How do I create a new JFrame?

Question

I'm a complete beginner to Java, and I'm finding some answers a bit too technical for me (even the most basic tutorials seem to give me syntax errors when I run the code). How, in really simple terms do I add a JButton to a JFrame? I've got as far as:

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

public class JF {

    public static void main(String[] args) {
        JFrame myFrame = new JFrame();
        /*some pretty basic code to initialize the JFrame i.e.
        myFrame.setSize(300, 200);
        This is as far as I got
        */
    }

}

I would seriously appreciate some help!

Answer 1

Creating a new JFrame

The way to create a new instance of a JFrame is pretty simple. All you have to do is:

JFrame myFrame = new JFrame("Frame Title");

But now the Window is hidden, to see the Window you must use the setVisible(boolean flag) method. Like this:

myFrame.setVisible(true);

Adding Components

There are many ways to add a Component to a JFrame.

The simplest way is:

myFrame.getContentPane().add(new JButton());//in this case we are adding a Button

This will just add a new Component that will fill the JFrame().

If you do not want the Component to fill the screen then you should either make the ContentPane of the JFrame a new custom Container

myFrame.getContentPane() = new JPanel();

OR add a custom Container to the ContentPane and add everything else there.

JPanel mainPanel = new JPanel();
myFrame.getContentPane().add(mainPanel);

If you do not want to write the myFrame.getContentPane() every time then you could just keep an instance of the ContentPane.

JPanel pane = myFrame.getContentPane();

Basic Properties

The most basic properties of the JFrame are:

• Size
• Location
• CloseOperation

You can either set the Size by using:

myFrame.setSize(new Dimension(300, 200));//in pixels

Or packing the JFrame after adding all the components (Better practice).

myFrame.pack();

You can set the Location by using:

myFrame.setLocation(new Point(100, 100));// starting from top left corner

Finally you can set the CloseOperation (what happens when X is pressed) by

setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

There are 4 different actions that you can choose from:

• DO_NOTHING_ON_CLOSE //Nothing happens
• HIDE_ON_CLOSE //setVisible(false)
• DISPOSE_ON_CLOSE //Closes JFrame, Application still runs
• EXIT_ON_CLOSE //Closes Application

Using Event Dispatch Thread

You should initialize all GUI in Event Dispatch Thread, you can do this by simply doing:

class GUI implements Runnable {

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

    @Override
    public void run() {
        JFrame myFrame = new JFrame("Frame Title");

        myFrame.setLocation(new Point(100, 100));
        myFrame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        JPanel mainPanel = new JPanel();
        mainPanel.setLayout(new BorderLayout());
        myFrame.getContentPane().add(mainPanel);
        mainPanel.add(new JButton("Button Text"), BorderLayout.CENTER);

        myFrame.pack();
        myFrame.setLocationByPlatform(true);
        myFrame.setVisible(true);
    }

}

Answer 2

//I hope this will help

import javax.swing.JFrame;
import javax.swing.JButton;
import javax.swing.JPanel;
public class JF extends JFrame
{
    private JButton myButton;//Here you begin by declaring the button
    public JF()//Here you create you constructor. Constructors are used for initializing variable
    {
        myButton = new JButton();//We initialize our variable
        myButton.setText("My Button"); //And give it a name
        JPanel panel1 = new JPanel();//In java panels are useful for holding content
        panel1.add(myButton);//Here you put your button in the panel

        add(panel1);//This make the panel visible together with its contents

        setSize(300,400);//Set the size of your window
        setVisible(true);//Make your window visible
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
    public static void main(String[] args)
    {
        JFrame frame = new JF();
        frame.setTitle("My First Button");
        frame.setLocation(400,200);
    }
}