在JavaFX中更改标签的文本

Question

这个问题已在这里提出,但未能找到任何答案.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

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

<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

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

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);
        }
    }
}

控制台输出

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

但可以看到标签没有变化.我错过了一些重要的东西吗？

Answer 1

您可以更改Connector类以接收Controller实例:

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,您可能希望使用任务,因此您不会冻结您的UI.要更新Label,您必须绑定text属性,然后使用该updateMessage()方法更新Text值.

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;
        }
    }

}