CODEWITHSUNDEEP
javaswinguser-interfaceawt
Andrew Swan
Andrew Swan

Reputation: 13627

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?

Upvotes: 139

Views: 244108

Answers (21)

Sergey Lysenko
Sergey Lysenko

Reputation: 19

This is minimalistic variant which centers a frame on screen defined by parameter

private void centerThisWindow(int screen) {
    GraphicsDevice[] screens = GraphicsEnvironment.getLocalGraphicsEnvironment().getScreenDevices();
    int i = (screen >= screens.length || 0 > screen) ? 0 : screen;
    Rectangle r = screens[i].getDefaultConfiguration().getBounds();
    setLocation(((r.width - getWidth()) / 2) + r.x, ((r.height - getHeight()) / 2) + r.y);
}

Upvotes: 0

Cardinal System
Cardinal System

Reputation: 3422

I'd like to modify Dónal's answer to accommodate a multiple display setup:

public static void centerWindow(Window frame) {
    Rectangle bounds = frame.getGraphicsConfiguration().getBounds();
    Dimension dimension = bounds.getSize();
    int x = (int) (((dimension.getWidth() - frame.getWidth()) / 2) + bounds.getMinX());
    int y = (int) (((dimension.getHeight() - frame.getHeight()) / 2) + bounds.getMinY());
    frame.setLocation(x, y);
}

Upvotes: 1

Tolga Acgul
Tolga Acgul

Reputation: 1

If you want to push center of your app window, you can do solved to follow.

int x = (Toolkit.getDefaultToolkit().getScreenSize().width) - getSize().width) / 2;
int y = (Toolkit.getDefaultToolkit().getScreenSize().height) - getSize().height) / 2;
setLocation(x,y);

getSize() function is app frame size... getScreenSize() is your pc screen size.

Upvotes: 0

Suraj
Suraj

Reputation: 11

If you want a simple answer for Java NetBeans:

Right click on the JFrame, go to properties, then go to code and select generate center option.

Look image for reference: [1]: https://i.sstatic.net/RFXbL.png

Upvotes: 0

Tuhin Mitra
Tuhin Mitra

Reputation: 727

In addition to Donal's answer, I would like to add a small calculation that makes sure that the Java window is perfectly at the center of the window. Not just the "TOP LEFT" of the window is at the center of the window.

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

        // calculate perfect center
        int perf_x = (int) x - width/2;
        int perf_y = (int) y - height/2;

        frame.setLocation(perf_x, perf_y);
    }

Upvotes: 0

Adir Dayan
Adir Dayan

Reputation: 1617

The order of the calls is important:

first -

pack();

second -

setLocationRelativeTo(null);

Upvotes: 2

Dzmitry Sevkovich
Dzmitry Sevkovich

Reputation: 901

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

Upvotes: 44

Thulani Chivandikwa
Thulani Chivandikwa

Reputation: 3539

frame.setLocationRelativeTo(null);

Full example:

public class BorderLayoutPanel {

    private JFrame mainFrame;
    private JButton btnLeft, btnRight, btnTop, btnBottom, btnCenter;

    public BorderLayoutPanel() {
        mainFrame = new JFrame("Border Layout Example");
        btnLeft = new JButton("LEFT");
        btnRight = new JButton("RIGHT");
        btnTop = new JButton("TOP");
        btnBottom = new JButton("BOTTOM");
        btnCenter = new JButton("CENTER");
    }

    public void SetLayout() {
        mainFrame.add(btnTop, BorderLayout.NORTH);
        mainFrame.add(btnBottom, BorderLayout.SOUTH);
        mainFrame.add(btnLeft, BorderLayout.EAST);
        mainFrame.add(btnRight, BorderLayout.WEST);
        mainFrame.add(btnCenter, BorderLayout.CENTER);
        //        mainFrame.setSize(200, 200);
        //        or
        mainFrame.pack();
        mainFrame.setVisible(true);

        //take up the default look and feel specified by windows themes
        mainFrame.setDefaultLookAndFeelDecorated(true);

        //make the window startup position be centered
        mainFrame.setLocationRelativeTo(null);

        mainFrame.setDefaultCloseOperation(mainFrame.EXIT_ON_CLOSE);
    }
}

Upvotes: 3

Peter Szabo
Peter Szabo

Reputation: 1126

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.

Upvotes: 22

Borja
Borja

Reputation: 3610

public class SwingExample implements Runnable {

    @Override
    public void run() {
        // Create the window
        final JFrame f = new JFrame("Hello, World!");
        SwingExample.centerWindow(f);
        f.setPreferredSize(new Dimension(500, 250));
        f.setMaximumSize(new Dimension(10000, 200));
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    public static void centerWindow(JFrame frame) {
        Insets insets = frame.getInsets();
        frame.setSize(new Dimension(insets.left + insets.right + 500, insets.top + insets.bottom + 250));
        frame.setVisible(true);
        frame.setResizable(false);

        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);
    }
}

Upvotes: 0

Manikant Gautam
Manikant Gautam

Reputation: 3591

You could try this also.

Frame frame = new Frame("Centered Frame");
Dimension dimemsion = Toolkit.getDefaultToolkit().getScreenSize();
frame.setLocation(dimemsion.width/2-frame.getSize().width/2, dimemsion.height/2-frame.getSize().height/2);

Upvotes: 1

Marinel P
Marinel P

Reputation: 41

Example: Inside myWindow() on line 3 is the code you need to set the window in the center of the screen. 

JFrame window;

public myWindow() {

    window = new JFrame();
    window.setSize(1200,800);
    window.setLocationRelativeTo(null); // this line set the window in the center of thr screen
    window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    window.getContentPane().setBackground(Color.BLACK);
    window.setLayout(null); // disable the default layout to use custom one.
    window.setVisible(true); // to show the window on the screen.
}

Upvotes: 2

Andrew Swan
Andrew Swan

Reputation: 13627

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.

Upvotes: 279

Kevin Day
Kevin Day

Reputation: 16383

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.

Upvotes: 27

Aman Goel
Aman Goel

Reputation: 3541

below is code for displaying a frame at top-centre of existing window.

public class SwingContainerDemo {

private JFrame mainFrame;

private JPanel controlPanel;

private JLabel msglabel;

Frame.setLayout(new FlowLayout());

  mainFrame.addWindowListener(new WindowAdapter() {
     public void windowClosing(WindowEvent windowEvent){
        System.exit(0);
     }        
  });    
  //headerLabel = new JLabel("", JLabel.CENTER);        
 /* statusLabel = new JLabel("",JLabel.CENTER);    
  statusLabel.setSize(350,100);
 */ msglabel = new JLabel("Welcome to TutorialsPoint SWING Tutorial.", JLabel.CENTER);

  controlPanel = new JPanel();
  controlPanel.setLayout(new FlowLayout());

  //mainFrame.add(headerLabel);
  mainFrame.add(controlPanel);
 // mainFrame.add(statusLabel);

  mainFrame.setUndecorated(true);
  mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  mainFrame.getRootPane().setWindowDecorationStyle(JRootPane.NONE);
  mainFrame.setVisible(true);  

  centreWindow(mainFrame);

}

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, 0);
}


public void showJFrameDemo(){
 /* headerLabel.setText("Container in action: JFrame");   */
  final JFrame frame = new JFrame();
  frame.setSize(300, 300);
  frame.setLayout(new FlowLayout());       
  frame.add(msglabel);

  frame.addWindowListener(new WindowAdapter() {
     public void windowClosing(WindowEvent windowEvent){
        frame.dispose();
     }        
  });    



  JButton okButton = new JButton("Capture");
  okButton.addActionListener(new ActionListener() {
     public void actionPerformed(ActionEvent e) {
  //      statusLabel.setText("A Frame shown to the user.");
      //  frame.setVisible(true);
        mainFrame.setState(Frame.ICONIFIED);
        Robot robot = null;
        try {
            robot = new Robot();
        } catch (AWTException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
        final Dimension screenSize = Toolkit.getDefaultToolkit().
                getScreenSize();
        final BufferedImage screen = robot.createScreenCapture(
                new Rectangle(screenSize));

        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new ScreenCaptureRectangle(screen);
            }
        });
        mainFrame.setState(Frame.NORMAL);
     }
  });
  controlPanel.add(okButton);
  mainFrame.setVisible(true);

} public static void main(String[] args) throws Exception {

new SwingContainerDemo().showJFrameDemo();

}

Below is the ouput of above code-snippet:enter image description here

Upvotes: 4

TheLooker
TheLooker

Reputation: 61

I finally got this bunch of codes to work in NetBeans using Swing GUI Forms in order to center main jFrame:

package my.SampleUIdemo;
import java.awt.*;

public class classSampleUIdemo extends javax.swing.JFrame {
    /// 
    public classSampleUIdemo() {
        initComponents();
        CenteredFrame(this);  // <--- Here ya go.
    }
    // ...
    // void main() and other public method declarations here...

    ///  modular approach
    public void CenteredFrame(javax.swing.JFrame objFrame){
        Dimension objDimension = Toolkit.getDefaultToolkit().getScreenSize();
        int iCoordX = (objDimension.width - objFrame.getWidth()) / 2;
        int iCoordY = (objDimension.height - objFrame.getHeight()) / 2;
        objFrame.setLocation(iCoordX, iCoordY); 
    } 

}

OR

package my.SampleUIdemo;
import java.awt.*;

public class classSampleUIdemo extends javax.swing.JFrame {
        /// 
        public classSampleUIdemo() {
            initComponents(); 
            //------>> Insert your code here to center main jFrame.
            Dimension objDimension = Toolkit.getDefaultToolkit().getScreenSize();
            int iCoordX = (objDimension.width - this.getWidth()) / 2;
            int iCoordY = (objDimension.height - this.getHeight()) / 2;
            this.setLocation(iCoordX, iCoordY); 
            //------>> 
        } 
        // ...
        // void main() and other public method declarations here...

}

OR 

    package my.SampleUIdemo;
    import java.awt.*;
    public class classSampleUIdemo extends javax.swing.JFrame {
         /// 
         public classSampleUIdemo() {
             initComponents();
             this.setLocationRelativeTo(null);  // <<--- plain and simple
         }
         // ...
         // void main() and other public method declarations here...
   }

Upvotes: 6

Clay Ellis
Clay Ellis

Reputation: 5330

There's something really simple that you might be overlooking after trying to center the window using either setLocationRelativeTo(null) or setLocation(x,y) and it ends up being a little off center.

Make sure that you use either one of these methods after calling pack() because the you'll end up using the dimensions of the window itself to calculate where to place it on screen. Until pack() is called, the dimensions aren't what you'd think thus throwing off the calculations to center the window. Hope this helps.

Upvotes: 2

Julien
Julien

Reputation: 1318

The following code center the Window in the center of the current monitor (ie where the mouse pointer is located).

public static final void centerWindow(final Window window) {
    GraphicsDevice screen = MouseInfo.getPointerInfo().getDevice();
    Rectangle r = screen.getDefaultConfiguration().getBounds();
    int x = (r.width - window.getWidth()) / 2 + r.x;
    int y = (r.height - window.getHeight()) / 2 + r.y;
    window.setLocation(x, y);
}

Upvotes: 1

Viswanath Lekshmanan
Viswanath Lekshmanan

Reputation: 10083

Actually frame.getHeight() and getwidth() doesnt return values , check it by System.out.println(frame.getHeight()); directly put the values for width and height ,then it will work fine in center. eg: as below

Dimension dimension = Toolkit.getDefaultToolkit().getScreenSize();      
int x=(int)((dimension.getWidth() - 450)/2);
int y=(int)((dimension.getHeight() - 450)/2);
jf.setLocation(x, y);

both 450 is my frame width n height

Upvotes: 0

Jonathan Caraballo
Jonathan Caraballo

Reputation: 55

The following doesn't work for JDK 1.7.0.07:

frame.setLocationRelativeTo(null);

It puts the top left corner at the center - not the same as centering the window. The other one doesn't work either, involving frame.getSize() and dimension.getSize():

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);

The getSize() method is inherited from the Component class, and therefore frame.getSize returns the size of the window as well. Thus subtracting half the vertical and horizontal dimensions from the vertical and horizontal dimensions, to find the x,y coordinates of where to place the top-left corner, gives you the location of the center point, which ends up centering the window as well. However, the first line of the above code is useful, "Dimension...". Just do this to center it:

Dimension dimension = Toolkit.getDefaultToolkit().getScreenSize();
JLabel emptyLabel = new JLabel("");
emptyLabel.setPreferredSize(new Dimension( (int)dimension.getWidth() / 2, (int)dimension.getHeight()/2 ));
frame.getContentPane().add(emptyLabel, BorderLayout.CENTER);
frame.setLocation((int)dimension.getWidth()/4, (int)dimension.getHeight()/4);

The JLabel sets the screen-size. It's in FrameDemo.java available on the java tutorials at the Oracle/Sun site. I set it to half the screen size's height/width. Then, I centered it by placing the top left at 1/4 of the screen size's dimension from the left, and 1/4 of the screen size's dimension from the top. You can use a similar concept.

Upvotes: 3

D&#243;nal
D&#243;nal

Reputation: 187529

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);
}

Upvotes: 75

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