Question

将选项添加到我的选择框的简单尝试会产生InvocationTargetException。我真的不明白为什么抛出这个异常的原因，所以解释和解决方案会很棒！这是我在FXMLDocumentController类中的代码：

public class FXMLDocumentController implements Initializable {

    @FXML
    private ChoiceBox<?> pilot;

    public FXMLDocumentController(){  

         setMembersList();
    }


    private void setMembersList(){
        List<String> list = new ArrayList<String>();
        list.add("Item A");
        list.add("Item B");
        list.add("Item C");
        ObservableList obList = FXCollections.observableList(list);
        pilot.setItems(obList);
    }
}

这是我得到的......：

Exception in Application start method

java.lang.reflect.InvocationTargetException

    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:367)
    at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:305)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.RuntimeException: Exception in Application start method
    at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:894)
    at com.sun.javafx.application.LauncherImpl.access$000(LauncherImpl.java:56)
    at com.sun.javafx.application.LauncherImpl$1.run(LauncherImpl.java:158)
    at java.lang.Thread.run(Thread.java:745)

使用试验和错误时，行pilot.setItems(obList);中肯定会抛出异常，因为它在没有任何异常时启动，当我摆脱这一行时。

Answer 1

在调用构造函数时，FXML - 注入的ChoiceBox将不会被初始化，因此您将获得NullPointerException（pilot为null ）。

相反，从initialize()方法调用您的代码。我还要正确输入您的ChoiceBox和ObservableList：

public class FXMLDocumentController {

    @FXML
    private ChoiceBox<String> pilot;

    public void initialize(){  

         setMembersList();
    }


    private void setMembersList(){
        List<String> list = new ArrayList<String>();
        list.add("Item A");
        list.add("Item B");
        list.add("Item C");
        ObservableList<String> obList = FXCollections.observableList(list);
        pilot.setItems(obList);
    }
}

Answer 2

从构造函数中删除ChoiceBox对象（基本上是在FXML文件中定义的每个对象）初始化，并将其置于（最佳）initialize方法中。

尝试使用javafx将项目分配给选择框时发生InvocationTargetException

2 个答案: