如何在我的程序中动态添加 TextFields？

Question

在 FXML 中，我有根BorderPane ，在它的中心是另一个BorderPane ，在第二个Borderpane的中心我有 GridPane。 我想根据数组的大小添加TextField 。 我不知道如何访问那个 GridPane。 在 FXML 中我设置了 fx:id，但在我的 controller 中它不可见。（ @FXML GridPane nameInFxml ）

    <BorderPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="466.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/10.0.2-internal" xmlns:fx="http://javafx.com/fxml/1" fx:id="rootBorderPane">
   <left>
      <TableView fx:id="repairsTable" prefHeight="372.0" prefWidth="151.0" BorderPane.alignment="CENTER">
         <columns>
             <TableColumn fx:id="data" prefWidth="55.0" text="Data">
                 <cellValueFactory>
                     <PropertyValueFactory property="data" />
                 </cellValueFactory>
             </TableColumn>
             <TableColumn fx:id="mechanik" prefWidth="41.0" text="Mechanik">
                 <cellValueFactory>
                     <PropertyValueFactory property="mechanik" />
                 </cellValueFactory>
             </TableColumn>
         </columns></TableView>
   </left>
   <center>
      <BorderPane prefHeight="200.0" prefWidth="200.0" BorderPane.alignment="CENTER" fx:id="borderPane">
         <center>
            <GridPane alignment="CENTER" hgap="5.0" prefHeight="300.0" prefWidth="448.0" BorderPane.alignment="CENTER" fx:id="details" >
              <columnConstraints>
                <ColumnConstraints halignment="CENTER" hgrow="SOMETIMES" maxWidth="220.0" minWidth="10.0" prefWidth="71.0" />
                <ColumnConstraints halignment="CENTER" hgrow="SOMETIMES" maxWidth="346.0" minWidth="10.0" prefWidth="244.0" />
                  <ColumnConstraints halignment="CENTER" hgrow="SOMETIMES" maxWidth="346.0" minWidth="10.0" prefWidth="66.0" />
                  <ColumnConstraints halignment="CENTER" hgrow="SOMETIMES" maxWidth="346.0" minWidth="10.0" prefWidth="80.0" />
              </columnConstraints>
              <rowConstraints>
                <RowConstraints maxHeight="95.0" minHeight="0.0" prefHeight="25.0" vgrow="SOMETIMES" />
                <RowConstraints maxHeight="200.0" minHeight="0.0" prefHeight="23.0" vgrow="SOMETIMES" />
                <RowConstraints maxHeight="290.0" minHeight="10.0" prefHeight="290.0" vgrow="SOMETIMES" />
              </rowConstraints>
               <children>

                  <Label fx:id="coByloRobioneLabel" text="Co było robione" GridPane.columnIndex="0" />
                  <Label fx:id="nettoLabel" text="Netto" GridPane.columnIndex="01" />
                  <Label fx:id="bruttoLabel" text="Brutto" GridPane.columnIndex="2" />
               </children>
               <padding>
                  <Insets bottom="10.0" left="10.0" right="10.0" top="10.0" />
               </padding>
            </GridPane>
         </center>
         <top>
            <GridPane prefHeight="51.0" prefWidth="449.0" BorderPane.alignment="CENTER">
              <columnConstraints>
                <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
                <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
                  <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
                  <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
                  <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
                  <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
              </columnConstraints>
              <rowConstraints>
                <RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
              </rowConstraints>
               <children>
                  <Label fx:id="mechanikLabel" text="Mechanik   " GridPane.columnIndex="0" />
                  <Label text="Data" GridPane.columnIndex="2" />
                  <Label text="Nr Rej." GridPane.columnIndex="4" />
                  <TextField fx:id="mechanikTextField" GridPane.columnIndex="1" />
                  <TextField fx:id="dataTextField" GridPane.columnIndex="3" />
                  <TextField fx:id="nrRejTextField" GridPane.columnIndex="5" />
               </children>
               <padding>
                  <Insets bottom="10.0" left="10.0" right="10.0" top="10.0" />
               </padding>
            </GridPane>
         </top>
      </BorderPane>
   </center>
   <bottom>
      <HBox alignment="CENTER" prefHeight="44.0" prefWidth="600.0" spacing="20" BorderPane.alignment="CENTER">
         <children>
            <TextField fx:id="searchTextField" />
            <Button fx:id="nowyButton" mnemonicParsing="false" text="Nowy" />
            <Button fx:id="zapiszButton" mnemonicParsing="false" text="Zapisz" />
            <Button fx:id="usunButton" mnemonicParsing="false" text="Usuń" />
            <Button fx:id="newRecord" mnemonicParsing="false" text="Nowa pozycja w naprawie" />
         </children>
      </HBox>
   </bottom>
</BorderPane>

我想用 fx:id = "details" 访问那个 GridPane。

Controller：

public class RepairsController {
    @FXML
    TextField mechanikTextField;
    @FXML
    TextField dataTextField;
    @FXML
    TextField nrRejTextField;
    @FXML
    Button nowyButton;
    @FXML
    Button usunButton;
    @FXML
    Button zapiszButton;
    @FXML
    TextField searchTextField;
    @FXML
    TableView<Repair> repairsTable;
    @FXML
    GridPane details;





    private ObservableList<Repair> repairs;
    private Car car;

    public RepairsController() {

    }

    public Car getCar() {
        return car;
    }

    public void setCar(Car car) {
        this.car = car;
    }

    public void initialize(){

        repairs = DataSource.getInstance().queryAllRepairs(car.getNrRej());

        filter(repairs);
        onChangeListener();
        repairsTable.getSelectionModel().selectFirst();

        nowyButtonPressed();
        usunButtonPressed();


    }

    @FXML
    public void filter(ObservableList<Repair> list) {

        FilteredList<Repair> filteredData = new FilteredList<>(list, p -> true);

        searchTextField.textProperty().addListener((observable, oldValue, newValue) -> {

            filteredData.setPredicate(repair-> {
                if (newValue == null || newValue.isEmpty()) {
                    return true;
                }
                String loweCaseFilter = newValue.toLowerCase();
                if (repair.getData().toLowerCase().contains(loweCaseFilter)) {
                    return true;
                }

                if((repair.getMechanik().toLowerCase().contains(loweCaseFilter))){
                    return true;
                }

                return false;

            });

        });
        SortedList<Repair> sortedData = new SortedList<>(filteredData);
        sortedData.comparatorProperty().bind(repairsTable.comparatorProperty());
        repairsTable.setItems(sortedData);

    }

    private void onChangeListener(){
        repairsTable.getSelectionModel().selectedItemProperty().addListener(new ChangeListener<Repair>() {
            @Override
            public void changed(ObservableValue<? extends Repair> observableValue, Repair repair, Repair t1) {
                if(t1 != null) {
                    mechanikTextField.setText(repairsTable.getSelectionModel().getSelectedItem().getMechanik());
                    dataTextField.setText(repairsTable.getSelectionModel().getSelectedItem().getData());
                }



                TextField[] coTextField = new TextField[30];
                if(repairsTable.getSelectionModel().getSelectedItem().getRepairDetailsList() !=null) {

                    for (int i = 0; i < repairsTable.getSelectionModel().getSelectedItem().getRepairDetailsList().size(); i++) {
//at this point I get the exception
                       details.add(coTextField[i], 2, 2);

                    }
                }
            }
        });
    }

    public void nowyButtonPressed(){
        nowyButton.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent actionEvent) {
                Repair repair = new Repair();
                repairs.add(repair);
            }
        });
    }

    public void usunButtonPressed(){
        usunButton.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent actionEvent) {
                repairs.remove(repairsTable.getSelectionModel().getSelectedItem());
            }
        });
    }




}

Answer 1

您正在收到指向此行的 Null 指针

TextField[] coTextField = new TextField[30];

此数组中没有任何文本字段已初始化您刚刚创建了一个大小为 30 的空数组，可以容纳文本字段

如果您将此代码放在该行之后（ TextField[] coTextField = new TextField[30]; ）我认为您的 NPE 将消失

for (int i = 0; i < coTextField.length; i++) 
    coTextField[i] = new TextField();

此代码将为数组中的每个索引创建一个new Textfield的文本字段

如果您对这篇文章中的任何内容有任何其他问题，请告诉我