How to get the EXACT middle of a screen, even when re-sized

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From the sounds of what you are saying, I think you misunderstand what the dimensions of a normal (decorated) frame include.

A JFrame consists of a window/frame (normally decorated with a border), a JRootPane, which contains a JLayeredPane which contains the content pane, JMenuBar and glass pane.

enter image description here

This is, one of the, reasons why you should never override a top level containers paint method, because you won’t actually be painting within the content/view area.

So, the actual “paintable” region of a frame is it’s width - border.width x height - border.height

enter image description here

The red line indicates the frame, the blue indicates the content pane.

This raises a very important question, where’s the center of the frame? From the frames perspective, it’s 100×100, but from the content pane’s perspective, it’s 92×81. Depending on what you want, will depend on which value you will use. For positioning the frame, you will want to to use the frames center point, for painting, your will want to use the content panes.

Now, the easiest way to center a frame on the screen is simply to call Window#setLocationRelativeTo(null) otherwise, I would suggest you use Timr’s solution 😉

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