使用 JButton、JTextArea 和 showInputDialog 来自 ArrayList 的 GUI 显示信息

Question

有谁知道如何使用 actionPerformed 方法遍历 ArrayList 并检索项目？

基本上我试图让用户点击一个按钮。单击该按钮后，会出现一个 showInputDialog，然后用户例如输入学生的 ID 号。该学生的所有详细信息都将显示在 jtextArea 或 showMessageDialog 框中。

谁能告诉我？ 这是我只是以学生为例的实际代码。

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

public class DepotAdmin 
{
    private ArrayList<Vehicle> DepoVehicle = new ArrayList<Vehicle>(); 
    public DepotAdmin(String hd,String c, String m, String d,Fuel p,int EngSize)
    {
          DepoVehicle = new ArrayList<Vehicle>();

    }


     private void setupDepot(){
        //DepotArraylist vehicles = new DepotArraylist("1111","1111","1111","1111",new Fuel(""),0);

        DepoVehicle.add(new Car("BobMart","567890","Volvo","04/06/2014", new Fuel("Diesel"),6000));
        DepoVehicle.add(new Car("BobMart","465783","BMW","12/052014", new Fuel ("Petrol"), 8000));
        DepoVehicle.add(new Car("BobMart","348709","Ford","13/08/2014",new Fuel ("Petrol"), 3000));
        DepoVehicle.add(new Car("BobMart","145367","Lexus","18/08/2015",new Fuel ("Diesel"), 2000));
        DepoVehicle.add(new RentableCar("BobMart","847469","Citreon","08/07/2015",new             Fuel("Diesel"),1000));
        Car car1 = new Car("BobMart","567890","Volvo","04/06/2014", new Fuel("Diesel"),6000);



    public Vehicle byMake(String make)
    {
            String st[]=DepoVehicle.toArray(new String[DepoVehicle.size()]); 
              for ( Vehicle v : DepoVehicle)
         if (v.getMake().equals(make)){
            return v;
            }
           return null;

      }




    private JFrame Depot ;
    private JMenu Vehicles;
    private JMenu searchVehicle;    
    private JMenu rentVehicle;    
    private JMenu returnVehicle;
    private JMenuItem vehicles1;
    private JMenuItem searchVehicle1;
    private JMenuItem rentVehicle1;
    private JMenuItem returnVehicle1; 
    private JTextArea textArea;
    private JMenuBar menubar;
    private JList vList;
    private ResDepotAdmin listener;
    private ResDepotAdmin listener1;
    private ResDepotAdmin listener2;
    private ResDepotAdmin listener3;
    private JLabel repeatLabel;
    private JTextField inputText;
    private JPanel textPanel;
    public DepotAdmin(){
    //creating the frame to place the menu bar
    Depot = new JFrame ("Depot");
    //creating the menubar to place the menu items
    menubar = new JMenuBar();
    //set the menu bar in the frame
    Depot.setJMenuBar(menubar);
    //set the menus on the menu bar
    Vehicles = new JMenu ("vehicles");
    menubar.add(Vehicles);
    searchVehicle = new JMenu ("search");
    menubar.add(searchVehicle);
    rentVehicle = new JMenu ("rent");
    menubar.add(rentVehicle);
    returnVehicle = new JMenu ("return");
    menubar.add(returnVehicle);
    //set the menu items on the menues
    vehicles1 = new JMenuItem ("Vehicle List");
    Vehicles.add(vehicles1);
    searchVehicle1 = new JMenuItem ("Search Vehicle");
    searchVehicle.add(searchVehicle1);
    rentVehicle1 = new JMenuItem ("Rent Vehicle");
    rentVehicle.add(rentVehicle1);
    returnVehicle1 = new JMenuItem ("Return Vehicle");
    returnVehicle.add(returnVehicle1);
    //data display section
    textArea = new JTextArea(70,70);
    textPanel = new JPanel();
    //add textarea to panel
    textPanel.add(textArea);
    //add panel to frame
    Depot.add((textPanel),BorderLayout.CENTER);
    listeners to respond to click by uaer
    listener = new ResDepotAdmin();
    listener1 = new ResDepotAdmin();
    listener2 = new ResDepotAdmin();
    listener3 = new ResDepotAdmin();
    vehicles1.addActionListener(listener);
    searchVehicle1.addActionListener(listener1);
    rentVehicle1.addActionListener(listener2);
    returnVehicle.addActionListener(listener3);


    String vehicleMake = "make";
    //JOptionPane.showInputDialog(searchVehicle1,"Enter vehicle make");
    //set the size of the frame
    Depot.setSize(600,600);
    //aet the visibility of the frame
    Depot.setVisible(true);
    //prevent the running the the program on exit
    Depot.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);



         }
         public class ResDepotAdmin implements ActionListener
    {


       private String make; 
     private void setupDepot(){
        DepotArraylist vehicles = new DepotArraylist("1111","1111","1111","1111",new Fuel(""),0);
        vehicles.addVehicle(new Car("BobMart","567890","Volvo","04/06/2014", new Fuel("Diesel"),6000));
        vehicles.addVehicle(new Car("BobMart","465783","BMW","12/052014", new Fuel ("Petrol"), 8000));
        vehicles.addVehicle(new Car("BobMart","348709","Ford","13/08/2014",new Fuel ("Petrol"), 3000));
        vehicles.addVehicle(new Car("BobMart","145367","Lexus","18/08/2015",new Fuel ("Diesel"), 2000));
        vehicles.addVehicle(new RentableCar("BobMart","847469","Citreon","08/07/2015",new Fuel("Diesel"),1000));
        Car car1 = new Car("BobMart","567890","Volvo","04/06/2014", new Fuel("Diesel"),6000);



}


         public Vehicle findVehicle(String make)
          {
           for (Vehicle dv : DepoVehicle)
             if (dv.getMake().equals(make))
            return dv;
              return null;
            }


             public void actionPerformed(ActionEvent e)
             {
                       //DepotAdmin DepoVehicle = new DepotAdmin("null","null","null","null",new Fuel(""),0);

                       ArrayList<Vehicle> DepoVehicle = new ArrayList<Vehicle>();
                               DepoVehicle.add(new Car("BobMart","567890","Volvo","04/06/2014",    new Fuel("Diesel"),6000));
                               DepoVehicle.add(new Car("BobMart","348709","Ford","13/08/2014",new Fuel ("Petrol"), 3000));


                     if ( e.getSource() == vehicles1){
                     textArea.append(DepoVehicle.toString()+"\n"+"\n");
                     }


                     String make = JOptionPane.showInputDialog(null,"Enter vehicle make");

                      if (e.getSource()== searchVehicle1){

                           for ( Vehicle v : DepoVehicle){ if (v.getMake().equals(make)){
                                                        textArea.append(make);

                                                                  }
                                                     }

                     }
            }
      }
}

Answer 1

我真的不知道如何解释您有关于汽车的消息这一事实，但您希望学生作为输入。所以我稍微改变了一下。相应地进行更改。

我刚刚循环，如果学生 ID 与输入匹配，我将学生附加到文本区域

public void actionPerformed{

   String stuId = JOptionPane.showInputDialog(null,"Enter Student ID");

   for (Student student : pupils){
       if (student.getId().equals(stuId)){
           textArea.append(student);
           break;
       }
   }
}

---

• 另外，我注意到您在 main 方法中有一个 actionPerformed。您是否正在尝试创建 GUI 程序？因为此时，您的代码远未完成。

• 您似乎在main 中也有一个方法，这是一个不可以的方法。您的代码绝不会编译。请发布一个可编译的程序，这样我们就可以准确地看到您要完成的工作。因为你帖子里的代码很垃圾。

---

我注意到的另一个巨大错误在这里

    String name;
    String id;
    public Student (String n, String i) {
        n = name;
        i = id;
    }

你的构造函数是错误的。 n = name 什么都不做。相反，你想要

    name = n;
    id = i;

---

同样Student 接受一个字符串输入，但您正在尝试添加一个int。也许这只是为了尝试 SSCCE，但它是从文本字段中获取这些输入，它会起作用，但如果你很难对其进行编码，它们需要是字符串。

    pupils.add(new Student("james", "2345"));
    pupils.add(new Student ("taylor", "5768"));
    pupils.add(new Student("andy", "9874"));

---

对于你的Student 类，如果你想要Student 对象的String 表示，你应该@Override toString() 方法，像这样

    public String toString() {
       //am i wrong here?  
        return "Student Name: " + name + ", ID: " + id;
    }

---

这是一个简单的完整的可运行程序，因此您可以了解所有内容是如何组合在一起的。检查它，看看你可能哪里出错了。随时提问。

import java.awt.BorderLayout;
import java.awt.event.*;
import java.util.ArrayList;
import javax.swing.*;

public class StudentGUI extends JFrame {

    private JTextArea jtaStudent = new JTextArea(10, 30);
    private JButton showStudents = new JButton("Show Students");
    ArrayList<Student> pupils = new ArrayList<>();

    public StudentGUI() {
        pupils.add(new Student("james", "2345"));
        pupils.add(new Student("taylor", "5768"));
        pupils.add(new Student("andy", "9874"));

        add(showStudents, BorderLayout.SOUTH);
        add(jtaStudent, BorderLayout.CENTER);

        showStudents.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                for (Student student : pupils) {
                    jtaStudent.append(student + "\n");
                }
            }
        });
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                JFrame frame = new StudentGUI();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);

            }
        });
    }
}

class Student {
    String name;
    String id;

    public Student(String n, String i) {
        name = n;
        id = i;
    }

    public String getName() {
        return name;
    }

    public String getId() {
        return id;
    }

    public String toString() {
        // am i wrong here?
        return "Student Name: " + name + ", ID: " + id;
    }
}

Answer 2

您创建了一个构造函数：

public Students(parameter, parameter){}

，但您没有为以下各项创建构造函数：

public Student(){}

通常，如果你自己不创建任何构造函数，编译器会为你创建一个无参数的协程函数，但是当你自己创建任何构造函数时，你需要自己创建一个无参数的构造函数。希望这会有所帮助。