启动画面未加载 mainFxml 文件

Question

我正在尝试制作像这样的启动画面 SplashScreen ，但是我的代码不会加载 mainFxml.fxml ...每件事情都很好我认为启动画面加载得很好但是加载后我收到此错误：

`Exception in Application start method
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
    at istehkakat.Istehkakat.changed(Istehkakat.java:163)
    at istehkakat.Istehkakat.changed(Istehkakat.java:157)
    at com.sun.javafx.binding.ExpressionHelper$SingleChange.fireValueChangedEvent(ExpressionHelper.java:182)
    at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81)
    at javafx.beans.property.ObjectPropertyBase.fireValueChangedEvent(ObjectPropertyBase.java:105)
    at javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:112)
    at javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:145)
    at javafx.concurrent.Task.setState(Task.java:693)
    at javafx.concurrent.Task$TaskCallable.lambda$call3(Task.java:1420)
    at javafx.concurrent.Task$TaskCallable$$Lambda7/1990300023.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$null4(PlatformImpl.java:292)
    at com.sun.javafx.application.PlatformImpl$$Lambda/1527683020.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater5(PlatformImpl.java:291)
    at com.sun.javafx.application.PlatformImpl$$Lambda/1174361318.run(Unknown Source)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
    at com.sun.glass.ui.gtk.GtkApplication.lambda$null(GtkApplication.java:126)
    at com.sun.glass.ui.gtk.GtkApplication$$Lambda/1768305536.run(Unknown Source)
    at java.lang.Thread.run(Thread.java:745)
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:483)
    at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:363)
    at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:303)
    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:483)
    at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.RuntimeException: Exception in Application start method
    at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:875)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication7(LauncherImpl.java:157)
    at com.sun.javafx.application.LauncherImpl$$Lambda/1972439101.run(Unknown Source)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
    at istehkakat.Istehkakat.showMainStage(Istehkakat.java:130)
    at istehkakat.Istehkakat.start(Istehkakat.java:103)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication13(LauncherImpl.java:821)
    at com.sun.javafx.application.LauncherImpl$$Lambda4/86108265.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait6(PlatformImpl.java:323)
    at com.sun.javafx.application.PlatformImpl$$Lambda/1717159510.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$null4(PlatformImpl.java:292)
    at com.sun.javafx.application.PlatformImpl$$Lambda/1527683020.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater5(PlatformImpl.java:291)
    at com.sun.javafx.application.PlatformImpl$$Lambda/1174361318.run(Unknown Source)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
    at com.sun.glass.ui.gtk.GtkApplication.lambda$null(GtkApplication.java:126)
    at com.sun.glass.ui.gtk.GtkApplication$$Lambda/1768305536.run(Unknown Source)
    ... 1 more
Exception running application istehkakat.Istehkakat
Java Result: 1`

我的主要 java class 是：

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package istehkakat;

import controller.MainFxmlController;
import java.io.IOException;
import javafx.animation.FadeTransition;
import javafx.application.Application;
import javafx.application.Preloader;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.collections.ObservableList;
import javafx.concurrent.Task;
import javafx.concurrent.Worker;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.fxml.FXMLLoader;
import javafx.geometry.Pos;
import javafx.geometry.Rectangle2D;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.ProgressBar;
import javafx.scene.effect.DropShadow;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.Pane;
import javafx.scene.layout.VBox;
import javafx.scene.web.WebView;
import javafx.stage.Screen;
import javafx.stage.Stage;
import javafx.stage.StageStyle;
import javafx.stage.WindowEvent;
import javafx.util.Duration;

/**
 *
 * @author combozo
 */
public class Istehkakat extends Application {

    private Pane splashLayout;
    private ProgressBar loadProgress;
    private Label progressText;
    private Stage mainStage;
    private static final int SPLASH_WIDTH = 676;
    private static final int SPLASH_HEIGHT = 227;

    @Override
    public void init() {
        ImageView splash = new ImageView(new Image(getClass().getResourceAsStream("/imgs/SplashScreenIll.png")));
        loadProgress = new ProgressBar();
        loadProgress.setPrefWidth(SPLASH_WIDTH - 20);
        progressText = new Label("تحميل بيانات البرنامج ...");
        splashLayout = new VBox();
        splashLayout.getChildren().addAll(splash, loadProgress, progressText);
        progressText.setAlignment(Pos.CENTER);
        splashLayout.setStyle("-fx-padding: 5; -fx-background-color: cornsilk; -fx-border-width:5; -fx-border-color: linear-gradient(to bottom, chocolate, derive(chocolate, 50%));");
        splashLayout.setEffect(new DropShadow());
    }

    @Override
    public void start(Stage initStage) throws Exception {
        notifyPreloader(new Preloader.StateChangeNotification(Preloader.StateChangeNotification.Type.BEFORE_START));
        final Task preloaderTask = new Task() {
            @Override
            protected Object call() throws InterruptedException {
                updateMessage("Loading Chancecoin");
                /*  FXMLLoader fxmloader = new FXMLLoader();
                 Parent root = fxmloader.load(getClass().getResource("/views/mainFxml.fxml"));
                 MainFxmlController c = (MainFxmlController) fxmloader.getController();
                 Scene scene = new Scene(root);
                 //////////////////////


                 Rectangle2D primaryScreenBounds = Screen.getPrimary().getVisualBounds();


                 stage.getIcons().add(new Image(getClass().getResourceAsStream("/imgs/favIco.png")));

                 stage.setX(primaryScreenBounds.getMinX());
                 stage.setY(primaryScreenBounds.getMinY());
                 stage.setWidth(primaryScreenBounds.getWidth());
                 stage.setHeight(primaryScreenBounds.getHeight());
                 stage.setTitle("أستحــقاقــات");
                 /////////////////////////////////



                 stage.setScene(scene);
                 stage.show();

                 */
                return null;
            }
        };

        showSplash(initStage, preloaderTask);
        new Thread(preloaderTask).start();
        showMainStage();

    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        launch(args);
    }





    private void showMainStage() throws IOException {
        // create the scene
        FXMLLoader fxmloader = new FXMLLoader();
                 Parent root = fxmloader.load(getClass().getResource("/views/mainFxml.fxml"));
                 Scene scene = new Scene(root);
                 //////////////////////


                 Rectangle2D primaryScreenBounds = Screen.getPrimary().getVisualBounds();


                 mainStage.getIcons().add(new Image(getClass().getResourceAsStream("/imgs/favIco.png")));

                 mainStage.setX(primaryScreenBounds.getMinX());
                 mainStage.setY(primaryScreenBounds.getMinY());
                 mainStage.setWidth(primaryScreenBounds.getWidth());
                 mainStage.setHeight(primaryScreenBounds.getHeight());
                 mainStage.setTitle("أستحــقاقــات");
                 /////////////////////////////////



                 mainStage.setScene(scene);
                 mainStage.show();

        mainStage.setOnCloseRequest(new EventHandler<WindowEvent>() {
            @Override
            public void handle(WindowEvent event) {
                System.exit(0);
            }
        });
    }



    private void showSplash(final Stage initStage, Task task) {
        progressText.textProperty().bind(task.messageProperty());
        loadProgress.progressProperty().bind(task.progressProperty());
        task.stateProperty().addListener(new ChangeListener<Worker.State>() {
            @Override
            public void changed(ObservableValue<? extends Worker.State> observableValue, Worker.State oldState, Worker.State newState) {
                if (newState == Worker.State.SUCCEEDED) {
                    loadProgress.progressProperty().unbind();
                    loadProgress.setProgress(1);
                    mainStage.setIconified(false);
                    initStage.toFront();
                    FadeTransition fadeSplash = new FadeTransition(Duration.seconds(1.2), splashLayout);
                    fadeSplash.setFromValue(1.0);
                    fadeSplash.setToValue(0.0);
                    fadeSplash.setOnFinished(new EventHandler<ActionEvent>() {
                        @Override
                        public void handle(ActionEvent actionEvent) {
                            initStage.hide();
                        }
                    });
                    fadeSplash.play();
                }
            }
        });

        Scene splashScene = new Scene(splashLayout);
        initStage.initStyle(StageStyle.UNDECORATED);
        final Rectangle2D bounds = Screen.getPrimary().getBounds();
        initStage.setScene(splashScene);
        initStage.setX(bounds.getMinX() + bounds.getWidth() / 2 - SPLASH_WIDTH / 2);
        initStage.setY(bounds.getMinY() + bounds.getHeight() / 2 - SPLASH_HEIGHT / 2);
        initStage.show();
    }
}

Answer 1

问题

您已经声明了一个 MainStage，但从未对其进行初始化。因此，在下一行中使用它会在 :

处抛出 NPE

mainStage.setIconified(false);

解决方案

您可以通过在声明时初始化 mainStage 来解决它：

private Stage mainStage = new Stage();

或者您可以在 showSplash() 中第一次使用它之前对其进行初始化：

private void showSplash(final Stage initStage, Task task) {
    ...
    mainStage = new Stage();
    mainStage.setIconified(false);
    ...
}

Answer 2

在 showMainStage() 方法中包含这一行：

Scene scene = new Scene(root);
mainStage = new Stage();   // include this

这将解决您的问题。

Answer 3

我环绕启动画面,我制作了一个预加载器，它对我来说很完美这是代码：

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package istehkakat.preloader;

import javafx.animation.FadeTransition;
import javafx.application.Preloader;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.ProgressBar;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.BorderPaneBuilder;
import javafx.scene.paint.Color;
import javafx.stage.Stage;
import javafx.stage.StageStyle;
import javafx.util.Duration;

/**
 * Simple Preloader Using the ProgressBar Control
 *
 * @author TattoApps
 */
public class Istehkakat_Preloader extends Preloader {

    private ProgressBar bar;
    private Stage stage;
    private boolean isEmbedded = false;

    public void start(Stage stage) throws Exception {
        isEmbedded = (stage.getWidth() > 0);
        this.stage = stage;
        stage.initStyle(StageStyle.UNDECORATED);
        stage.initStyle(StageStyle.TRANSPARENT);
        stage.setScene(createPreloaderScene());

        stage.show();
    }

    @Override
    public void handleProgressNotification(ProgressNotification pn) {
        bar.setProgress(pn.getProgress());
    }

    @Override
    public void handleStateChangeNotification(StateChangeNotification evt) {
        if (evt.getType() == StateChangeNotification.Type.BEFORE_START) {
            if (isEmbedded && stage.isShowing()) {
                // fade out, hide stage at the end of animation
                final FadeTransition ft = new FadeTransition(Duration.seconds(5.2), stage.getScene().getRoot());
                ft.setFromValue(1.0);
                ft.setToValue(0.0);
                final Stage s = stage;
                final EventHandler<ActionEvent> eh = new EventHandler<ActionEvent>() {
                    public void handle(ActionEvent t) {
                        s.hide();
                    }
                };
                ft.setOnFinished(eh);
                ft.play();
            } else {
                stage.hide();
            }
        }
    }

    private Scene createPreloaderScene() {
        bar = new ProgressBar();
        final BorderPane p = BorderPaneBuilder
                .create()
                .center(new ImageView(new Image(this.getClass()
                                        .getResourceAsStream("/imgs/SplashScreenIll.png"))))
                .bottom(bar).build();
        return new Scene(p, 676, 207, Color.TRANSPARENT);
    }
}

谢谢大家

启动画面未加载 mainFxml 文件

splash Screen not load the mainFxml file

java

javafx

splash-screen