Add JButtons to JPanel

Question

I want to add a number of JButtons to a JPanel using a For loop. When the user presses a button, the following code is run:

for (i = 0; i < 10; i++)
{
  JButton aButton = new JButton();
  mainPanel.add(aButton);
  mainPanel.revalidate();
  mainPanel.repaint();
  System.out.println("Added: " + (i + 1) + "buttons");
}

However, when I press the button, no JButtons are added to the JPanel, but the program prints the appropriate number of buttons that should be added.

Not sure what the problem is here =/

Solution 1

I've solved my problem. I'm using NetBeans and apparently Free Layout doesn't work, so I set the JPanel's layout to Grid Layout and voila, the buttons appear

Solution 2

I would use the following.

for (i = 0; i < 10; i++) {
    mainPanel.add(new JButton("Button text"));
    System.out.println("Added: " + (i + 1) + "buttons");
}

mainPanel.invalidate();
mainPanel.repaint();

Comments

[Rémi Vennereau]

if you need invalidate and repaint you are most likely doing something wrong?

[Matti Lyra]

You still don't want to be calling the repaint method inside the for loop. There is no reason to repaint the panel ten times.

[Flynn]

Thanks. Will repaint outside the loop

[camickr]

All you need is revalidate(). This will cause the layout manager to be invoked.