将Javafx textfield中的十进制输入转换为double

Question

            //takes in the users input and trims spaces
            holder[i] = txtFld.getText().trim();
            while(run == false) {
                try {
                    //attempts to parse the stripped text to a double
                    amt[i] = Double.parseDouble(holder[i]);
                    //allows the loop to break
                    run = true;
                }catch(NumberFormatException ex) {
                    txtFld.setText("");
                    //tells the user about the error
                    grid.add(Err, 0, 3);
                }
            }

Answer 1

您不应该在JavaFX中执行这样的循环，原因有几个：

• 这样的循环会阻塞应用程序线程。这将导致循环运行时不处理任何输入。
• 即使输入没有完成，也要修改文本。考虑用户希望输入-1e3的场景。代码允许此输入的唯一方法是像这样逐步更改文本:“”->“1”->“-1”->“-13”->“-1e3”

最简单的修复方法是检查“提交”数据。或者，监听textfield.text属性，并显示一些无效输入的指示（例如某个图标），但不要在每次更改时都修改文本。

@Override
public void start(Stage primaryStage) {
    TextField textField = new TextField();

    TextFormatter<Double> formatter = new TextFormatter<>(new DoubleStringConverter(), 0d);
    textField.setTextFormatter(formatter);

    formatter.valueProperty().addListener((o, oldValue, newValue) -> System.out.println("value changed to " + newValue));

    Button button = new Button("some other focusable element");

    Scene scene = new Scene(new VBox(textField, button));
    primaryStage.setScene(scene);
    primaryStage.show();
}

@Override
public void start(Stage primaryStage) {
    TextField textField = new TextField();
    Label textErrorLabel = new Label();
    textErrorLabel.setTextFill(Color.RED);

    HBox textBox = new HBox(10, textField, textErrorLabel);
    textBox.setPrefWidth(300);

    Button button = new Button("Submit");
    button.setOnAction(evt -> {
        boolean valid = true;
        double value = 0;
        try {
            value = Double.parseDouble(textField.getText());
            textErrorLabel.setText("");
            textField.setStyle(null);
        } catch (NumberFormatException ex) {
            valid = false;
            textErrorLabel.setText("erroneous input");
            textField.setStyle("-fx-control-inner-background: red;");
        }

        // you could do more input validation here...

        if (valid) {
            System.out.println("successfully submitted "+ value);
        }
    });

    Scene scene = new Scene(new VBox(textBox, button));
    primaryStage.setScene(scene);
    primaryStage.show();
}