CODEWITHSUNDEEP
javaswinguser-interfacejframejbutton
Illorum
Illorum

Reputation: 123

Java GUI Help (JFrame, JButton, etc)

Ok so im new to programming GUIs in Java and I need some help on how to add buttons and Labels. I went around looking at an example and I figured it this was how it worked to basically add a button:

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


public class GUI_Tests extends JFrame{
    public static void main(String[] args){
        private JButton button;
        button = new JButton("pls work");
        add(button);

    }

}

Well that didnt work at all... Can someone show me how its done and give me some pointers?

Upvotes: 0

Views: 2065

Answers (5)

Durandal
Durandal

Reputation: 5663

You need to add your button to a JFrame The basic flow should look something like this:

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

public class GUITests extends JFrame{

    public GUITests() {
        setTitle("Simple example");

        setLocationRelativeTo(null);
        setDefaultCloseOperation(EXIT_ON_CLOSE);  
        JButton button = new JButton("pls work");
        add(button);
        pack();
    }

    public static void main(String[] args){
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                GUITests ex = new GUITests();
                ex.setVisible(true);
            }
        });

    }
}

The GUITests class extends the JFrame class so you can call all the methods that are visible on the JFrame class. In the main method It's just some boiler plate code that calls your constructor for you so that you can see your basic example.

Check out the tutorials here: http://zetcode.com/tutorials/javaswingtutorial/firstprograms/

Upvotes: 1

Paul Samsotha
Paul Samsotha

Reputation: 209002

  • You should note that a JFrame has a default BorderLayout which, if not specified, will add a component to a BorderLayout.CENTER position.

  • When adding components to JFrame, if a different Layout is not specified, then you want to set a component's position, like add(button, BorderLayout.SOUTH);

  • Also you should use a constructor. Something like this

    public class GUI_Tests extends JFrame {
    public GUI_Tests(){
        JButton button = new JButton("Pls work");
        JLabel label = new JLabel("Pls work");
        add(button, BorderLayout.CENTER);
        add(label, BorderLayout.SOUTH);
    }
}

  • Also you need to remember to set the frame visible.

A simple running program would be something like this 

import java.awt.BorderLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingUtilities;

public class GUI_Tests extends JFrame {

    public GUI_Tests() {
        JButton button = new JButton("Pls work");
        JLabel label = new JLabel("Pls work");
        add(button, BorderLayout.CENTER);
        add(label, BorderLayout.WEST);

        pack();
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
        setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable(){
            public void run(){
                new GUI_Tests();
            }
        });
    }
}
  • The main method may look somewhat crazy to you, but all it is doing is causing the program to run on the Event Dispatch Thread (EDT). I won't go into this too much as you are still a beginner.
  • What is going on in the run is that all I do is create an instance of me program, which extends JFrame. If I didn't extend JFrame, I would have to explicitly create a JFrame to run the program. All GUI programs need some top-level container to run.

  • Also you can see in the constructor, that when I added the button and label I set a layout position

    add(button, BorderLayout.CENTER);
add(label, BorderLayout.SOUTH);

    as I stated earlier, when using a JFrame without specifying a different layout, you should use position with the default `BorderLayout. Other possible positions are

    BorderLayout.EAST
BorderLayout.WEST
BorderLayout.CENTER
BorderLayout.NORTH
BorderLayout.SOUTH

    Take a look at [Laying Out Components Within a Container]Laying Out Components Within a Container)

  • Also, noticed I used pack(). What this does is make the frame the perfect with for the preferrsed sizes of the components. It is preferred to pack() rather then setSize() of a frame.
  • setDefaultCloseOperation(EXIT_ON_CLOSE); makes it so that when x out the frame, the program shuts down.
  • setLocationRelativeTo(null); set the frame's location in the center of the screen
  • setVisible(true); makes the frame visible. This should always be called to make the frame visible on start of the program.

Please have a look at the Swing tutorials

Upvotes: 3

doomsdaymachine
doomsdaymachine

Reputation: 647

public class GUI_Tests extends JFrame {

    private JButton button;

    public GUI_Tests() {
        setTitle("Title");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // so that the application properly closes when you click close
        button = new JButton("pls work");
        add(button);
        pack(); // resize the frame to its contents
        setLocationRelativeTo(null); // center the frame on the screen
    }

    public static void main(String args[]) {
        // properly start a swing application
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                GUI_Tests gui = new GUI_Tests();
                gui.setVisible(true); // set the frame visible 
            }
        });
    }
}

hope this helps you understand it a bit more. i didn't use any layouts in this code as its just a simple example, however, i highly recommend you to read on built-in layouts in swing and how to use them. Here's one good start

Upvotes: 1

user2570465
user2570465

Reputation: 2497

type

setVisible( true );
setSize( 500 , 500 );

and I think you'll see something. Also get rid of private in the statement private JButton button But you should really put your code in the constructor of the GUI_Tests:

import javax.swing.*;

public class GUI_Tests extends JFrame {
    public GUI_Tests() {
        JButton button = new JButton( "Hello World" );
        add( button );
        setVisible( true );
        setSize( 500 , 500 );
    }

    final public static void main( String[] args ) {
        GUI_Tests tests = new GUI_Tests();
    }
}

Check out the Java tutorial for more help, possibly here: http://docs.oracle.com/javase/tutorial/uiswing/start/index.html

Upvotes: 0

ccjmne
ccjmne

Reputation: 9618

You are supposed to add your JButton to a JFrame, but it seems to me that you haven't even created a JFrame yet. You should first create an instance of GUI_Tests, then use the JFrame#add method with your JButton. For example:

public class GUI_Tests extends JFrame {
    public GUI_Tests() {
        super("My first Swing frame!");

        this.setPreferredSize(new Dimension(640, 480));
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        // Create your GUI here
        this.add(new JButton("Click on me :)"));

        this.setVisible(true);
    }
}

Actually, I wouldn't be mean to you, but I think you tried to go too fast: in my opinion, you should start by following some tutorial on how to deal with Swing :)

Upvotes: 1

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