我们是JavaFX和Scene Builder的新手，并且遇到以下问题。
如果我们在FXML文档中定义我们的控制器（使用Scene Builder创建），我们会在下面发布异常。
在这里，您可以看到我们的Application，Controller和FXML文档类的代码。
申请类：
public class Projekt5 extends Application {
public static Connection c= null;
private static final String driverClass = "com.mysql.jdbc.Driver";
private static final String connectionDescriptor = "jdbc:mysql://i-med-ts:3306/md_projekt";
private static String user= "root";
private static String password= "root";
public void start(Stage stage) throws Exception {
try{
c = DriverManager.getConnection(connectionDescriptor, user,password);
System.out.println("Connection");
}
catch (SQLException e) {
Alert alert = new Alert(AlertType.INFORMATION);
alert.setTitle("Information");
alert.setHeaderText(null);
alert.setContentText("A database error occured.");
alert.showAndWait();
}
FXMLLoader loader= new FXMLLoader(getClass().getResource("/projekt5/FXMLDocument.fxml"));
loader.setController(new FXMLDocumentController(c));
AnchorPane root = loader.load();
FXMLDocumentController control = new FXMLDocumentController(c);
Scene scene = new Scene(root);
stage.setScene(scene);
stage.show();
}
public static void main(String[] args) {
launch(args);
}
}
控制器类：
public class FXMLDocumentController implements Initializable {
Connection c=null;
private static PreparedStatement getUser = null;
private static ResultSet rs = null;
private TextField textName;
private TextField textPassword;
private Label nameLabel;
private Label label;
private Button button;
public FXMLDocumentController (Connection con) {
c = con;
}
public void loginApplication(ActionEvent event) {
String Name = textName.getText();
String Password = textPassword.getText();
String queryCheck = "SELECT * "+ "FROM user_tab " + " WHERE user_id = ? "+ " and pw = ?";
try {
getUser = c.prepareStatement(queryCheck);
getUser.setString (1, Name);
getUser.setString (2, Password);
rs = getUser.executeQuery();
while (rs.next())
{
String name = rs.getString("user_id");
String pw = rs.getString("pw");
}
} catch (SQLException e1) {
Alert alert = new Alert(AlertType.INFORMATION);
alert.setTitle("Information");
alert.setHeaderText(null);
alert.setContentText("A database error occured.");
alert.showAndWait();
}
}
public void handle(ActionEvent event) {
throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
}
@Override
public void initialize(URL location, ResourceBundle resources) {
throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
}
}
FXML（使用场景构建器创建）：
<AnchorPane id="AnchorPane" prefHeight="600.0" prefWidth="900.0" xmlns:fx="http://javafx.com/fxml/1" fx:controller="projekt5.FXMLDocumentController">
<children>
<VBox layoutX="228.0" layoutY="100.0" prefHeight="208.0" prefWidth="425.0">
<children>
<GridPane>
<columnConstraints>
<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 minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints maxHeight="24.0" minHeight="10.0" prefHeight="14.0" vgrow="SOMETIMES" />
<RowConstraints maxHeight="46.0" minHeight="10.0" prefHeight="46.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
</rowConstraints>
<children>
<Label fx:id="nameLabel" prefHeight="30.0" prefWidth="61.0" text="Name" textOverrun="CLIP" GridPane.rowIndex="2">
<opaqueInsets>
<Insets />
</opaqueInsets>
</Label>
<Label fx:id="label" minHeight="16" minWidth="69" text="Password" GridPane.rowIndex="4" />
<TextField fx:id="textName" GridPane.columnIndex="1" GridPane.rowIndex="2" />
<TextField fx:id="textPassword" GridPane.columnIndex="1" GridPane.rowIndex="4" />
</children>
</GridPane>
</children>
</VBox>
<Button fx:id="button" contentDisplay="CENTER" layoutX="381.0" layoutY="352.0" onAction="#loginApplication" prefHeight="51.0" prefWidth="126.0" text="Log in " textAlignment="CENTER">
<effect>
<Blend />
</effect>
<contextMenu>
<ContextMenu>
<items>
<MenuItem mnemonicParsing="false" text="Unspecified Action" />
</items>
</ContextMenu>
</contextMenu>
</Button>
</children>
<effect>
<Blend />
</effect>
</AnchorPane>
引发此异常：
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:498)
at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
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:498)
at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.RuntimeException: Exception in Application start method
at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$155(LauncherImpl.java:182)
at java.lang.Thread.run(Thread.java:745)
Caused by: javafx.fxml.LoadException: Controller value already specified.
file:/home/aadalen/NetBeansProjects/projekt5/dist/run550935368/projekt5.jar!/projekt5/FXMLDocument.fxml:16
at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2597)
at javafx.fxml.FXMLLoader.access$100(FXMLLoader.java:103)
at javafx.fxml.FXMLLoader$ValueElement.processAttribute(FXMLLoader.java:914)
at javafx.fxml.FXMLLoader$InstanceDeclarationElement.processAttribute(FXMLLoader.java:971)
at javafx.fxml.FXMLLoader$Element.processStartElement(FXMLLoader.java:220)
at javafx.fxml.FXMLLoader$ValueElement.processStartElement(FXMLLoader.java:744)
at javafx.fxml.FXMLLoader.processStartElement(FXMLLoader.java:2707)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2527)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2441)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2409)
at projekt5.Projekt5.start(Projekt5.java:49)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$162(LauncherImpl.java:863)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$175(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
at com.sun.glass.ui.gtk.GtkApplication.lambda$null$49(GtkApplication.java:139)
... 1 more
Exception running application projekt5.Projekt5
Java Result: 1