java如何修复滚动时的TableView

1 月，1 周 Questions & Answers 1892

我是JavaFX的新手，不知道如何解决这个问题。因此，我在TableView中有一个复选框列。例如，我先选择3个框，然后向下滚动表格。但当我转到表的顶部时，复选框不会被选中。下面是一些代码：

import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;
import javafx.util.Callback;
import java.util.LinkedList;
import java.util.List;

public class App extends Application
{
List<User> list = new LinkedList<>();
TableColumn<User, Integer> id;
TableColumn<User, String> firstName;
TableColumn<User, Boolean> selected;
TableView<User> tableView;

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

@Override
public void start(Stage stage) throws Exception
{
    stage.setHeight(500);
    stage.setWidth(500);
    stage.setMinHeight(200);
    stage.setMinHeight(100);
    stage.setTitle("Table view");

    tableView = new TableView<>();

    ObservableList<User> list = FXCollections.observableArrayList();
    for(int i = 0; i < 40; i++)
    {
        list.add(new User(i, "first name", "last name"));
    }

    id = new TableColumn("ID");
    id.setCellValueFactory(new PropertyValueFactory<User, Integer>("id"));

    firstName = new TableColumn("First Name");
    firstName.setCellValueFactory(new PropertyValueFactory<User, String>("firstName"));

    TableColumn<User, String> lastName = new TableColumn("Last Name");
    lastName.setCellValueFactory(new PropertyValueFactory<User, String>("lastName"));

    selected = new TableColumn("Select");

    Callback<TableColumn<User, Boolean>, TableCell<User, Boolean>> booleanCellFactory =     new Callback<TableColumn<User, Boolean>, TableCell<User, Boolean>>()
    {
        @Override
        public TableCell<User, Boolean> call(TableColumn<User, Boolean> p)
        {
            return new CheckBoxCell();
        }
    };
    selected.setCellValueFactory(new PropertyValueFactory<User, Boolean>("active"));
    selected.setCellFactory(booleanCellFactory);

    tableView.getColumns().addAll(id, firstName, lastName, selected);
    tableView.setItems(list);

    BorderPane pane = new BorderPane();
    pane.setCenter(tableView);

    Scene scene = new Scene(pane);
    stage.setScene(scene);
    stage.show();
}

class CheckBoxCell extends TableCell<User, Boolean>
{
    private CheckBox checkbox;

    @Override
    protected void updateItem(Boolean item, boolean empty)
    {
        super.updateItem(item, empty);
        checkbox = new CheckBox();
        checkbox.setAlignment(Pos.CENTER);
        setAlignment(Pos.CENTER);
        setGraphic(checkbox);
        checkbox.setOnAction(new EventHandler<ActionEvent>()
        {
            @Override
            public void handle(ActionEvent actionEvent)
            {

                if(!checkbox.isSelected())
                {
                    list.remove(tableView.getItems().get(getTableRow().getIndex()));
                } else
                {
                    list.add(tableView.getItems().get(getTableRow().getIndex()));
                }
                System.out.println(list);
            }
        });
    }
}
}

以及数据类“用户”：

public class User
{
private int id;
private String firstName;
private String lastName;

User(int id, String firstName, String lastName)
{
    this.id = id;
    this.firstName = firstName;
    this.lastName = lastName;
}

public int getId()
{
    return id;
}

public void setId(int id)
{
    this.id = id;
}

public String getFirstName()
{
    return firstName;
}

public void setFirstName(String firstName)
{
    this.firstName = firstName;
}

public String getLastName()
{
    return lastName;
}

public void setLastName(String lastName)
{
    this.lastName = lastName;
}

}

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共 (2) 个答案

# 1 楼答案

在表列“slected”的代码中

selected.setCellValueFactory(new PropertyValueFactory<User, Boolean>("active"));

您正在将propertyvalue工厂设置为“active”，但用户类中没有“active”属性。当您移动滚动条tableview时，触发updateItem方法，因为您没有活动属性（即使您的属性默认值为false）复选框。（项目1）；行将取消选中复选框，因为项目值始终为false

若要解决此问题，请在用户类中定义一个活动的BooleanProperty，并在用户选中/取消选中复选框时更新属性值

下面是正在运行的完整代码

import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.stage.Stage;
import javafx.util.Callback;
import javafx.scene.layout.BorderPane;
import java.util.LinkedList;
import java.util.List;

public class TestApp extends Application {

        List<User> list = new LinkedList<>();
        TableColumn<User, Integer> id;
        TableColumn<User, String> firstName;
        TableColumn<User, Boolean> selected;
        TableView<User> tableView;

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

@Override
public void start(Stage stage) throws Exception
        {
        stage.setHeight(500);
        stage.setWidth(500);
        stage.setMinHeight(200);
        stage.setMinHeight(100);
        stage.setTitle("Table view");

        tableView = new TableView<>();

        ObservableList<User> list = FXCollections.observableArrayList();
        for(int i = 0; i < 40; i++)
        {
        list.add(new User(i, "first name", "last name"));
        }

        id = new TableColumn("ID");
        id.setCellValueFactory(new PropertyValueFactory<User, Integer>("id"));

        firstName = new TableColumn("First Name");
        firstName.setCellValueFactory(new PropertyValueFactory<User, String>("firstName"));

        TableColumn<User, String> lastName = new TableColumn("Last Name");
        lastName.setCellValueFactory(new PropertyValueFactory<User, String>("lastName"));

        selected = new TableColumn("Select");

        Callback<TableColumn<User, Boolean>, TableCell<User, Boolean>> booleanCellFactory =     new Callback<TableColumn<User, Boolean>, TableCell<User, Boolean>>()
        {
@Override
public TableCell<User, Boolean> call(TableColumn<User, Boolean> p)
        {
        return new CheckBoxCell();
        }
        };
        selected.setCellValueFactory(new PropertyValueFactory<User, Boolean>("active"));
        selected.setCellFactory(booleanCellFactory);

        tableView.getColumns().addAll(id, firstName, lastName, selected);
        tableView.setItems(list);

        BorderPane pane = new BorderPane();
        pane.setCenter(tableView);

        Scene scene = new Scene(pane);
        stage.setScene(scene);
        stage.show();
       }

class CheckBoxCell extends TableCell<User, Boolean>
{
    private CheckBox checkbox = new CheckBox();
    public CheckBoxCell(){
        checkbox.setOnAction(new EventHandler<ActionEvent>()
        {
            @Override
            public void handle(ActionEvent actionEvent)
            {

                if(!checkbox.isSelected())
                {
                    list.remove(tableView.getItems().get(getTableRow().getIndex()));
                    User user = getTableView().getItems().get(getTableRow().getIndex());
                    user.setActive(false);
                } else
                {
                    list.add(tableView.getItems().get(getTableRow().getIndex()));
                    User user = getTableView().getItems().get(getTableRow().getIndex());
                    user.setActive(true);
                }
                System.out.println(list);
            }
        });
    }

    @Override
    protected void updateItem(Boolean item, boolean empty)
    {
        super.updateItem(item, empty);
       if(!empty && item != null) {
           checkbox.setAlignment(Pos.CENTER);
           checkbox.setSelected(item);
           setAlignment(Pos.CENTER);
           setGraphic(checkbox);
       }
    }
}

用户类别：

public class User
{
    private IntegerProperty id;
    private StringProperty firstName;
    private StringProperty lastName;
    private BooleanProperty active;

    User(int id, String firstName, String lastName)
    {
        this.id = new SimpleIntegerProperty(id);
        this.firstName = new SimpleStringProperty(firstName);
        this.lastName = new SimpleStringProperty(lastName);
        this.active = new SimpleBooleanProperty(false);
    }

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

    public IntegerProperty idProperty() {
        return id;
    }

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

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

    public StringProperty firstNameProperty() {
        return firstName;
    }

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

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

    public StringProperty lastNameProperty() {
        return lastName;
    }

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

    public boolean getActive() {
        return active.get();
    }

    public BooleanProperty activeProperty() {
        return active;
    }

    public void setActive(boolean active) {
        this.active.set(active);
    }
}

# 2 楼答案
有很多问题

首先，TableCell实例将被重用。您需要将CheckBox的值设置为item的值
```
@Override
protected void updateItem(Boolean item, boolean empty)
{
    super.updateItem(item, empty);
    checkbox = new CheckBox();

    if(!empty && item != null)
        checkbox.setSelected(item);

    ....

  }
```
其次，您有两个名为list的变量。TableView没有绑定到顶部声明的List<User>，这可能就是您的行没有删除自己的原因

您应该替换此行：
```
List<User> list = new LinkedList<>();
```
为此：
```
ObservableList<User> list = FXCollections.observableArrayList();
```
最后，您应该为您的数据对象使用JavaFX属性，使用TableView（无需使用反射来访问值）它们将执行得更快，并且将提供更好的JavaFX控件处理

You can learn about the properties on the Oracle website.

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java如何修复滚动时的TableView

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