Java 写入程序未将任何内容写入文件

您在输出文件打开后立即关闭它，而不写入任何内容

调用start时在主线程中运行open和close，而单击SButton时在事件线程中尝试写入

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一个简单的修复方法是在执行写入操作的SButton action listener中打开和关闭fos。

这是代码的一个选项

我认为您不需要作为全局变量成为Writer类。 只要在每次修改文件时打开并写入内容即可

我刚刚修复了一些错误并使其运行

public class AddDetails extends Application {
    private final String FileName = "C:\\Users\\marsh\\OneDrive\\Documents\\CustomPrograms\\CalcProb\\Players.txt";
    private String Name;
    private char Hand1, Hand1;
    private double Skill1, Skill2;
    File file = new File(FileName);
    FileOutputStream fos = null;
    Writer writer = null;
    static Stage classStage = new Stage();
    String x = null;

    public AddDetails() {
        Name = "";
        Hand = '\0';
        Skill = 0.0;
        BHand = '\0';
        BSkill = 0.0;
    }

    @SuppressWarnings("restriction")
    @Override
    public void start(Stage myStage) throws IOException {
        classStage = myStage;
        myStage.setTitle("Details");

        GridPane rootNode = new GridPane();
        rootNode.setPadding(new Insets(15));
        rootNode.setHgap(5);
        rootNode.setVgap(5);
        rootNode.setAlignment(Pos.CENTER);

        Scene myScene = new Scene(rootNode, 300, 200);

        rootNode.add(new Label("Name:"), 0, 0);
        TextField name = new TextField();
        rootNode.add(name, 1, 0);
        rootNode.add(new Label("Hand:"), 0, 1);
        TextField hand = new TextField();
        rootNode.add(hand, 1, 1);
        rootNode.add(new Label("Skill:"), 0, 2);
        TextField skill = new TextField();
        rootNode.add(skill, 1, 2);
        rootNode.add(new Label("Skill:"), 0, 3);
        TextField Bskill = new TextField();
        rootNode.add(Bskill, 1, 3);
        rootNode.add(new Label("Hand:"), 0, 4);
        TextField Bhand = new TextField();
        rootNode.add(Bhand, 1, 4);
        Button SButton = new Button("Store");
        rootNode.add(SButton, 1, 5);
        GridPane.setHalignment(SButton, HPos.LEFT);
        Button EButton = new Button("Finish");
        rootNode.add(EButton, 1, 5);
        GridPane.setHalignment(EButton, HPos.RIGHT);
        name.setPromptText("Enter Name");
        hand.setPromptText("Enter Hand );
            skill.setPromptText("Enter Skill");
        Bhand.setPromptText("Enter Hand");
        Bskill.setPromptText("Enter Skill");

        myStage.setScene(myScene);
        myStage.show();

        try {
            BufferedReader in = new BufferedReader(new InputStreamReader(new FileInputStream(file), "UTF-8"));
            fos = new FileOutputStream(file, true);
            writer = new OutputStreamWriter(fos, "UTF-8");

            EButton.setOnAction(e -> {
                myStage.close();
                try {
                    writer.close();
                } catch (IOException writerclose) {
                    Alert alert = new Alert(AlertType.ERROR);
                    alert.setTitle("Error");
                    alert.setHeaderText("Error Encountered");
                    alert.setContentText("Error: " + writerclose.getMessage());
                }
            });

            SButton.setOnAction(e -> {
                Name = name.getText();
                Hand = hand.getText().charAt(0);
                Skill = Double.valueOf(skill.getText());
                BSkill = Double.valueOf(Bskill.getText());
                BHand = Bhand.getText().charAt(0);
                Hand = Character.toUpperCase(Hand);
                BHand = Character.toUpperCase(BHand);

                System.out.println(Name + "\t" + Hand + "\t" + Skill + "\t" + BHand + "\t" + BSkill);

                try {

                    writer.write(Name + "\t" + Hand + "\t" + Skill + "\t" + BHand + "\t" + BSkill);

                    name.clear();
                    hand.clear();
                    skill.clear();
                    Bskill.clear();
                    Bhand.clear();

                } catch (IOException br) {

                    Alert alert = new Alert(AlertType.ERROR);
                    alert.setTitle("Error");
                    alert.setHeaderText("Error Encountered");
                    alert.setContentText("Error: " + br.getMessage());

                }
            });
        } catch (IOException e) {
            Alert alert = new Alert(AlertType.ERROR);
            alert.setTitle("Error");
            alert.setHeaderText("Error Encountered");
            alert.setContentText("Error: " + e.getMessage());
        } finally {
            try {
                if (writer != null)
                    writer.close();
                if (fos != null)
                    fos.close();
            } catch (IOException finalclose) {
                Alert alert = new Alert(AlertType.ERROR);
                alert.setTitle("Error");
                alert.setHeaderText("Error Encountered");
                alert.setContentText("Error: " + finalclose.getMessage());
            }
        }
    }

    public static void main(String[] Args) {
        launch(Args);
    }
}

所以，完整的来源在这里

SButton.setOnAction(e -> {
    //.... skip

    try {
        fos = new FileOutputStream(file, true);
        writer = new OutputStreamWriter(fos, "UTF-8");

        writer.write(Name + "\t" + Hand + "\t" + Skill + "\t" + BHand + "\t" + BSkill);

        name.clear();
        hand.clear();
        skill.clear();
        Bskill.clear();
        Bhand.clear();

        writer.flush();

    } catch (IOException br) {

        Alert alert = new Alert(AlertType.ERROR);
        alert.setTitle("Error");
        alert.setHeaderText("Error Encountered");
        alert.setContentText("Error: " + br.getMessage());

    }
    finally {
        try {
            if (writer != null)
                writer.close();
            if (fos != null)
                fos.close();
        } catch (IOException finalclose) {
            Alert alert = new Alert(AlertType.ERROR);
            alert.setTitle("Error");
            alert.setHeaderText("Error Encountered");
            alert.setContentText("Error: " + finalclose.getMessage());
        }
    }
});

输入变量如下图所示

保存的文件如下所示：

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关于，

首先，您的代码格式不正确，其次，创建一个最小、完整且可验证的示例：

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;

import javafx.application.Application;
import javafx.geometry.HPos;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.GridPane;
import javafx.stage.Stage;

public class AddDetails extends Application {
    private final String FileName = "C:\\Users\\marsh\\OneDrive\\Documents\\CustomPrograms\\CalcProb\\Players.txt";
    private String Name;
    private char Hand, BHand;
    private double Skill, BSkill;
    private final File file = new File(FileName);

    static Stage classStage = new Stage();
    String x = null;

    public AddDetails() {
        Name = "";
        Hand = '\0';
        Skill = 0.0;
        BHand = '\0';
        BSkill = 0.0;
    }

    @SuppressWarnings("restriction")
    @Override
    public void start(Stage myStage) throws IOException {
        classStage = myStage;
        myStage.setTitle("Details");

        GridPane rootNode = new GridPane();
        rootNode.setPadding(new Insets(15));
        rootNode.setHgap(5);
        rootNode.setVgap(5);
        rootNode.setAlignment(Pos.CENTER);

        Scene myScene = new Scene(rootNode, 300, 200);

        rootNode.add(new Label("Name:"), 0, 0);
        TextField name = new TextField();
        rootNode.add(name, 1, 0);
        rootNode.add(new Label("Hand:"), 0, 1);
        TextField hand = new TextField();
        rootNode.add(hand, 1, 1);
        rootNode.add(new Label("Skill:"), 0, 2);
        TextField skill = new TextField();
        rootNode.add(skill, 1, 2);
        rootNode.add(new Label("Skill:"), 0, 3);
        TextField Bskill = new TextField();
        rootNode.add(Bskill, 1, 3);
        rootNode.add(new Label("Hand:"), 0, 4);
        TextField Bhand = new TextField();
        rootNode.add(Bhand, 1, 4);
        Button SButton = new Button("Store");
        rootNode.add(SButton, 1, 5);
        GridPane.setHalignment(SButton, HPos.LEFT);
        Button EButton = new Button("Finish");
        rootNode.add(EButton, 1, 5);
        GridPane.setHalignment(EButton, HPos.RIGHT);
        name.setPromptText("Enter Name");
        hand.setPromptText("Enter Hand ");
            skill.setPromptText("Enter Skill");
        Bhand.setPromptText("Enter Hand");
        Bskill.setPromptText("Enter Skill");

        myStage.setScene(myScene);
        myStage.show();


        EButton.setOnAction(e -> {
            myStage.close();

        });

        SButton.setOnAction(e -> {
            Name = name.getText();
            Hand = hand.getText().charAt(0);
            Skill = Double.valueOf(skill.getText());
            BSkill = Double.valueOf(Bskill.getText());
            BHand = Bhand.getText().charAt(0);
            Hand = Character.toUpperCase(Hand);
            BHand = Character.toUpperCase(BHand);
            FileOutputStream fos = null;
            Writer writer = null;

            System.out.println(Name + "\t" + Hand + "\t" + Skill + "\t" + BHand + "\t" + BSkill);

            try {
                fos = new FileOutputStream(file, true);
                writer = new OutputStreamWriter(fos, "UTF-8");

                writer.write(Name + "\t" + Hand + "\t" + Skill + "\t" + BHand + "\t" + BSkill);

                name.clear();
                hand.clear();
                skill.clear();
                Bskill.clear();
                Bhand.clear();

                writer.flush();

            } catch (IOException br) {

                Alert alert = new Alert(AlertType.ERROR);
                alert.setTitle("Error");
                alert.setHeaderText("Error Encountered");
                alert.setContentText("Error: " + br.getMessage());

            }
            finally {
                try {
                    if (writer != null)
                        writer.close();
                    if (fos != null)
                        fos.close();
                } catch (IOException finalclose) {
                    Alert alert = new Alert(AlertType.ERROR);
                    alert.setTitle("Error");
                    alert.setHeaderText("Error Encountered");
                    alert.setContentText("Error: " + finalclose.getMessage());
                }
            }
        });

    }

    public static void main(String[] Args) {
        launch(Args);
    }
}