为什么 JavaFX TextArea 中的 selectRange() 有时不突出显示所选内容

将低级事件处理(如鼠标和键盘事件处理程序)添加到高级UI控件从来都不是一个特别好的主意.您总是面临干扰控件的内置功能的风险，或者内置功能干扰事件处理程序导致无法提供您想要的功能的风险.

在您的例子中，后一种情况正在发生:当按下键时，TextArea已经实现了更改 Select .如果在没有修改键的情况下按下箭头键，则 Select 将被清除.此默认行为正在发生after您的按键被调用，因此默认行为是您所看到的行为.

您可以通过添加以下内容查看正在发生的情况

textArea.selectionProperty().addListener((obs, oldSel, newSel) -> 
    System.out.printf("Selection change: %s -> %s%n", oldSel, newSel)
);

注您可以通过将event.consume()添加到键事件处理程序中的两个if() { ... }块来解决此问题，但我不认为这是一个特别好的解决方案:下面的解决方案更好.

看起来您只是在这里使用了错误的控件.如果您有一个不可编辑的TextArea，其中您将每一行都视为一个不同的项目，那么听起来您似乎正在try 重新实现ListView，它已经实现了 Select 各个项目之类的事情.您可以使用以下命令重新实现您的示例:

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.ListView;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

import java.util.Random;

public class Main extends Application {
    public static void main(String[] args) {
        Application.launch(args);
    }

    private ListView<String> listView;

    @Override
    public void start(Stage primaryStage) {
        System.out.println("Starting JavaFX Window...");
        StackPane rootPane = new StackPane();
        listView = new ListView<>();


        listView.getItems().add("TEST");
        createRandomOptions(8);


        rootPane.getChildren().add(listView);
        Scene scene = new Scene(rootPane, 900, 500);
        primaryStage.setScene(scene);
        primaryStage.show();
        System.out.println("Created window.");
        System.out.println("\nNow press up and down keys to navigate:\n"
                + "Notice, that although a new selection is displayed in the console, it is not\n"
                + "highlighted in the window itself. Even a call to getSelectedText() works fine.\n");
    }


    /**
     * Creates a bunch of random options in textArea.
     * @param newOptionCount
     */
    private void createRandomOptions(int newOptionCount) {
        for (int i = 0; i < newOptionCount; i++) {
            listView.getItems().add("SEL" + (new Random().nextInt(10000)));
        }
    }

}

如果您确实想要修改文本区域中的选定内容，请使用带有可修改所选内容的滤镜的TextFormatter.这看起来会像这样(不过，我再次认为这只是重新发明轮子).注意:这也是您(可能)希望鼠标点击时的行为方式:

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.IndexRange;
import javafx.scene.control.TextArea;
import javafx.scene.control.TextFormatter;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

import java.util.Random;

public class Main extends Application {
    public static void main(String[] args) {
        Application.launch(args);
    }

    private TextArea textArea;

    @Override
    public void start(Stage primaryStage) {
        System.out.println("Starting JavaFX Window...");
        StackPane rootPane = new StackPane();
        textArea = new TextArea();

        textArea.selectionProperty().addListener((obs, oldSel, newSel) -> System.out.printf("Selection change: %s -> %s%n", oldSel, newSel));

        textArea.setText("TEST");
        textArea.setEditable(false);
        createRandomOptions(8);

        textArea.setTextFormatter(new TextFormatter<String>(this::modifySelection));

        rootPane.getChildren().add(textArea);
        Scene scene = new Scene(rootPane, 900, 500);
        primaryStage.setScene(scene);
        primaryStage.show();
        System.out.println("Created window.");
        System.out.println("\nNow press up and down keys to navigate:\n"
                + "Notice, that although a new selection is displayed in the console, it is not\n"
                + "highlighted in the window itself. Even a call to getSelectedText() works fine.\n");
    }
    
    private TextFormatter.Change modifySelection(TextFormatter.Change change) {
        IndexRange selection = change.getSelection();
        String[] lines = change.getControlNewText().split("\n");
        int lineStart = 0 ;
        for (String line : lines) {
            int lineEnd = lineStart + line.length();
            if (lineStart <= selection.getStart() && lineEnd >= selection.getStart()) {
                change.setAnchor(lineStart);
            }
            if (lineStart <= selection.getEnd() && lineEnd >= selection.getEnd()) {
                change.setCaretPosition(lineEnd);
            }
            lineStart += line.length() + 1; // +1 to account for line terminator itself
        }
        return change;
    }

    /**
     * Creates a bunch of random options in textArea.
     * @param newOptionCount
     */
    private void createRandomOptions(int newOptionCount) {
        for (int i = 0; i < newOptionCount; i++) {
            textArea.appendText("\nSEL" + (new Random().nextInt(10000)));
        }
    }

}