如何使用JAR文件显示启动画面？

Question

package misc;

import java.awt.*;
import java.awt.event.*;

public class SplashDemo extends Frame implements ActionListener {

    static void renderSplashFrame(Graphics2D g, int frame) {
        final String[] comps = {"foo", "bar", "baz"};
        g.setComposite(AlphaComposite.Clear);
        g.fillRect(120,140,200,40);
        g.setPaintMode();
        g.setColor(Color.BLACK);
        g.drawString("Loading "+comps[(frame/5)%3]+"...", 120, 150);
    }
    public SplashDemo() {
        super("SplashScreen demo");
        setSize(300, 200);
        setLayout(new BorderLayout());
        Menu m1 = new Menu("File");
        MenuItem mi1 = new MenuItem("Exit");
        m1.add(mi1);
        mi1.addActionListener(this);
        this.addWindowListener(closeWindow);

        MenuBar mb = new MenuBar();
        setMenuBar(mb);
        mb.add(m1);
        
        //
        final SplashScreen splash = SplashScreen.getSplashScreen();
        if (splash == null) {
            System.out.println("SplashScreen.getSplashScreen() returned null");
            return;
        }
        Graphics2D g = splash.createGraphics();
        if (g == null) {
            System.out.println("g is null");
            return;
        }
        for(int i=0; i<50; i++) {
            renderSplashFrame(g, i);
            splash.update();
            try {
                Thread.sleep(90);
            }
            catch(InterruptedException e) {
            }
        }
        splash.close();
        
        // setVisible(true);
        // toFront();
    }
    public void actionPerformed(ActionEvent ae) {
        System.exit(0);
    }
    
    private static WindowListener closeWindow = new WindowAdapter(){
        public void windowClosing(WindowEvent e){
            e.getWindow().dispose();
        }
    };
}

在JAR的主类中：

public static void main(String[] args) {
    new SplashDemo(); //splash with image
    ...

当我从控制台运行它时，我得到

SplashScreen.getSplashScreen() 返回 null

项目文件夹如下

project root > src > misc > SplashDemo.java
project root > src > main > resources > META-INF > MANIFEST.MF
// made a few locations for the picture to pick up from somewhere.
project root > src > main > resources > images > `image here`
project root > images > `image here`
project root > src > images > `image here`

和清单文件

Manifest-Version: 1.0
Main-Class: main.MainClassName
SplashScreen-Image: images/splash.gif

pom 文件

<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://maven.apache.org/POM/4.0.0"
    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>com.creator</groupId>
    <artifactId>myapp</artifactId>
    <version>0.1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <dependencies> ... </dependencies>

    <build>
        <sourceDirectory>src</sourceDirectory>

        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.7.0</version>
                <configuration>
                    <source>${project.java.version}</source>
                    <target>${project.java.version}</target>
                    <encoding>${project.build.sourceEncoding}</encoding>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-dependency-plugin</artifactId>
                <executions>
                    <execution>
                        <id>copy-dependencies</id>
                        <phase>prepare-package</phase>
                        <goals>
                            <goal>copy-dependencies</goal>
                        </goals>
                        <configuration>
                            <outputDirectory>
                                ${project.build.directory}/libs
                            </outputDirectory>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>
                <version>3.3.0</version>
                <configuration>
                    <archive>
                        <manifest>
                            <addClasspath>true</addClasspath>
                            <classpathPrefix>libs/</classpathPrefix>
                            <mainClass>main.MainClassName</mainClass>
                        </manifest>
                    </archive>
                </configuration>
            </plugin>
        </plugins>

    </build>
</project>

但是，应用程序在通过清单文件选项启动时并未创建启动屏幕，即 getSplashScreen 方法返回 null。怎么解决？

创建的 JAR 文件包含一个图像文件夹，根目录中有图像。

Answer 1

以下内容适用于您似乎正在使用的

tutorial

中的 SplashDemo 类：

                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-jar-plugin</artifactId>
                    <version>3.3.0</version>
                    <configuration>
                        <archive>
                            <manifest>
                                <addClasspath>true</addClasspath>
                                <classpathPrefix>libs/</classpathPrefix>
                                <mainClass>misc.SplashDemo</mainClass>
                            </manifest>
                            <manifestEntries>
                                <SplashScreen-Image>splash.gif</SplashScreen-Image>
                            </manifestEntries>
                        </archive>
                    </configuration>
                </plugin>

演示 zip 位于 此处 (

mvn package && java -jar target/misc-1.0-SNAPSHOT.jar

)