java - 如何通过代码初始化JavaFX fxml文件中定义的树形控件

Question

我想要实现的效果如下，都是代码创建的。

代码如下，这个方法可以达到我想要的结果，因为在start方法中，先初始化TreeView，然后创建场景，添加进去，然后显示成功。示例1:

public class treeViewDemo_4 extends Application {

    // Node图标
    private final Node rootIcon = new ImageView(
        new Image(getClass().getResourceAsStream("/icon/file.png"))
    );

    private TreeView<String> createTreeView(TreeItem<String> root1,TreeItem<String> root2) {
        TreeItem<String> dummyRoot = new TreeItem<>();
        dummyRoot.getChildren().addAll(root1,root2);
        TreeView<String> tree = new TreeView<>(dummyRoot);
        tree.setShowRoot(false);
        return tree ;
    }

    final TreeItem<String> root1 = new TreeItem<>("root 1");
    final TreeItem<String> root2 = new TreeItem<>("root 2");

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

    @Override
    public void start(Stage primaryStage) {
        primaryStage.setTitle("Tree View Sample");
        // 每个Item下又可以添加新的Item
        for (int i = 1; i < 6; i++) {
            TreeItem<String> item = new TreeItem<> ("Message" + i);
            item.getChildren().add(new TreeItem<String>("第三级"));
            root1.getChildren().add(item);
        }
        // 创建TreeView
        TreeView<String> tree = createTreeView(root1,root2);

        StackPane root = new StackPane();
        root.getChildren().add(tree);
        primaryStage.setScene(new Scene(root, 300, 250));
        primaryStage.show();
    }
} 

但是我想通过fxml文件来实现这个效果，但是不知道怎么做。首先是我的代码，Example2:

fxml

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

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.TreeView?>
<?import javafx.scene.layout.AnchorPane?>

<AnchorPane fx:controller="com.fendo.flying.demo.treeview.demo5.demo5Controller" fx:id="rootPane" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="705.0" prefWidth="1113.0" xmlns="http://javafx.com/javafx/8.0.171" xmlns:fx="http://javafx.com/fxml/1" >
   <children>
       <TreeView fx:id="treeView" layoutX="3.0" layoutY="94.0" prefHeight="608.0" prefWidth="214.0">

       </TreeView>
      <Button layoutX="300.0" layoutY="93.0" mnemonicParsing="false" text="Button" />
      <Button layoutX="715.0" layoutY="93.0" mnemonicParsing="false" text="Button" />
      <Button layoutX="597.0" layoutY="93.0" mnemonicParsing="false" text="Button" />
      <Button layoutX="393.0" layoutY="93.0" mnemonicParsing="false" text="Button" />
      <Button layoutX="492.0" layoutY="93.0" mnemonicParsing="false" text="Button" />
   </children>
</AnchorPane>

Controller

public class demo5Controller implements Initializable {

    @FXML
    private TreeView treeView;

    final TreeItem<String> root1 = new TreeItem<>("root 1");
    final TreeItem<String> root2 = new TreeItem<>("root 2");
    final TreeView<String> tree = createTreeView(root1,root2);

    private TreeView<String> createTreeView(TreeItem<String> root1,TreeItem<String> root2) {
        TreeItem<String> dummyRoot = new TreeItem<>();
        dummyRoot.getChildren().addAll(root1,root2);
        TreeView<String> tree = new TreeView<>(dummyRoot);
        tree.setShowRoot(false);
        return tree ;
    }


    public demo5Controller() {
        treeView = createTreeView(root1,root2);
    }

    @Override
    public void initialize(URL location, ResourceBundle resources) {
        treeView = createTreeView(root1,root2);
    }
}

示例2 运行后无效。 Treeview没有初始化成功，显示为空，我想知道如何通过代码初始化fxml中定义的TreeView？

或者，我在 fxml 中定义了一个 TreeView 。如何在 Controller 中初始化或覆盖它？实现示例1的效果

示例2中如何实现，即示例1中以下代码的效果:

// create TreeView
TreeView<String> tree = createTreeView(root1,root2);

StackPane root = new StackPane();
root.getChildren().add(tree);
primaryStage.setScene(new Scene(root, 300, 250));
primaryStage.show();

Answer 1

要完全通过 fxml 创建和配置 TreeView，请在 <TreeView> 中添加 treeItem 结构。标签，基本上类似于:

<TreeView fx:id="treeView"> 
      <TreeItem value = "treeRoot" expanded="true">
            <children>
                <TreeItem value="firstChild" />
                <TreeItem value="secondChild" />
            </children>
      </TreeItem>
</TreeView>

要进行更深层次的嵌套，请对子项执行相同的操作。

要通过 fxml 创建 TreeView 并通过代码配置其内容，请在 Controller 的初始化中执行后者(重要:不要手动实例化 TreeView!)

@FXML private TreeView<String> treeView;

@FXML
private void initialize() {
    treeView.setRoot(createItemHierarchy(new TreeItem<String>("root1"), new TreeItem<String>("root2")));
}

private TreeItem<String> createItemHierarchy(TreeItem<String>... root1) {
    TreeItem<String> root = new TreeItem<>("base root");
    root.getChildren().addAll(root1);
    return root ;
}