Why is my text field not appearing?

Question

I have to create a text field, a text area, and two buttons, but I am stuck on the text field because I cant get it to appear when I run my program. My JFrame keeps appearing empty.

public class SentanceBuilder extends JFrame {
    private JTextField textField = new JTextField(50);
    private JTextArea textArea = new JTextArea(200,200);
    private JButton Submit = new JButton();
    private JButton Cancel = new JButton();

public SentanceBuilder(){
   textField.setVisible(true);
   textField.setLocation(50, 50);
   this.textField();
   this.setSize(400, 300);
   this.setLocationRelativeTo(null);
   this.setVisible(true);
   }

public void textField(){


    String textContent = textField.getText();

}
}

`textField.setLocation(50, 50);` 1) Java GUIs have to work on different OS', screen size, screen resolution etc. As such, they are not conducive to pixel perfect layout. Instead use layout managers, or [combinations of them](http://stackoverflow.com/a/5630271/418556) along with layout padding and borders for [white space](http://stackoverflow.com/a/17874718/418556). 2) For better help sooner, post an [MCVE](http://stackoverflow.com/help/mcve) (Minimal Complete Verifiable Example). — Andrew Thompson, Oct 15 '14 at 23:24
`private JTextArea textArea = new JTextArea(200,200);` You really want this text area to be 200 columns by 200 rows? I don't have a monitor big enough to render that! I suspect you thought those were pixels values.. — Andrew Thompson, Oct 15 '14 at 23:26

score 3 · Answer 1 · edited May 23 '17 at 10:25

You never add the textField variable to a container such as a JPanel that is held by the top-level window, such as a JFrame. In fact, in your code, you add nothing to your JFrame!

If this were my GUI, I'd

Create my JTextField
Create a main JPanel to hold my components.
Add it and other components to the main JPanel via the JPanel's add(...) method.
Add the main JPanel to the JFrame's contentPane via the JFrame's add(...) method.
Call pack() and then setVisible(true) on the JFrame, but only after adding all components to it, not before.
Read the Swing tutorials since this beats guessing every time. You can get links to the tutorials at the Swing Tag Info link.

e.g.,

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;

public class MyFoo extends JFrame {
   private static final long serialVersionUID = 1L;
   private JTextField textField = new JTextField(10);
   private JButton button = new JButton("Foo Button");

   public MyFoo() {
      super("My JFrame");
      // so Java will end when GUI is closed
      setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

      // code to be called when button is pushed
      button.addActionListener(new ActionListener() {

         @Override
         public void actionPerformed(ActionEvent e) {
            // TODO code that runs when button is pushed.
         }
      });

      // panel to hold everything
      JPanel mainPanel = new JPanel();
      // add all to the panel
      mainPanel.add(new JLabel("Text Field:"));
      mainPanel.add(textField);
      mainPanel.add(button);

      // add the panel to the main GUI
      add(mainPanel);
   }

   // start up code
   private static void createAndShowGui() {
      JFrame mainFrame = new MyFoo();
      mainFrame.pack();
      mainFrame.setLocationRelativeTo(null);
      mainFrame.setVisible(true);
   }

   public static void main(String[] args) {
      // call start up code in a Swing thread-safe way
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}

Why is my text field not appearing?

1 Answers1