JButton disappears when resize

Question

anyone know or have an idea as to why my button disappears after i resize the applet?

this is my code:


import java.awt.event.*;
import javax.swing.*;
import acm.program.*;

public class button extends ConsoleProgram {

    public void init(){

        hiButton = new JButton("hi");
        add(hiButton, SOUTH);
        addActionListeners();


    }

    public   void actionPerformed(ActionEvent e){
        if(hiButton == e.getSource()){
           println("hello") ;
        }

    }
private JButton hiButton;


}

yeah, says it's an applet on the top. but, yeah its an acm program. — Elias Sanchez, Sep 02 '12 at 00:29
It's not homework. simply learning java through Stanford University youtube channel. Anyway, seems like the answer is not to use ACM lol .. — Elias Sanchez, Sep 02 '12 at 22:51
You could try running it under Java 1.5, like they did [here](http://stackoverflow.com/q/12130335/261156). — Catalina Island, Sep 03 '12 at 13:13
@AndrewThompson The homework tag has been [deprecated](http://meta.stackexchange.com/questions/147100/the-homework-tag-is-now-officially-deprecated) and should be phased out. — Vala, Oct 22 '12 at 13:27

score 1 · Answer 1 · answered Jan 12 '13 at 20:14

I'm not sure if it is a good Idea to redefine the init-method. When I have a look at http://jtf.acm.org/javadoc/student/acm/program/ConsoleProgram.html I would expect that you have implement only the run-method. Overriding init without calling super.init() Looks strange to me.

Maybe I would be better to derive from JApplet directly for your first steps in Applet programming.

score 0 · Answer 2 · answered Jan 03 '13 at 21:36

Assuming that

your ConsoleProgram extends (directly or indirectly) JApplet
You declared SOUTH as a static final variable that has the value BorderLayout.SOUTH (otherwise your code doesn't compile)

The code should work, no need to repaint (unless you would like to do some application-specific optimization). I just copied and pasted your code (by expliciting the two assumptions above), I see the applet and the button doesn't disappear on resize.

Anyway there are few "not good" things in the code:

First of all, a naming convention issue: the class name should be "Button" with the first letter capitalized (on top of that, it's a poor name for an Applet)
Second, action listeners should be attached before adding the component;
Third, as Oracle doc suggests here, the code that builds the GUI should be a job that runs on the event dispatcher thread. You can do that by wrapping the build gui code in a Runnable using a SwingUtilities.invokeAndWait(Runnable()

score 0 · Answer 3 · answered Jan 18 '13 at 01:09

0

Have you tried calling super.init() at the start of your init() method?

answered Jan 18 '13 at 01:09

Edward Falk

9,991
11
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score 0 · Answer 4 · answered Feb 16 '13 at 23:36

0

Try explicitly using a layout for your Console and then use relative positioning.

answered Feb 16 '13 at 23:36

user2078263

1
1

score -1 · Answer 5 · answered Jan 06 '13 at 09:49

To re-size a button in Applet:

public class Button extends JApplet implements ActionListener {

   private JButton button;

   public void init() {
      Container container = getContentPane();
      container.setLayout(null);
      container.setBackground(Color.white);
      button = new JButton("Press Me");
      button.setSize(getWidth()/2,20);
      button.setLocation(getWidth()/2-button.getSize().width/2, getHeight()/2-button.getSize().height/2);
      container.add(button);
      button.addActionListener(this);
   }

   public void actionPerformed(ActionEvent e) {
      int width = (button.getSize().width == getWidth()/2) ? getWidth()/4 : getWidth()/2;
      int height = button.getSize().height;
      button.setSize(width,height);
      button.setLocation(getWidth()/2-width/2, getHeight()/2-height/2);
   }
}

To re-size a button in JFrame:

public class Button extends JFrame implements ActionListener {
   private JButton button;

   public Button(String title) {
      Container container = getContentPane();
      container.setLayout(null);
      container.setBackground(Color.white);
      setTitle(title);
      setSize(400,400);
      button = new JButton("Press Me");
      button.setSize(getWidth()/2,20);
      button.setLocation(getWidth()/2-button.getSize().width/2,
                     getHeight()/2-button.getSize().height/2);
      container.add(button);
      button.addActionListener(this);
    }

   public void actionPerformed(ActionEvent e) {
      int width = (button.getSize().width == getWidth()/2) ? getWidth()/4 : getWidth()/2;
      int height = button.getSize().height;
      button.setSize(width,height);
      button.setLocation(getWidth()/2-width/2, getHeight()/2-height/2);
   }

   public static void main(String[] args) {
      Button button = new Button("Test");
      button.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      button.setVisible(true);
   }
}

-1 for recommending a null layout (aka: manual sizing/locating of components): whatever the problem, that's **not** the Swing'ish way of a solution. — kleopatra, Jan 06 '13 at 12:52
@kleopatra What is the problem of using a null layout for "Absolute Positioning". It is in the docs (http://docs.oracle.com/javase/tutorial/uiswing/layout/none.html) and my code is an example. — Ahmed Hassanien, Jan 07 '13 at 01:57
the main problem is that you have to re-do all the calculations when any property on any of the children which effects the layout changes - which is exactly what a manager does. Doing so manually is not only a waste of time (you have to re-code lots of code) but also tricky to get right: you need to listen to all those changes and still might not get notified on all (missing manual re/validation, f.i.) — kleopatra, Jan 07 '13 at 10:16

score -2 · Answer 6 · answered Sep 06 '12 at 09:47

-2

Have you declared the repaint method...???

You are using swing. It needs to have declared a repaint.

Please define a custom repaint mwthod

answered Sep 06 '12 at 09:47

Fr_nkenstien

1,923
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JButton disappears when resize

6 Answers6