How to add a JPanel object, with components, to a JFrame

Question

I want to add an object of type JPanel to a JFrame.

I'm trying this, but the Jpanel is not added.

the idea is: Add to P2 a P5 that has the components defined in class P5.

What could be happening ?, I do not want to create all the JPanel in the class First_view, since the code would be messed up a lot.

CODE:

import javax.swing.*;
import java.awt.*;

public class First_view extends JFrame {

    Container Frame;

    public First_view() {
        super("title");
        Frame = this.getContentPane();
        Frame.setLayout(new BorderLayout());

        Frame.add((new P2()), BorderLayout.WEST);

        setSize(900, 500);
        setLocationRelativeTo(null);
        setVisible(true);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    }
}

class P2 extends JPanel {

    public P2() {
        this.setLayout(new BorderLayout());

        add((new P5()), BorderLayout.NORTH);
    }
}

class P5 extends JPanel {

    JScrollPane informacion = new JScrollPane(JScrollPane.HORIZONTAL_SCROLLBAR_NEVER, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
    JTextArea T1 = new JTextArea();

    public P5() {
        setLayout(new FlowLayout());
        setBorder(BorderFactory.createEmptyBorder(20, 10, 0, 0));
        add(setInformacion());
    }

    private JScrollPane setInformacion() {
        T1.append("Information, bla bla bla");

        T1.setEditable(false);
        T1.setBorder(BorderFactory.createLineBorder(Color.BLACK));
        T1.setLineWrap(true);
        informacion.add(T1);
        informacion.setBorder(BorderFactory.createLineBorder(Color.BLACK));
        return informacion;
    }
}

PIC:

General advice: 1) Don't extend `JFrame` or `JPanel` unless there is a need to do so. There is no need in either of these classes. 2) Use descriptive names for classes, and learn common Java nomenclature (naming conventions - e.g. `EachWordUpperCaseClass`, `firstWordLowerCaseMethod()`, `firstWordLowerCaseAttribute` unless it is an `UPPER_CASE_CONSTANT`) and use it consistently. `First_view` should be `FirstView`. `P2` should be something like `ApplicationContainer`. 3) For better help sooner, post a [MCVE] or [Short, Self Contained, Correct Example](http://www.sscce.org/). .. — Andrew Thompson, Nov 24 '16 at 10:06
.. 4) Provide ASCII art or a simple drawing of the *intended* layout of the GUI at minimum size, and if resizable, with more width and height. 5) A single blank line of white space in source code is all that is *ever* needed. Blank lines after `{` or before `}` are also typically redundant. — Andrew Thompson, Nov 24 '16 at 10:08
Ignore the comment re the MCVE - I did not notice the definition of `P5` was included, but I'm not deleting the comment and renumbering everything now. :P 6) `JTextArea T1 = new JTextArea();` should be more like `JTextArea T1 = new JTextArea(20,3); // suggest a size in columns & rows` — Andrew Thompson, Nov 24 '16 at 10:11

user85421 · Accepted Answer · 2016-11-24T10:29:15.623

The component to display in the JScrollPane should not be added, use setViewportView instead.

private JScrollPane setInformacion() {
    T1.append("Information, bla bla bla");
    ...

    informacion.setViewportView(T1);

    ...
    informacion.setBorder(BorderFactory.createLineBorder(Color.BLACK));
    return informacion;
}

Obs: the arguments passed to the constructor of JScrollPane are in the wrong order, that is, the vertical police comes first:

JScrollPane informacion = new JScrollPane(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, 
                                          JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);

Edit: as Andrew commented it is not a good idea to extend a class just to use it (JFrame, JPanel). Example, I tried not to change too much of your original flow: package cfh.test;

import javax.swing.*;
import java.awt.*;


public class FirstView {

    private JFrame frame;
    private JTextArea informacionText;  // not sure if that is needed as field

    public FirstView() {
        informacionText = new JTextArea();
        informacionText.setEditable(false);
        informacionText.setBorder(BorderFactory.createLineBorder(Color.BLACK));
        informacionText.setLineWrap(true);
        informacionText.append("Information, bla bla bla");


        JScrollPane scrollPane = new JScrollPane(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, 
                                                 JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
        scrollPane.setBorder(BorderFactory.createLineBorder(Color.BLACK));
        scrollPane.setViewportView(informacionText);


        JPanel infoPanel = new JPanel();
        infoPanel.setLayout(new FlowLayout());
        infoPanel.add(scrollPane);


        JPanel leftPanel = new JPanel();
        leftPanel.setLayout(new BorderLayout());
        leftPanel.add(infoPanel, BorderLayout.NORTH);
        // TODO consider moving above code to an own method returning the left panel

        frame = new JFrame("title");

        frame.setLayout(new BorderLayout());
        frame.add(leftPanel, BorderLayout.WEST);

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(900,500);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}

How to add a JPanel object, with components, to a JFrame

1 Answers1