JavaFX 组合框 setButtonCell

Question

我需要有关设置组合框 buttonCell 的帮助。 我使用一个组合框来显示来自可观察列表的数据，该列表包含来自具有两列“Step”和“NextStep”的表中的数据（NextStep 包含插入在列 Step 中的一个项目）；我需要做的是显示带有“Step”列表的组合框列表单元和带有相对“NextStep”的按钮单元。现在，我可以正确看到列表单元，但我的按钮单元始终是空的。

代码：

    // SET THE VALUE STEP TO THE LISTCELL 
    comboStatoSuccessivo.setCellFactory(new Callback<ListView<StatoEsiti>, ListCell<StatoEsiti>>() {
        @Override public ListCell<StatoEsiti> call(ListView<StatoEsiti> p) {
            return new ListCell<StatoEsiti>() { 
                    @Override
                    protected void updateItem(StatoEsiti t, boolean bln) {
                        super.updateItem(t, bln);
                        if(t != null){
                            setText(t.statoProperty().getValue());
                            System.out.println("SET PROPERTY " + t.statoProperty().getValue());
                        } else {
                            setText(null);
                        }    

                    }                       
            };
        }
    });


    // SET THE VALUE NEXTSTEP TO THE BUTTONCELL
    comboStatoSuccessivo.setButtonCell(new ListCell<StatoEsiti>() {
        @Override
        protected void updateItem(StatoEsiti t, boolean bln) {
            super.updateItem(t, bln); 
            if (t != null) { <<<<<<<<<<<<<<-------------ALWAYS NULL----WHY??????
                setText(t.statoSuccessivoProperty().getValue());
                System.out.println("SET PROPERTY BUTTONCELL " + t.statoSuccessivoProperty().getValue());
            } else {
                setText(null);
                System.out.println("SET PROPERTY BUTTONCELL NULL");
            }

        }
    });

提前致谢。

Answer 1

我已使用以下演示 SSCCE 代码研究了您的用例。
它按预期工作，就像从组合框的下拉菜单中选择项目时，按钮单元格会更新为相关的“下一步”：

public class ComboDemo extends Application {

    @Override
    public void start(Stage primaryStage) {
        List<Person> list = new ArrayList<Person>();
        list.add(new Person("step 1212", 12));
        list.add(new Person("step 4545", 45));
        list.add(new Person("step 5656", 56));
        list.add(new Person("step 9090", 90));

        ComboBox<Person> comboBox = new ComboBox<>(FXCollections.observableList(list));

        comboBox.setCellFactory(new Callback<ListView<Person>, ListCell<Person>>() {
            @Override
            public ListCell<Person> call(ListView<Person> p) {
                return new ListCell<Person>() {
                    @Override
                    protected void updateItem(Person t, boolean bln) {
                        super.updateItem(t, bln);
                        if (t != null) {
                            setText(t.getStepProperty().getValue());
                            System.out.println("SET PROPERTY " + t.getStepProperty().getValue());
                        } else {
                            setText(null);
                        }
                    }
                };
            }
        });

        // SET THE VALUE NEXTSTEP TO THE BUTTONCELL
        comboBox.setButtonCell(new ListCell<Person>() {
            @Override
            protected void updateItem(Person t, boolean bln) {
                super.updateItem(t, bln);
                if (t != null) {
                    setText(t.getNextStepProperty().getValue().toString());
                    System.out.println("SET PROPERTY BUTTONCELL " + t.getNextStepProperty().getValue());
                } else {
                    setText(null);
                    System.out.println("SET PROPERTY BUTTONCELL NULL");
                }

            }
        });

        StackPane root = new StackPane();
        root.getChildren().add(comboBox);

        Scene scene = new Scene(root, 300, 250);

        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static class Person {
        private StringProperty stepProperty = new SimpleStringProperty();
        private IntegerProperty nextStepProperty = new SimpleIntegerProperty();

        public Person(String step, Integer nextStep) {
            this.stepProperty.setValue(step);
            this.nextStepProperty.setValue(nextStep);
        }

        public StringProperty getStepProperty() {
            return stepProperty;
        }

        public void setStepProperty(StringProperty stepProperty) {
            this.stepProperty = stepProperty;
        }

        public IntegerProperty getNextStepProperty() {
            return nextStepProperty;
        }

        public void setNextStepProperty(IntegerProperty nextStepProperty) {
            this.nextStepProperty = nextStepProperty;
        }
    }

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

}

和你的比较一下。