发现没有 Maven css 文件的 JavaFX : Maven project cannot find css files,

Question

对不起，奇怪的标题，不知道该写什么。我正在使用 Java8 开发 JavaFX 应用程序。为此，我从 com.zenjava 获得了 javafx-maven-plugin。我有一个简单的测试代码，其中有一个主类和一个用于样式设置的 css 页面。我在没有 Maven 的情况下有相同的元素，并且工作正常。但是对于 Maven，我无法让它运行。我得到了 CSS 文件的 NPE-。我已经尝试了多种选择。你能帮忙的话，我会很高兴。谢谢。

错误日志:

Exception in Application start method
Exception in thread "main" java.lang.RuntimeException: Exception in Application start method
    at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$155(LauncherImpl.java:182)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
    at View.Main.start(Main.java:110)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$162(LauncherImpl.java:863)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$175(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
    at com.sun.glass.ui.gtk.GtkApplication.lambda$null$49(GtkApplication.java:139)
    ... 1 more

POM.xml :

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>MavenFX</groupId>
    <artifactId>MavenFX</artifactId>
    <version>1.0-SNAPSHOT</version>
    <properties>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>
    <dependencies>

    </dependencies>

    <build>
        <plugins>
      <plugin>

          <groupId>com.zenjava</groupId>
          <artifactId>javafx-maven-plugin</artifactId>
          <version>8.2.0</version>
          <configuration>
              <mainClass>View.Main</mainClass>
          </configuration>
      </plugin>
        </plugins>
    </build>
</project>

主类:

package View;

import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.PasswordField;
import javafx.scene.control.TextField;
import javafx.scene.effect.DropShadow;
import javafx.scene.effect.Reflection;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.HBox;
import javafx.scene.paint.Color;
import javafx.scene.text.Font;
import javafx.scene.text.FontWeight;
import javafx.scene.text.Text;
import javafx.stage.Stage;

public class Main extends Application {


    String user = "JavaFX2";
    String pw = "password";
    String checkUser, checkPw;


    @Override
    public void start(Stage primaryStage) throws Exception{
        primaryStage.setTitle("Test Login");

        BorderPane bp = new BorderPane();
        bp.setPadding(new Insets(10,50,50,50));

        //Adding HBox
        HBox hb = new HBox();
        hb.setPadding(new Insets(20,20,20,30));

        //Adding GridPane
        GridPane gridPane = new GridPane();
        gridPane.setPadding(new Insets(20,20,20,20));
        gridPane.setHgap(5);
        gridPane.setVgap(5);

        //Implementing Nodes for GridPane
        Label lblUserName = new Label("Username");
        final TextField txtUserName = new TextField();
        Label lblPassword = new Label("Password");
        final PasswordField pf = new PasswordField();
        Button btnLogin = new Button("Login");
        final Label lblMessage = new Label();

        //Adding Nodes to GridPane layout
        gridPane.add(lblUserName, 0, 0);
        gridPane.add(txtUserName, 1, 0);
        gridPane.add(lblPassword, 0, 1);
        gridPane.add(pf, 1, 1);
        gridPane.add(btnLogin, 2, 1);
        gridPane.add(lblMessage, 1, 2);


        //Reflection for gridPane
        Reflection r = new Reflection();
        r.setFraction(0.7f);
        gridPane.setEffect(r);

        //DropShadow effect
        DropShadow dropShadow = new DropShadow();
        dropShadow.setOffsetX(5);
        dropShadow.setOffsetY(5);

        //Adding text and DropShadow effect to it
        Text text = new Text("Test Login");
        text.setFont(Font.font("Courier New", FontWeight.BOLD, 28));
        text.setEffect(dropShadow);

        //Adding text to HBox
        hb.getChildren().add(text);

        //Add ID's to Nodes
        bp.setId("bp");
        gridPane.setId("root");
        btnLogin.setId("btnLogin");
        text.setId("text");

        //Action for btnLogin
        btnLogin.setOnAction(event -> {
            checkUser = txtUserName.getText();
            checkPw = pf.getText();
            if(checkUser.equals(user) && checkPw.equals(pw)){
                lblMessage.setText("Congratulations!");
                lblMessage.setTextFill(Color.GREEN);
            }
            else{
                lblMessage.setText("Incorrect user or pw.");
                lblMessage.setTextFill(Color.RED);
            }
            txtUserName.setText("");
            pf.setText("");
        });

        //Add HBox and GridPane layout to BorderPane Layout
        bp.setTop(hb);
        bp.setCenter(gridPane);

        //Adding BorderPane to the scene and loading CSS
        Scene scene = new Scene(bp);

        scene.getStylesheets().add(getClass().getClassLoader().getResource("UI/login.css").toExternalForm());
        primaryStage.setScene(scene);
        primaryStage.setTitle("Test Login");
        /*primaryStage.titleProperty().bind(
                scene.widthProperty().asString().
                        concat(" : ").
                        concat(scene.heightProperty().asString()));*/
        primaryStage.setResizable(false);
        primaryStage.show();
    }


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

CSS 文件:

#root {
    -fx-background-color:  linear-gradient(lightgray, gray);
    -fx-border-color: white;
    -fx-border-radius: 20;
    -fx-padding: 10 10 10 10;
    -fx-background-radius: 20;
}

#bp {
    -fx-background-color:  linear-gradient(gray,DimGrey );

}

#btnLogin {
    -fx-background-radius: 30, 30, 29, 28;
    -fx-padding: 3px 10px 3px 10px;
    -fx-background-color: linear-gradient(orange, orangered );
}

#text {
    -fx-fill:  linear-gradient(orange , orangered);
}

如果我运行 mvn jfx:jar，我得到了 jar 文件，但它也有同样的问题。为什么如果是 Maven 元素，JavaFX 在查找文件时会遇到问题。你能帮忙的话，我会很高兴。谢谢。

Answer 1

您可以尝试输出资源文件的路径:

       System.err.println(getClass().getClassLoader().getResource("UI/login.css"));

并查看它指向的位置。 maven 可能更改了您的资源位置。我不确定，但你可以试试。请告诉我。