JTextField堆叠在JTextArea的顶部

Question

I'm working on a small GUI project that builds a book manger to mange a book. In my layout, I want a textArea to display information about my book, a text JLabel underneath my textArea and a JTextArea for me to input information same column of JLabel and 1 row next to Label . However when I run my program, textArea and Label is completely cover over my textArea .

How can I fix this problem. Thanks!!

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

public class Design extends JFrame {

    JButton button1;
    JTextArea outputArea;
    JLabel stockLabel, bookPriceLabel;
    JTextField stockTextField, priceTextField;
    JPanel panel;
    GridBagConstraints gc;

    public Design(){
        super("Book Info");

        gc = new GridBagConstraints ();
        panel = new JPanel();
        outputArea = new JTextArea(20, 50);
        stockLabel = new JLabel ("Books In Stock");
        bookPriceLabel = new JLabel("Book Price");
        stockTextField = new JTextField(10);
        button1 = new JButton ("button1");

        panel.setLayout(new GridBagLayout());
        panel.setSize(600, 600);

        gc.anchor = GridBagConstraints.NORTHWEST;
        gc.weightx = 1;
        gc.weighty = 1;
        panel.add(outputArea, gc);

        gc.gridx = 2;
        gc.gridy = 2;
        panel.add(stockLabel, gc);

        gc.gridx = 3;
        gc.gridy = 2;
        panel.add(stockTextField, gc);

        this.getContentPane().add(panel);

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(600,600);
        setVisible(true);
        setLocationRelativeTo(null);
    }

    public static void main (String args[]){
        Design frame = new Design();
    }
}

Answer 1

You could apply a gridWidth constraint to the JTextArea which would allow it to span multiple columns.

Remember, GridBagLayout is still based around the concept of a grid (rows and columns), but which provides a lot of flexibility to customise how components fill and span through out that grid

Maybe something like...

import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Design extends JFrame {

    JButton button1;
    JTextArea outputArea;
    JLabel stockLabel, bookPriceLabel;
    JTextField stockTextField, priceTextField;
    JPanel panel;
    GridBagConstraints gc;

    public Design() {
        super("Book Info");

        gc = new GridBagConstraints();
        panel = new JPanel();
        outputArea = new JTextArea(20, 50);
        stockLabel = new JLabel("Books In Stock");
        bookPriceLabel = new JLabel("Book Price");
        stockTextField = new JTextField(10);
        button1 = new JButton("button1");

        panel.setLayout(new GridBagLayout());

        gc.anchor = GridBagConstraints.NORTHWEST;
        gc.gridx = 0;
        gc.gridy = 0;
        gc.weightx = 1;
        gc.weighty = 1;
        gc.gridwidth = GridBagConstraints.REMAINDER;
        panel.add(new JScrollPane(outputArea), gc);

        gc.weightx = 0;
        gc.weighty = 0;
        gc.anchor = GridBagConstraints.WEST;
        gc.gridwidth = 1;
        gc.gridx = 0;
        gc.gridy = 2;
        panel.add(stockLabel, gc);

        gc.gridx++;
        gc.gridy = 2;
        panel.add(stockTextField, gc);

        this.getContentPane().add(panel);

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        pack();
        setVisible(true);
        setLocationRelativeTo(null);
    }

    public static void main(String args[]) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                Design frame = new Design();
            }
        });
    }
}

See How to Use GridBagLayout for more details

Some general feedback:

• There's no point in calling setSize on a component which will be added to a container which using a layout manager, the action will simply be ignored and the layout manager will call setSize with what it wants to use
• JTextArea really should be contained within a JScrollPane , you'll get some weird results if you don't (it will want to grow as the text occupies more space)
• Prefer JFrame#pack over JFrame#setSize , this will take into account the frame borders, wrapping the frame around the contents
• You really should avoid extending directly from top level containers like JFrame , apart from locking you into a single use case, you're really not adding any new functionality to the frame. Instead, start with something like a JPanel , build you core UI ontop of that and then, when you need to, add that to what ever container you want