Why does the JFrame setSize method not set the size correctly

Question

So I ve been programming in java for a semester or so  and I ve had this problem a few times and finally got around to asking   If I make a JFrame and then set the size  like setSize 400 800  for example  The frame is not actually 800 pixels long  From what I can tell it is actually more like 770  or maybe 769  pixels long  Also  if you set the vertical size very low  below 30   the frame doesn t even show up  only the top window bar from the OS and the frame doesn t get bigger until you go to a value over 30  so setSize 400 0  looks the same as setSize 400 20    Why is this  it s not hard to fix but its weird and I m curious why this is   If you need more information about anything just ask and I ll get it to you

User · Answer

On OS X  you need to take into account existing window decorations  They add 22 pixels to the height  So on a JFrame  you need to tell the program this   frame setSize width  height   22

User · Answer

It s probably because size of a frame includes the size of the border      A Frame is a top-level window with a title and a border  The size of the frame includes any area designated for the border  The dimensions of the border area may be obtained using the getInsets method  Since the border area is included in the overall size of the frame  the border effectively obscures a portion of the frame  constraining the area available for rendering and or displaying subcomponents to the rectangle which has an upper-left corner location of  insets left  insets top   and has a size of width -  insets left   insets right  by height -  insets top   insets bottom      Source  http   download oracle com javase tutorial uiswing components frame html

User · Answer

The top border of frame is of size 30 You can write code for printing the coordinate  of any point on the frame using MouseInputAdapter You will find when the cursor is just below the top border of the frame the y coordinate is not zero   its close to 30 Hence if you give size to frame 300   300   the size available for putting the components on the frame is only 300   270 So if you need to have size 300    300  give 300   330 size of the frame

User · Answer

I know that this question is about 6  years old  but the answer by  Kyle doesn t work   Using this  setSize width -  getInsets   left   getInsets   right   height -  getInsets   top   getInsets   bottom      But this always work in any size   setSize width   14  height   7     If you don t want the border to border  and only want the white area  here   setSize width   16  height   39     Also this only works on Windows 10  for MacOS users  use  ben s answer

User · Answer

There are lots of good reasons for setting the size of a frame  One is to remember the last size the user set  and restore those settings  I have this code which seems to work for me   package javatools swing  import java util prefs    import java awt    import java awt event     import javax swing JFrame   public class FramePositionMemory       public static final String WIDTH PREF    -width        public static final String HEIGHT PREF    -height        public static final String XPOS PREF    -xpos        public static final String YPOS PREF    -ypos       String prefix      Window frame      Class lt   gt  cls       public FramePositionMemory String prefix  Window frame  Class lt   gt  cls            this prefix   prefix          this frame   frame          this cls   cls             public void loadPosition             Preferences prefs    Preferences Preferences userNodeForPackage cls           Restore the most recent mainframe size and location         int width   prefs getInt prefix   WIDTH PREF  frame getWidth             int height   prefs getInt prefix   HEIGHT PREF  frame getHeight             System out println  WID      width     HEI      height           Dimension screenSize   Toolkit getDefaultToolkit   getScreenSize            int xpos    screenSize width - width    2          int ypos    screenSize height - height    2          xpos   prefs getInt prefix   XPOS PREF  xpos           ypos   prefs getInt prefix   YPOS PREF  ypos           frame setPreferredSize new Dimension width  height            frame setLocation xpos  ypos           frame pack               public void storePosition             Preferences prefs    Preferences Preferences userNodeForPackage cls           prefs putInt prefix   WIDTH PREF  frame getWidth             prefs putInt prefix   HEIGHT PREF  frame getHeight             Point loc   frame getLocation            prefs putInt prefix   XPOS PREF   int loc getX             prefs putInt prefix   YPOS PREF   int loc getY             System out println  STORE      frame getWidth           frame getHeight           loc getX           loc getY             public class Main   void main String   args            JFrame frame   new Frame               SET UP YOUR FRAME HERE          final FramePositionMemory fm   new FramePositionMemory  scannacs2   frame  Main class           frame setSize 400  400      default size in the absence of previous setting         fm loadPosition             setDefaultCloseOperation WindowConstants EXIT ON CLOSE           Runtime getRuntime   addShutdownHook new Thread                  Override             public void run                     fm storePosition                                      frame setVisible true

User · Answer

JFrame SetSize   contains the the Area   Border   I think you have to set the size of ContentPane of that   jFrame getContentPane   setSize 800 400     So I would advise you to use JPanel embedded in a JFrame and you draw on that JPanel  This would minimize your problem   JFrame jf   new JFrame    JPanel jp   new JPanel    jp setPreferredSize new Dimension 400 800      changed it to preferredSize  Thanks  jf getContentPane   add  jp      adding to content pane will work here  Please read the comment bellow  jf pack      I am reading this from Javadoc     The JFrame class is slightly   incompatible with Frame  Like all   other JFC Swing top-level containers    a JFrame contains a JRootPane as its   only child  The content pane provided   by the root pane should  as a rule    contain all the non-menu components   displayed by the JFrame  This is   different from the AWT Frame case  For   example  to add a child to an AWT   frame you d write       frame add child        However using JFrame you need to add   the child to the JFrame s content pane   instead       frame getContentPane   add child

[java] Why does the JFrame setSize() method not set the size correctly?

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