Swing GUI problems with BorderLayout

Question

I'm currently trying to get along with Layouts, considering that I never really understood them and only did nullLayout instead, absolutely positioning all elements then.

However, I currently have a suitable small project, where I am trying to learn it, which is some small chat service.

Here is a picture right now:

And here is a picture, of how I imagine it to be finished (Please note that this is just some concept, but it should give you the right idea. I'm not a graphic artist):

Here is my current code:

public class Gui {

JFrame frame;
JTextArea textfield;
JTextField enterMessage;

    public Gui(){
        
        frame = new JFrame();
        frame.setSize(600, 400);
        
        
        textfield = new JTextArea();
        textfield.setText("Textfield");
        textfield.setSize(400, 300);
        
        JPanel messagePanel = new JPanel();
    
        JTextField chatMessage = new JTextField();
        chatMessage.setText("Send me");
        
        JButton send = new JButton();
        send.setText("Send");
        
    
        messagePanel.add(chatMessage, BorderLayout.WEST);
        messagePanel.add(send, BorderLayout.EAST);
        
        frame.add(textfield, BorderLayout.WEST);
        frame.add(messagePanel, BorderLayout.SOUTH);
        frame.setVisible(true);
    }
}

My idea, together with the understanding of BorderLayouts so far was to put the Textfield, where the chat dialog ends up in later on, right inside the frame, on the WEST-side.

The button to send and the field to enter some text will be inside a panel, with an own borderlayout, while the button has some smaller part on the right and the rest of the width is being filled with the textfield.

The whole panel then ends on the SOUTH-side of the frame.

However, right now I have the problem, that the elements keep shrinking to the least possible size.

I tried to fix this with setSize(); , but that does not have an impact at all, it is just being completely ignored.

Any help to point me into the right direction?

Answer 1

Initially, you've got one simple problem:

//          should be new JPanel(new BorderLayout())
JPanel messagePanel = new JPanel();

Then, after that, generally BorderLayout likes to stretch the component in BorderLayout.CENTER. So you want to put your textfield and chatMessage in the center.

public Gui(){
    frame = new JFrame();
    frame.setSize(600, 400);

    textfield = new JTextArea();
    textfield.setText("Textfield");
//    textfield.setSize(400, 300);

    JPanel messagePanel = new JPanel(new BorderLayout());

    JTextField chatMessage = new JTextField("Send me");
    JButton send = new JButton("Send");

    messagePanel.add(chatMessage, BorderLayout.CENTER);
    messagePanel.add(send, BorderLayout.EAST);

    frame.add(textfield, BorderLayout.CENTER);
    frame.add(messagePanel, BorderLayout.SOUTH);
    frame.setVisible(true);
}

Once you do that, you should get something like this:

But, as a few words of advice:

• Don't rely on setSize of a JFrame. Instead, you should use setPreferredSize on a single component which the entire UI should size itself around. (Probably the main text area.) The size of a JFrame includes, for example, the title bar.
• You should consider wrapping your JTextArea in a scroll pane. You can then instead setPreferredSize on the viewport.
• After you have a component with a preferred size, call pack() on the JFrame before calling setVisible(true). This will size it automatically.

Something like:

frame = new JFrame();
// frame.setSize(600, 400);

...

JScrollPane pane = new JScrollPane(
    textfield,
    JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
    JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
// specifying initial size for the
// visible portion of the scroll pane
pane.getViewport().setPreferredSize(new Dimension(320, 200));

frame.add(pane, BorderLayout.CENTER);
frame.add(messagePanel, BorderLayout.SOUTH);
// entire UI sizes around the scroll pane view
frame.pack();
frame.setVisible(true);