why repaint is not updating GUI?

[S Reddy]

I am newbie in Swing. I am developing a simple program to add 2 numbers. It contains 2 TextFields and 1 Button. When clicked on button, button handler will add 2 numbers in text fields and puts it in label, add it to the panel. (All components are panel, and panel is added to the frame.)

The problem is that after adding the label to the panel, I am calling repaint method on panel, or frame not updating the GUI. But, when I resize the window with mouse, it updating. If hiding the panel, or frame by using setVisible and making it visible again updating the GUI.

But, I didn't understand why repaint is not updating the GUI? Please give me some hints...

[Maneesh Godbole]

Call panel.revalidate() along with panel.repaint()

[S Reddy]

Thank you Maneesh Godbole. panel.revalidate() alone working. But, I am curious to know why repaint is not updating the GUI?

[Ulf Dittmer]

Creating the layout from scratch is an overhead that the creators of AWT probably thought unnecessary during painting, given that painting occurs much more frequently than changes to the UI. Considering that most GUIs do not change after they are created, that seems like a good decision.

[S Reddy]

Thank you every one.

[Maneesh Godbole]

Ulf,

My experience is that sometimes, only revalidate() works where as sometimes repaint() is required too? Any idea why this happens?