Question

我是JavaFX的初学者，希望能对您有所帮助。我正在创建GUI，该GUI具有一些按钮和带有日期和时间的标签，并且除一个例外外，其他所有功能均正常运行。当我尝试通过按钮打开新窗口时，出现一些错误NullPointerException。新窗口显示正确，但错误每隔1秒钟定期刷新一次，如日期和时间标签。日期和时间始终在GUI中正确显示。我知道问题出在哪里，但我不知道如何解决。

我有Main.java其中和FXMLDocumentController.java。 GUI.fxml包含在FXMLDocumentController中声明的Panes和Label。

public class FXMLDocumentController implements Initializable {


@FXML
public Pane close_button;
@FXML
public Pane MainPane;
@FXML
public Label dateTime;

@FXML
private void close_button(MouseEvent event) {
    Parent Close_window;
    try {
        Close_window = FXMLLoader.load(getClass().getResource("close_window.fxml"));
        Stage close_window = new Stage();
        close_window.setTitle("Potwierdzenie zamknięcia");
        close_window.setScene(new Scene(Close_window, 400, 100));
        close_window.show();
    } catch (IOException e) {
        e.printStackTrace();
    }
}
@FXML
private void close_confirm(MouseEvent event) {
    Platform.exit();
}
@FXML
private void close_cancel(MouseEvent event) {
    final Node close_window = (Node) event.getSource();
    final Stage Close_window = (Stage) close_window.getScene().getWindow();
    Close_window.close();
}

@FXML
private void initClock() {
    Timeline clock = new Timeline(new KeyFrame(Duration.seconds(0), e -> {
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        dateTime.setText(LocalDateTime.now().format(formatter));
    }), new KeyFrame(Duration.seconds(1)));
    clock.setCycleCount(Animation.INDEFINITE);
    clock.play();
}

@Override
public void initialize(URL url, ResourceBundle rb) {
    initClock();
}

Main.java

public class Main extends Application {

public static void main(String[] args) {
    launch(args);
}

@Override
public void init(){
System.out.println("Program opened");

}
@Override
public void start(Stage primaryStage) throws Exception{

    /*************OPENING MAIN WINDOW*****************/

    Parent login_window = FXMLLoader.load(getClass().getResource("GUI.fxml"));
    primaryStage.setTitle("Panel diagnostyczny");
    primaryStage.resizableProperty().setValue(Boolean.FALSE);
    primaryStage.initStyle(StageStyle.UNDECORATED);
    primaryStage.setScene(new Scene(login_window, 800, 600));
    primaryStage.show();

}
@Override
public void stop()
{
    System.out.println("Program stopped");
}

错误

Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at sample.FXMLDocumentController.lambda$initClock$0(FXMLDocumentController.java:136)
at com.sun.scenario.animation.shared.TimelineClipCore.visitKeyFrame(TimelineClipCore.java:226)
at com.sun.scenario.animation.shared.TimelineClipCore.playTo(TimelineClipCore.java:167)
at javafx.animation.Timeline.impl_playTo(Timeline.java:176)
at javafx.animation.AnimationAccessorImpl.playTo(AnimationAccessorImpl.java:39)
at com.sun.scenario.animation.shared.InfiniteClipEnvelope.timePulse(InfiniteClipEnvelope.java:126)
at javafx.animation.Animation.impl_timePulse(Animation.java:1102)
at javafx.animation.Animation$1.lambda$timePulse$24(Animation.java:186)
at java.security.AccessController.doPrivileged(Native Method)
at javafx.animation.Animation$1.timePulse(Animation.java:185)
at com.sun.scenario.animation.AbstractMasterTimer.timePulseImpl(AbstractMasterTimer.java:344)
at com.sun.scenario.animation.AbstractMasterTimer$MainLoop.run(AbstractMasterTimer.java:267)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:506)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:490)
at com.sun.javafx.tk.quantum.QuantumToolkit.lambda$runToolkit$346(QuantumToolkit.java:319)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
at com.sun.glass.ui.gtk.GtkApplication.lambda$null$450(GtkApplication.java:139)
at java.lang.Thread.run(Thread.java:748)

FXMLDocumentController的136行是dateTime.setText（LocalDateTime.now（）。format（formatter））;可能有问题，但我不知道有什么解决方案。

JavaFX NullPointerException打开新的阶段，在后台计时

0 个答案: