JComponent size issue

Question

I have a JComponent subclass that I am using to draw shapes onto my screen. In the constructor, I am trying to set ballX and ballY to half

Answer 1

Override getPreferredSize() in your JComponent to return your preferred size, and start with half the width and height of that Dimension. To the same end, this KineticModel invokes setPreferredSize() in DisplayPanel.

Addendum: By way of explanation, your current approach fails because the results from getWidth() and getHeight() are invalid until validate() has been called on the enclosing container, typically as the result of pack().

Answer 2

I agree with trashgod's answer. (+1)

Move the ballX and ballY in the paintComponent(g) like this

if (ballX==0 && ballY==0) {
    ballX = getWidth()/2;
    ballY = getHeight()/2;
}