JavaFX ScrollPane setVvalue() not working properly

Question

I am testing the JavaFX ScrollPane class and realized that it is not working as I expect, I don't know why. I have the following code:

public class Client3 extends Application {

int indexMsg = 0;

Button send;

GridPane root;
ScrollPane msgPane;
GridPane msgPaneContent;
FlowPane writePane;
TextField writeMsg;

Scene scene;

@Override
public void start(Stage primaryStage) {

    root = new GridPane();
    root.setAlignment(Pos.CENTER);
    root.setVgap(10);
    root.setPadding(new Insets(10, 10, 10, 10));

    msgPane = new ScrollPane();
    msgPane.setPrefSize(280, 280);
    msgPane.setHbarPolicy(ScrollPane.ScrollBarPolicy.NEVER);

    msgPaneContent = new GridPane();
    msgPaneContent.setPrefWidth(270);
    msgPaneContent.setVgap(10);

    writePane = new FlowPane(10, 10);
    writePane.setAlignment(Pos.CENTER);
    writePane.setPrefWidth(280);

    writeMsg = new TextField();
    writeMsg.setPrefWidth(150);
    writeMsg.setPromptText("Write your message");

    writePane.getChildren().add(writeMsg);

    GridPane.setConstraints(msgPane, 0, 0);
    GridPane.setConstraints(writePane, 0, 1);

    msgPane.setContent(msgPaneContent);
    root.getChildren().addAll(msgPane, writePane);

    writeMsg.setOnAction((ev) -> {

        if (!writeMsg.getText().isEmpty()) {

            TextArea msg = new TextArea(writeMsg.getText());

            msg.setMaxWidth(135);
            msg.setPrefRowCount(msg.getLength() / 21 + 1);
            msg.setWrapText(true);

            GridPane.setConstraints(msg, 0, indexMsg);

            indexMsg++;

            writeMsg.deleteText(0, writeMsg.getText().length());
            msgPaneContent.getChildren().add(msg);

            msgPane.setVvalue(1.0);

        }

    });

    scene = new Scene(root, 300, 300);

    primaryStage.setTitle("Chat App");
    primaryStage.setScene(scene);
    primaryStage.show();

}

public static void main(String[] args) {

    launch(args);

}

}

Basically, I have a GridPane as the root with a ScrollPane and a GridPane as its children. The ScrollPane has a children GridPane. There is a TextField with an EventHandler which generates a TextArea inside the GridPane (the ScrollPane's children). Each TextArea object is created in the vertical direction, downwards. I want to set the scrollbar always at its maximum value (setVvalue(1.0)) each time a new TextArea is added. The thing is that it doesn't seem to work as it should because the vertical value is never set to the maximum after handling the event, but it seems to be set to the maximum value that it had before handling it (the bottom of the previous TextArea added).

Any solution for this? Thanks in advance.