Why we use JPanel

JPanel we will help java programmer to create more complex graphical user interface. But how ? It answer is, it allow other component to add into it. Component that i mean here like JButton, JLabel or JTextField or others. It also give ability to other JPanel add into it. For example, we has two JPanel called panelA and panelB. We can add panelA into panelB. So, if panelA also contains other components and panelB also contains other component beside panelA that we add before, how complex the graphical user interface...i hope you can imagine it.

Create JPanel in java

Source code below will show you how to create a JPanel in java and after that we will put the JPanel into a JFrame.

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COMPLETE SOURCE CODE FOR : CreateAJPanel.java
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import javax.swing.JFrame;
import javax.swing.JPanel;

public class CreateAJPanel
{
public static void main(String[]args)
{
 //Create a JPanel
 JPanel panel=new JPanel();

 //Create a JFrame that we will use to add the JPanel
 JFrame frame=new JFrame("Create a JPanel");

 //ADD JPanel INTO JFrame
 frame.add(panel);

 //Set default close operation for JFrame
 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

 //Set JFrame size to :
 //WIDTH : 400 pixels
 //HEIGHT : 400 pixels
 frame.setSize(400,400);

 //Make JFrame visible. So we can see it
 frame.setVisible(true);
}
}

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JFrame fullscreen

Source code below will show you, how to set JFrame to full screen follow to current computer screen

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COMPLETE SOURCE CODE FOR : FullScreenJFrame.java
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import javax.swing.JFrame;

import java.awt.Toolkit;

public class FullScreenJFrame
{
public static void main(String[]args)
{
 //Create a JFrame with title ( Full Screen JFrame )
 JFrame frame=new JFrame("Full Screen JFrame");

 //Set default close operation for JFrame
 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

 //Set JFrame size to full screen size follow current screen size
 frame.setSize(Toolkit.getDefaultToolkit().getScreenSize().width,Toolkit.getDefaultToolkit().getScreenSize().height);

 //Make JFrame visible
 frame.setVisible(true);
}
}

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Get JFrame size

Source code below will create a JFrame with a button in it. You can know current JFrame size by click the button. You also can try resize the JFrame first, and after that click the button.

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COMPLETE SOURCE CODE FOR : GetJFrameSize.java
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import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;

import java.awt.FlowLayout;

import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class GetJFrameSize extends JFrame
{
//Create ActionListener for listen when someone click button
ActionListener al=new ActionListener()
{
 //Overwrite abstract method ( actionPerformed ) in ActionListener class
 public void actionPerformed(ActionEvent event)
 {
  //Show message box that contain information about current JFrame width and height in pixels
  JOptionPane.showMessageDialog(null,"JFrame size in pixels is : \n"+"WIDTH : "+getSize().width+"\n"+"HEIGHT : "+getSize().height);
 }
};

public GetJFrameSize()
{
 //Create JFrame title ( Resize me and click button )
 super("Resize me and click button");

 //Set JFrame layout to FlowLayout
 setLayout(new FlowLayout());

 //Create a button with text ( Click me to see current JFrame size )
 JButton button=new JButton("Click me to see current JFrame size");

 //Add ActionListener to the button
 button.addActionListener(al);

 //Add the button into created JFrame
 add(button);

 //Set default close operation for JFrame
 setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

 //Set initial JFrame size to :
 //WIDTH = 500 pixels
 //HEIGHT = 500 pixels
 setSize(500,500);

 //Make JFrame visible
 setVisible(true);
}

public static void main(String[]args)
{
 GetJFrameSize gjfs=new GetJFrameSize();
}
}

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Set JFrame size

Source code below will show you, how to set JFrame size

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COMPLETE SOURCE CODE FOR : SetSizeForJFrame.java
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import javax.swing.JOptionPane;
import javax.swing.JFrame;

public class SetSizeForJFrame
{
public static void main(String[]args)
{
 //Receive user input for JFrame width
 String jframeWidth=JOptionPane.showInputDialog(null,"Put JFrame width in pixels here");

 //Receive user input for JFrame height
 String jframeHeight=JOptionPane.showInputDialog(null,"Put JFrame height in pixels here");

 //Create a JFrame
 JFrame frame=new JFrame("Set JFrame size");

 //Set default close operation for JFrame
 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

 //Set JFrame size base on user input
 frame.setSize(Integer.parseInt(jframeWidth),Integer.parseInt(jframeHeight));

 //Make JFrame visible. So we can see it
 frame.setVisible(true);
}
}

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Set JFrame title

Source code below will show how to set JFrame title

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COMPLETE SOURCE CODE FOR : SetJFrameTitle.java
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import javax.swing.JFrame;
import javax.swing.JOptionPane;

public class SetJFrameTitle
{
public static void main(String[]args)
{
 //Create input dialog that will use to receive JFrame title
 String jframeTitle=JOptionPane.showInputDialog(null,"Put JFrame title here");

 //Create a JFrame
 JFrame frame=new JFrame();

 //Set title for JFrame
 //Method setTitle() is use to set JFrame title
 frame.setTitle(jframeTitle);

 //Set default close operation for JFrame
 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

 //Set JFrame size
 frame.setSize(400,400);

 //Make JFrame visible
 frame.setVisible(true);
}
}

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Get JFrame title

Source code below will show how to get JFrame title.

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COMPLETE SOURCE CODE FOR : GetJFrameTitle.java
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import javax.swing.JFrame;
import javax.swing.JOptionPane;

public class GetJFrameTitle
{
public static void main(String[]args)
{
 //Create a JFrame with title ( My first window )
 JFrame frame=new JFrame("My first window");

 //Set default close operation for JFrame
 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

 //Set JFrame size
 frame.setSize(500,500);

 //Make JFrame visible
 frame.setVisible(true);

 //Create a message box that show JFrame title
 //Method getTitle() will get JFrame title
 JOptionPane.showMessageDialog(frame,"MY NAME IS : "+frame.getTitle());
}
}

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Determine when JFrame moved

Source code below will show you, how to determine when a JFrame is moved

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COMPLETE SOURCE CODE FOR : DetermineWhenAJFrameIsMoved.java
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import javax.swing.JFrame;
import javax.swing.JOptionPane;

import java.awt.event.ComponentEvent;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentListener;

public class DetermineWhenAJFrameIsMoved extends JFrame
{
//Create ComponentListener that will listen when JFrame is moving
ComponentListener cl=new ComponentAdapter()
{
 public void componentMoved(ComponentEvent event)
 {
  //Location that will show is base on top left corner of JFrame
  JOptionPane.showMessageDialog(null,"New location with :\n"+"X-coordinate : "+getLocation().getX()+"\n"+"Y-coordinate : "+getLocation().getY());
 }
};

public DetermineWhenAJFrameIsMoved()
{
 super("TRY MOVE ME");

 setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 setSize(300,300);
 setVisible(true);

 //Add ComponentListener to JFrame
 addComponentListener(cl);
}

public static void main(String[]args)
{
 DetermineWhenAJFrameIsMoved dwajfir=new DetermineWhenAJFrameIsMoved();
}
}

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Determine when JFrame resized

Source code below will show you, how to determine when JFrame re sized.

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COMPLETE SOURCE CODE FOR : DetermineWhenAJFrameIsResized.java
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import javax.swing.JFrame;
import javax.swing.JOptionPane;

import java.awt.event.ComponentEvent;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentListener;

public class DetermineWhenAJFrameIsResized extends JFrame
{
//Create ComponentListener that will listen when JFrame is resizing
ComponentListener cl=new ComponentAdapter()
{
 public void componentResized(ComponentEvent event)
 {
  JOptionPane.showMessageDialog(null,"New size with :\n"+"WIDTH : "+getSize().width+"\n"+"HEIGHT : "+getSize().height);
 }
};

public DetermineWhenAJFrameIsResized()
{
 super("TRY RESIZE ME");

 setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 setSize(300,300);
 setVisible(true);

 //Add ComponentListener to JFrame
 addComponentListener(cl);
}

public static void main(String[]args)
{
 DetermineWhenAJFrameIsResized dwajfir=new DetermineWhenAJFrameIsResized();
}
}

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Draw rectangle in JFrame

Source code below will show how to draw rectangle in JFrame.

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COMPLETE SOURCE CODE FOR : DrawRectangleInJFrame.java
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import javax.swing.JFrame;

import java.awt.Graphics;
import java.awt.Color;

public class DrawRectangleInJFrame extends JFrame
{
public DrawRectangleInJFrame()
{
 //Set JFrame title
 super("Draw A Rectangle In JFrame");

 //Set default close operation for JFrame
 setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

 //Set JFrame size
 setSize(400,400);

 //Make JFrame visible 
 setVisible(true);
}

public void paint(Graphics g)
{
 super.paint(g);

 //draw rectangle outline
 g.drawRect(50,50,300,100);

 //set color to RED
 //So after this, if you draw anything, all of it's result will be RED
 g.setColor(Color.RED);

 //fill rectangle with RED
 g.fillRect(50,50,300,100);
}

public static void main(String[]args)
{
 DrawRectangleInJFrame dlijf=new DrawRectangleInJFrame();
}
}

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