Question

我想自定义ListView单元格的显示。假设有一个ListView包含Person类的对象和两个按钮：

添加（生成）新的Person
删除所选的Person

我想实现以下目标：

如果未选择某个单元格，则必须显示getBasicView() Person字段的name。
选择单元格后，必须显示getExpandedView()的{{1}}，这是一个多行文字Person。

问题是什么？

我写的代码填写了上面给出的要求，但出现了其他错误：

当眨眼间添加新name + "/n" + surname时，单元格的显示会更改为未实现的Person方法（因此用户会看到toString()类似垃圾）。< / LI>

从最后一个单元格中移除sample.Person@c4f324时，奇怪的事情开始发生。已删除的Person Person仍保留在向下移动两个单元格的单元格中，因为它不再包含name对象 - 无法清除它。

我尝试向单元格Person添加侦听器，可以检查项目是否为itemProperty，之后我可以将文本设置为null但不幸的是它不起作用。有谁知道如何让我的代码完全正常运行？

提供SSCCE（假设所有文件都在""包中）：

Main.java：

sample

sample.fxml：

package sample;

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

public class Main extends Application {

  public void start(Stage stage) {
    FXMLLoader fxmlLoader = new FXMLLoader();
    fxmlLoader.setController(Controller.class);
    try {
      Parent parent = FXMLLoader.load(getClass().getResource("/sample/sample.fxml"));
      Scene scene = new Scene(parent);
      stage.setScene(scene);
      stage.show();
    } catch (IOException e) {
      e.printStackTrace();
    }
  }

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

Controller.java：

<?import javafx.scene.layout.HBox?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.ListView?>
<?import javafx.scene.layout.VBox?>

<HBox xmlns:fx="http://javafx.com/fxml" fx:controller="sample.Controller">
    <VBox>
        <Button text="Add Person" onAction="#addPerson"/>
        <Button text="Delete Person" onAction="#deletePerson"/>
    </VBox>
    <ListView prefHeight="400" prefWidth="400" fx:id="listView"/>
</HBox>

Person.java：

package sample;

import javafx.application.Platform;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.fxml.FXML;
import javafx.scene.control.ListView;
import javafx.scene.control.MultipleSelectionModel;
import javafx.scene.control.cell.TextFieldListCell;
import java.util.concurrent.ThreadLocalRandom;

public class Controller {

  @FXML
  private ListView<Person> listView;
  private ObservableList<Person> personList = FXCollections.observableArrayList();
  private String [] names = {"John", "Katherine", "Michael", "August", "Peter"};
  private String [] surnames = {"Jones", "Mayer", "Stevens", "Wayne", "Milton"};

  @FXML
  private void initialize() {
    initializeListCells();
    initializeList();
  }

  private void initializeList() {
    for (int i = 0 ; i < 5 ; i++) {
      personList.add(generatePerson());
    }
    listView.setItems(personList);
  }

  private void initializeListCells() {
    listView.setCellFactory(param -> {
      TextFieldListCell<Person> cell = new TextFieldListCell<Person>();
      cell.selectedProperty().addListener((observable, oldValue, newValue) -> handleCellDisplaying(cell));
      cell.itemProperty().addListener((observable, oldValue, newValue) -> handleCellDisplaying(cell));
      return cell;
    });
  }

  private void handleCellDisplaying(TextFieldListCell<Person> cell) {
    Person person = cell.getItem();
    if (person != null) {
      Platform.runLater(() -> {
        if (!cell.isSelected()) {
          cell.setText(person.getBasicView());
        } else {
          cell.setText(person.getExpandedView());
        }
      });
    } else {
      cell.setText("");
    }
  }

  @FXML
  private void addPerson() {
    personList.add(generatePerson());
  }

  @FXML
  private void deletePerson() {
    MultipleSelectionModel<Person> selectionModel = listView.getSelectionModel();
    if (!selectionModel.isEmpty()) {
      int selectedIndex = selectionModel.getSelectedIndex();
      personList.remove(selectedIndex);
    }
  }

  private Person generatePerson() {
    int nameRandom = ThreadLocalRandom.current().nextInt(1,5);
    int surnameRandom = ThreadLocalRandom.current().nextInt(1,5);
    return new Person(names[nameRandom],surnames[surnameRandom]);
  }
}

Answer 1

问题是TextFieldListCell实现了单元格生命周期方法（updateItem等）并在各个点有效地调用setText(item.toString())。这显然会干扰您尝试实施的行为。（例如，删除最后一个单元格的问题似乎发生，因为setText("")在之前被调用 TextFieldListCell将文本重置为其先前的值。如果您使用Platform.runLater(...) 1}} hack以便它包围完整的if - else子句，然后这个问题就消失了。但是......）

如果您不需要单元格可编辑，则无需使用TextFieldListCell：只需使用普通ListCell。（另请注意，处理程序中不需要Platform.runLater(...)更改项目/选定状态。）

package sample; import java.util.concurrent.ThreadLocalRandom; import javafx.collections.FXCollections; import javafx.collections.ObservableList; import javafx.fxml.FXML; import javafx.scene.control.ListCell; import javafx.scene.control.ListView; import javafx.scene.control.MultipleSelectionModel; public class Controller { @FXML private ListView<Person> listView; private ObservableList<Person> personList = FXCollections.observableArrayList(); private String[] names = { "John", "Katherine", "Michael", "August", "Peter" }; private String[] surnames = { "Jones", "Mayer", "Stevens", "Wayne", "Milton" }; @FXML private void initialize() { initializeListCells(); initializeList(); } private void initializeList() { for (int i = 0; i < 5; i++) { personList.add(generatePerson()); } listView.setItems(personList); } private void initializeListCells() { listView.setCellFactory(param -> { ListCell<Person> cell = new ListCell<Person>(); cell.selectedProperty().addListener((observable, oldValue, newValue) -> handleCellDisplaying(cell)); cell.itemProperty().addListener((observable, oldValue, newValue) -> handleCellDisplaying(cell)); return cell; }); } private void handleCellDisplaying(ListCell<Person> cell) { Person person = cell.getItem(); if (person != null) { if (!cell.isSelected()) { cell.setText(person.getBasicView()); } else { cell.setText(person.getExpandedView()); } } else { cell.setText(""); } } @FXML private void addPerson() { personList.add(generatePerson()); } @FXML private void deletePerson() { MultipleSelectionModel<Person> selectionModel = listView.getSelectionModel(); if (!selectionModel.isEmpty()) { int selectedIndex = selectionModel.getSelectedIndex(); personList.remove(selectedIndex); } } private Person generatePerson() { int nameRandom = ThreadLocalRandom.current().nextInt(1, 5); int surnameRandom = ThreadLocalRandom.current().nextInt(1, 5); return new Person(names[nameRandom], surnames[surnameRandom]); } }

ListView - 如何正确配置单元格的显示？

1 个答案: