How do I create a new JFrame, whos' location is set to the middle of another JFrame?

Question

I'm new to Java and this is what I'm trying to do:

I have frame1, which has a JButton that, once clicked, creates a new JFrame on top of frame1, which I call frame2. I basically want frame2 to be created in the middle of frame1. How do I do this?

You create it the same way you created number 1, just give it a smaller dimension. — takendarkk, Dec 13 '14 at 17:44
yes but then it just appears on the top-left of the screen by default. I want it on top of the first frame. Does it have something to do with setLocationRelativeTo(...)? — user2603506, Dec 13 '14 at 17:49
As a general rule, it's bad practice to throw a bunch Frames at the user. If this is just for practice, it doesn't matter too much, but I would recommend finding a better way to do what you are trying to do. — Nikolai97, Dec 13 '14 at 17:55
See [The Use of Multiple JFrames, Good/Bad Practice?](http://stackoverflow.com/q/9554636/418556) — Andrew Thompson, Dec 14 '14 at 01:50

score 3 · Answer 1 · answered Dec 13 '14 at 17:51

3

You set the location of frame2 relative to the location of frame1.

//Initialize your frames
frame2.setLocationRelativeTo(frame1);

This should place frame2 right on top of frame1.

answered Dec 13 '14 at 17:51

Marv

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score 0 · Answer 2 · answered Dec 13 '14 at 17:55

The easiest way to do it is Marv's, but if you want to do it with Maths, try this instead.

Point offSet=frame1.getLocation();
Dimension loc1=frame1.getSize();
Dimension loc2=frame2.getSize();

double newX=offSet.getX()+loc1.getWidth()/2.0-loc2.getWidth()/2.0;
double newY=offSet.getY()+loc1.getHeight()/2.0-loc2.getHeight()/2.0;

frame2.setLocation((int)Math.floor(newX), (int)Math.floor(newY));
frame2.setVisible(true);

This will center frame2 on top of frame1.
If you choose the .setLocationRelativeTo() method, don't forget to re-use frame2.setVisible(true) if you did frame2.setVisible(true) before frame1.setVisible(true)

score 0 · Answer 3 · edited May 23 '17 at 12:12

0

Use setLocationRelativeTo(Component c) (use this doc if you're using Java 8) as follows:

// center in parent
frame2.setLocationRelativeTo(frame1);

You can also center the component in the screen using

// center in screen
frame2.setLocationRelativeTo( null );

Check out this question if you're still having issues.

edited May 23 '17 at 12:12

Community

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answered Dec 13 '14 at 17:55

Chris Sprague

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Don't forget to use [this link](http://docs.oracle.com/javase/8/docs/api/java/awt/Window.html#setLocationRelativeTo-java.awt.Component-) if the OP uses Java 8 – Charlie Dec 13 '14 at 18:00
@Charlie I edited the post to include Java 8 doc link. Good call - thanks! (I think Marv's answer perfectly fine anyway.) – Chris Sprague Dec 13 '14 at 18:06

How do I create a new JFrame, whos' location is set to the middle of another JFrame?

3 Answers3