java：表单加载时将焦点设置为文本字段

Question

I have a jTextfield. I want to set focus on this when the form is loaded. How can I do this? I am using Netbeans. I use requestFocus() but it is not working.

Answer 1

This link might be helpful for you: How to Use the Focus Subsystem

I would suggest that you use requestFocusInWindow() instead of requestFocus() to achieve the desired functionality.

The reason: (from the same link)

These methods are now deprecated. Another method, requestFocus, is discouraged because it tries to give the focus to the component's window, which is not always possible. As of JDK 1.4, you should instead use the requestFocusInWindow method, which does not attempt to make the component's window focused. The method returns a boolean value indicating whether the method succeeded.

This would be a crude example, but I think you can use this to get started:

import java.awt.BorderLayout;
import java.awt.Dimension;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextField;

public class TestFrame extends JFrame {

    JButton button1;
    JButton button2;

    JTextField textField;

    public TestFrame() {
        initComponents();
    }

    private void initComponents(){
        button1 = new JButton("Button 1");
        button2 = new JButton("Button 2");
        textField = new JTextField();

        button1.setPreferredSize(new Dimension(100,20));
        button2.setPreferredSize(new Dimension(100,20));
        textField.setPreferredSize(new Dimension(300,20));

        this.setSize(new Dimension(600, 300));
        this.setLayout(new BorderLayout());

        getContentPane().add(button1, BorderLayout.WEST);
        getContentPane().add(button2, BorderLayout.CENTER);
        getContentPane().add(textField, BorderLayout.EAST);
        this.pack();
        this.setVisible(true);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //This will set focus on the text field
        textField.requestFocusInWindow();
    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new TestFrame();
            }
        });
    }
}

LATEST EDIT : FOR NETBEANS

CODE USED :

package focusexample;

public class FocusExample extends javax.swing.JFrame {

    public FocusExample() {
        initComponents();
        jTextField1.requestFocusInWindow();
    }

    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void initComponents() {

        jButton1 = new javax.swing.JButton();
        jButton2 = new javax.swing.JButton();
        jTextField1 = new javax.swing.JTextField();
        jTextField2 = new javax.swing.JTextField();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jButton1.setText("jButton1");

        jButton2.setText("jButton2");

        jTextField1.setText("jTextField1");

        jTextField2.setText("jTextField2");

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(87, 87, 87)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                    .addComponent(jButton1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addComponent(jTextField1))
                .addGap(69, 69, 69)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                    .addComponent(jButton2, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addComponent(jTextField2))
                .addContainerGap(98, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(95, 95, 95)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jButton1)
                    .addComponent(jButton2))
                .addGap(58, 58, 58)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jTextField2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addContainerGap(104, Short.MAX_VALUE))
        );

        pack();
    }// </editor-fold>


    public static void main(String args[]) {

        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(FocusExample.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(FocusExample.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(FocusExample.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(FocusExample.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        java.awt.EventQueue.invokeLater(new Runnable() {

            public void run() {
                new FocusExample().setVisible(true);                
            }
        });
    }
    // Variables declaration - do not modify
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private javax.swing.JTextField jTextField1;
    private javax.swing.JTextField jTextField2;
    // End of variables declaration
}

Answer 2

I used the textfield.requestFocusInWindow(); line given above, in a GUI that contains a number of form elements (several of which are textfields). It works great. Just replace "textfield" with whatever name you have given the element in question. In my case it's repId. So I use repID.requestFocusInWindow(); and put the line at the bottom of my ENTER button handler. Now, when a user types data into the form fields and presses ENTER, focus returns to the first textfield: "repID". Thanks for the answer.

Answer 3

Also of note, make sure you place the requestFocusInWindow() method after the pack() method. When I was placing the requestFocusInWindow() method before the pack() method, it didn't work. I placed the requestFocusInWindow() method after the pack() method and it worked. Little things like that just make life so much easier for us n00bs.

Answer 4

I hope this example will help you:

        JTextField inputText = new JTextField(20);

        frame.addWindowFocusListener(new WindowAdapter() {
        public void windowGainedFocus(WindowEvent e) {
            inputText.requestFocusInWindow();
        }
    });