NullPointerException异常JavaFX中初始化TableView中

Question

我有这个控制器类显示一个TableView中数据库查询，但我有NullPointerException异常的错误与“setCellValueFactory（新PropertyValueFactory”

package aplicativo; 

import java.net.URL; 
import java.util.ResourceBundle; 

import javafx.collections.FXCollections; 
import javafx.collections.ObservableList; 
import javafx.fxml.FXML; 
import javafx.fxml.Initializable; 
import javafx.scene.control.Button; 
import javafx.scene.control.TableColumn; 
import javafx.scene.control.TableView; 
import javafx.scene.control.TextField; 
import javafx.scene.control.cell.PropertyValueFactory; 

public class Controle implements Initializable{ 
    @FXML 
    private TextField txtCampo,txtCampo2; 
    @FXML 
    private Button btAdicionar,btConsultar; 
    @FXML 
    private TableView<Pessoa> tabValues; 
    @FXML 
    private TableColumn<Pessoa, Integer> tbcCod; 
    private TableColumn<Pessoa, String>tbcNome; 
    ObservableList<Pessoa> List = FXCollections.observableArrayList(); 
    @FXML 
    private void btAdd(){ 
     insertBD a = new insertBD(txtCampo.getText()); 
     consultaBD b = new consultaBD(); 
     List = b.consultaTudo(); 
     tabValues.setItems(List); 
     txtCampo.clear(); 
    } 
    @FXML 

    private void btCons(){ 
     String tx = txtCampo2.getText(); 
     if(tx.isEmpty()){ 

     }else{ 
     consultaBD a = new consultaBD(); 
     a.consultaParecido(tx, "nome"); 
     txtCampo2.clear(); 
     } 
    } 
    @Override 
    public void initialize(URL arg0, ResourceBundle arg1) { 

     // TODO Auto-generated method stub 
     tbcCod.setCellValueFactory(new PropertyValueFactory<Pessoa, Integer>("cod")); 
     tbcNome.setCellValueFactory(new PropertyValueFactory<Pessoa, String>("nome")); 
     tabValues.setItems(List); 
     tabValues.getColumns().addAll(tbcCod,tbcNome); 
    } 
} 

的NullPointerExcepetion：

Exception in Application start method 
java.lang.reflect.InvocationTargetException 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
    at java.lang.reflect.Method.invoke(Unknown Source) 
    at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(Unknown Source) 
    at com.sun.javafx.application.LauncherImpl.launchApplication(Unknown Source) 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) 
    at java.lang.reflect.Method.invoke(Unknown Source) 
    at sun.launcher.LauncherHelper$FXHelper.main(Unknown Source) 
Caused by: java.lang.RuntimeException: Exception in Application start method 
    at com.sun.javafx.application.LauncherImpl.launchApplication1(Unknown Source) 
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$152(Unknown Source) 
    at com.sun.javafx.application.LauncherImpl$$Lambda$50/1645995473.run(Unknown Source) 
    at java.lang.Thread.run(Unknown Source) 
Caused by: javafx.fxml.LoadException: 
/C:/Users/lucas/workspace/BDFX/bin/aplicativo/Tela.fxml 

    at javafx.fxml.FXMLLoader.constructLoadException(Unknown Source) 
    at javafx.fxml.FXMLLoader.loadImpl(Unknown Source) 
    at javafx.fxml.FXMLLoader.loadImpl(Unknown Source) 
    at javafx.fxml.FXMLLoader.loadImpl(Unknown Source) 
    at javafx.fxml.FXMLLoader.loadImpl(Unknown Source) 
    at javafx.fxml.FXMLLoader.loadImpl(Unknown Source) 
    at javafx.fxml.FXMLLoader.loadImpl(Unknown Source) 
    at javafx.fxml.FXMLLoader.loadImpl(Unknown Source) 
    at javafx.fxml.FXMLLoader.load(Unknown Source) 
    at aplicativo.Main.start(Main.java:13) 
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$159(Unknown Source) 
    at com.sun.javafx.application.LauncherImpl$$Lambda$53/1031257736.run(Unknown Source) 
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$172(Unknown Source) 
    at com.sun.javafx.application.PlatformImpl$$Lambda$45/186276003.run(Unknown Source) 
    at com.sun.javafx.application.PlatformImpl.lambda$null$170(Unknown Source) 
    at com.sun.javafx.application.PlatformImpl$$Lambda$48/1529876784.run(Unknown Source) 
    at java.security.AccessController.doPrivileged(Native Method) 
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$171(Unknown Source) 
    at com.sun.javafx.application.PlatformImpl$$Lambda$47/237061348.run(Unknown Source) 
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(Unknown Source) 
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method) 
    at com.sun.glass.ui.win.WinApplication.lambda$null$145(Unknown Source) 
    at com.sun.glass.ui.win.WinApplication$$Lambda$36/2117255219.run(Unknown Source) 
    ... 1 more 
Caused by: java.lang.NullPointerException 
    at aplicativo.Controle.initialize(Controle.java:52) 
    ... 23 more 
Exception running application aplicativo.Main 

任何解决方案？

Answer 1

一个在你的控制器实例字段是缺少@FXML注解。仙如果该字段是私有的，则FXML加载程序无法在加载期间将控制引用注入该字段。以下是您的实例字段声明：

@FXML 
private TextField txtCampo,txtCampo2; 

@FXML 
private Button btAdicionar,btConsultar; 

@FXML 
private TableView<Pessoa> tabValues; 

@FXML 
private TableColumn<Pessoa, Integer> tbcCod; 

private TableColumn<Pessoa, String>tbcNome; 

请注意，最后一个字段tbcNome没有注释。因此，调用初始化方法时，tbcNome字段包含null引用，导致异常。

要解决您的问题，您可能需要做的就是将@FXML注释添加到tbcNome的实例字段声明中。

你可能鼓励这个错误，采用在你的类型声明中列出多个变量的习惯，例如。 private Button btAdicionar, btConsultar;。在我看来，这是一个坏习惯，可以鼓励这样的错误发生。我建议你尝试采用每种实例字段都有自己的类型声明语句的编码风格。