ListView CellFactory - 如何正确删除单元格？ [英] ListView CellFactory - How to remove cells correctly?

问题描述

我有一个 ListView ，我正在努力将 ContextMenu 添加到。我有 ContextMenu 工作查找，但有另一个问题。

I have a ListView that I am working to add a ContextMenu to. I have the ContextMenu working find but have another issue.

我的 setCellFactory 代码，用于设置上下文菜单：

My setCellFactory code, used to setup the context menus:

lvAppetites.setCellFactory(lv -> {
    ListCell<Appetite> cell = new ListCell<>();
    ContextMenu contextMenu = new ContextMenu();

    MenuItem editAppetiteMenu = new MenuItem();

    editAppetiteMenu.textProperty().bind(Bindings.format("Edit ..."));
    editAppetiteMenu.setOnAction(event -> {
        // Code to load the editor window
        editAppetite(cell.getItem());
    });
    contextMenu.getItems().add(editAppetiteMenu);

    MenuItem deleteAppetiteMenu = new MenuItem();
    deleteAppetiteMenu.textProperty().bind(Bindings.format("Delete ..."));
    deleteAppetiteMenu.setOnAction(event -> {
        // Code to delete the appetite
    });
    contextMenu.getItems().add(deleteAppetiteMenu);

    contextMenu.getItems().add(new SeparatorMenuItem());

    MenuItem addAppetiteMenu = new MenuItem();
    addAppetiteMenu.textProperty().bind(Bindings.format("Add New ..."));
    addAppetiteMenu.setOnAction(event -> {
        // Code to delete the appetite
    });
    contextMenu.getItems().add(addAppetiteMenu);

    cell.textProperty().bind(cell.itemProperty().asString());

    // If nothing selected, remove the context menu
    cell.emptyProperty().addListener((obs, wasEmpty, isNowEmpty) -> {
        if (isNowEmpty) {
            cell.setContextMenu(null);
        } else {
            cell.setContextMenu(contextMenu);
        }
    });
    return cell;
});

我的 ListView 可通过<$搜索带听众的c $ c> TextField ;当用户输入时，监听器会过滤 ListView 中的项目。

My ListView is searchable through a TextField with a listener; the listener filters the items in the ListView as the user types.

现在的问题是，作为列表过滤后，任何空单元格现在显示 null 。

The problem now, is that as the list is filtered, any empty cells now display null.

从另一个问题，我相信 ListView 仍然是显示已删除单元格的图形。我知道如何通过覆盖 updateItem 方法在ListView中处理它，但是如何从我的 setCellFactory 方法改为？

From reading another question, I'm fairly confident that the ListView is still displaying a graphic for the removed cells. I know how to handle that within the ListView by overriding the updateItem method, but how would I handle this from within my setCellFactory method instead?

这是可能的还是我需要重构我的整个 ListView ？

Is that even possible or will I need to refactor my entire ListView?

一如既往地感谢您的帮助！

Thank you, as always, for all your help!

推荐答案

出现问题从行

cell.textProperty().bind(cell.itemProperty().asString());

当单元格为空时，该项目将为空，因此绑定将（我相信）评估到字符串null。

When the cell is empty, the item will be null, so the binding will (I believe) evaluate to the string "null".

尝试测试单元格为空或项目为空的内容，例如

Try something that tests for the cell being empty or the item being null, e.g.

cell.textProperty().bind(Bindings
    .when(cell.emptyProperty())
    .then("")
    .otherwise(cell.itemProperty().asString()));

或（感谢@fabian提炼此版本）

or (thanks to @fabian for refining this version)

cell.textProperty().bind(Bindings.createStringBinding(
    () -> Objects.toString(cell.getItem(), ""),
    cell.itemProperty()));

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