需求描述:
两个fxml界面，当一个界面的输入框TextField填入内容,点击确定后另一个界面Label显示出TextField的内容

假设两个界面的控制器分别是:
ResultController(显示结果的界面 ResultPage.fxml)
InputController(输入字符串的界面Input.fxml)

目录结构

• 首先定义一个数据模型AppModel.java

import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;

public class AppModel
{
    private StringProperty text = new SimpleStringProperty();

    public AppModel()
    {
        this.text = new SimpleStringProperty();
    }

    public StringProperty textProperty() {
        return text;
    }

    public final String getText() {
        return textProperty().get();
    }

    public final void setText(String text) {
        textProperty().set(text);
    }
}

• 然后，在要显示结果的界面控制器ResultController定义一个ApplModel实例，在初始化方法中绑定属性监听

import java.io.IOException;
import java.net.URL;
import java.util.ResourceBundle;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.fxml.Initializable;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.stage.Stage;

public class ResultController implements Initializable
{
    // 必须static 类型
    public  static AppModel model = new AppModel();
    @FXML
    private Label txtView;

    @Override
    public void initialize(URL location, ResourceBundle resources) {
        // update text area if text in model changes:
        model.textProperty().addListener((obs, oldText, newText) -> txtView.setText(newText));
    }

    public static void setText(String text)
    {
        model.setText(text);
    }

    // 打开文本输入窗口
    public void open(ActionEvent event) {
        // 从模板列表选择一个
        try
        {
            Parent root = FXMLLoader.load(getClass().getResource("Input.fxml"));
            Stage stage = new Stage();
            stage.setTitle("文本输入窗口");
            stage.setScene(new Scene(root));
            stage.setFocused(true);
            stage.show();
        } catch (IOException e)
        {
            e.printStackTrace();
        }
    }

}

• 在输入内容的控制器界面InputController，调用ResultController的setText方法

import java.io.IOException;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Node;
import javafx.scene.control.TextField;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.Pane;

public class InputController
{
    @FXML
    private TextField textEnter;

    // action event handler for button:
    @FXML
    private void sendText() {
        // 获取结果界面控制器
        FXMLLoader loader = new FXMLLoader(getClass().getResource("ResultPage.fxml"));
        try
        {
            AnchorPane login = (AnchorPane) loader.load();
        } catch (IOException e)
        {
            e.printStackTrace();
        }
        ResultController control = (ResultController) loader.getController();
        // 设置结果界面内容
        control.model.setText(textEnter.getText());
    }

    public void confirm(ActionEvent actionEvent)
    {
        //改变模板设置控制器的模板名列表属性，触发观察者
        String inputContent=textEnter.getText();
        ResultController.setText(inputContent);
        //关闭窗口
        ((Node) (actionEvent.getSource())).getScene().getWindow().hide();
    }

}

附上界面代码:
Input.fxml:

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.layout.AnchorPane?>

<AnchorPane prefHeight="180.0" prefWidth="210.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="application.InputController">
   <children>
      <TextField fx:id="textEnter" layoutX="14.0" layoutY="42.0" />
      <Button layoutX="14.0" layoutY="79.0" mnemonicParsing="false" onAction="#confirm" text="确定" />
   </children>
</AnchorPane>

ResultPage.xml:

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.layout.AnchorPane?>

<AnchorPane prefHeight="297.0" prefWidth="285.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="application.ResultController">
   <children>
      <Label fx:id="txtView" layoutX="48.0" layoutY="46.0" prefHeight="34.0" prefWidth="135.0" text="result：" />
      <Button layoutX="48.0" layoutY="95.0" mnemonicParsing="false" onAction="#open" text="打开文本输入窗口" />
   </children>
</AnchorPane>

程序入口类Main.java

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.stage.Stage;
import javafx.scene.Parent;
import javafx.scene.Scene;
public class Main extends Application
{
    @Override
    public void start(Stage primaryStage) {
        Parent root;
        try
        {
            root = FXMLLoader.load(getClass().getResource("ResultPage.fxml"));
            Scene scene = new Scene(root);
            primaryStage.setTitle("控制器间数据传递");
            primaryStage.setScene(scene);
            primaryStage.show();
        } catch (Exception e)
        {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        launch(args);
    }
}