java – Initialize方法在Main类中的指定方法之前运行
内容导读
互联网集市收集整理的这篇技术教程文章主要介绍了java – Initialize方法在Main类中的指定方法之前运行，小编现在分享给大家，供广大互联网技能从业者学习和参考。文章包含11828字，纯文字阅读大概需要17分钟。
内容图文
我试图将一个对象从一个控制器传递到另一个控制器.我传入BookViewController的rowData-object对初始化方法起作用至关重要,如果没有设置数据,那么NullPointerException确实会发生在我的情况下.
似乎initialize-method在setRowData-method之前运行.正如我所说,initialize-method依赖于setRowData-method已执行.
我在这里错过了什么？
Main.java
public class Main extends Application {
private static Stage primaryStage;
private static BorderPane mainLayout;
@Override
public void start(Stage primaryStage) throws Exception {
Main.primaryStage = primaryStage;
Main.primaryStage.setTitle("BookingApp");
showMainView();
}
private void showMainView() throws IOException {
FXMLLoader loader = new FXMLLoader();
loader.setLocation(Main.class.getResource("MainView.fxml"));
mainLayout = loader.load();
Scene scene = new Scene(mainLayout);
primaryStage.setScene(scene);
primaryStage.show();
}
public static void showBookView(Trip rowData) throws IOException {
FXMLLoader loader = new FXMLLoader();
loader.setLocation(Main.class.getResource("BookView.fxml"));
BorderPane bookTrip = loader.load();
BookViewController bvc = loader.getController();
// The below method never runs.. why?
bvc.setRowData(rowData);
Stage bookStage = new Stage();
bookStage.setTitle("BookingApp");
bookStage.initModality(Modality.WINDOW_MODAL);
bookStage.initOwner(primaryStage);
Scene scene = new Scene(bookTrip);
bookStage.setScene(scene);
bookStage.showAndWait();
}
public static void main(String[] args) {
launch(args);
}
}
BookViewController.java
public class BookViewController implements Initializable {
private String dbUrl = "jdbc:postgresql://localhost:5432/BookingApp";
private String dbUsername = "postgres";
private String dbPassword = "secret";
@FXML
private TextField personnr;
@FXML
private TextField name;
@FXML
private TextField email;
@FXML
private TextField telnr;
@FXML
private Button addTraveler;
@FXML
private Button removeTraveler;
@FXML
private TableView<Traveler> travelers;
@FXML
private TableColumn<?, ?> personnrColumn;
@FXML
private TableColumn<?, ?> nameColumn;
@FXML
private TableColumn<?, ?> emailColumn;
@FXML
private TableColumn<?, ?> telnrColumn;
@FXML
private TableView<Trip> trips;
@FXML
private TableColumn<?, ?> originColumn;
@FXML
private TableColumn<?, ?> destinationColumn;
@FXML
private TableColumn<?, ?> departureColumn;
@FXML
private TableColumn<?, ?> arrivalColumn;
@FXML
private TableColumn<?, ?> driverColumn;
@FXML
private TableColumn<?, ?> priceAmountColumn;
@FXML
private TableColumn<?, ?> seatsColumn;
@FXML
private Button bookTrip;
private Trip rowData;
private ObservableList<Trip> tripData;
public void setRowData(Trip rowData) {
this.rowData = rowData;
// The below println is never printed to the console..
System.out.println("Test");
}
@Override
public void initialize(URL arg0, ResourceBundle arg1) {
addTraveler.setDisable(true);
removeTraveler.setDisable(true);
populateTravelPlan();
}
@FXML
private void populateTravelPlan() {
try {
Connection conn = DriverManager.getConnection(dbUrl, dbUsername, dbPassword);
tripData = FXCollections.observableArrayList();
ResultSet rs = null;
System.out.println(rowData.getTrip1()); // Here it breaks
System.out.println(rowData.getTrip2());
System.out.println(rowData.getTrip3());
if(rowData.getTrip1() != 0 && rowData.getTrip2() == 0 && rowData.getTrip3() == 0) {
rs = conn.createStatement().executeQuery(
"select trip.tripid, connexion.origin, connexion.destination, trip.departure, trip.arrival, trip.driverpnr, trip.priceamount, trip.seats\r\n" +
"from trip, connexion\r\n" +
"where trip.tripid = " + rowData.getTrip1() + "\r\n" +
"and trip.connexionid = connexion.connexionid\r\n" +
"order by departure;");
} else if(rowData.getTrip1() != 0 && rowData.getTrip2() != 0 && rowData.getTrip3() == 0) {
rs = conn.createStatement().executeQuery(
"select trip.tripid, connexion.origin, connexion.destination, trip.departure, trip.arrival, trip.driverpnr, trip.priceamount, trip.seats\r\n" +
"from trip, connexion\r\n" +
"where trip.tripid = " + rowData.getTrip1() + "\r\n" +
"and trip.connexionid = connexion.connexionid\r\n" +
"union\r\n" +
"select trip.tripid, connexion.origin, connexion.destination, trip.departure, trip.arrival, trip.driverpnr, trip.priceamount, trip.seats\r\n" +
"from trip, connexion\r\n" +
"where trip.tripid = " + rowData.getTrip2() + "\r\n" +
"and trip.connexionid = connexion.connexionid\r\n" +
"order by departure;");
} else if(rowData.getTrip1() != 0 && rowData.getTrip2() != 0 && rowData.getTrip3() != 0) {
rs = conn.createStatement().executeQuery(
"select trip.tripid, connexion.origin, connexion.destination, trip.departure, trip.arrival, trip.driverpnr, trip.priceamount, trip.seats\r\n" +
"from trip, connexion\r\n" +
"where trip.tripid = " + rowData.getTrip1() + "\r\n" +
"and trip.connexionid = connexion.connexionid\r\n" +
"union\r\n" +
"select trip.tripid, connexion.origin, connexion.destination, trip.departure, trip.arrival, trip.driverpnr, trip.priceamount, trip.seats\r\n" +
"from trip, connexion\r\n" +
"where trip.tripid = " + rowData.getTrip2() + "\r\n" +
"and trip.connexionid = connexion.connexionid\r\n" +
"union\r\n" +
"select trip.tripid, connexion.origin, connexion.destination, trip.departure, trip.arrival, trip.driverpnr, trip.priceamount, trip.seats\r\n" +
"from trip, connexion\r\n" +
"where trip.tripid = " + rowData.getTrip3() + "\r\n" +
"and trip.connexionid = connexion.connexionid\r\n" +
"order by departure;");
}
tripData.add(new Trip(rs.getInt(1), rs.getString(2), rs.getString(3), ""+rs.getTimestamp(4), ""+rs.getTimestamp(5), rs.getString(6), ""+rs.getInt(7), ""+rs.getInt(8)));
while(rs.next()) {
tripData.add(new Trip(rs.getInt(1), rs.getString(2), rs.getString(3), ""+rs.getTimestamp(4), ""+rs.getTimestamp(5), rs.getString(6), ""+rs.getInt(7), ""+rs.getInt(8)));
}
} catch (SQLException e) {
e.printStackTrace();
}
trips.setItems(tripData);
}
}
例外
javafx.fxml.LoadException:
/C:/Users/David/Desktop/eclipse/BookingApp1/bin/booking/BookView.fxml
at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2601)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2579)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2441)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2409)
at booking.Main.showBookView(Main.java:35)
at booking.MainViewController$1.handle(MainViewController.java:227)
at booking.MainViewController$1.handle(MainViewController.java:1)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.scene.Scene$ClickGenerator.postProcess(Scene.java:3470)
at javafx.scene.Scene$ClickGenerator.access$8100(Scene.java:3398)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3766)
at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:381)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$353(GlassViewEventHandler.java:417)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:416)
at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
at com.sun.glass.ui.View.notifyMouse(View.java:937)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NullPointerException
at booking.BookViewController.populateTravelPlan(BookViewController.java:109)
at booking.BookViewController.initialize(BookViewController.java:100)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2548)
... 39 more
解决方法:
It seems that the initialize-method runs BEFORE the setRowData-method.
这确实是对的.作为执行load()的一部分,FXMLLoader调用initialize()方法,这必须在你有机会调用setRowData(…)之前发生.
What am I missing out on here?
真的没什么.
有几种可能的修复方法.一种是简单地避免让initialize()方法依赖于传递给setRowData()的数据,并将依赖于这些数据的任何代码移动到后一种方法.在这种情况下,这非常简单：
public void setRowData(Trip rowData) {
this.rowData = rowData;
populateTravelPlan();
}
@Override
public void initialize(URL arg0, ResourceBundle arg1) {
addTraveler.setDisable(true);
removeTraveler.setDisable(true);
// don't do this here:
// populateTravelPlan();
}
如果您不喜欢该解决方案,另一个选择是将控制器设置为代码而不是FXML.简而言之,您将从FXML文件中删除fx：controller属性,然后在加载FXML时,创建一个控制器实例,调用setRowData()(或以其他方式初始化行数据,例如通过构造函数),并调用setController( )在FXMLLoader上.该解决方案在Passing Parameters JavaFX FXML中详细描述.
该解决方案的一个缺点是,如果您使用Scene Builder进行FXML设计,Scene Builder将失去一些功能(因为它不再知道用于创建控制器的类).如果要保留该功能,可以使用控制器工厂.
对于该解决方案,我将修改控制器,以便将行数据传递给构造函数：
public class BookViewController implements Initializable {
// @FXML-annotated fields omitted...
private final Trip rowData;
public BookViewController(Trip rowData) {
this.rowData = rowData ;
}
// remove this, it is now initialized in the constructor
// public void setRowData(Trip rowData) {
// this.rowData = rowData;
// // The below println is never printed to the console..
// System.out.println("Test");
// }
@Override
public void initialize(URL arg0, ResourceBundle arg1) {
addTraveler.setDisable(true);
removeTraveler.setDisable(true);
populateTravelPlan();
}
// etc...
}
此构造函数将阻止FXMLLoader使用其默认方法创建控制器实例,因此向加载器提供控制器工厂以覆盖控制器的创建方式：
public static void showBookView(Trip rowData) throws IOException {
FXMLLoader loader = new FXMLLoader();
loader.setLocation(Main.class.getResource("BookView.fxml"));
loader.setControllerFactory(type -> {
if (type == BookViewController.class) {
return new BookViewController(rowData);
}
// default behavior: need this in case there are <fx:include> in the FXML
try {
return type.getConstructor().newInstance();
} catch (Exception exc) {
// fatal...
throw new RuntimeException(exc);
}
});
BorderPane bookTrip = loader.load();
Stage bookStage = new Stage();
bookStage.setTitle("BookingApp");
bookStage.initModality(Modality.WINDOW_MODAL);
bookStage.initOwner(primaryStage);
Scene scene = new Scene(bookTrip);
bookStage.setScene(scene);
bookStage.showAndWait();
}
内容总结
以上是互联网集市为您收集整理的java – Initialize方法在Main类中的指定方法之前运行全部内容，希望文章能够帮你解决java – Initialize方法在Main类中的指定方法之前运行所遇到的程序开发问题。 如果觉得互联网集市技术教程内容还不错，欢迎将互联网集市网站推荐给程序员好友。
内容备注
版权声明：本文内容由互联网用户自发贡献，该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容， 请发送邮件至 gblab@vip.qq.com 举报，一经查实，本站将立刻删除。
内容手机端
扫描二维码推送至手机访问。
来源：【匿名】