JavaFX 滚动监听器列表视图

Question

我创建了以下示例，其中包含 ListView 和已注册的滚动事件侦听器。不幸的是，侦听器只会在通过鼠标滚轮滚动时触发，而不是在使用侧面的滚动条时触发。代码有什么问题？

Controller.java

package sample;

import java.net.URL;
import java.util.Arrays;
import java.util.ResourceBundle;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.ListView;

public class Controller implements Initializable {
    @FXML
    private ListView lstPreview;

    private ObservableList items = FXCollections.observableArrayList();

    public Controller() {
    }

    @Override
    public void initialize(URL location, ResourceBundle resources) {

        items.addAll(Arrays.asList("Test 1", "Test 2", "Test 3", "Test 4", "Test 5", "Test 6", "Test 7", "Test 8", "Test 9", "Test 10"));
        lstPreview.setItems(items);
        lstPreview.addEventFilter(javafx.scene.input.ScrollEvent.ANY, event -> { System.out.println("ScrollEvent!"); });
        lstPreview.addEventFilter(javafx.scene.control.ScrollToEvent.ANY, event -> { System.out.println("ScrollToEvent!"); });

    }
}

Main.java

package sample;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) throws Exception{
        Parent root = FXMLLoader.load(getClass().getResource("sample.fxml"));
        primaryStage.setTitle("Hello World");
        primaryStage.setScene(new Scene(root, 300, 275));
        primaryStage.show();
    }


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

sample.fxml

<?xml version="1.0" encoding="UTF-8"?>

<?import java.net.*?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<?import javafx.geometry.Insets?>
<?import javafx.scene.layout.GridPane?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import java.net.URL?>

<GridPane alignment="center" hgap="10" vgap="10" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Controller">
   <stylesheets>
      <URL value="@style.css" />
   </stylesheets>
   <columnConstraints>
      <ColumnConstraints />
      <ColumnConstraints hgrow="ALWAYS" />
   </columnConstraints>
   <rowConstraints>
      <RowConstraints />
      <RowConstraints vgrow="ALWAYS" />
   </rowConstraints>
   <children>
      <ListView fx:id="lstPreview" GridPane.columnIndex="1" GridPane.hgrow="ALWAYS" GridPane.rowIndex="1" GridPane.vgrow="ALWAYS" />
   </children>
</GridPane>

解决方案

我最终使用了@Uluk Biy 解决方案，也许有一天 Java 8 JDK 会得到这样的函数：

/**
 * Looks up the first found scrollbar of a given control matching the desired orientation. If none found, null is returned
 *
 * @param control
 * @param orientation
 * @return
 */
public static javafx.scene.control.ScrollBar getScrollbarComponent(javafx.scene.control.Control control, javafx.geometry.Orientation orientation) {
    javafx.scene.Node n = control.lookup(".scroll-bar");
    if (n instanceof javafx.scene.control.ScrollBar) {
        final javafx.scene.control.ScrollBar bar = (javafx.scene.control.ScrollBar) n;
        if (bar.getOrientation().equals(orientation)) {
            return bar;
        }
    }
    return null;
}

这样使用：

javafx.scene.control.ScrollBar timelineBar = de.elara.asgard.util.FxUtils.getScrollbarComponent(listTimeline, javafx.geometry.Orientation.HORIZONTAL);
        if (timelineBar != null) {
            timelineBar.addEventFilter(ScrollToEvent.ANY, event -> { doScrollingTimeline(); });
        }

Answer 1

根据 Documentation:

Scroll event indicates that user performed scrolling by mouse wheel, track pad, touch screen or other similar device.

所以跟ListView的ScrollBar没有关系。由于它们是实现细节，除了做一些反射技巧外，访问它们并不容易。

Answer 2

这里有一个简单的方法，不需要任何反射技巧：

首先，您应该实现自己的 ListViewSkin 扩展，例如 CustomListViewSkin。稍后您将使用 .setSkin 方法在列表视图上设置外观。（您可以扩展 ListView 并重写 createDefaultSkin 方法以使自定义皮肤也起作用）。现在，您应该扩展 VirtualFlow（比如 CustomVirtualFlow）并让 CustomListViewSkin 在运行时通过覆盖 CustomVirtualFlow class 的 createVirtualFlow 创建一个 CustomVirtualFlow 实例。然后，您应该将此方法添加到 CustomVirtualFlow 以完成工作。

import com.sun.javafx.scene.control.skin.VirtualFlow;
import com.sun.javafx.scene.control.skin.VirtualScrollBar;
import javafx.scene.control.ListCell;

public class CustomVirtualFlow<T> extends VirtualFlow<ListCell<T>>
{

   public VirtualScrollBar getVerticalBar()
   {
       return getVbar();
   }

   public VirtualScrollBar getHorizontalBar()
   {
       return getHbar();
   }

}

最后，将此方法添加到您的 CustomListViewSkin 实现中：

public CustomVirtualFlow<ListCell<T>> getFlow()
{
    return (CustomVirtualFlow<ListCell<T>>) flow;
}

现在：

ListView lv = new ListView();
CustomListViewSkin skin = new CustomListViewSkin(lv);
lv.setSkin(skin);

//add the list view to some scene

CustomVirtualFlow flow = skin.getFlow();
ScrollBar vb = flow.getVerticalBar();
//do whatever you like with the vb instance now

JavaFX 滚动监听器列表视图

JavaFX ScrollListener ListView

listview

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fxml