JavaFX ScrollPane setVvalue（）无法正常工作

Question

我正在测试JavaFX ScrollPane类，并意识到它没有按照我的预期工作，我不知道为什么。我有以下代码：

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);

}

}

基本上，我有一个GridPane作为根，ScrollPane和GridPane作为其子项。 ScrollPane有一个孩子GridPane。 TextField EventHandler TextArea会在GridPane（ScrollPane的子项内部生成TextArea。每个setVvalue(1.0)对象都是在垂直方向向下创建的。我想在每次添加新的TextArea时始终将滚动条设置为其最大值（a = ["a","b","c"] b = [1,2,3] c = [4,5,6] new_dict = {i:[j, k] for i, j, k in zip(a, b, c)} ）。事情是它似乎没有工作，因为垂直值在处理事件后从未设置为最大值，但似乎设置为处理它之前的最大值（底部的之前的TextArea已添加）。

任何解决方案？提前谢谢。