将面板添加到面板

Question

I anted to add a JPanel to my already existing JPanel so I could have a small window with a JTextField on top with a name and a scrollable JTextArea below it with some description. I made a class that extends JPanel with the following constructor:

import javax.swing.*;
import javax.swing.border.EtchedBorder;
import javax.swing.border.TitledBorder;
import java.awt.*;

public class LocationWindow extends JPanel {
    public JTextField name;
    public JTextArea desc;
    public JScrollPane scroll;

    public LocationWindow(){
        super();
        setBorder (new TitledBorder(new EtchedBorder(), "Display Area"));
        setLayout(new BorderLayout());
        setVisible(true);
        setBounds(30, 40, 700, 290);
        name = new JTextField(10);
        name.setText("name");
        desc = new JTextArea(5,10);
        scroll = new JScrollPane(desc);
        scroll.setVerticalScrollBarPolicy ( ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS );
        desc.setEditable (true);
        desc.setLineWrap(true);
        desc.setText("random text");
        add(name);
        add(desc);
        add(scroll);
        validate();
    }
}

It almost works, as it gives me the window with the borders and a scroll, but both the JTextField and JTextArea are missing.

Answer 1

As you are using BorderLayout for the JPanel,

  setLayout(new BorderLayout());   

the components will always be added to the center if you dont specify the position. add(scroll); is same as add(scroll,BorderLayout.CENTER); as you're adding all via add the last added component only be visible.Refer this as well

The next is you are adding JTextArea seperately so it will be removed from ScrollPane.Just add scrollpane to Panel no need to add all components.[Add the parent component alone]

    add(name,BorderLayout.NORTH);
    //add(desc);Noo need to add desc as it is already added in JScrollPane
    add(scroll,BorderLayout.CENTER);

There is no need for setVisible for JPanel.JPanel needs to be embedded in Container like JFrame to be visible

         //setVisible(true);Wont do anything

So call like this

    JFrame frame = new JFrame();
    frame.add(new LocationWindow());
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.pack();
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);

Answer 2

You can use below code to adding panel to panel.

 public static void main(String[] args) {
    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    LocationWindow loc = new LocationWindow();
    frame.add(loc);
    frame.setSize(300, 200);
    frame.setVisible(true);
}