JavaFX-CSS: How to “move” style of parent to a child?

问题

The trigger for this was a quick experiment to solve TreeItem selection width: the requirement is to highlight only the text, not the whole tree cell. Nothing easier than that (said Frederik :)

implement a custom TreeCell with a Label as graphic (and configure the label with the item as needed)
remove the selection style (mostly the highlight background from the cell
add the highlight style to the label

Something like (a runnable example using this is at the end):

public static class MyTreeCell extends TreeCell<String> {

    private Label label;

    public MyTreeCell() {
        getStyleClass().add("tree-text-only");
    }
    @Override
    public void updateItem(String item, boolean empty) {
        super.updateItem(item, empty);
        if (empty) {
            setText(null);
            setGraphic(null);
        } else {
            if (label == null) {
                label = new Label();
            }
            label.setText(item);
            setGraphic(label);
        }
    }
}

The css:

/* remove the highlight from cell as a whole, 
   c&p'd the unselected style from modena */
.tree-text-only:filled:selected {
    -fx-background: -fx-control-inner-background; 
    -fx-background-color: -fx-background;
}
/* c&p'd selected style */
/* using > doesn't make a different to the behaviour */ 
/* .tree-text-only:filled:selected > .label { */

.tree-text-only:filled:selected .label {
    /* following is the selection color from themes, doesn't show */
    -fx-background: -fx-selection-bar; 
    /* hard-coded color does show */
    /*   -fx-background-color: -fx-accent ; */
    /* auto-adjust text fill */
    /* no effect for hard-coded color, showing nothing for selection bar */
    -fx-text-fill: -fx-text-background-color;
}

Expected behaviour

label has highlighted background when using selection-bar
text auto-adjusts its fill

Actual behaviour:

using the "semantic" (?) highlight color selection-bar, the background color of the label is not changed to the highlight color but the text fill is changed to the "white", so the text doesn't show
using a hard-coded color (any, even the accent as above) changes the label's background but the text fill isn't updated

The obvious question: How to make it work as expected?

For convenience, a runnable example:

public class TreeCellExample extends Application {

    public static class MyTreeCell extends TreeCell<String> {

        private Label label;

        public MyTreeCell() {
            getStyleClass().add("tree-text-only");
        }
        @Override
        public void updateItem(String item, boolean empty) {
            super.updateItem(item, empty);
            if (empty) {
                setText(null);
                setGraphic(null);
            } else {
                if (label == null) {
                    label = new Label();
                }
                label.setText(item);
                setGraphic(label);
            }
        }
    }

    private Parent getContent() {
        TreeItem root = createSubTree("root");
        root.setExpanded(true);
        TreeView tree = new TreeView(root);
        tree.getStylesheets().add(
                getClass().getResource("treetextonly.css").toExternalForm());
        tree.setCellFactory(p -> new MyTreeCell());
        BorderPane pane = new BorderPane(tree);
        return pane;
    }

    ObservableList rawItems = FXCollections.observableArrayList(
            "9-item", "8-item", "7-item", "6-item", 
            "5-item", "4-item", "3-item", "2-item", "1-item");

    protected TreeItem createSubTree(Object value) {
        TreeItem child = new TreeItem(value);
        child.getChildren().setAll((List<TreeItem>) rawItems.stream()
                .map(TreeItem::new)
                .collect(Collectors.toList()));
        return child;
    }

    @Override
    public void start(Stage primaryStage) throws Exception {
        Scene scene = new Scene(getContent());
        primaryStage.setScene(scene);
        primaryStage.show();
    }

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

回答1:

The reason why it doesn't work is because .label doesn't have a rule where -fx-background is applied, so any value assigned to it won't affect any of the Label properties.

What's more, Label doesn't use a -fx-background-color property.

So an easy solution would be adding it:

.tree-text-only > .label {
    -fx-background-color: -fx-background; 
}

Now you can apply all the style using only this "semantic" colors.

Note I've added also the case where the control doesn't have the focus:

/* 
 * remove the highlight from cell as a whole 
 */

/* Selected rows */
.tree-view:focused > .virtual-flow > .clipped-container > .sheet > .tree-text-only:filled:selected {
    -fx-background: -fx-control-inner-background; 
}
/* Selected when control is not focused */
.tree-text-only:filled:selected {
    -fx-background: -fx-control-inner-background; 
}
/* focused cell (keyboard navigation) */
.tree-view:focused > .virtual-flow > .clipped-container > .sheet > .tree-text-only:focused {
    -fx-cell-focus-inner-border: -fx-control-inner-background; 
}

/* 
 * highlight only the label
 */

// Add background color rule
.tree-text-only > .label {
    -fx-background-color: -fx-background; 
}
/* Selected rows */
.tree-view:focused > .virtual-flow > .clipped-container > .sheet > .tree-text-only:filled:selected > .label {
    -fx-background: -fx-selection-bar; 
}
/* Selected when control is not focused */
.tree-text-only:filled:selected > .label {
    -fx-background: -fx-selection-bar-non-focused;
}
/* focused cell (keyboard navigation) */
.tree-view:focused > .virtual-flow > .clipped-container > .sheet > .tree-text-only:focused > .label {
    -fx-background: -fx-selection-bar; 
}

回答2:

Again, I'm not 100% sure I understand your requirements, but following quick test works for me (Label is assigned to a graphic property of a Button):

.button {
    -fx-text-fill: red;
    -fx-background-color: yellow;
}

.button > .label {
    -fx-text-fill: blue;
    -fx-background-color: yellow;
}

.button:pressed > .label {
    -fx-text-fill: white;
    -fx-background-color: black;
}

来源：https://stackoverflow.com/questions/28113294/javafx-css-how-to-move-style-of-parent-to-a-child

标签

java

javafx-8

treecell

javafx-css