在扩展JFrame的类中的另一个JFrame上绘制一条线

Question

I have a class with two JFrames and am trying to draw a line on a particular frame .

I tried the code below but it only appears in the first frame which is the success frame.

It also appears above all the other components of the success frame thus making all other

components invisible. It does not appear in the comp Frame.

How do I correct this.

Here is the code I have so far :

import javax.swing.*;
import java.awt.*;
import java.awt.geom.*;
import java.awt.event.*;

public class lineGUI{
public static void main(String []args){
Success s=new Success();
s.setVisible(true);
  }
}

class Success extends JFrame{

JPanel alas =new JPanel();
JFrame comp =new JFrame();
public Success(){
JPanel panel=new JPanel();
getContentPane().add(panel);
setSize(450,450);

JButton button =new JButton("press");
panel.add(button);

  comp.setSize(650,500);
  comp.setTitle("View Report");

  JRootPane compPane=comp.getRootPane();
  Container contePane=compPane.getContentPane();
  contePane.add(alas);


    ActionListener action =new ActionListener(){
      public void actionPerformed(ActionEvent e){
        if (e.getSource()==button){
          comp.setVisible(true);
        }
      }
    };
    button.addActionListener(action);

  JButton button2=new JButton("access");
  alas.add(button2);
 }

public void paint(Graphics g) {
comp.paint(g);
Graphics2D g2 = (Graphics2D) g;
Line2D lin = new Line2D.Float(100, 100, 250, 260);
g2.draw(lin);
  }
}

Answer 1

You've got some crazy code up there. Suggestions:

• Don't draw directly in a JFrame, but in a the paintComponent method of an object derived from JComponent such as JPanel or JComponent itself.
• Your drawing directly in another component's paint(...) method is not kosher at all. Why not simply share the data between classes, and use the data (the ints) to draw where desired.
• You would rarely want to have a GUI display more than one JFrame at a time. Usually one window is the main window (the JFrame), and it often owns any other windows which would be dialog windows such as JDialogs.
• Read the graphics tutorials to learn the correct way to do Swing Graphics

Answer 2

Two things:

If you want to draw in the "comp" frame, then you should extend that frame explicitly to overload its paint method. Right now you're overloading the paint method of "Success" frame. The line comp.paint(g) is using the paint method of comp (a standard JFrame) to draw on the Graphics object of the "Success" frame. You probably want to make that into super.paint(g) instead, then put this paint function into it's own JFrame and create comp from that.

http://pastebin.com/ZLYBHpmj

(Sorry, first post, couldn't figure out how to get Stackoverflow to quit complaining about format)