java - 有没有办法在 JavaFX 中的不同类文件中使用线程？

Question

好吧，我对 Java 编程并不陌生，但我对在 Java 程序中使用线程很陌生。我正在上学，刚刚读完关于线程和 Java 网络的章节。我正在编写一个客户端 GUI，将贷款信息(年利率、年数和贷款金额)发送到服务器。服务器有自己的 GUI，计算每月还款额和贷款总额，并将其发送回客户端并显示给用户，并更新服务器 GUI。

书中有这样的代码作为示例:

public class Server extends Application {
/** Variables */
private TextArea textArea = new TextArea();
private double rate;
private int year;
private double loan;

public void start(Stage serverStage)
{
    // Creating server GUI
    Scene scene = new Scene(new ScrollPane(textArea), 400, 200);
    serverStage.setTitle("Server");
    serverStage.setScene(scene);
    serverStage.show();

    new Thread(() ->{

        try
        {
            // create server socket
            ServerSocket serverSocket = new ServerSocket(8000);
            textArea.appendText("Server started at " + new Date() + "\n");

            while(true)
            {
                // listen for a connection request
                Socket socket = serverSocket.accept();

                Platform.runLater(() -> {
                    InetAddress inetAddress = socket.getInetAddress();
                    textArea.appendText("Connected to " + inetAddress.getHostAddress() + " at " + new Date() + "\n");
                });


                // create and start a new thread for every connection
                new Thread(new HandleAClient(socket)).start();

            }
        }
        catch(IOException ex)
        {
            ex.printStackTrace();
        }
    }).start();
}

class HandleAClient implements Runnable {

    private Socket socket; // A connected socket
    private double rate;
    private int year;
    private double loan;

    /** costruct a thread */
    public HandleAClient(Socket socket)
    {
        this.socket = socket;
    }

    /** run a thread */
    public void run(){
        try
        {
            // create data input and output streams
            DataInputStream inputFromClient = new DataInputStream(socket.getInputStream());
            DataOutputStream outputToClient = new DataOutputStream(socket.getOutputStream());

            // continuously serve the client
            while(true) {
                // read data from client

                rate = inputFromClient.readDouble();
                year = inputFromClient.readInt();
                loan = inputFromClient.readDouble();


                // calculate monthly payment of loan and total payment

                outputToClient.writeDouble(calculateMonthlyPayment(rate, year, loan));
                outputToClient.writeDouble(calculateTotalPayment(rate, year, loan));

                Platform.runLater( () -> {
                    textArea.appendText("The rate is : " + rate + "\n");
                    textArea.appendText("The number of years is: " + year + "\n");
                    textArea.appendText("Loan amount is: " + loan + "\n\n");});




            }
        }
        catch(IOException e)
        {
            e.printStackTrace();
        }
    }
}

// calculateMonthlyPayment method calculates the monthly payment of a loan given
// the required information

public double calculateMonthlyPayment(double interestRate, int years, double loanAmt)
{
    double monthlyRate;
    int termInMonths;
    double monthlyPayment;

    // Convert the interest rate to a decimal
    interestRate = interestRate / 100;

    // convert annual interest rate to monthly interest rate
    monthlyRate = interestRate / 12;

    // calculate the term in months which is years * 12
    termInMonths = years * 12;

    monthlyPayment = (loanAmt*monthlyRate) / (1-Math.pow(1+monthlyRate, -termInMonths));

    return monthlyPayment;
}



// method that calculates and returns the total payment of the loan
public double calculateTotalPayment(double rate, int year, double loan)
 {
    double totalPayment;
    double monthlyPay;

    monthlyPay = calculateMonthlyPayment(rate, year, loan);


    totalPayment = monthlyPay * 12 * year;

    return totalPayment;
  }

}

正如您在示例代码中看到的，他们(本书的作者)使用一个新的线程来附加服务器 GUI 的文本。然而，为了能够处理多个客户端，需要在 while 循环内部创建一个新线程来处理每个单独的客户端。

我尝试将 HandleAClient 类创建为单独的 Java 类，而不是将其插入到 Server 类中，但这导致服务器 GUI 未使用 Platform.runLater 代码进行更新

Platform.runLater( () -> {
                    textArea.appendText("The rate is : " + rate + "\n");
                    textArea.appendText("The number of years is: " + year + "\n");
                    textArea.appendText("Loan amount is: " + loan + "\n\n");});

所以我的问题是:为什么当 HandleAClient 类位于 Server 类内部时它可以工作，而当 HandleAClient 类位于扩展 Server 的单独 Java 类文件中时它不起作用？我认为它必须与线程做一些事情？为了能够在自己的 Java 类文件中包含 HandleAClient 类，我需要进行哪些更改？

我很好奇并试图很好地理解线程是如何工作的。预先感谢您。

更新这是独立的类(class)，对我来说不起作用。我扩展了 Server 类，并在 Server 类中保护了 TextArea 字段。

class HandleAClient extends Server implements Runnable {

private Socket socket; // A connected socket
private double rate;
private int year;
private double loan;


public HandleAClient(Socket socket)
{
    this.socket = socket;
}

/** run a thread */
public void run(){
    try
    {
        // create data input and output streams
        DataInputStream inputFromClient = new DataInputStream(socket.getInputStream());
        DataOutputStream outputToClient = new DataOutputStream(socket.getOutputStream());

        // continuously serve the client
        while(true) {
            // read data from client

            rate = inputFromClient.readDouble();
            year = inputFromClient.readInt();
            loan = inputFromClient.readDouble();


            // calculate monthly payment of loan and total payment

            outputToClient.writeDouble(calculateMonthlyPayment(rate, year, loan));
            outputToClient.writeDouble(calculateTotalPayment(rate, year, loan));

            Platform.runLater( () -> {
                textArea.appendText("The rate is : " + rate + "\n");
                textArea.appendText("The number of years is: " + year + "\n");
                textArea.appendText("Loan amount is: " + loan + "\n\n");});

        }
    }
    catch(IOException e)
    {
        e.printStackTrace();
    }
  }
}

Platform.runLater 中的代码不会像该类位于 Server 类内部时那样出现在服务器 GUI 中。我想了解为什么会发生这种情况。

Answer 1

您需要您的HandleAClient实例来更新属于 Server 的文本区域创建它们的对象:textArea属于那个Server实例是在 UI 中显示的实例。根据您的设置，每个 HandleAClient实例有自己的 textArea ，并且每个都更新自己的 textArea 。当然，这些都不会显示。

对于我来说 HandleAClient 真的没有意义延长Server 。您需要做的(无论您是否拥有该继承)是为 HandleAClient 提供一种方法。更新属于 Server 的文本区域。最简单(但不一定是最好)的方法是将文本区域传递给 HandleAClient实例:

class HandleAClient implements Runnable {

    private Socket socket; // A connected socket
    private double rate;
    private int year;
    private double loan;

    private final TextArea textArea ;

    public HandleAClient(Socket socket, TextArea textArea)
    {
        this.socket = socket;
        this.textArea = textArea ;
    }

    /** run a thread */
    public void run(){
        try
        {
            // create data input and output streams
            DataInputStream inputFromClient = new DataInputStream(socket.getInputStream());
            DataOutputStream outputToClient = new DataOutputStream(socket.getOutputStream());

            // continuously serve the client
            while(true) {
                // read data from client

                rate = inputFromClient.readDouble();
                year = inputFromClient.readInt();
                loan = inputFromClient.readDouble();


                // calculate monthly payment of loan and total payment

                outputToClient.writeDouble(calculateMonthlyPayment(rate, year, loan));
                outputToClient.writeDouble(calculateTotalPayment(rate, year, loan));

                Platform.runLater( () -> {
                    textArea.appendText("The rate is : " + rate + "\n");
                    textArea.appendText("The number of years is: " + year + "\n");
                    textArea.appendText("Loan amount is: " + loan + "\n\n");});

            }
        }
        catch(IOException e)
        {
            e.printStackTrace();
        }
    }
}

然后当然是Server您将其修改为

while(true)
{
    // listen for a connection request
    Socket socket = serverSocket.accept();

    Platform.runLater(() -> {
        InetAddress inetAddress = socket.getInetAddress();
        textArea.appendText("Connected to " + inetAddress.getHostAddress() + " at " + new Date() + "\n");
    });


    // create and start a new thread for every connection
    new Thread(new HandleAClient(socket, textArea)).start();

}

<小时/>

让 HandleAClient 感觉有点不自然类(负责通信)依赖于对 TextArea 的引用(这是特定于 UI 的)。更自然的方法如下。

我可能会定义一个简单的类来表示利率、年份和贷款:

public class LoanData {

    private final double rate ;
    private final int year ;
    private final double loan ;

    public LoanData(double rate, int year, double loan) {
        this.rate = rate ;
        this.year = year ;
        this.loan = loan ;
    }

    public double getRate() {
        return rate ;
    }
    public int getYear() {
        return year ;
    }
    public double getLoan() {
        return loan ;
    }
}

然后给出HandleAClient A类Consumer<LoanData>用于处理贷款数据:

class HandleAClient implements Runnable {

    private Socket socket; // A connected socket

    private final Consumer<LoanData> dataProcessor ;

    public HandleAClient(Socket socket, Consumer<LoanData> dataProcessor)
    {
        this.socket = socket;
        this.dataProcessor = dataProcessor ;
    }

    /** run a thread */
    public void run(){
        try
        {
            // create data input and output streams
            DataInputStream inputFromClient = new DataInputStream(socket.getInputStream());
            DataOutputStream outputToClient = new DataOutputStream(socket.getOutputStream());

            // continuously serve the client
            while(true) {
                // read data from client

                double rate = inputFromClient.readDouble();
                double year = inputFromClient.readInt();
                double loan = inputFromClient.readDouble();


                // calculate monthly payment of loan and total payment

                outputToClient.writeDouble(calculateMonthlyPayment(rate, year, loan));
                outputToClient.writeDouble(calculateTotalPayment(rate, year, loan));

                dataProcessor.accept(new LoanData(rate, year, loan));

            }
        }
        catch(IOException e)
        {
            e.printStackTrace();
        }
    }
}

现在在服务器中执行

Consumer<LoanData> textAreaUpdater = 
    loanData -> Platform.runLater(() -> {
        textArea.appendText("The rate is : " + loanData.getRate() + "\n");
        textArea.appendText("The number of years is: " + loanData.getYear() + "\n");
        textArea.appendText("Loan amount is: " + loanData.getLoan() + "\n\n");
    });

new Thread(new HandleAClient(socket, textAreaUpdater)).start();

这使得 UI 数据功能正确地隔离在 UI 类中。