在JavaFX中更改标签的文本 [英] Changing the text of a label from a different class in JavaFX

问题描述

这个问题已经被问到这里但是无法找到任何答案。我已经复制了类似的情况，我想使用控制器从另一个类更改标签的文本

This question was already asked here but was not able to find any answers. I have reproduced a similar situation where I would like to change the text of a label from another class using the controller

FXMLDocumentController.java

FXMLDocumentController.java

public class FXMLDocumentController implements Initializable {

    @FXML
    private Label label;

    @FXML
    private void handleButtonAction(ActionEvent event) {
        System.out.println("FXMLDocumentController.#handleButtonAction");
        label.setText("Hello World!");
        Connector.Connecting();
    }

    @Override
    public void initialize(URL url, ResourceBundle rb) {
        // TODO
    }    

    public void setLabelText(String text)
    {
        System.out.println("FXMLDocumentController.setLabelText(): Called");
        label.setText(text);
    }

}

FXMLDocument.fxml

FXMLDocument.fxml

<AnchorPane id="AnchorPane" prefHeight="200" prefWidth="320" xmlns:fx="http://javafx.com/fxml/1" fx:controller="demo5.FXMLDocumentController">
    <children>
        <Button layoutX="126" layoutY="90" text="Click Me!" onAction="#handleButtonAction" fx:id="button" />
        <Label layoutX="126" layoutY="120" minHeight="16" minWidth="69" fx:id="label" />
    </children>
</AnchorPane>

Demo5.java

Demo5.java

public class Demo5 extends Application {

    @Override
    public void start(Stage stage) throws Exception {
        Parent root = FXMLLoader.load(getClass().getResource("FXMLDocument.fxml"));

        Scene scene = new Scene(root);

        stage.setScene(scene);
        stage.show();
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        launch(args);
    }

}

Connector.java

Connector.java

public class Connector {
    public static void Connecting() {
        try {
            System.out.println("Connector.Connecting(): Called");

            FXMLLoader loader = new FXMLLoader(FXMLDocumentController.class.getResource("FXMLDocument.fxml"));
            loader.load();
            FXMLDocumentController controller = (FXMLDocumentController) loader.getController();

            controller.setLabelText("Bye World");
        } catch (IOException ex) {
            Logger.getLogger(Connector.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

在控制台输出

Connector.Connecting(): Called
FXMLDocumentController.setLabelText(): Called

但是标签上看不到任何变化。我错过了一些主要的东西吗？

But could see no changes in the label. Am I missing something major here ?

推荐答案

您可以更改您的Connector类以接收Controller实例：

You can change your Connector class to receive the Controller instance:

public class Connector {
    public static void Connecting(FXMLDocumentController controller) {
        try {
            System.out.println("Connector.Connecting(): Called");
            controller.setLabelText("Bye World");
        } catch (IOException ex) {
            Logger.getLogger(Connector.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}


public class FXMLDocumentController implements Initializable {

    @FXML
    private Label label;

    @FXML
    private void handleButtonAction(ActionEvent event) {
        System.out.println("FXMLDocumentController.#handleButtonAction");
        label.setText("Hello World!");
        Connector.Connecting(this);
    }

    @Override
    public void initialize(URL url, ResourceBundle rb) {
        // TODO
    }    

    public void setLabelText(String text)
    {
        System.out.println("FXMLDocumentController.setLabelText(): Called");
        label.setText(text);
    }

}

注意：

如果您的连接器需要更长的时间来执行它所需的任何内容，您可能需要使用任务，因此您不会冻结您的UI。要更新Label，您必须绑定text属性，然后使用 updateMessage（）方法更新Text值。

If your Connector is going to take longer to execute whatever it needs to, you might want to use a Task, so you don't freeze your UI. To update the Label, you have to bind the text property and then update the Text value using the updateMessage() method.

public class FXMLDocumentController implements Initializable {

    @FXML
    private Label label;

    @FXML
    private void handleButtonAction(ActionEvent event) {
        System.out.println("FXMLDocumentController.#handleButtonAction");
        label.setText("Hello World!");

        Task<Boolean> connectorTask = new ConnectorTask();
        label.textProperty().bind(connectorTask.messageProperty());
        connectorTask.setOnSucceeded(e -> {
            // this is going to be called if the task ends up without error
            label.textProperty().unbind();
        });
        new Thread(connectorTask).start();
    }

    @Override
    public void initialize(URL url, ResourceBundle rb) {
        // TODO
    }    

    //public void setLabelText(String text)
    //{
    //    System.out.println("FXMLDocumentController.setLabelText(): Called");
    //    label.setText(text);
    //}


    public class ConnectorTask extends Task<Boolean> {

        @Override
        protected Boolean call() throws Exception {
            // ... do whatever you need here

            // then you call this method to update the TextProperty from the Label that was bound.
            updateMessage("Bye World");

            return Boolean.TRUE;
        }
    }

}

这篇关于在JavaFX中更改标签的文本的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！