即使打印数据，Javafx SQLite Tableview也不会填充

Question

使用 Apache Netbeans IDE 11.3。目前无法填充 tableview，即使我可以打印数据。

我正在构建一个 Operator GUI 的东西。目前正在尝试使用 Operator 数据填充 tableview 但做不到。

控制器类：

public class OperatorenController implements Initializable {

    DatabaseController db = new DatabaseController();
    private ObservableList<Operatoren> OperatorenList;

    @FXML
    private TableView<Operatoren> Operatorentable = new TableView<>();
    @FXML
    private TableColumn<Operatoren, Integer> id = new TableColumn<>();
    @FXML
    private TableColumn<Operatoren, String> name = new TableColumn<>();
    @FXML
    private TableColumn<Operatoren, String> nachname = new TableColumn<>();
    @FXML
    private TableColumn<Operatoren, String> firmname = new TableColumn<>();


    @FXML
    private void handleDisplayTables(ActionEvent event) throws NullPointerException {
        try {Connection conn = db.ConnectDB();
            String dbliste = "SELECT * FROM [operatoren]";
            Statement st = conn.createStatement();
            ResultSet rs = st.executeQuery(dbliste);
            OperatorenList = FXCollections.observableArrayList();

            while (rs.next()) {
                int id = rs.getInt("id");
                String name = rs.getString("name");
                String nachname = rs.getString("nachname");
                String firmname = rs.getString("firmname");
                OperatorenList.add(new Operatoren(id, name, nachname,firmname));
                System.out.println(id + " " + name+" " + nachname+" " + firmname+" ");


            }
        } catch (Exception e) {
            System.out.println(e);
        }

        id.setCellValueFactory(new PropertyValueFactory<>("id"));
        name.setCellValueFactory(new PropertyValueFactory<>("name"));
        nachname.setCellValueFactory(new PropertyValueFactory<>("nachname"));
        firmname.setCellValueFactory(new PropertyValueFactory<>("firmname"));

        name.setCellValueFactory(cellData -> { return (new SimpleStringProperty(((Operatoren)cellData.getValue()).getName()));});
        nachname.setCellValueFactory(cellData -> { return (new SimpleStringProperty(((Operatoren)cellData.getValue()).getNachname()));});
        firmname.setCellValueFactory(cellData -> { return (new SimpleStringProperty(((Operatoren)cellData.getValue()).getFirmname()));});
        id.setCellValueFactory(cellData -> { return (new SimpleIntegerProperty(((Operatoren)cellData.getValue()).getId())).asObject();});

        Operatorentable.setItems(OperatorenList);
        Operatorentable.getColumns().addAll(id,name,nachname,firmname);
        Operatorentable.refresh();

    }

    @Override
    public void initialize(URL url, ResourceBundle rb) {

     }
}

我可以从数据库打印数据，所以我不认为数据库是这里的问题。

运算符java类

public class Operatoren {
    public SimpleStringProperty name,nachname,firmname;
    public SimpleIntegerProperty id;

public Operatoren(int id,String name,String nachname,String firmname){
    this.id = new SimpleIntegerProperty(id);
    this.name = new SimpleStringProperty(name);
    this.nachname = new SimpleStringProperty(nachname);
    this.firmname = new SimpleStringProperty(firmname);

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

    }

    public String getName() {
        return name.get();
    }

    public SimpleStringProperty getNameProperty() {
        return name;
    }

    public String getNachname() {
        return nachname.get();
    }

    public SimpleStringProperty getNachnameProperty() {
        return nachname;
    }

    public String getFirmname() {
        return firmname.get();
    }

    public SimpleStringProperty getFirmnameProperty() {
        return firmname;
    }

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

    public SimpleIntegerProperty getIdProperty() {
        return id;
    }
}

最后是 FXML，我正在使用 SceneBuilder :

<AnchorPane id="AnchorPane" prefHeight="600.0" prefWidth="800.0" style="-fx-background-color: #313455;" xmlns="http://javafx.com/javafx/11.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="inf202.OperatorenController">
   <children>
      <Button layoutX="140.0" layoutY="235.0" mnemonicParsing="false" onAction="#personEkle" prefHeight="25.0" prefWidth="109.0" style="-fx-background-color: #f5f5f5;" text="Person ekle" />
      <Button layoutX="136.0" layoutY="354.0" mnemonicParsing="false" onAction="#personSil" prefHeight="25.0" prefWidth="109.0" style="-fx-background-color: #f5f5f5;" text="person sil" />
      <Button layoutX="136.0" layoutY="443.0" mnemonicParsing="false" onAction="#personList" prefHeight="25.0" prefWidth="109.0" style="-fx-background-color: #f5f5f5;" text="person listele" />
      <Button layoutX="136.0" layoutY="400.0" mnemonicParsing="false" onAction="#handleDisplayTables" prefHeight="25.0" prefWidth="109.0" style="-fx-background-color: #f5f5f5;" text="Person duzenle" />
      <Text fill="#948f8f" layoutX="122.0" layoutY="87.0" strokeType="OUTSIDE" strokeWidth="0.0" text="Go Back">
         <font>
            <Font name="System Bold" size="18.0" />
         </font>
      </Text>
      <Line endX="84.0" endY="11.0" layoutX="25.0" layoutY="57.0" startX="68.0" startY="23.0" stroke="#948f8f" strokeWidth="2.0" />
      <Line endX="-85.0" endY="12.0" fill="#868686" layoutX="195.0" layoutY="81.0" startX="-103.4141845703125" startY="0.414215087890625" stroke="#948f8f" strokeWidth="2.0" />
      <Button layoutX="86.0" layoutY="68.0" mnemonicParsing="false" onAction="#Operatoren" opacity="0.0" prefHeight="25.0" prefWidth="109.0" text="Button" />
      <TextField layoutX="121.0" layoutY="126.0" />
      <TextField layoutX="121.0" layoutY="165.0" />
      <TextField layoutX="121.0" layoutY="200.0" />
      <Text fill="#948f8f" layoutX="61.0" layoutY="145.0" strokeType="OUTSIDE" strokeWidth="0.0" text="Name">
         <font>
            <Font name="System Bold" size="18.0" />
         </font>
      </Text>
      <Text fill="#948f8f" layoutX="20.0" layoutY="184.0" strokeType="OUTSIDE" strokeWidth="0.0" text="Nachname">
         <font>
            <Font name="System Bold" size="18.0" />
         </font>
      </Text>
      <Text fill="#948f8f" layoutX="21.0" layoutY="220.0" strokeType="OUTSIDE" strokeWidth="0.0" text="FirmName">
         <font>
            <Font name="System Bold" size="18.0" />
         </font>
      </Text>
      <TextField layoutX="121.0" layoutY="316.0" />
      <Text fill="#948f8f" layoutX="77.0" layoutY="335.0" strokeType="OUTSIDE" strokeWidth="0.0" text="ID">
         <font>
            <Font name="System Bold" size="18.0" />
         </font>
      </Text>
      <Line endX="22.0" endY="249.0" layoutX="350.0" layoutY="49.0" startX="-323.0" startY="249.0" />
      <Line endX="-100.5" endY="231.5" layoutX="473.0" layoutY="67.0" startX="-100.5" startY="-50.0" />
      <Line endX="-102.25" endY="-188.79290771484375" layoutX="475.0" layoutY="488.0" startX="-102.25" startY="99.0" />
      <TextArea layoutX="28.0" layoutY="507.0" prefHeight="69.0" prefWidth="325.0" />
      <Text fill="#948f8f" layoutX="152.0" layoutY="494.0" strokeType="OUTSIDE" strokeWidth="0.0" text="Ergebnis" wrappingWidth="77.1845703125">
         <font>
            <Font name="System Bold" size="18.0" />
         </font>
      </Text>
      <TableView layoutX="389.0" layoutY="35.0" prefHeight="543.0" prefWidth="379.0">
         <columns>
            <TableColumn prefWidth="75.0" text="ID" />
            <TableColumn prefWidth="75.0" text="Name" />
            <TableColumn prefWidth="75.0" text="Nachname" />
            <TableColumn prefWidth="75.0" text="Firmname" />
         </columns>
      </TableView>
   </children>
</AnchorPane>

Answer 1

永远不要初始化带有 @FXML 注释的字段。

如果您删除控制器中的初始化，则会出现空指针异常的原因是您忘记将fx:ids 放在 FXML 文件中的元素上。

您要向其传递数据的TableView 是控制器中定义的那个，而不是FXML 文件中定义的那个（并显示在场景中）。同样，您在其上设置单元格值工厂的TableColumns 是您在控制器中创建的，而不是您在 FXML 文件中定义的那些。因此，FXML 文件中定义的表格列没有单元格值工厂，因此无法显示任何数据。

所以替换

@FXML
private TableView<Operatoren> Operatorentable = new TableView<>();
@FXML
private TableColumn<Operatoren, Integer> id = new TableColumn<>();
@FXML
private TableColumn<Operatoren, String> name = new TableColumn<>();
@FXML
private TableColumn<Operatoren, String> nachname = new TableColumn<>();
@FXML
private TableColumn<Operatoren, String> firmname = new TableColumn<>();

与

@FXML
private TableView<Operatoren> Operatorentable ;
@FXML
private TableColumn<Operatoren, Integer> id ;
@FXML
private TableColumn<Operatoren, String> name ;
@FXML
private TableColumn<Operatoren, String> nachname ;
@FXML
private TableColumn<Operatoren, String> firmname ;

并在 FXML 文件中添加 fx:id 属性：

  <TableView fx:id="Operatorentable" layoutX="389.0" layoutY="35.0" prefHeight="543.0" prefWidth="379.0">
     <columns>
        <TableColumn fx:id="id" prefWidth="75.0" text="ID" />
        <TableColumn fx:id="name" prefWidth="75.0" text="Name" />
        <TableColumn fx:id="nachname" prefWidth="75.0" text="Nachname" />
        <TableColumn fx:id="firmname" prefWidth="75.0" text="Firmname" />
     </columns>
  </TableView>

注意你在模型类中的方法命名是非标准的：对于一个属性prop，get方法应该是getProp()，set方法应该是setProp()，属性访问器方法应该是@987654332 @，不是getPropProperty()。如果您使用 PropertyValueFactory 类（我实际上并不推荐），这可能会使事情无法正常工作。

public class Operatoren {
    public SimpleStringProperty name,nachname,firmname;
    public SimpleIntegerProperty id;

public Operatoren(int id,String name,String nachname,String firmname){
    this.id = new SimpleIntegerProperty(id);
    this.name = new SimpleStringProperty(name);
    this.nachname = new SimpleStringProperty(nachname);
    this.firmname = new SimpleStringProperty(firmname);

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

    }

    public String getName() {
        return name.get();
    }

    public SimpleStringProperty nameProperty() {
        return name;
    }

    public String getNachname() {
        return nachname.get();
    }

    public SimpleStringProperty nachnameProperty() {
        return nachname;
    }

    public String getFirmname() {
        return firmname.get();
    }

    public SimpleStringProperty firmnameProperty() {
        return firmname;
    }

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

    public SimpleIntegerProperty idProperty() {
        return id;
    }
}

设置单元格值工厂并立即用本质上等效的工厂替换它们也没有任何意义，您应该在初始化时执行此操作，而不是在事件处理程序中。最后，由于您在模型类中定义了 JavaFX 属性，因此无需为单元工厂创建新属性，只需引用现有属性即可：

@FXML
private void handleDisplayTables(ActionEvent event) throws NullPointerException {
    try {Connection conn = db.ConnectDB();
        String dbliste = "SELECT * FROM [operatoren]";
        Statement st = conn.createStatement();
        ResultSet rs = st.executeQuery(dbliste);
        OperatorenList = FXCollections.observableArrayList();

        while (rs.next()) {
            int id = rs.getInt("id");
            String name = rs.getString("name");
            String nachname = rs.getString("nachname");
            String firmname = rs.getString("firmname");
            OperatorenList.add(new Operatoren(id, name, nachname,firmname));
            System.out.println(id + " " + name+" " + nachname+" " + firmname+" ");


        }
    } catch (Exception e) {
        System.out.println(e);
    }


    Operatorentable.setItems(OperatorenList);

}

@Override
public void initialize(URL url, ResourceBundle rb) {
    name.setCellValueFactory(cellData -> cellData.getValue().nameProperty());
    nachname.setCellValueFactory(cellData -> cellData.getValue().nachnameProperty());
    firmname.setCellValueFactory(cellData -> cellData.getValue().firmnameProperty());
    id.setCellValueFactory(cellData -> cellData.getValue().idProperty().asObject());


 }