CODEWITHSUNDEEP
javajframe
bluehandle
bluehandle

Reputation: 11

Can't set JFrame layout

I have tried setting the layout of a JFrame, and it doesn't seem to work. Is this possible?

JFrame frame = new JFrame();
frame.setLayout(new FlowLayout());
System.out.println(frame.getLayout().toString());

The output I get from this is:

java.awt.BorderLayout[hgap=0,vgap=0]

Upvotes: 0

Views: 224

Answers (1)

MadProgrammer
MadProgrammer

Reputation: 347314

You've run into a minor hierarchal issue associated with JFrame.

JFrame isn't actually a single component, it's a composite component. This means it contains a number of layers, which make up the actual structure of the window, for example...

JFrame's rootpane

Prior to 1.5 (I think), you would have been required to use JFrame#getContentPane#setLayout and JFrame#getContentPane#getLayout, which, as you can imagine, is tedious to type.

Since 1.5, you can now call JFrame#setLayout directly and the call will be forwarded directly to the contentPane instead. The problem is, getLayout still needs to return the layout manager used by the frame itself, which is the hole you've found yourself in.

If, instead, you use ...

frame.setLayout(new FlowLayout());
System.out.println(frame.getContentPane().getLayout());

It will print java.awt.FlowLayout[hgap=5,vgap=5,align=center]

Yes, I know, it's not entirely obvious, which is why the original API required you to be specific about your intent, calling getContentPane directly, rather then passing the call on automatically

Upvotes: 1

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