Button

Button is a component class in AWT package. When a button is pushed, an action can happen. An application that wants to perform some action when the button is pushed has to implement ActionLister interface and registers the new listener to receive events from the button by calling the addActionListener(ActionListener listener) method. The code to perform actions when the button is pushed will be placed in the actionPerformed(ActionEvent e) method of the ActionLister interface.

Constructors of Button class:
-Button()
creates a button with empty label.
-Button(String label)
creates a button with string label.
Useful methods of Button class:
-addActionListener(ActionListener listener): void
registers the new listener to receive events from the button.
-getLabel(): String
reads the label on the button.
-setLabel(String label): void
  set the label to the button.

Example:

import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.Dimension;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Label;
import java.awt.Panel;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;
class ShowImage extends Label{
BufferedImage bi=null;
public void paint(Graphics g){
if(bi!=null)
g.drawImage(bi,0,0,null);
}

public void loadImage(String filename){
try{
bi=ImageIO.read(new File(filename));
}catch(IOException ie){System.out.println("Can't read the image file");}
}
}

class InterfaceShow extends Frame implements ActionListener{
InterfaceShow(String title){
setTitle(title);
setSize(new Dimension(350,300));
setLayout(new BorderLayout());
addWindowListener(new WindowAdapter(){
public void windowClosing(WindowEvent e){
System.exit(0);
}
});
Button btshow=new Button("Show image");
btshow.addActionListener(this);
Panel panel=new Panel();
panel.add(btshow);
add(panel, BorderLayout.NORTH);
setVisible(true);

}

public void actionPerformed(ActionEvent e){
ShowImage si=new ShowImage();
si.loadImage("d:/earth.png");
add(si,BorderLayout.CENTER);
validate();

}
}
public class AWTControls {
public static void main(String[] args){
new InterfaceShow("Using Button");

}
}