ComboBox不会更新所选项目

时间:2016-06-02 14:04:03

标签: java javafx javafx-2 javafx-8

当底层对象发生更改时,JavaFx ComboBox不会更新其选定的项目。举一个简单的例子:

StringProperty item1 = new SimpleStringProperty("Item-1");
StringProperty item2 = new SimpleStringProperty("Item-2");
StringProperty item3 = new SimpleStringProperty("Item-3");

ObservableList<StringProperty> items = FXCollections.observableArrayList(item1, item2, item3);

ComboBox comboBox = new ComboBox();
comboBox.setItems(items);
comboBox.getSelectionModel().select(item1);

StackPane root = new StackPane();
root.getChildren().add(comboBox);
Scene scene = new Scene(root, 300, 250);
primaryStage.setScene(scene);
primaryStage.show();

Timeline timeline1 = new Timeline(new KeyFrame(
Duration.millis(1000), ae -> {
                item1.set("Changing the string");
}));
timeline1.play();

希望ComboBox反映我对item1所做的更改。有没有办法做到这一点?

1 个答案:

答案 0 :(得分:2)

假设您已经在组合框中定义了单元工厂和按钮单元格,以便您可以很好地显示列表中的元素,如果您实现了将单元格的text属性绑定到相应的属性,它将起作用:< / p>

public static class StringPropertyCell extends ListCell<StringProperty> {

    @Override
    protected void updateItem(StringProperty item, boolean empty) {
        super.updateItem(item, empty);
        textProperty().unbind();
        if (item != null && ! empty) {
            textProperty().bind(item);
        }
    }

}

然后,显然,

ComboBox<StringProperty> comboBox = new ComboBox<>();
comboBox.setItems(items);
comboBox.getSelectionModel().select(item1);

comboBox.setCellFactory(lv -> new StringPropertyCell());
comboBox.setButtonCell(new StringPropertyCell());

否则,您需要使用extractor构建基础列表:

ObservableList<StringProperty> items = 
    FXCollections.observableArrayList(e -> new Observable[] {e});
items.addAll(item1, item2, item3);

另请注意,您只需使用普通String列表而不是StringProperty列表来实际达到预期效果(至少在您发布的示例代码中):

import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.Scene;
import javafx.scene.control.ComboBox;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
import javafx.util.Duration;

public class ComboBoxTest extends Application {

    @Override
    public void start(Stage primaryStage) {

        ObservableList<String> items = FXCollections.observableArrayList("Item-1", "Item-2", "Item-3");

        ComboBox<String> comboBox = new ComboBox<>();
        comboBox.setItems(items);
        comboBox.getSelectionModel().select(0);

        StackPane root = new StackPane();
        root.getChildren().add(comboBox);
        Scene scene = new Scene(root, 300, 250);
        primaryStage.setScene(scene);
        primaryStage.show();

        Timeline timeline1 = new Timeline(new KeyFrame(
        Duration.millis(1000), ae -> {
            items.set(0, "Changing the string");
        }));
        timeline1.play();

        primaryStage.setScene(new Scene(new StackPane(comboBox), 300, 100));
        primaryStage.show();
    }


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