更新列表视图

Question

我正在更新我的GUI的列表视图并发出以下错误：＆＃39;线程中的异常＆＃34; JavaFX应用程序线程＆＃34;显示java.lang.NullPointerException＆＃39;我这样做了：

            // loading the existing notebooks
            File file = new File(System.getProperty("user.home") +
                            "/Documents/Pappel");

            String[] directories = file.list(new FilenameFilter() {
                    @Override
                    public boolean accept(File current, String name) {
                            return new File(current, name).isDirectory();
                    }
            });

            int i = 0;
            while (i < directories.length){
                    notebooksContainer.getItems().add(directories[i]);
                    i ++;
            }

错误发生在＆＃39; notebooksContainer.getItems（）。add（notebookTitle）;＆＃39;。 notebooksContainer是一个listView，它使用字符串填充，也可以从不同的类继承。此外，notebookTitle不为null，因为它由print语句打印。有什么想法吗？

这是我在要扩展的类中填充视图列表的位置。

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.geometry.*?>
<?import javafx.scene.text.*?>
<?import javafx.scene.image.*?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>

<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="600.0" prefWidth="1000.0" xmlns="http://javafx.com/javafx/8.0.65" xmlns:fx="http://javafx.com/fxml/1" fx:controller="PappelNotebookController">
   <children>
      <VBox layoutX="10.0" layoutY="51.0" prefHeight="512.0" prefWidth="137.0" spacing="5.0" AnchorPane.bottomAnchor="37.0" AnchorPane.topAnchor="51.0">
         <children>
            <HBox fx:id="notebooks" alignment="CENTER_LEFT" prefHeight="44.0" prefWidth="106.0" spacing="10.0">
               <children>
              <ImageView fitHeight="37.0" fitWidth="34.0" pickOnBounds="true" preserveRatio="true">
                     <image>
                    <Image url="@open-iconic-master/png/book-8x.png" />
                     </image>
                   </ImageView>
                 <Label text="Notebooks">
                   <font>
                        <Font size="15.0" />
                    </font>
                  </Label>
               </children>
            </HBox>
        <HBox fx:id="notes" alignment="CENTER_LEFT" prefHeight="44.0" prefWidth="205.0" spacing="10.0">
           <children>
              <ImageView fitHeight="37.0" fitWidth="34.0" pickOnBounds="true" preserveRatio="true">
                 <image>
                    <Image url="@open-iconic-master/png/document-8x.png" />
                 </image>
              </ImageView>
              <Label text="Notes">
                 <font>
                    <Font size="15.0" />
                 </font>
              </Label>
           </children>
        </HBox>
          </children>
         <padding>
            <Insets bottom="5.0" left="5.0" right="5.0" top="5.0" />
     </padding>
  </VBox>
  <Label layoutX="56.0" layoutY="24.0" text="Library" />
  <TextArea fx:id="noteContent" layoutX="370.0" layoutY="80.0" prefHeight="512.0" prefWidth="622.0" promptText="Start writing!" AnchorPane.bottomAnchor="8.0" AnchorPane.leftAnchor="370.0" AnchorPane.rightAnchor="8.0" AnchorPane.topAnchor="80.0" />
  <TextField fx:id="noteTitle" layoutX="370.0" layoutY="23.0" prefHeight="26.0" prefWidth="247.0" promptText="Title" AnchorPane.leftAnchor="370.0" AnchorPane.rightAnchor="383.0">
     <font>
        <Font size="25.0" />
     </font>
  </TextField>
  <Label layoutX="215.0" layoutY="24.0" text="Notebooks" />
  <HBox fx:id="addNotebook" alignment="CENTER" layoutX="147.0" layoutY="557.0" prefHeight="35.0" prefWidth="205.0" spacing="10.0" AnchorPane.bottomAnchor="8.0">
     <children>
        <ImageView fitHeight="26.0" fitWidth="24.0" pickOnBounds="true" preserveRatio="true">
           <image>
              <Image url="@open-iconic-master/png/plus-8x.png" />
           </image>
        </ImageView>
        <Label text=" New notebook">
           <font>
              <Font size="15.0" />
           </font>
        </Label>
     </children>
  </HBox>
  <ListView fx:id="notebooksContainer" layoutX="158.0" layoutY="49.0" prefHeight="503.0" prefWidth="185.0" AnchorPane.bottomAnchor="48.0" AnchorPane.topAnchor="49.0" />
   </children>
</AnchorPane>

这是我的fxml：

cont.push