有沒有辦法在JavaFX的不同類文件中使用線程？

Question

好吧，所以我在Java編程方面並不陌生，但我在使用Java程序中的線程方面很新穎。我在學校，剛剛完成了關於線程和Java網絡的章節。我正在編寫一個將貸款信息（年利率，年數和貸款金額）發送到服務器的客戶端GUI。服務器有自己的圖形用戶界面（GUI），計算每月付款和貸款總額，並將其發送回客戶端並顯示給用戶以及更新服務器GUI。

書中有這樣的代碼爲例：

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; 
    } 

} 

正如您在示例代碼中看到，他們（本書的作者）使用一個新的線程來能夠的文本追加服務器GUI。然而，爲了能夠處理多個客戶端，在while循環內部創建了一個新線程來處理每個客戶端。

我試圖創建HandleAClient類作爲一個單獨的Java類，而不是在服務器級別將其插入的，但是這導致服務器GUI不與Platform.runLater代碼

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");}); 

所以我的問題更新：爲什麼它在HandleAClient類位於Server類內部時起作用，而當HandleAClient類位於擴展Server的單獨Java類文件中時不起作用？我認爲它必須對線程做些什麼？爲了能夠在自己的Java類文件中擁有HandleAClient類，我該怎麼做？

我很好奇，並試圖很好地理解線程是如何工作的。先謝謝你。

UPDATE 這是沒有爲我工作的獨立類。我擴展了Server類，並且在Server類中保留了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中的代碼沒有出現在服務器GUI中，因爲它是在類位於Server類內部時出現的。我想明白爲什麼會發生這種情況。

Answer 1

你需要你的HandleAClient實例來更新屬於創建它們的Server對象文本區域：屬於該Server實例textArea是顯示在用戶界面中的一個。通過您的設置，每個HandleAClient實例都有自己的textArea，並且每個實例都更新自己的textArea。當然，這些都沒有被展示過。

HandleAClient擴展Server對我沒有意義。您需要執行的操作（無論是否具有該繼承）爲HandleAClient提供了更新屬於Server的文本區域的方法。最簡單的（但不一定是最好的）方式就是文本區域傳遞給HandleAClient實例：當然

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(); 
     } 
    } 
} 

然後在Server修改它

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(); 

} 

---

感覺有點不自然讓HandleAClient類（它負責通信）依靠引用TextArea（這是UI特定的）。更自然的方法如下。

我可能會定義一個簡單的類來表示利率，一年，貸款：

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 ; 
    } 
} 

然後給HandleAClient類Consumer<LoanData>用於處理貸款數據：

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(); 
     } 
    } 
} 

現在服務器做

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(); 

這使得UI數據功能在UI類中正確隱蔽。