How to center a Window in Java

Question

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

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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

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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  lt  allDevices length  amp  amp  screen  gt  -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

User · Answer

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

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The order of the calls is important  first - pack     second - setLocationRelativeTo null

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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

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setLocationRelativeTo null  should be called after you either use setSize x y   or use pack

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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        lt --- 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                   ------ gt  gt  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                  ------ gt  gt                                        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        lt  lt --- plain and simple                                        void main   and other public method declarations here

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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

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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

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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

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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

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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

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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

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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

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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

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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

[java] How to center a Window in Java?

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