如何将侦听器添加到使用CheckBoxListCell的列表视图中的复选框

Question

我有一个listview,使用a CheckBoxListCell来显示列表,其中包含项目旁边的复选框.如何向此复选框添加侦听器以了解项目何时被选中或未被选中？

Answer 1

解

您不会向该复选框添加侦听器.您可以通过CheckBoxListCell.forListView例程向该对象的observable属性添加一个侦听器,该对象与该复选框关联.

建立关联:

ListView<Task> checklist = new ListView<>(tasks);
checklist.setCellFactory(CheckBoxListCell.forListView(Task::selectedProperty));

为所有项添加侦听器:

tasks.forEach(task -> task.selectedProperty().addListener((observable, wasSelected, isSelected) -> {
    if (isSelected) {
        // . . .
    } else {
        // . . .
    }
}));

文档

这个过程在CheckBoxListCell.forListView javadoc中描述如下:

getSelectedProperty - 给定类型为T的对象(从ListView.items列表中取出的值)的回调函数,将返回一个ObservableValue,表示是否选择了给定的项目.此ObservableValue将双向绑定(意味着单元格中的CheckBox将根据用户交互设置/取消设置此属性,并且CheckBox将反映ObservableValue的状态,如果它在外部更改).

示例程序

一个示例程序,演示了一些可以与CheckBoxListCell一起使用的模式:

import javafx.application.Application;
import javafx.beans.property.*;
import javafx.collections.*;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.ListView;
import javafx.scene.control.cell.CheckBoxListCell;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;
import javafx.util.StringConverter;

import java.util.*;
import java.util.stream.Collectors;

public class CheckList extends Application {
    @Override
    public void start(Stage stage) throws Exception{
        ObservableList<Task> tasks = FXCollections.observableArrayList(
                Arrays.stream(taskNames).map(Task::new).collect(Collectors.toList())
        );

        ListView<String> reactionLog = new ListView<>();
        tasks.forEach(task -> task.selectedProperty().addListener((observable, wasSelected, isSelected) -> {
            if (isSelected) {
                reactionLog.getItems().add(reactionStrings.get(task.getName()));
                reactionLog.scrollTo(reactionLog.getItems().size() - 1);
            }
        }));

        ListView<Task> checklist = new ListView<>(tasks);
        checklist.setCellFactory(CheckBoxListCell.forListView(Task::selectedProperty, new StringConverter<Task>() {
            @Override
            public String toString(Task object) {
                return object.getName();
            }

            @Override
            public Task fromString(String string) {
                return null;
            }
        }));

        HBox layout = new HBox(10, checklist, reactionLog);
        layout.setPrefSize(350, 150);
        layout.setPadding(new Insets(10));
        Scene scene = new Scene(layout);
        stage.setScene(scene);
        stage.show();
    }

    public static class Task {
        private ReadOnlyStringWrapper name = new ReadOnlyStringWrapper();
        private BooleanProperty selected = new SimpleBooleanProperty(false);

        public Task(String name) {
            this.name.set(name);
        }

        public String getName() {
            return name.get();
        }
        public ReadOnlyStringProperty nameProperty() {
            return name.getReadOnlyProperty();
        }

        public BooleanProperty selectedProperty() {
            return selected;
        }
        public boolean isSelected() {
            return selected.get();
        }
        public void setSelected(boolean selected) {
            this.selected.set(selected);
        }
    }

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

    private static final String[] taskNames = {
            "Walk the dog",
            "Skin the cat",
            "Feed the pig"
    };

    private static final Map<String, String> reactionStrings = new HashMap<>();
    static {
        reactionStrings.put("Walk the dog", "The dog thanks you");
        reactionStrings.put("Skin the cat", "The cat hates you");
        reactionStrings.put("Feed the pig", "The pig wants more");
    }
}

选择第一个项目一次和第三个项目三次后的样本输出.