小编dav*_*ave的帖子

我想并排添加两个jPanel到JFrame.两个框是jpanels,外框是jframe

我有这些代码行.我有一个名为seatinPanel的类,它扩展了JPanel,在这个类中我有一个构造函数和一个名为utilityButtons的方法,它返回一个JPanel对象.我希望utilityButtons JPanel在右侧.我这里的代码只在运行时显示utillityButtons JPanel.

public guiCreator()
    {
        setTitle("Passenger Seats");
        //setSize(500, 600);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        Container contentPane = getContentPane();

        seatingPanel seatingPanel1 = new seatingPanel();//need to declare it here separately so we can add the utilityButtons
        contentPane.add(seatingPanel1); //adding the seats
        contentPane.add(seatingPanel1.utilityButtons());//adding the utility buttons

        pack();//Causes this Window to be sized to fit the preferred size and layouts of its subcomponents
        setVisible(true);  
    }

我试图改变源的背景颜色,但java给我内部致命错误发生消息.你能告诉我我做错了吗？

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

    class ButtonPanel extends JPanel 
    {  
        private JButton yellowButton = new JButton("Yellow");

        public ButtonPanel()//constructor
        {  

              //setLayout is a method in JPanel that is called in this constructor
              setLayout (new FlowLayout(FlowLayout.LEFT));
              add(yellowButton);
              actions actionsSpecified = new actions();

              yellowButton.addActionListener(actionsSpecified);
           }
        }

    class actions implements ActionListener
    {
        //actionPerformed is an interface that muse be overriden
        public void actionPerformed(ActionEvent evt)
        {  
            // knows where the event is generated from(from a button, scrollbar etc...)
              JButton source = (JButton) evt.getSource(); …

我有这些代码行.我知道你不能将非final变量传递给内部类,但我需要将变量传递i给匿名内部类以用作seatID.你能建议这样做的方法吗？

JButton [] seats = new JButton [40]; //creating a pointer to the buttonsArray
for (int i = 0; i < 40; i++)
{
    seats[i] = new JButton();//creating the buttons
    seats[i].setPreferredSize(new Dimension(50,25));//button width
    panel4seating.add(seats[i]);//adding the buttons to the panels

    seats[i].addActionListener(new ActionListener()
    {  //anonymous inner class
        public void actionPerformed(ActionEvent evt)
        {  
            String firstName = (String)JOptionPane.showInputDialog("Enter First Name");
            String lastName = (String)JOptionPane.showInputDialog("Enter Last Name");

            sw101.AddPassenger(firstName, lastName, seatingID);
        }
    });
}

在大多数代码示例中,我看到人们这样做.

import javax.swing.*; // for the frame
import java.awt.*; // for the checkBox and the label
import java.awt.event.*; // for the checkBox listener

如果我说的是导入java.awt.*它是正确的,它会导入其中的所有内容,因此不需要说import java.awt.event.*; 还是有提速？任何人都可以解释导入库的作用,是导入一个简单的文本类,包含在源代码中还是告诉jvm包含导入的字节代码？所以在java中导入只会切换命名空间,所以我不必输入长类名？

我为什么会收到错误.在eclipse中,它表示构造函数调用应该是第一行.这是第一线.或者你不能扩展Main？

import javax.swing.JFrame;
import javax.swing.JLabel;

    public class Main extends JFrame{

        /**
         * @param args
         */
        public static void main(String[] args) {
            // TODO Auto-generated method stub
            //JLabel testLabel1 = new JLabel();
            public Main(){
                super("title bar");
            }
        }

    }

(pass[i]!= null) && (pass[i].getName()!= "nullnull")< - 当我调试它时返回true,即使我在调试pass[i].getName() == "nullnull"时使用eclipse中的Expressions窗口检查它时的值

我使用输入对话框输入两个名字

String firstName = (String)JOptionPane.showInputDialog("Enter First Name");
String lastName = (String)JOptionPane.showInputDialog("Enter Last Name");

并返回

public String getName()
    {
        return FirstName + LastName;
    }