未显示JTextArea

为什么JTextArea没有显示在GUI中？

public class AddMovie extends JTextField {

    static JFrame frame;
    private JLabel description;
    JTextArea movieDescription;

    public JPanel createContentPane() throws IOException
    {

        JPanel totalGUI = new JPanel();
        totalGUI.setLayout(null);
        totalGUI.setBackground(Color.WHITE);

        description = new JLabel("Description  ");
            description.setLocation(15,285);
            description.setSize(120, 25);
            description.setFont(new java.awt.Font("Tahoma", 0, 12));
            movieDescription=new JTextArea();
          movieDescription.setLocation(15,320);
          movieDescription.setSize(420, 110);

        JScrollPane scrollPane = new JScrollPane(movieDescription);    
        totalGUI.add(description);
        totalGUI.add(movieDescription);
        totalGUI.add(cancel);
        totalGUI.add(scrollPane);                   
        return totalGUI;
    }


    static void createAndShowGUI() throws IOException
    {

        JFrame.setDefaultLookAndFeelDecorated(true);
        frame = new JFrame("New Movie");
        //Create and set up the content pane.
        AddMovie demo = new AddMovie();
        frame.setContentPane(demo.createContentPane());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(515, 520);
        frame.setLocation(480,120);
        frame.setVisible(true);
    }

    public void setVisible(boolean b) {
        // TODO Auto-generated method stub

    }

}

---

解决方案

如here和here所示，null布局会招致麻烦。因为您的显示以描述为中心，所以使用JTextArea构造函数，该构造函数允许您以行和列指定大小。当您pack()包围的Window时，它将调整大小以适应文本区域。我添加了一些临时文本来说明效果。我还编写了updated允许文本区域在调整框架大小时增长的代码。

import java.awt.EventQueue;
import java.awt.GridLayout;
import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

/**
 * @see https://stackoverflow.com/a/38282886/230513
 */
public class Test {

    private JPanel createPanel() {
        JPanel panel = new JPanel(new GridLayout());
        //panel.setBorder(BorderFactory.createTitledBorder("Description"));
        JTextArea movieDescription = new JTextArea(10, 20);
        panel.add(new JScrollPane(movieDescription));
        movieDescription.setLineWrap(true);
        movieDescription.setWrapStyleWord(true);
        movieDescription.setText(movieDescription.toString());
        return panel;
    }

    private void display() {
        JFrame f = new JFrame("Test");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setContentPane(createPanel());
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Test()::display);
    }
}