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所以，我正在做一個JavaFX多視圖GUI應用程序。多屏幕java.lang.NullPointerException JavaFX/FXML
下面是代碼，以便您可以參考它，不要讀通過它找到一個錯誤的是，我將解釋第一下面的問題;）
我有一個主要的 - 這將啓動應用程序
public class MyFXMLMain extends Application {
@Override
public void start(Stage stage) throws Exception {
Parent root = FXMLLoader.load(getClass().getResource("Wireframe.fxml"));
stage.setTitle("My Fitness App");
Scene mainScene = new Scene(root,805,809);
stage.setScene(mainScene);
stage.show();
}
public static void main(String[] args) {
launch(args);
}
ScreensController - 控制加載/設置屏幕。
public class ScreensController extends StackPane {
private HashMap<String, Node> screens = new HashMap<>();
public ScreensController() {
super();
}
public void addScreen(String name, Node screen) {
screens.put(name, screen);
}
public Node getScreen(String name) {
return screens.get(name);
}
public boolean loadScreen(String name, String resource) {
try {
FXMLLoader myLoader = new FXMLLoader(getClass().getResource(resource));
Parent loadScreen = (Parent) myLoader.load();
ControlledScreen myScreenController = ((ControlledScreen) myLoader.getController());
myScreenController.setScreenParent(this);
addScreen(name, loadScreen);
return true;
}catch(Exception e) {
System.out.println(e.getMessage());
return false;
}
}
public boolean setScreen(final String name) {
if (screens.get(name) != null) { //screen loaded
final DoubleProperty opacity = opacityProperty();
if (!getChildren().isEmpty()) { //if there is more than one screen
Timeline fade = new Timeline(
new KeyFrame(Duration.ZERO, new KeyValue(opacity, 1.0)),
new KeyFrame(new Duration(1000), new EventHandler<ActionEvent>() {
@Override
public void handle(ActionEvent t) {
getChildren().remove(0); //remove the displayed screen
getChildren().add(0, screens.get(name)); //add the screen
Timeline fadeIn = new Timeline(
new KeyFrame(Duration.ZERO, new KeyValue(opacity, 0.0)),
new KeyFrame(new Duration(800), new KeyValue(opacity, 1.0)));
fadeIn.play();
}
}, new KeyValue(opacity, 0.0)));
fade.play();
} else {
setOpacity(0.0);
getChildren().add(screens.get(name)); //no one else been displayed, then just show
Timeline fadeIn = new Timeline(
new KeyFrame(Duration.ZERO, new KeyValue(opacity, 0.0)),
new KeyFrame(new Duration(2500), new KeyValue(opacity, 1.0)));
fadeIn.play();
}
return true;
} else {
System.out.println("screen hasn't been loaded!!! \n");
return false;
}
}
public boolean unloadScreen(String name) {
if (screens.remove(name) == null) {
System.out.println("Screen didn't exist");
return false;
} else {
return true;
}
}
}
屏幕框架 - 將屏幕鏈接到FXML文件。
一個FXML控制器 - 它鏈接到FXML文件並告訴FXML單擊某件事時該做什麼。
public class MyFXMLController implements ControlledScreen{
@FXML private TextField givenName;
@FXML private Text targetText;
//@FXML private static TableView<Mass> theTable;
//@FXML private static TableColumn<Mass, String> dateCol;
//@FXML private static TableColumn<Mass, String> massCol;
@FXML private static LineChart<Number,Number> weightChart;
@FXML private static NumberAxis axisX;
@FXML private static NumberAxis axisY;
@FXML private static Label myLabel;
//private static User theUser = new User();
private static ScreensController myController;
@Override
public void setScreenParent(ScreensController screenPage) {
myController = screenPage;
}
@FXML protected void handlePressedCalendarButtonAction(ActionEvent event){
System.out.println("Hello");
}
@FXML protected void mouseclickedcal(MouseEvent mec){
myController.setScreen(ScreensFramework.calendarScreen);
}
}
一個controlledscreen - 做這個：
public interface ControlledScreen {
public void setScreenParent(ScreensController screenPage);
}
而且一個CalendarScreenController - 一個控制多屏幕
public class CalendarScreenController implements Initializable, ControlledScreen {
ScreensController myController;
@Override
public void initialize(URL url, ResourceBundle rb) {
}
public void setScreenParent(ScreensController screenParent){
myController = screenParent;
}
@FXML
private void goToMain(ActionEvent event){
myController.setScreen(ScreensFramework.MAIN_SCREEN);
}
}
問題BELOW
當我運行我的程序中的一個它工作正常，但如果我點擊一個按鈕激活日曆onclick代碼在這裏：
@FXML protected void mouseclickedcal(MouseEvent mec){
myController.setScreen(ScreensFramework.calendarScreen);
}
應設定屏幕爲CalendarScreen.fxml，我的多屏幕之一，而是，它會導致如下的錯誤：125
java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(Unknown Source)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventUtil.fireEventImpl(Unknown Source)
at com.sun.javafx.event.EventUtil.fireEvent(Unknown Source)
at javafx.event.Event.fireEvent(Unknown Source)
at javafx.scene.Scene$ClickGenerator.postProcess(Unknown Source)
at javafx.scene.Scene$ClickGenerator.access$8600(Unknown Source)
at javafx.scene.Scene$MouseHandler.process(Unknown Source)
at javafx.scene.Scene$MouseHandler.process(Unknown Source)
at javafx.scene.Scene$MouseHandler.access$1900(Unknown Source)
at javafx.scene.Scene.impl_processMouseEvent(Unknown Source)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Unknown Source)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(Unknown Source)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(Unknown Source)
at com.sun.glass.ui.View.handleMouseEvent(Unknown Source)
at com.sun.glass.ui.View.notifyMouse(Unknown Source)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.access$100(Unknown Source)
at com.sun.glass.ui.win.WinApplication$3$1.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: 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 sun.reflect.misc.Trampoline.invoke(Unknown Source)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.reflect.misc.MethodUtil.invoke(Unknown Source)
... 31 more
Caused by: java.lang.NullPointerException
at myfxml.MyFXMLController.mouseclickedcal(MyFXMLController.java:125)
... 40 more
線是代碼：
@FXML protected void mouseclickedcal(MouseEvent mec){
myController.setScreen(ScreensFramework.calendarScreen);
}
非常感謝你看看這個。我似乎無法找到該錯誤;（