为什么JScrollPane不在我的JTextField周围出现？

Question

I'm pretty new to GUI but I'm trying to create a simple version of notepad and would like scroll bars to appear around the text area. However, I'm not sure why it isn't appearing.

public class NutPad extends JPanel {

public static void main(String[] args) {

    JFrame frame = new JFrame("NutPad");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.getContentPane().add(new NutPad(), BorderLayout.CENTER);
    frame.setSize(500,300);
    frame.setVisible(true);
}

private NutPad() {
    add(makeTextAreaPanel());

}

private JPanel makeTextAreaPanel() {
    JPanel textAreaPanel = new JPanel();
    textAreaPanel.setSize(100,100);

    JTextArea textArea = new JTextArea(20, 60); //15,43
    JScrollPane scrollPane = new JScrollPane(textArea); 

    textAreaPanel.add(scrollPane,BorderLayout.CENTER);
    textAreaPanel.add(textArea);

    return textAreaPanel;
}

}

Thanks

Answer 1

If you're going to use the BorderLayout.CENTER constraint, then the container needs to have its layout set to BorderLayout .

Also you don't need textAreaPanel since you can just add the scrollPane straight into your NutPad panel.

private NutPad() {
    setLayout(new BorderLayout());
    add(makeScrollPane(), BorderLayout.CENTER);
}

private JScrollPane makeScrollPane() {
    JTextArea textArea = new JTextArea();
    JScrollPane scrollPane = new JScrollPane(textArea);

    return scrollPane;
}

Now your text area will fill the frame and the scrollbars will appear when the text takes up more than the available space.

Hope that helps :)