JavaFX - 如何在TableView中识别ScrollBar的位置

我写了这个小例子应用程序:

package application;

import javafx.application.Application;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableColumn.CellEditEvent;
import javafx.scene.control.TableView;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.scene.control.cell.TextFieldTableCell;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class Main extends Application {

    public class Person {

        private StringProperty firstName = new SimpleStringProperty();
        private StringProperty lastName = new SimpleStringProperty();

        public Person(String firstName, String lastName) {

            this.firstName.set(firstName);
            this.lastName.set(lastName);
        }

        public String getFirstName() {
            return firstName.get();
        }

        public String getLastName() {
            return lastName.get();
        }

        public StringProperty firstNameProperty() {
            return firstName;
        }

        public StringProperty lastNameProperty() {
            return lastName;
        }

    }

    @Override
    public void start(Stage primaryStage) {

        try {
            StackPane root = new StackPane();

            TableView tv = new TableView<>();
            TableColumn col = new TableColumn("FirstName");
            col.setCellValueFactory(new PropertyValueFactory("firstName"));

            tv.getColumns().add(col);
            tv.setEditable(true);

            col = new TableColumn("LastName");
            col.setCellValueFactory(new PropertyValueFactory("lastName"));
            col.setCellFactory(TextFieldTableCell.forTableColumn());
            col.setOnEditCommit(new EventHandler>() {

                @Override
                public void handle(CellEditEvent event) {

                    System.out.println(tv.getItems().get(1).getLastName());
                }
            });

            tv.getColumns().add(col);

            for (int i = 0; i < 30; i++) {
                tv.getItems().add(new Person("Test" + i, "Test" + i));
            }

            root.getChildren().add(tv);

            Scene scene = new Scene(root, 400, 200);
            primaryStage.setScene(scene);
            primaryStage.show();

            tv.addEventFilter(MouseEvent.MOUSE_RELEASED, event -> {
                // ...
            });
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

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

我想在ScrollBar到达底部时执行操作.然后我想从数据库重新加载更多数据.但只有这样,当用户看到所有已经加载的数据时(=底部的滚动条).你有什么好建议来解决这个问题吗？

我的第一个想法是捕捉MOUSE_RELEASED事件(当用户拖动栏时),TableView然后检查以下位置ScrollBar: - getValue()获取栏的位置 - getMax()最大值(= bottom).

但我找不到一种方法(不使用通过这种方法的css选择器)来获取ScrollBar给定的TableView.所以我无法确定它的位置TableView.

你有什么想法？？

我很兴奋.谢谢你的帮助.

获取滚动条的唯一方法是通过查找,这有点像黑客,但只要你在场景上渲染表后就可以工作.你需要

ScrollBar verticalBar = (ScrollBar) table.lookup(".scroll-bar:vertical");

请注意,不需要弄乱用户事件:您可以直接观察滚动条的value属性:

verticalBar.valueProperty().addListener((obs, oldValue, newValue) -> {
    if (newValue.doubleValue() >= verticalBar.getMax()) {
        // add more data...
    }
});

SSCCE:

import java.util.ArrayList;
import java.util.List;
import java.util.function.Function;

import javafx.application.Application;
import javafx.beans.property.IntegerProperty;
import javafx.beans.property.SimpleIntegerProperty;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
import javafx.beans.value.ObservableValue;
import javafx.concurrent.Task;
import javafx.scene.Scene;
import javafx.scene.control.ScrollBar;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;

public class AddMoreTableDataOnScrollToBottom extends Application {

    @Override
    public void start(Stage primaryStage) {
        TableView table = new TableView<>();
        table.getColumns().add(column("Item", Item::nameProperty));
        table.getColumns().add(column("Value", Item::valueProperty));


        addMoreData(table, 20);

        Scene scene = new Scene(new BorderPane(table), 400, 400);
        primaryStage.setScene(scene);
        primaryStage.show();

        ScrollBar verticalBar = (ScrollBar) table.lookup(".scroll-bar:vertical");
        verticalBar.valueProperty().addListener((obs, oldValue, newValue) -> {
            if (newValue.doubleValue() >= verticalBar.getMax()) {
                addMoreData(table, 20);
            }
        });
    }

    private void addMoreData(TableView table, int numItems) {
        Task> dataRetrieveTask = new Task>() {
            @Override
            public List call() throws Exception {
                // mimic connect to db:
                Thread.sleep(500);
                List items = new ArrayList<>();
                int nextItem = table.getItems().size() + 1 ;
                for (int i = nextItem; i < nextItem + numItems; i++ ){
                    items.add(new Item("Item "+i, i));
                }
                return items ;
            }
        };
        dataRetrieveTask.setOnSucceeded(e -> table.getItems().addAll(dataRetrieveTask.getValue()));
        new Thread(dataRetrieveTask).start();
    }

    private  TableColumn column(String title, Function> prop) {
        TableColumn col = new TableColumn<>(title);
        col.setCellValueFactory(cellData -> prop.apply(cellData.getValue()));
        return col ;
    }

    public static class Item {

        private final StringProperty name = new SimpleStringProperty();
        private final IntegerProperty value = new SimpleIntegerProperty();

        public Item(String name, int value) {
            setName(name);
            setValue(value);
        }

        public final StringProperty nameProperty() {
            return this.name;
        }


        public final String getName() {
            return this.nameProperty().get();
        }


        public final void setName(final String name) {
            this.nameProperty().set(name);
        }


        public final IntegerProperty valueProperty() {
            return this.value;
        }


        public final int getValue() {
            return this.valueProperty().get();
        }


        public final void setValue(final int value) {
            this.valueProperty().set(value);
        }


    }

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