How to set JFrame to appear centered, regardless of monitor resolution?

java

custom-ui

multi-monitor

centering

byAlex Kataev·Feb 21, 2025

To center a JFrame, frame.setLocationRelativeTo(null) is called after sizing the frame with frame.setSize(width, height); or frame.pack();. Remember to use this method before making the frame visible to get a centered JFrame on any monitor resolution.

JFrame frame = new JFrame();
frame.setSize(300, 300); // Smaller than your first "Hello World" program!
frame.setLocationRelativeTo(null); // Make it the center of attention
frame.setVisible(true); // It's showtime!

(Humor disclaimer: The comments contain less caffeine than your average developer)

Customized Center

setLocationRelativeTo(null) works like a charm for centering, but hey, you love control (who doesn't?)! For those seeking precision, go the extra mile by calculating center point manually:

Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
int x = (screenSize.width - frame.getWidth()) / 2; // One for you...
int y = (screenSize.height - frame.getHeight()) / 2; // And one for symmetry!
frame.setLocation(x, y); // And... perfect landing!

Your JFrame now considers its own dimensions too. This is your secret recipe for working with custom UIs and multi-monitor setups.

Multi-monitor Detection

With great power (of multiple monitors) comes great responsibility (of handling them right). Use the GraphicsEnvironment for a failproof method that works well with multi-monitor setups:

GraphicsDevice gd = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice();
int width = gd.getDisplayMode().getWidth();
int height = gd.getDisplayMode().getHeight();
frame.setLocation((width - frame.getWidth()) / 2, (height - frame.getHeight()) / 2); // Extra effort for those extra monitors

Bingo! Now your software acknowledges the primary monitor's resolution like a pro.

Sneaky Tips and Workarounds

IDE Power: NetBeans got your back with a 'Generate Center' property. Click. Centered. Magic!
Heavy Reflections: Watch out for mirrored displays. setLocationRelativeTo(null) sees them as one big monitor.
Dynamic Frames: JFrame's shape shifting? Call the centering code using frame.setLocationRelativeTo(null) again.
Pesky Bugs: Centering acting out? Make sure your code runs in the Event Dispatch Thread (EDT).

Key Considerations

UI Preference: While horizontal centering is a crowd-pleaser, the vertical position may vary as per UI guidelines or user preference.
On The Move: For dynamically resizing JFrames, consider centering upon each resize.
HiDPI Awareness: Make sure your centering logic is a friend of high-DPI settings.