如何在java fx 8中处理按钮操作?

这是我的源代码--- 单击demo.java-

package Application;

import java.io.FileInputStream;
import javafx.application.Application;
import static javafx.application.Application.launch;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.layout.AnchorPane;
import javafx.stage.Stage;


public class ClickDemo extends Application{

    @Override
    public void start(Stage stage) throws Exception {
        FXMLLoader loader = new FXMLLoader();
        // Path to the FXML File
        String fxmlDocPath = "src/View/sample1.fxml";
        FileInputStream fxmlStream = new FileInputStream(fxmlDocPath);

        // Create the Pane and all Details
        AnchorPane root = (AnchorPane) loader.load(fxmlStream);

        // Create the Scene
        Scene scene = new Scene(root);
        // Set the Scene to the Stage
        stage.setScene(scene);
        // Set the Title to the Stage
        stage.setTitle("A SceneBuilder Example");
        // Display the Stage
        stage.show();
    }


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

}

/*
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 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package Controllers;

import java.net.URL;
import java.util.ResourceBundle;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextArea;
import javafx.scene.input.MouseEvent;

/**
 * FXML Controller class
 *
 * @author Dell
 */
public class Sample1Controller {

    /**
     * Initializes the controller class.
     */
    @FXML
    private Button btn;
    @FXML
    private Label label;
    @FXML
    private TextArea textarea;

    @FXML
    void btn1handle(ActionEvent event) {

        // label.setText("Hello world");
        textarea.textProperty().addListener(new ChangeListener<String>() {
            @Override
            public void changed(ObservableValue<? extends String> observable, String oldValue, String newValue) {
                //System.out.println(newValue);
                label.setText(newValue);
            }

        });
    }

    @FXML
    void textareaHandle(MouseEvent event) {

    }
}

样本1.fxml

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

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.TextArea?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.text.Font?>


<AnchorPane id="AnchorPane" prefHeight="400.0" prefWidth="600.0" xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/8.0.111" fx:controller="Controllers.Sample1Controller">
   <children>
      <Button fx:id="btn" layoutX="274.0" layoutY="230.0" mnemonicParsing="false" onAction="#btn1handle" text="Button" />
      <Label fx:id="label" layoutX="210.0" layoutY="58.0" prefHeight="42.0" prefWidth="233.0" text="This is Text 1">
         <font>
            <Font size="31.0" />
         </font>
      </Label>
      <TextArea fx:id="textarea" layoutX="101.0" layoutY="121.0" onDragDetected="#textareaHandle" prefHeight="79.0" prefWidth="399.0" />
   </children>
</AnchorPane>