VirtualFlow 中的 JavaFX 内存泄漏？

我在 VirtualFlow 中遇到了一种行为，不确定这是否是内存泄漏或者是否是这样设计的。

在 TableView 中，我希望当不使用 TableRow 实例时，它们应该能够被垃圾收集。但是，当我按照以下步骤操作时：

Step #1:我打开了一个带有 TableView 的阶段，其中没有数据。我检查了内存中是否有 TableRow 的实时实例，但没有看到任何实例（这是我所期望的）。

Step #2:我用一些数据填充了 TableView，这会根据所需的空间生成 TableRows。在我的场景中，假设它生成了 38 个 TableRow 对象的实例。

Step #3:我清除了 TableView 中的项目并显示占位符消息。当我检查 TableRow 实例时（执行多次 GC 后），它仍然具有 VirtualFlow 中强烈保留的 TableRows 的所有 38 个引用cellsArrayLinkedlist，如下图所示：

这是内存泄漏还是已经考虑到的预期行为？

这是我用来检查上述场景的代码：

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.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Priority;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class TableViewMemoryLeakDemo extends Application {

    public static void main(String... a) {
        Application.launch(a);
    }

    @Override
    public void start(final Stage primaryStage) {
        final ObservableList<TableDataObj> items = FXCollections.observableArrayList();
        final TableView<TableDataObj> table = buildTable();
        table.setItems(items);

        Button clear = new Button("Clear All");
        clear.setOnAction(e -> {
            items.clear();
        });

        Button add = new Button("Add 50 Rows");
        add.setOnAction(e -> {
            for (int i = 0 + 1; i < 50; i++) {
                final String firstName = "First Name " + i;
                final String lastName = "Last Name " + i;
                final String city = "City " + i;
                items.add(new TableDataObj(i, firstName, lastName, city));
            }
        });
        HBox row = new HBox(add, clear);
        row.setSpacing(10);

        final VBox root = new VBox(row, table);
        root.setSpacing(10);
        root.setPadding(new Insets(10));
        VBox.setVgrow(table, Priority.ALWAYS);

        final Scene sc = new Scene(root, 1200, 950);
        primaryStage.setScene(sc);
        primaryStage.setTitle("TableView MemoryLeak Demo " + System.getProperty("javafx.runtime.version"));
        primaryStage.show();
    }

    private TableView<TableDataObj> buildTable() {
        final TableColumn<TableDataObj, Integer> idCol = new TableColumn<>();
        idCol.setText("Id");
        idCol.setCellValueFactory(param -> param.getValue().idProperty().asObject());
        idCol.setPrefWidth(100);

        final TableColumn<TableDataObj, String> fnCol = new TableColumn<>();
        fnCol.setText("First Name");
        fnCol.setCellValueFactory(param -> param.getValue().firstNameProperty());
        fnCol.setPrefWidth(150);

        final TableColumn<TableDataObj, String> lnCol = new TableColumn<>();
        lnCol.setText("Last Name");
        lnCol.setCellValueFactory(param -> param.getValue().lastNameProperty());
        lnCol.setPrefWidth(150);

        final TableColumn<TableDataObj, String> cityCol = new TableColumn<>();
        cityCol.setText("City");
        cityCol.setCellValueFactory(param -> param.getValue().cityProperty());
        cityCol.setPrefWidth(150);

        final TableView<TableDataObj> tableView = new TableView<>();
        tableView.getColumns().addAll(idCol, fnCol, lnCol, cityCol);
        return tableView;
    }

    /**
     * Data object.
     */
    class TableDataObj {
        private final IntegerProperty id = new SimpleIntegerProperty();
        private final StringProperty firstName = new SimpleStringProperty();
        private final StringProperty lastName = new SimpleStringProperty();
        private final StringProperty city = new SimpleStringProperty();

        public TableDataObj(final int i, final String fn, final String ln, final String cty) {
            setId(i);
            setFirstName(fn);
            setLastName(ln);
            setCity(cty);
        }

        public StringProperty cityProperty() {
            return city;
        }

        public StringProperty firstNameProperty() {
            return firstName;
        }

        public int getId() {
            return id.get();
        }

        public IntegerProperty idProperty() {
            return id;
        }

        public StringProperty lastNameProperty() {
            return lastName;
        }

        public void setCity(final String city1) {
            city.set(city1);
        }

        public void setFirstName(final String firstName1) {
            firstName.set(firstName1);
        }

        public void setId(final int idA) {
            id.set(idA);
        }

        public void setLastName(final String lastName1) {
            lastName.set(lastName1);
        }
    }
}

正如上面的评论和插图中所指出的here，许多 JavaFX 视图组件提供蝇量级渲染：调用工厂方法创建少量可重复用于渲染的实例visible内容。TableView通常只需要one TableRow每个可见（或部分可见）行。最大化封闭阶段说明了这种效果。作为@James_Dobserves，“这肯定是预期的行为吗？”

In normal use, the underlying data would be updated in situ, as shown in your example. Should the need arise in the larger context of VirtualFlow, the variation below adds a Refresh button to examine the effect of invoking refresh() on the table. This allows unused table rendering apparatus to be collected in a future pass. As a test, enlarge the stage, and note the larger number of rows. Shrink the stage, click Refresh and request garbage collection. Note the reduced number of TableRow instances.

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.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Priority;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

/**
 * @see https://stackoverflow.com/q/76487091/230513
 */
public class TableViewLeak extends Application {

    public static void main(String... a) {
        Application.launch(a);
    }

    @Override
    public void start(final Stage primaryStage) {
        final ObservableList<TableDataObj> items = FXCollections.observableArrayList();
        final TableView<TableDataObj> table = buildTable();
        table.setItems(items);

        Button add = new Button("Add 50 Rows");
        add.setOnAction(e -> {
            for (int i = 0 + 1; i < 50; i++) {
                final String firstName = "First Name " + i;
                final String lastName = "Last Name " + i;
                final String city = "City " + i;
                items.add(new TableDataObj(i, firstName, lastName, city));
            }
        });
        Button clear = new Button("Clear All");
        clear.setOnAction(e -> {
            items.clear();
        });
        Button remove = new Button("Refresh");
        remove.setOnAction((e) -> {
            table.refresh();
        });

        HBox row = new HBox(add, clear, remove);
        row.setSpacing(10);
        final VBox root = new VBox(row, table);
        root.setSpacing(10);
        root.setPadding(new Insets(10));
        VBox.setVgrow(table, Priority.ALWAYS);

        final Scene sc = new Scene(root);
        primaryStage.setScene(sc);
        primaryStage.setTitle("TableView MemoryLeak Demo "
            + System.getProperty("javafx.runtime.version"));
        primaryStage.show();
    }

    private TableView<TableDataObj> buildTable() {
        final TableColumn<TableDataObj, Integer> idCol = new TableColumn<>();
        idCol.setText("Id");
        idCol.setCellValueFactory(param -> param.getValue().idProperty().asObject());
        idCol.setPrefWidth(100);

        final TableColumn<TableDataObj, String> fnCol = new TableColumn<>();
        fnCol.setText("First Name");
        fnCol.setCellValueFactory(param -> param.getValue().firstNameProperty());
        fnCol.setPrefWidth(150);

        final TableColumn<TableDataObj, String> lnCol = new TableColumn<>();
        lnCol.setText("Last Name");
        lnCol.setCellValueFactory(param -> param.getValue().lastNameProperty());
        lnCol.setPrefWidth(150);

        final TableColumn<TableDataObj, String> cityCol = new TableColumn<>();
        cityCol.setText("City");
        cityCol.setCellValueFactory(param -> param.getValue().cityProperty());
        cityCol.setPrefWidth(150);

        final TableView<TableDataObj> tableView = new TableView<>();
        tableView.getColumns().addAll(idCol, fnCol, lnCol, cityCol);
        return tableView;
    }

    /**
     * Data object.
     */
    private static final class TableDataObj {

        private final IntegerProperty id = new SimpleIntegerProperty();
        private final StringProperty firstName = new SimpleStringProperty();
        private final StringProperty lastName = new SimpleStringProperty();
        private final StringProperty city = new SimpleStringProperty();

        public TableDataObj(final int i, final String fn, final String ln, final String cty) {
            setId(i);
            setFirstName(fn);
            setLastName(ln);
            setCity(cty);
        }

        public StringProperty cityProperty() {
            return city;
        }

        public StringProperty firstNameProperty() {
            return firstName;
        }

        public int getId() {
            return id.get();
        }

        public IntegerProperty idProperty() {
            return id;
        }

        public StringProperty lastNameProperty() {
            return lastName;
        }

        public void setCity(final String city1) {
            city.set(city1);
        }

        public void setFirstName(final String firstName1) {
            firstName.set(firstName1);
        }

        public void setId(final int idA) {
            id.set(idA);
        }

        public void setLastName(final String lastName1) {
            lastName.set(lastName1);
        }
    }
}