将JTextArea更改为JScrollPane使其不可见

Question

I am having an issue with JScrollPanes and JTextArea objects and getting them to work together.

If I just add a JTextArea to my JPanel, it works fine and shows up where I tell it to. However, if I change the contentPane.add(textArea) to contentPane.add(new JScrollPane(textArea)), the textArea is not longer visible and there is no sign of the textarea either.

Here is my code:

public docToolGUI() {

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 611, 487);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        setContentPane(contentPane);
        contentPane.setLayout(null);

        textField = new JTextField();
        textField.setBounds(253, 323, 86, 20);
        contentPane.add(textField);
        textField.setColumns(10);

        JLabel lblEnterRootDirectory = new JLabel("Enter Root Directory");
        lblEnterRootDirectory.setBounds(253, 293, 127, 20);
        contentPane.add(lblEnterRootDirectory);

        JButton btnGo = new JButton("Go");
        btnGo.addMouseListener(new MouseAdapter() {
            @Override
            public void mouseClicked(MouseEvent arg0) {
                new ToolWorker().execute();
            }
        });
        btnGo.setBounds(253, 361, 89, 23);
        contentPane.add(btnGo);

        textArea = new JTextArea();
        textArea.setWrapStyleWord(true);
        textArea.setEditable(false);
        textArea.setBounds(25, 11, 560, 276);
        contentPane.add(new JScrollPane(textArea));




    }

Answer 1

Try using the constructor for JTextArea that uses 2 int values:

textArea = new JTextArea(rows, columns);

From the tutorial :

The two arguments to the JTextArea constructor are hints as to the number of rows and columns, respectively, that the text area should display. The scroll pane that contains the text area pays attention to these hints when determining how big the scroll pane should be.

EDIT: The sample above is a hint for the LayoutManager, but I just noticed that you're not using one. Unless you have a really good reason not to, you should be.

Answer 2

This is because you have to set the bounds of the JScrollPane and you have to make the scroll pane visible instead of the text area.

textArea = new JTextArea();
textArea.setWrapStyleWord(true);
textArea.setEditable(false);

JScrollPane scrollPane = new JScrollPane(textArea);
scrollPane.setBounds(25, 11, 560, 276);
scrollPane.setVisible(true);

contentPane.add(scrollPane);