Changing the JFrame title

问题

This code compiles, I just can't get the name to change on the title bar.

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;  
import java.awt.event.ActionListener;  
import javax.swing.JButton;  
import javax.swing.JFrame;  
import javax.swing.JLabel;  
import javax.swing.JPanel;  
import javax.swing.JTabbedPane;  
import javax.swing.JTextArea;  
import javax.swing.JTextField;  
public class VolumeCalculator extends JFrame implements ActionListener  
{  
    private JTabbedPane jtabbedPane;  
    private JPanel options;  
    JTextField poolLengthText, poolWidthText, poolDepthText, poolVolumeText, hotTub,  
            hotTubLengthText, hotTubWidthText, hotTubDepthText, hotTubVolumeText, temp, results,
            myTitle;  
    JTextArea labelTubStatus;  
    public VolumeCalculator()  
    {  
        setSize(400, 250);  
        setVisible(true);  
        setSize(400, 250);  
        setVisible(true);  
        setTitle("Volume Calculator");  
        setSize(300, 200);  
        JPanel topPanel = new JPanel();  
        topPanel.setLayout(new BorderLayout());  
        getContentPane().add(topPanel);  

        createOptions();  

        jtabbedPane = new JTabbedPane();  

        jtabbedPane.addTab("Options", options);  

        topPanel.add(jtabbedPane, BorderLayout.CENTER);  
    } 
    /* CREATE OPTIONS */ 

    public void createOptions()  
    {  
        options = new JPanel();  
        options.setLayout(null);  
        JLabel labelOptions = new JLabel("Change Company Name:");  
        labelOptions.setBounds(120, 10, 150, 20);  
        options.add(labelOptions);  
        JTextField newTitle = new JTextField("Some Title"); 
        newTitle.setBounds(80, 40, 225, 20);  
        options.add(newTitle);
        myTitle = new JTextField();   
        myTitle.setBounds(80, 40, 225, 20); 
        myTitle.add(labelOptions); 
        JButton newName = new JButton("Set New Name");  
        newName.setBounds(60, 80, 150, 20);  
        newName.addActionListener(this);  
        options.add(newName);  
        JButton Exit = new JButton("Exit");  
        Exit.setBounds(250, 80, 80, 20);  
        Exit.addActionListener(this);  
        options.add(Exit);  
    }  
    public void actionPerformed(ActionEvent event)  
    {  
        JButton button = (JButton) event.getSource();  
        String buttonLabel = button.getText();  
        if ("Exit".equalsIgnoreCase(buttonLabel))  
        {  
            Exit_pressed();  
            return;  
        }  
        if ("Set New Name".equalsIgnoreCase(buttonLabel))  
        {  
            New_Name();  
            return;  
        }  
    }  
    private void Exit_pressed()  
    {  
        System.exit(0);  
    }  
    private void New_Name()  
    {  
        this.setTitle(myTitle.getText());  
    }  
    private void Options()  
    {  
    }  
    public static void main(String[] args)  
    {  
        JFrame frame = new VolumeCalculator();  
        frame.setSize(380, 350);  
        frame.setVisible(true);  
    }  
}

回答1:

If your class extends JFrame then use this.setTitle(newTitle.getText());

If not and it contains a JFrame let's say named myFrame, then use myFrame.setTitle(newTitle.getText());

Now that you have posted your program, it is obvious that you need only one JTextField to get the new title. These changes will do the trick:

JTextField poolLengthText, poolWidthText, poolDepthText, poolVolumeText, hotTub,
        hotTubLengthText, hotTubWidthText, hotTubDepthText, hotTubVolumeText, temp, results,
        newTitle;

and:

    public void createOptions()
    {
        options = new JPanel();
        options.setLayout(null);
        JLabel labelOptions = new JLabel("Change Company Name:");
        labelOptions.setBounds(120, 10, 150, 20);
        options.add(labelOptions);
        newTitle = new JTextField("Some Title");
        newTitle.setBounds(80, 40, 225, 20);
        options.add(newTitle);
//        myTitle = new JTextField("My Title...");
//        myTitle.setBounds(80, 40, 225, 20);
//        myTitle.add(labelOptions);
        JButton newName = new JButton("Set New Name");
        newName.setBounds(60, 80, 150, 20);
        newName.addActionListener(this);
        options.add(newName);
        JButton Exit = new JButton("Exit");
        Exit.setBounds(250, 80, 80, 20);
        Exit.addActionListener(this);
        options.add(Exit);
    }

and:

private void New_Name()
{
    this.setTitle(newTitle.getText());
}

回答2:

newTitle is a local variable where you create the fields. So when that functions ends, the variable newTitle, does not exist anymore. (The JTextField that was referenced by newTitle does still exist however.)

Thus, increase the scope of the variable, so that you can access it another method.

public SomeFrame extends JFrame {
   JTextField myTitle;//can be used anywhere in this class

   creationOfTheFields()
   {
   //other code
      myTitle = new JTextField("spam");  
      myTitle.setBounds(80, 40, 225, 20);
      options.add(myTitle);
   //blabla other code
   }

   private void New_Name()  
   {  
      this.setTitle(myTitle.getText());  
   } 
}

回答3:

I strongly recommend you learn how to use layout managers to get the layout you want to see. null layouts are fragile, and cause no end of trouble.

Try this source & check the comments.

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTabbedPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;

public class VolumeCalculator extends JFrame implements ActionListener {
    private JTabbedPane jtabbedPane;
    private JPanel options;
    JTextField poolLengthText, poolWidthText, poolDepthText, poolVolumeText, hotTub,
            hotTubLengthText, hotTubWidthText, hotTubDepthText, hotTubVolumeText, temp, results,
            myTitle;
    JTextArea labelTubStatus;

    public VolumeCalculator(){
        setSize(400, 250);
        setVisible(true);
        setSize(400, 250);
        setVisible(true);
        setTitle("Volume Calculator");
        setSize(300, 200);
        JPanel topPanel = new JPanel();
        topPanel.setLayout(new BorderLayout());
        getContentPane().add(topPanel);

        createOptions();

        jtabbedPane = new JTabbedPane();

        jtabbedPane.addTab("Options", options);

        topPanel.add(jtabbedPane, BorderLayout.CENTER);
    }
    /* CREATE OPTIONS */

    public void createOptions(){
        options = new JPanel();
        //options.setLayout(null);
        JLabel labelOptions = new JLabel("Change Company Name:");
        labelOptions.setBounds(120, 10, 150, 20);
        options.add(labelOptions);
        JTextField newTitle = new JTextField("Some Title");
        //newTitle.setBounds(80, 40, 225, 20);    
        options.add(newTitle);
        myTitle = new JTextField(20);
        // myTitle WAS NEVER ADDED to the GUI!
        options.add(myTitle);
        //myTitle.setBounds(80, 40, 225, 20);
        //myTitle.add(labelOptions);
        JButton newName = new JButton("Set New Name");
        //newName.setBounds(60, 80, 150, 20);
        newName.addActionListener(this);
        options.add(newName);
        JButton Exit = new JButton("Exit");
        //Exit.setBounds(250, 80, 80, 20);
        Exit.addActionListener(this);
        options.add(Exit);
    }

    public void actionPerformed(ActionEvent event){
        JButton button = (JButton) event.getSource();
        String buttonLabel = button.getText();
        if ("Exit".equalsIgnoreCase(buttonLabel)){
            Exit_pressed();
            return;
        }
        if ("Set New Name".equalsIgnoreCase(buttonLabel)){
            New_Name();
            return;
        }
    }

    private void Exit_pressed(){
        System.exit(0);
    }

    private void New_Name(){
        System.out.println("'" + myTitle.getText() + "'");
        this.setTitle(myTitle.getText());
    }

    private void Options(){
    }

    public static void main(String[] args){
        JFrame frame = new VolumeCalculator();
        frame.pack();
        frame.setSize(380, 350);
        frame.setVisible(true);
    }
}

回答4:

these methods can help setTitle("your new title"); or super("your new title");

来源：https://stackoverflow.com/questions/5487615/changing-the-jframe-title

标签

java

eclipse

jframe