有没有人知道如何使用actionPerformed方法迭代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showInputDialog，然后用户输入学生的ID号。所有学生的详细信息都将显示在jtextArea或showMessageDialog框中。
有人能告诉我吗？ 这是我刚刚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);
}
}
}
}
}
}
答案 0 :(得分：1)
我真的不确定如何解释你有关于汽车的信息，但你希望学生作为输入。所以我改变了一下。相应地进行更改。
我只是循环播放，如果学生ID与输入匹配，我将学生添加到文本区域
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，我注意到你在main方法中有一个actionPerformed。您是否正在尝试创建GUI程序？因为在这一点上，你的代码远未完成它。
你似乎也有一个main内的方法，这是一个不可以。你的代码绝对不会编译。请发布一个可编译的程序，以便我们可以准确地看到您要完成的任务。因为帖子中的代码是垃圾。
我注意到的另一个巨大错误就在这里
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什么也没做。相反，你想要
name = n;
id = i;
同样Student接受字符串输入，但您尝试添加int。也许这仅仅是为了SSCCE尝试，但是它从文本字段中获取这些输入，它可以工作，但如果你正在编写它，它们需要是String。
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，类似这样
public String toString() {
//am i wrong here?
return "Student Name: " + name + ", ID: " + id;
}
这是一个简单的完整可运行程序，因此您可以看到所有内容如何组合在一起。检查它，看看你可能出错的地方。随意提问。
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;
}
}
答案 1 :(得分：-1)
您为：
创建了一个构造函数public Students(parameter, parameter){}
，但您没有为：
创建构造函数public Student(){}
通常，如果您自己不创建任何构造函数，编译器将为您创建一个no-arg cosntructor，但是当您自己创建任何构造函数时，您将需要自己创建一个无参数构造函数。希望这会有所帮助。