JavaFX-将FXML包装到Java类 Controller

我有一个具有TreeView控件的FXML文件:

<AnchorPane id="AnchorPane" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="500.0" xmlns:fx="http://javafx.com/fxml" fx:controller="test.MyControllerClass">

<TreeView fx:id="locationTreeView" layoutX="12.0" layoutY="158.0" prefHeight="193.0" prefWidth="471.0" />

然后，我的Java类 Controller 需要使用此TreeView包装并动态添加TreeItem。这就是问题所在，它没有加载那些TreeItem。这是来自我的 Controller 的以下测试代码:

public class MyControllerClass extends Application {

    @FXML
    private TreeView<String> locationTreeView;

    @Override
    public void start(Stage stage) throws Exception {

        stage.initStyle(StageStyle.TRANSPARENT);
        stage.getIcons().add(new Image(getClass().getResourceAsStream("myIcon.png")));

        Parent root = FXMLLoader.load(getClass().getResource("myInterface.fxml"));

        Scene scene = new Scene(root);
        stage.setScene(scene);

        loadTreeItems();

        stage.show();
    }

    // Just a simple example that still doesn't works
    private void loadTreeItems() {

        try {
            TreeItem<String> root = new TreeItem<String>("Root Node");
            root.setExpanded(true);
            root.getChildren().addAll(
                new TreeItem<String>("Item 1"),
                new TreeItem<String>("Item 2"),
                new TreeItem<String>("Item 3")
            );

            locationTreeView = new TreeView<String>(root);

        } catch (Exception exc) {
            System.out.println("Error: " + exc.getMessage());
        }
    }

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

任何想法为什么它不起作用？

最佳答案

您的应用程序无法正常工作的原因有两个:

您需要将Controller和Application分开设置类。

您应该允许FXML系统注入(inject)TreeView实例，而不是创建一个新实例(正如Aaron在他的回答中指出的那样)。

当前使应用程序结构化的方式将是:

Java系统将在启动时创建MyControllerClass的实例(并调用它的start方法)。

每次加载FXMLLoader文件时，MyControllerClass将创建另一个myInterface.fxml实例。

FXMLLoader将创建一个新的TreeView实例，并对其创建的新locationTreeView实例的MyControllerClass成员执行FXML注入(inject)。

FXMLLoader将尝试在新的initialize(您没有)上调用MyControllerClass方法。

FXMLLoader将不会在新的start上调用MyControllerClass方法。

对原始start的原始MyControllerClass方法调用将继续处理并创建另一个新的TreeView实例，它将把旧locationTreeView实例的MyControllerClass成员设置为该实例。

我更新了您的代码，以进行上面建议的修改，现在代码可以正常工作了。更新的code is available。

运行代码的示例屏幕截图为:

MyApplicationClass.java

import javafx.animation.*;
import javafx.application.Application;
import javafx.event.*;
import javafx.fxml.FXMLLoader;
import javafx.scene.*;
import javafx.scene.image.Image;
import javafx.scene.input.MouseEvent;
import javafx.stage.*;
import javafx.util.Duration;

/** Sample application to demonstrate programming an FXML interface. */
public class MyApplicationClass extends Application {
  @Override public void start(final Stage stage) throws Exception {
    // load the scene fxml UI.
    // grabs the UI scenegraph view from the loader.
    // grabs the UI controller for the view from the loader.
    final FXMLLoader loader = new FXMLLoader(getClass().getResource("myInterface.fxml"));
    final Parent root = (Parent) loader.load();
    final MyControllerClass controller = loader.<MyControllerClass>getController();

    // continuously refresh the TreeItems.
    // demonstrates using controller methods to manipulate the controlled UI.
    final Timeline timeline = new Timeline(
      new KeyFrame(
        Duration.seconds(3),
        new TreeLoadingEventHandler(controller)
      )
    );
    timeline.setCycleCount(Timeline.INDEFINITE);
    timeline.play();

    // close the app if the user clicks on anywhere on the window.
    // just provides a simple way to kill the demo app.
    root.addEventFilter(MouseEvent.MOUSE_CLICKED, new EventHandler<MouseEvent>() {
      @Override public void handle(MouseEvent t) {
        stage.hide();
      }
    });

    // initialize the stage.
    stage.setScene(new Scene(root));
    stage.initStyle(StageStyle.TRANSPARENT);
    stage.getIcons().add(new Image(getClass().getResourceAsStream("myIcon.png")));
    stage.show();
  }

  /** small helper class for handling tree loading events. */
  private class TreeLoadingEventHandler implements EventHandler<ActionEvent> {
    private MyControllerClass controller;
    private int idx = 0;

    TreeLoadingEventHandler(MyControllerClass controller) {
      this.controller = controller;
    }

    @Override public void handle(ActionEvent t) {
      controller.loadTreeItems("Loaded " + idx, "Loaded " + (idx + 1), "Loaded " + (idx + 2));
      idx += 3;
    }
  }

  // main method is only for legacy support - java 8 won't call it for a javafx application.
  public static void main(String[] args) { launch(args); }
}

MyControllerClass.java

import javafx.fxml.FXML;
import javafx.scene.control.*;

/** Sample controller class. */
public class MyControllerClass {
  // the FXML annotation tells the loader to inject this variable before invoking initialize.
  @FXML private TreeView<String> locationTreeView;

  // the initialize method is automatically invoked by the FXMLLoader - it's magic
  public void initialize() {
    loadTreeItems("initial 1", "initial 2", "initial 3");
  }

  // loads some strings into the tree in the application UI.
  public void loadTreeItems(String... rootItems) {
    TreeItem<String> root = new TreeItem<String>("Root Node");
    root.setExpanded(true);
    for (String itemString: rootItems) {
      root.getChildren().add(new TreeItem<String>(itemString));
    }

    locationTreeView.setRoot(root);
  }
}

myInterface.fxml

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

<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>

<AnchorPane id="AnchorPane" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" xmlns:fx="http://javafx.com/fxml" fx:controller="test.MyControllerClass">
  <TreeView fx:id="locationTreeView" layoutX="0" layoutY="0" prefHeight="193.0" prefWidth="471.0" />
</AnchorPane>