我正在一个项目上，我需要为MySQL数据库的每一行添加一个带有3个ComboBox的HBox到VBox。
我已经尝试过一些方法，但是总是出错。所以我尝试了诸如动态变量名之类的方法。
@FXML
private VBox mon_routes;
public void initialize(URL url, ResourceBundle rb) {
PreparedStatement pr;
ResultSet rs;
String sql = "SELECT * FROM routes";
try {
pr = this.connection.prepareStatement(sql);
rs = pr.executeQuery();
int n = 1;
HBox r[] = new HBox[n];
while (rs.next()) {
r[n].getChildren().add(new CheckBox());
r[n].getChildren().add(new ComboBox());
r[n].getChildren().add(new ComboBox());
mon_routes.getChildren().add(r[n]);
n++;
}
} catch (SQLException e1) {
e1.printStackTrace();
}
}
我希望获得具有7个HBox的VBox，因为我的数据库有7行。 但是我只会遇到很多错误。
javafx.fxml.LoadException:
unknown path
at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2601)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2579)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2425)
at loginapp.LoginController.adminLogin(LoginController.java:110)
at loginapp.LoginController.login(LoginController.java:92)
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.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1769)
at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1657)
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.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.scene.Node.fireEvent(Node.java:8411)
at javafx.scene.control.Button.fire(Button.java:185)
at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
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.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$MouseHandler.process(Scene.java:3757)
at javafx.scene.Scene$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$MouseEventNotification.run(GlassViewEventHandler.java:394)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$358(GlassViewEventHandler.java:432)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:431)
at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
at com.sun.glass.ui.View.notifyMouse(View.java:937)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$152(WinApplication.java:177)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NullPointerException
at adminapp.AdminController.initialize(AdminController.java:56)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2548)
... 61 more
Process finished with exit code 0
答案 0 :(得分：1)
除非必须这样做，否则应避免使用Arrays。我会使用List中的HBoxes。您的代码应类似于以下代码。阅读代码中的注释。
VBox mon_routes = new VBox(); //You never create the VBox. This leads to a null pointer exception.
@Override
public void initialize(URL url, ResourceBundle rb) {
// TODO
PreparedStatement pr;
ResultSet rs;
String sql = "SELECT * FROM routes";
try {
pr = this.connection.prepareStatement(sql);
rs = pr.executeQuery();
List<HBox> r = new ArrayList();//Avoid Arrays. Use List instead.
while (rs.next()) {
HBox tempHBox = new HBox();//Create an HBox to store into the List or Array if you continue to use the Array.
tempHBox.getChildren().add(new CheckBox(rs.getString(0)));//You never retrieve anything from the result set. <- rs.getSomething(). Add the CheckBox to the HBox
tempHBox.getChildren().add(new CheckBox(rs.getString(1)));//You never retrieve anything from the result set. <- rs.getSomething(). Add the CheckBox to the HBox
tempHBox.getChildren().add(new CheckBox(rs.getString(2)));//You never retrieve anything from the result set. <- rs.getSomething(). Add the CheckBox to the HBox
r.add(tempHBox);//Add the HBox to the List
}
mon_routes.getChildren().addAll(r);//Add the List of HBox to the VBox.
} catch (SQLException e1) {
e1.printStackTrace();
}
}
答案 1 :(得分：0)
r[]的大小为1，添加第二个hbox会使事情中断。您可能只想创建一个List<HBox>。最好的办法可能是为要重复的组件和一个控制器创建一个FXML。创建一个基于传入的行来初始化值的方法。那么您只需创建该自定义视图并将其添加到每行的VBox中即可。