Java JFrame - Decodejava.com

JFrame

JFrame is a top-level container that is used to hold components in it.

Constructors of JFrame

Constructor	Description
public JFrame()	Creates a JFrame window with no name.
*public JFrame(String name)*	Creates a JFrame window with a name.

JFrame methods

Methods	Description
*public void add(Component comp)*	This method adds the component, comp, to the container JFrame.
public void setLayout(LayoutManager object)	This method sets the layout of the components in a container, JFrame.
public void remove(Component comp)	This method removes a component, comp, from the container, JFrame.
public void setSize(int widthPixel, int heightPixel)	This method sets the size of a JFrame in terms of pixels.
*public void setDefaultCloseOperation(int operation)*	This method sets the operation that will take place when a a user clicks on close(x) button of this JFrame. An operation may take any of the values- DO_NOTHING_ON_CLOSE HIDE_ON_CLOSE DISPOSE_ON_CLOSE EXIT_ON_CLOSE
public void setVisble(boolean b)	This method set the visibility of JFrame using boolean value.

BorderLayout is the default layout manager of JFrame.

The default layout of JFrame by which it positions the components in it is BoderLayout manager. Hence, if we add components to JFrame without calling it's setLayout() method, these components are added to the center region of by default.
Note Remember, using the BorderLayout manager, only one component can be placed in a region, hence if multiple elements are added to a region, only the last element will be visible.

import javax.swing.*;
//import java.awt.*;

class SwingEx implements Runnable
{

public static void main(String...ar)
{
SwingUtilities.invokeLater(new SwingEx());
}


public void run()
{
new A();
}

}


class A
{
JFrame frame;
JLabel label;
JButton button;

A()
{
frame = new JFrame("JFrame");
label = new JLabel("Hello there, how are you today? :-)");
button = new JButton("Button1");

//Adding JLabel and JButton to JFrame, which will added to BorderLayout.CENTER region of JFrame.
frame.add(label);
frame.add(button);

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(210,250);
frame.setVisible(true);
}

}

In the last code, two components i.e JLabel and JButton are added to top-level container, JFrame, without calling its setLayout() method. These components are added to BorderLayout.CENTER region of JFrame. Hence, only the last component added, i.e. JButton will be visible. When you run the code, you are presented a window that only shown a button.

Figure 1

An simple example displaying the use of JFrame.

In the upcoming code, we are going to add two componentsm i.e JLabel and JButtonto JFrame.
Before adding these components to JFrame, we will call setLayout() method to position components in JFrame according to FlowLayoutManager

import javax.swing.*;
//import java.awt.*;

class SwingEx implements Runnable
{

public static void main(String...ar)
{
SwingUtilities.invokeLater(new SwingEx());
}


public void run()
{
new A();
}

}


class A
{
JFrame frame;
JLabel label;
JButton button;

A()
{
frame = new JFrame("JFrame");
label = new JLabel("Hello there, how are you today? :-)");
button = new JButton("Button1");


//Setting the layout of  components in JFrame to FlowLayout
frame.setLayout(new FlowLayout()); 

frame.add(label);
frame.add(button);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(210,250);
frame.setVisible(true);
}

}

When you run the code, you are presented a window that contains a top-level container, JFrame, which includes two components that are positioned in JFrame using FlowLayout manager -

A JLabel displaying a message.
A JButton displaying a button.

Figure 2

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