BorderLayout only showing one object

问题

I decided to write a small Java program to experiment around with BorderLayout, because I'm developing a Java game and I need to have 2 objects placed in a single JFrame at the same time, and everyone I asked said I need BorderLayout to do that.

So the Java program I wrote is supposed to place a JButton on the JFrame and ALSO place a graphic component (a rectangle in this case). The problem is, only the button shows up, as can be seen in the image link below:

http://prntscr.com/3m5ek6

I can't post actual images due to my low reputation statistic.

Here is the code:

main.java --> The main method class + JFrame/JPanel/JButton constructor

import java.awt.BorderLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;


public class main {

public static void main(String[] args) {

    Infout m = new Infout();
    JFrame f = new JFrame();
    JPanel start = new JPanel();
    JPanel start2 = new JPanel();

    start.add(m);
    start2.add(new JButton("Hi"));

    f.add(start,BorderLayout.LINE_START);
    f.add(start2, BorderLayout.LINE_END);
    f.setVisible(true);
    f.setSize(300, 400);

}

}

Infout.java --> Rectangle constructor class

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Rectangle2D;
import javax.swing.JPanel;


public class Infout extends JPanel{

public void paintComponent(Graphics g){
    super.paintComponent(g);
    Graphics2D g2 = (Graphics2D) g;
    g2.fill(new Rectangle2D.Double(140, 270, 5, 300));
}

}

Can someone tell me what's wrong? Also, is using BorderLayout the best option for adding multiple static and/or dynamic objects to a JFrame?

Thanks!

回答1:

You need to override the getPreferredSize() method so the layout manager can determine the proper size for the component.

How do I do that?

Read the section from the Swing tutorial on Custom Painting for more information on custom painting, including a working example that shows how to override the getPreferredSize() method.

来源：https://stackoverflow.com/questions/23847889/borderlayout-for-objects

标签

java

swing

jpanel

border-layout

preferredsize