Question

我在将一些数据发送到另一个名为ValuesSubmitted.java的类文件时遇到了很大的麻烦，但是只能通过位于我的主Controller.java中的一种方法来发送数据。

我的问题是，在Controller.java类的所有其他区域中，我可以成功地将ValuesSubmitted.java类中的值设置为GET / GET。 ValuesSubmitted没有附加相应的FXML元素，因为ValuesSubmitted是用于数据源的。

请遵循我的代码，因为我的评论将进一步详细解释。

@FXML

    private void ResetPersonnel(){

        //Instantiating ValuesSubmitted java class
        ValuesSubmitted values = new ValuesSubmitted();

        try (Connection connection = DriverManager.getConnection(CONNECTION_STRING)) {


            //Fetching SQL DB - working as intended
            final String queryTitle = "SELECT * FROM PERSONNEL WHERE TRUCK_TYPE = '" + values.getTypeOfTruck() + "' AND TRUCK_NUMBER = '"
                                      + values.getTruckNumber() + "' AND SHIFT_COLOR = '" + values.getShiftColor()+"';";

            PreparedStatement statementTitle = connection.prepareStatement(queryTitle);

            String resultTitle;
            ResultSet resultSetTitle = statementTitle.executeQuery();
            while (resultSetTitle.next()) {

                // Each result
                resultTitle = resultSetTitle.getString("TITLE") + " " + resultSetTitle.getString("LAST_NAME");

                // THIS ADDS EACH ENTRY FOUND INTO OBSERVABLE "list" variable located in this Controller.java class.(this works.)
                list.add(resultTitle);

                // This is SUPPOSE to add each entry found into an observable list called "personnel" located in a single class file called ValuesSubmitted.java
                // ValuesSubmitted doesn't have a FXML page for it. It was intended for a data storage with all my setters and getters.
                values.setPersonnel(list);

            }

            // When I Sys-Out this line, it returns 0 upon this method being called.
            System.out.println(values.getPersonnel().size());

            // This is my ListView instance object with "list" being the variable of my observable list.
            // This populates my List view container successfully with the observable list located in Controller.java
            crewMembersList.setItems(list);

            /*
            My problem is that in all other areas of my Controller.java class I can successfully SET and GET values in my ValuesSubmitted.java class with no issues.
            Again, ValuesSubmitted not does have a corresponding FXML element attached to it, as ValuesSubmitted was intended for a data source.
             */

        } catch (SQLException e) {
            System.out.println(e.getMessage());
        }

    }

这是Controller.java中的另一种方法，可以成功将数据设置为ValuesSubmitted.java类。

@FXML

   private void addCrewMember() {

        //TODO FIX DUPLICATE ENTRIES WITH CASE SENSITIVITY
        TextInputDialog addPersonnel = new TextInputDialog();
        addPersonnel.setTitle("Personnel Names");
        addPersonnel.setHeaderText("Enter personnel title then last name.");
        addPersonnel.setContentText("ex. \"FF Smith\"");
        Optional<String> result = addPersonnel.showAndWait();

        if (result.isPresent() && !addPersonnel.getResult().isEmpty()) {
            values.setPersonnelMembers(addPersonnel.getResult());


        }

    // This line validates that the entry above was indeed added to the list.
        System.out.println(values.getPersonnel());

    }

Answer 1

list.add(resultTitle);

我想这是在ValuesSubmitted values中分配人员列表的中间步骤，没关系。我建议先检查其大小或打印元素。

对于似乎有问题的setPersonnel(List list)，请尝试将临时列表中的每个元素复制到ValuesSubmitted.personnelList。您可以使用java.util.ArrayList.addAll(Collection<? extends E> c)

的addAll方法

因此您需要类似values.getPersonnel().addAll(list);

Answer 2

这些方法之间的区别在于，第二个方法values是一个可能在其他用户交互期间填充的字段。

在第一种方法中，您创建一个存储在局部变量中的新鲜实例：

ValuesSubmitted values = new ValuesSubmitted();

此实例的属性可能未初始化。加载fxml时，您可能需要将实例传递给控制器，请参见Passing Parameters JavaFX FXML。

一件奇怪的事情是您在每次循环迭代中都传递了列表。您可能应该将此语句移出循环：

values.setPersonnel(list);

此外，由于list似乎是一个可重用的字段，因此在检索数据之前可能有必要清除它。

Java-FX非控制器类文件

2 个答案: