Question

我正在创建一个TreeView，它应该为不同级别的树结构提供不同的图形。它是一个三层结构，隐藏了根。

可扩展节点的图形： http://i.imgur.com/wv00CEi.png

叶子节点的图形：

只是hBox中的标签。

这是我到目前为止所尝试过的，但是我得到一个nullPointerException，基本上说getTreeView为null：

CustomTreeCellFactory

public final class CustomTreeCellFactory extends TreeCell<String>{
private TextField textField;
private HBox hBox;

public CustomTreeCellFactory(){
    super();
    if (getTreeView()==null){
        System.out.println("Her er problem");
    }
    if (getTreeView().getTreeItemLevel(getTreeItem())==1){
        try {
            hBox = (HBox) FXMLLoader.load(getClass().getResource("/Views/TreCell.fxml"));
        } catch (IOException e) {
            System.out.println("This didn't work");
            e.printStackTrace();
        }
    }
    else if (getTreeView().getTreeItemLevel(getTreeItem())==2){
        try {
            hBox = (HBox) FXMLLoader.load(getClass().getResource("/Views/TreCellLowestLevel.fxml"));
        } catch (IOException e) {
            System.out.println("This didn't work");
            e.printStackTrace();
        }
    }


}

我设置Cell Factory的代码段

TreeView<String> tree = (TreeView) parent.getChildren().get(0);
    tree.setRoot(root);
    tree.setShowRoot(false);
    tree.setEditable(true);
    tree.setCellFactory(new Callback<TreeView<String>, TreeCell<String>>() {
        @Override
        public TreeCell<String> call(TreeView<String> param) {
            return new CustomTreeCellFactory();
        }
    });

Answer 1

我发现了问题所在。

设置TreeView时，我需要在update-method中完成所需的操作。

这是解决问题的代码：

**Constructor**
public CustomTreeCellFactory(){
    try {
        hBox = (HBox) FXMLLoader.load(getClass().getResource("/Views/TreCell.fxml"));
    } catch (IOException e) {
        System.out.println("This didn't work");
        e.printStackTrace();
    }
    try {
        hBoxLeaf = (HBox) FXMLLoader.load(getClass().getResource("/Views/TreCellLowestLevel.fxml"));
    } catch (IOException e) {
        System.out.println("This didn't work");
        e.printStackTrace();
    }

}

更新方法

@Override
public void updateItem(String item, boolean empty) {
   super.updateItem(item, empty);

    if (item != null) {
        if (getTreeView().getTreeItemLevel(getTreeItem())==1) {
            setGraphic(this.hBox);
        }else if (getTreeView().getTreeItemLevel(getTreeItem())==2){
            setGraphic(this.hBoxLeaf);
        }
    } else {
        setGraphic(null);
    }
}

JavaFX TreeView：setGraphic（）用于不同级别的treeItem

1 个答案: