java - 如何将 StringProperty 绑定(bind)到 BigDecimal？

Question

我有一个ChangeListener当触发时， findGPA()方法被调用。

private void findGPA(){
    GPA = gradeCre/sum;
    decGPA = new BigDecimal(GPA);
    decGPA = decGPA.setScale(2, RoundingMode.CEILING);
    System.out.println("Your average GPA is: " + decGPA);
}

BigDecimal初始化如下:

private BigDecimal decGPA = BigDecimal.ZERO;

在 initialize()方法:

SubmitStageBorderPane.setBottom(AddStackCircle());

调用:

private StackPane AddStackCircle(){

    StackPane stackCircle = new StackPane();
    StringProperty gpa = new SimpleStringProperty("");
    gpa.bind(new SimpleStringProperty(decGPA.toString()));

    Text avgGPA = createText("Your semester GPA is: " + gpa);
    Circle resultCircle = createCircle(avgGPA);

    stackCircle.getStyleClass().add("stackCircle");
    stackCircle.getChildren().addAll(resultCircle, avgGPA);

    return stackCircle;
}

private Circle createCircle(Text avgGPA){

    Circle resultCircle = new Circle();
    resultCircle.setFill(Color.GREEN);
    resultCircle.setStroke(Color.GREY);
    resultCircle.setStrokeWidth(3);
    resultCircle.setRadius(getWidth(avgGPA) / 2 + 10);

    return resultCircle;
}

private Text createText(String text){

    Text avgGPA = new Text(text);
    avgGPA.setBoundsType(TextBoundsType.VISUAL);
    avgGPA.getStyleClass().add("avgGPA");

    return avgGPA;
}

但是，当我运行它时，它会生成以下标签文本 Your semester GPA is: StringProperty[bound, invalid] ，即使 decGPA 的值也不会改变。变化。

Answer 1

要更新文本，您需要绑定(bind) Text 节点的文本，而不是简单地设置文本。此外，您应该将其绑定(bind)到实际更新的属性，而不仅仅是永远不会修改的属性(例如 new SimpleStringProperty(decGPA.toString()))。

假设findGPA方法被正确调用，它应该像这样实现:

private final ObjectProperty<BigDecimal> decGPA = new SimpleObjectProperty(BigDecimal.ZERO);

private void findGPA(){
    GPA = gradeCre/sum;
    decGPA.set(BigDecimal.valueOf(GPA).setScale(2, RoundingMode.CEILING));
    System.out.println("Your average GPA is: " + decGPA.get());
}

private Text createText(ObservableValue<String> textExpression){

    Text avgGPA = new Text();
    avgGPA.textProperty().bind(textExpression);
    avgGPA.setBoundsType(TextBoundsType.VISUAL);
    avgGPA.getStyleClass().add("avgGPA");

    return avgGPA;
}

Text avgGPA = createText(decGPA.asString("Your semester GPA is: %s"));