javafx - 是否可以在 Javafx 中为 Listview 设置两次单元工厂

Question

我在 ListView 中设置了一个单元格工厂来更改所选单元格的颜色。另一个用于拖放操作。两者不能同时工作。细胞工厂:1个

listView.setCellFactory( new Callback<ListView<String>, ListCell<String>>()
        {
            @Override
            public ListCell<String> call( ListView<String> param )
            {
                ListCell<String> listCell = new ListCell<String>()
                {
                    @Override
                    protected void updateItem( String item, boolean empty )
                    {
                        super.updateItem( item, empty );
                        setText( item );
                    }
                };
Cell factory:2
listView.setCellFactory(list -> {

                    ListCell<String> cell = new ListCell<String>() {
                        @Override
                        protected void updateItem(String item, boolean empty) {
                            super.updateItem(item, empty);
                            setText(empty ? null : item);

                        }
                    };

Answer 1

setCellFactory 是一个设置方法，它的行为与任何其他设置方法一样:即它设置 ListView 的(唯一的) 的值cellFactory 属性。就像你有这样的代码一样

someObject.setIntValue(5);
someObject.setIntValue(42);

你会期望 someObject 的 intValue 属性是 42，如果你调用 setCellFactory 两次，细胞工厂将是您传递给它的第二个值。

您所说的最简单的方法是将所有功能简单地组合在一个细胞工厂中:

listView.setCellFactory(list -> {

    ListCell<String> cell = new ListCell<String>() {
        @Override
        protected void updateItem(String item, boolean empty) {
            super.updateItem(item, empty);
            setText(empty ? "" : item);

            // modify color here depending on item...
        }
    };

    cell.setOnDragDetected(e -> { /* ... */ });
    // other drag handlers...

    return cell ;
});

如果您真的想将事物分离到不同的工厂实现中，您可以使用“装饰器”类型的方法:

public class PlainCellFactory implements Callback<ListView<String, ListCell<String>> {
    @Override
    public ListCell<String> call(ListView<String> list) {
        return new ListCell<String>() {
            @Override
            protected void updateItem(String item, boolean empty) {
                super.updateItem(item, empty) ;
                setText(empty ? "" : item);
            }
        };
    }
}

添加颜色:

public class ColorListCellFactory implements Callback<ListView<String>, ListCell<String>> {

    private final Callback<ListView<String>, ListCell<String>> originalFactory ;

    public ColorListCellFactory(Callback<ListView<String>, ListCell<String>> originalFactory) {
        this.originalFactory = originalFactory ;
    }

    @Override
    public ListCell<String> call(ListView<String> list) {
        ListCell<String> cell = originalFactory.call(list);
        cell.itemProperty().addListener((obs, oldItem, newItem) -> {
            // change color depending on newItem (which might be null)...
        });
        return cell ;
    }
}

和拖放:

public class DragAndDropListCellFactory implements Callback<ListView<String>, ListCell<String>> {

    private final Callback<ListView<String>, ListCell<String>> originalFactory ;

    public DragAndDropListCellFactory(Callback<ListView<String>, ListCell<String>> originalFactory) {
        this.originalFactory = originalFactory ;
    }

    @Override
    public ListCell<String> call(ListView<String> list) {
        ListCell<String> cell = originalFactory.call(list);
        cell.setOnDragDetected(e -> { /* ... */ });
        // other drag handlers...
        return cell ;
    }
}

现在你可以做

PlainCellFactory plainFactory = new PlainCellFactory();
ColorListCellFactory colorFactory = new ColorListCellFactory(plainFactory);
DragAndDropListCellFactory dndFactory = new DragAndDropListCellFactory(colorFactory);
listView.setCellFactory(dndFactory);