SimpleStringProperty和SimpleIntegerProperty TableView JavaFX

Question

所以我正在尝试学习如何使用JavaFx Tableview,并且我在本教程中讨论了:

Oracle tableview教程

在本教程中,他们表明,为了填充tableView,你必须用字符串填充它,但不是只需要将你格式化String为任何字符串SimpleStringProperty

我尝试没有格式,结果是没有任何信息显示!

另外我发现如果你想Integer在表中添加一个,你必须将它声明为SimpleIntegerProperty

现在我对JavaFx还不熟悉,但这是否意味着当我创建一个对象时,我必须格式化所有的整数和字符串以便能够填充我的TableView？它似乎相当愚蠢,但也许有更高的目的？还是有办法避免它？

Answer 1

尽管在某些情况下需要使用Properties,但您不需要在表数据对象中使用Properties来显示它们.

以下代码将显示基于Person类的人员表,该Person类仅包含String字段.

import javafx.application.Application;
import javafx.collections.*;
import javafx.geometry.Insets;
import javafx.scene.*;
import javafx.scene.control.*;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.scene.layout.VBox;
import javafx.scene.text.Font;
import javafx.stage.Stage;

public class ReadOnlyTableView extends Application {
  private TableView<Person> table = new TableView<Person>();
  private final ObservableList<Person> data =
    FXCollections.observableArrayList(
      new Person("Jacob", "Smith", "jacob.smith@example.com"),
      new Person("Isabella", "Johnson", "isabella.johnson@example.com"),
      new Person("Ethan", "Williams", "ethan.williams@example.com"),
      new Person("Emma", "Jones", "emma.jones@example.com"),
      new Person("Michael", "Brown", "michael.brown@example.com")
    );

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

  @Override public void start(Stage stage) {
    stage.setTitle("Table View Sample");
    stage.setWidth(450);
    stage.setHeight(500);

    final Label label = new Label("Address Book");
    label.setFont(new Font("Arial", 20));

    TableColumn firstNameCol = new TableColumn("First Name");
    firstNameCol.setMinWidth(100);
    firstNameCol.setCellValueFactory(new PropertyValueFactory<Person, String>("firstName"));

    TableColumn lastNameCol = new TableColumn("Last Name");
    lastNameCol.setMinWidth(100);
    lastNameCol.setCellValueFactory(new PropertyValueFactory<Person, String>("lastName"));

    TableColumn emailCol = new TableColumn("Email");
    emailCol.setMinWidth(200);
    emailCol.setCellValueFactory(new PropertyValueFactory<Person, String>("email"));

    table.setItems(data);
    table.getColumns().addAll(firstNameCol, lastNameCol, emailCol);

    final VBox vbox = new VBox();
    vbox.setSpacing(5);
    vbox.setPadding(new Insets(10, 0, 0, 10));
    vbox.getChildren().addAll(label, table);

    stage.setScene(new Scene(new Group(vbox)));
    stage.show();
  }

  public static class Person {
    private String firstName;
    private String lastName;
    private String email;

    private Person(String fName, String lName, String email) {
      this.firstName = fName;
      this.lastName = lName;
      this.email = email;
    }

    public String getFirstName() { return firstName; }
    public void setFirstName(String fName) { firstName = fName; }
    public String getLastName() { return lastName; }
    public void setLastName(String lName) { lastName = lName; }
    public String getEmail() { return email; }
    public void setEmail(String inMail) { email = inMail; }
  }
}

说明

使用Properties和ObservableLists的目的是这些是可听元素.使用属性时,如果datamodel中属性属性的值发生更改,则TableView中项目的视图将自动更新以匹配更新的datamodel值.例如,如果某人的电子邮件属性的值设置为新值,则该更新将反映在TableView中,因为它会侦听属性更改.相反,如果使用普通的String来表示电子邮件,则TableView不会刷新,因为它不会意识到电子邮件值的更改.

该PropertyValueFactory文档详细描述了这一过程:

如何使用此类的示例是:

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

在此示例中,"firstName"字符串用作Person类类型中假定的firstNameProperty()方法的引用(这是TableView项列表的类类型).此外,此方法必须返回Property实例.如果找到满足这些要求的方法,则使用此ObservableValue填充TableCell.此外,TableView将自动向返回的值添加一个观察者,以便TableView将观察到触发的任何更改,从而导致单元格立即更新.

如果不存在与此模式匹配的方法,则会尝试调用get()或is()(即上例中的getFirstName()或isFirstName()).如果存在与此模式匹配的方法,则此方法返回的值将包装在ReadOnlyObjectWrapper中并返回到TableCell.但是,在这种情况下,这意味着TableCell将无法观察ObservableValue的更改(如上面第一种方法中的情况).

更新

下面是第一个示例的对比示例,该示例演示了TableView如何根据对项目的ObservableList的更改以及对基于属性的项属性的值的更改来观察和自动刷新.

import javafx.application.Application;
import javafx.beans.property.*;
import javafx.collections.*;
import javafx.event.*;
import javafx.geometry.Insets;
import javafx.scene.*;
import javafx.scene.control.*;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.scene.layout.VBox;
import javafx.scene.text.Font;
import javafx.stage.Stage;

public class PropertyBasedTableView extends Application {
  private TableView<Person> table = new TableView<Person>();
  private final ObservableList<Person> data = FXCollections.observableArrayList();
  private void initData() {
    data.setAll(
      new Person("Jacob", "Smith", "jacob.smith@example.com"),
      new Person("Isabella", "Johnson", "isabella.johnson@example.com"),
      new Person("Ethan", "Williams", "ethan.williams@example.com"),
      new Person("Emma", "Jones", "emma.jones@example.com"),
      new Person("Michael", "Brown", "michael.brown@example.com")
    );
  }

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

  @Override public void start(Stage stage) {
    initData();

    stage.setTitle("Table View Sample");
    stage.setWidth(450);
    stage.setHeight(500);

    final Label label = new Label("Address Book");
    label.setFont(new Font("Arial", 20));

    TableColumn firstNameCol = new TableColumn("First Name");
    firstNameCol.setMinWidth(100);
    firstNameCol.setCellValueFactory(new PropertyValueFactory<Person, String>("firstName"));

    TableColumn lastNameCol = new TableColumn("Last Name");
    lastNameCol.setMinWidth(100);
    lastNameCol.setCellValueFactory(new PropertyValueFactory<Person, String>("lastName"));

    TableColumn emailCol = new TableColumn("Email");
    emailCol.setMinWidth(200);
    emailCol.setCellValueFactory(new PropertyValueFactory<Person, String>("email"));

    table.setItems(data);
    table.getColumns().addAll(firstNameCol, lastNameCol, emailCol);
    table.setPrefHeight(300);

    final Button setEmailButton = new Button("Set first email in table to wizard@frobozz.com");
    setEmailButton.setOnAction(new EventHandler<ActionEvent>() {
      @Override public void handle(ActionEvent event) {
        if (data.size() > 0) {
          data.get(0).setEmail("wizard@frobozz.com");
        }  
      }
    });

    final Button removeRowButton = new Button("Remove first row from the table");
    removeRowButton.setOnAction(new EventHandler<ActionEvent>() {
      @Override public void handle(ActionEvent event) {
        if (data.size() > 0) {
          data.remove(0);
        }  
      }
    });

    final Button resetButton = new Button("Reset table data");
    resetButton.setOnAction(new EventHandler<ActionEvent>() {
      @Override public void handle(ActionEvent event) {
        initData();
      }
    });

    final VBox vbox = new VBox(10);
    vbox.setPadding(new Insets(10, 0, 0, 10));
    vbox.getChildren().addAll(label, table, setEmailButton, removeRowButton, resetButton);

    stage.setScene(new Scene(new Group(vbox)));
    stage.show();
  }

  public static class Person {
    private final StringProperty firstName;
    private final StringProperty lastName;
    private final StringProperty email;

    private Person(String fName, String lName, String email) {
      this.firstName = new SimpleStringProperty(fName);
      this.lastName = new SimpleStringProperty(lName);
      this.email = new SimpleStringProperty(email);
    }

    public String getFirstName() { return firstName.get(); }
    public void setFirstName(String fName) { firstName.set(fName); }
    public StringProperty firstNameProperty() { return firstName; }
    public String getLastName() { return lastName.get(); }
    public void setLastName(String lName) { lastName.set(lName); }
    public StringProperty lastNameProperty() { return lastName; }
    public String getEmail() { return email.get(); }
    public void setEmail(String inMail) { email.set(inMail); }
    public StringProperty emailProperty() { return email; }  // if this method is commented out then the tableview will not refresh when the email is set.
  }
}