ActionListener {

    private JButton testPane = new JButton(" Test Pane ");

    Test() {

        initComp();

    }

    private void initComp() {

        this.setSize(300, 200);
        this.setLocationRelativeTo(null);
        this.setTitle("Test");
        this.setAlwaysOnTop(true);
        this.setResizable(false);
        this.setDefaultCloseOperation(DISPOSE_ON_CLOSE);
        this.setLayout(null);

        testPane.setBounds(47, 25, 200, 120);
        this.add(testPane);
        testPane.addActionListener(this);

    }

    @Override
    public void actionPerformed(ActionEvent arg0) {

        JOptionPane.showMessageDialog(null, "Does it show?");

    }

}

Answer 1

First, you need to add the following statement in initComp so that the JFrame gets visible:

private void initComp() {
    ...
    this.setVisible(true);  // add this to show the frame

    ...
}

When displaying the dialog, set the parent component to the current JFrame so that it gets displayed in the frame itself:

@Override
public void actionPerformed(ActionEvent arg0) {
    JOptionPane.showMessageDialog(this, "Does it show?");  // add this as parent
}