How to center a Window in Java?

What's the easiest way to centre a java.awt.Window, such as a JFrame or a JDialog?

Solution 1:

From this link

If you are using Java 1.4 or newer, you can use the simple method setLocationRelativeTo(null) on the dialog box, frame, or window to center it.

Solution 2:

This should work in all versions of Java

public static void centreWindow(Window frame) {
    Dimension dimension = Toolkit.getDefaultToolkit().getScreenSize();
    int x = (int) ((dimension.getWidth() - frame.getWidth()) / 2);
    int y = (int) ((dimension.getHeight() - frame.getHeight()) / 2);
    frame.setLocation(x, y);
}

Solution 3:

setLocationRelativeTo(null) should be called after you either use setSize(x,y), or use pack().

Solution 4:

Note that both the setLocationRelativeTo(null) and Tookit.getDefaultToolkit().getScreenSize() techniques work only for the primary monitor. If you are in a multi-monitor environment, you may need to get information about the specific monitor the window is on before doing this kind of calculation.

Sometimes important, sometimes not...

See GraphicsEnvironment javadocs for more info on how to get this.

Solution 5:

On Linux the code

setLocationRelativeTo(null)

Put my window to random location each time I launched it, in a multi display environment. And the code

setLocation((Toolkit.getDefaultToolkit().getScreenSize().width  - getSize().width) / 2, (Toolkit.getDefaultToolkit().getScreenSize().height - getSize().height) / 2);

"cut" the window in half with placing it to the exact center, which is between my two displays. I used the following method to center it:

private void setWindowPosition(JFrame window, int screen)
{        
    GraphicsEnvironment env = GraphicsEnvironment.getLocalGraphicsEnvironment();
    GraphicsDevice[] allDevices = env.getScreenDevices();
    int topLeftX, topLeftY, screenX, screenY, windowPosX, windowPosY;

    if (screen < allDevices.length && screen > -1)
    {
        topLeftX = allDevices[screen].getDefaultConfiguration().getBounds().x;
        topLeftY = allDevices[screen].getDefaultConfiguration().getBounds().y;

        screenX  = allDevices[screen].getDefaultConfiguration().getBounds().width;
        screenY  = allDevices[screen].getDefaultConfiguration().getBounds().height;
    }
    else
    {
        topLeftX = allDevices[0].getDefaultConfiguration().getBounds().x;
        topLeftY = allDevices[0].getDefaultConfiguration().getBounds().y;

        screenX  = allDevices[0].getDefaultConfiguration().getBounds().width;
        screenY  = allDevices[0].getDefaultConfiguration().getBounds().height;
    }

    windowPosX = ((screenX - window.getWidth())  / 2) + topLeftX;
    windowPosY = ((screenY - window.getHeight()) / 2) + topLeftY;

    window.setLocation(windowPosX, windowPosY);
}

Makes the window appear right at the center of the first display. This is probably not the easiest solution.

Works properly on Linux, Windows and Mac.