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Message:

using Graphics in an application

Posted by Raj Muthusamy on January 21, 2002 at 1:01 AM

1. get Graphics object g by calling getGraphics() method of a component.

2. use drawing methods of the graphics object g for rendering.

Note: make sure that the component is made visible before calling
the getGraphics() method. Otherwise, g will be born null.

I have given a simple example below to illustrate the points.

-------------------------------------------------------
import java.awt.*;
import java.awt.event.*;

public class test{
Frame ff;
Button bb;
public static void main(String args[]){
test tt = new test();
tt.display();
}//main

public void display(){
ff=new Frame("test");
bb=new Button("click");
ff.setLayout(new FlowLayout());
ff.add(bb);
ff.setVisible(true);
ff.setSize(400,400);
actionListener act = new actionListener();
bb.addActionListener(act);
}//display

class actionListener implements ActionListener{
public void actionPerformed(ActionEvent evt){
Graphics g = ff.getGraphics();
g.fillRect(100,100,200,200);
}
}

}//class