java - 用于 GUI 应用程序的 JPanel

Question

所以我自学 Java，但遇到了一点困难。对于其中一项练习，这是我无法理解的说明。任何解释帮助将不胜感激。这是我对遇到问题的部分的尝试。

import java.awt.Dimension;  
import java.awt.GridLayout;  
import javax.swing.JButton;  
import javax.swing.JPanel;  
import javax.swing.JScrollPane;  
import javax.swing.JTextArea;  

public class ButtonPanel extends JPanel {


    public ButtonPanel(JButton[] buttons, JTextArea textArea) {
        //TODO: Create a sub-panel with a 4 row, 3 column GridLayout

        setLayout(new GridLayout(4,3)); //Layout of subPanel1

        JButton b1 = new JButton ("A");
        JButton b2 = new JButton ("B");
        JButton b3 = new JButton ("C");
        JButton b4 = new JButton ("1");
        JButton b5 = new JButton ("2");
        JButton b6 = new JButton ("3");
        JButton b7 = new JButton ("X");
        JButton b8 = new JButton ("Y");
        JButton b9 = new JButton ("Z");

        add(b1);
        add(b2);
        add(b3);
        add(b4);
        add(b4);
        add(b5);

        //TODO: Populate the grid with buttons

        //TODO: Add the grid panel to this panel

        //TODO: Create a JScrollPane containing textArea

        JButton cr = new JButton();

        //TODO: Set the preferred size of the scroll pane to 80x120
        setPreferredSize (new Dimension(80, 120));

        //TODO: Add the scroll pane to this panel

    }


}

Answer 1

这是一个基本概念。

要将组件添加到容器，您需要

1. 创建容器
2. 将布局管理器应用于该容器
3. 将组件添加到该容器
4. 将容器添加到父容器，该父容器(以某种方式)附加到顶级容器

例如

public void ButtonPanel(JButton[] buttons, JTextArea textArea) {
    //TODO: Create a sub-panel with a 4 row, 3 column GridLayout

    JPanel buttonPanel = new JPanel(new GridLayout(4,3)); //Layout of subPanel1

    JButton b1 = new JButton ("A");
    JButton b2 = new JButton ("B");
    JButton b3 = new JButton ("C");
    JButton b4 = new JButton ("1");
    JButton b5 = new JButton ("2");
    JButton b6 = new JButton ("3");
    JButton b7 = new JButton ("X");
    JButton b8 = new JButton ("Y");
    JButton b9 = new JButton ("Z");

    buttonPanel.add(b1);
    buttonPanel.add(b2);
    buttonPanel.add(b3);
    buttonPanel.add(b4);
    buttonPanel.add(b4);
    buttonPanel.add(b5);

    //TODO: Populate the grid with buttons

    //TODO: Add the grid panel to this panel

    //TODO: Create a JScrollPane containing textArea

    JButton cr = new JButton();

    //TODO: Set the preferred size of the scroll pane to 80x120
    // This is a bad idea
    setPreferredSize (new Dimension(80, 120));

    //TODO: Add the scroll pane to this panel

}

花时间阅读并理解 Creating a UI with Swing