Android Studio：JavaExec：找不到或加载主类

Question

作为构建脚本的一部分，我想在打包 APK 之前运行一些 Java 代码。

当我尝试构建我的项目时，我得到了错误：

Error: Could not find or load main class net.bgreco.myapp.build.BuildScript

BuildScript.java 位于app/src/main/java/net/bgreco/myapp/build/。

BuildScript.class 确实在我收到上述错误消息之前编译成功，我可以从命令行运行它而没有错误。

app/build.gradle：

task runBuildScript(type: JavaExec) {
    main = 'net.bgreco.myapp.build.BuildScript'
}

tasks.whenTaskAdded { theTask ->
    if (theTask.name.contains('package')) {
        theTask.dependsOn 'runBuildScript'
    }
}

Answer 1

在this answer 的帮助下，我通过如下修改类路径使其工作。我还需要引用一些 Android 库，所以我包含了 android.jar 的路径。

app/build.gradle：

task runBuildScript(type: JavaExec) {
    String flavor, buildType
    (flavor, buildType) = getCurrentFlavorAndBuildType()
    classpath files("build/intermediates/classes/" + flavor + "/" + buildType, "${android.getSdkDirectory().getAbsolutePath()}\\platforms\\${android.compileSdkVersion}\\android.jar")
    main = 'net.bgreco.myapp.build.BuildScript'
    args = [flavor] // Not needed unless you want to know the current flavor from within the BuildScript
}

tasks.whenTaskAdded { theTask ->
    if (theTask.name.contains('package')) {
        theTask.dependsOn 'runBuildScript'
    }
}

def getCurrentFlavorAndBuildType() {
    Gradle gradle = getGradle()
    String tskReqStr = gradle.getStartParameter().getTaskRequests().toString()

    Pattern pattern;

    if (tskReqStr.contains("assemble"))
        pattern = Pattern.compile("assemble(\\w+)(Release|Debug)")
    else
        pattern = Pattern.compile("generate(\\w+)(Release|Debug)")

    Matcher matcher = pattern.matcher(tskReqStr)

    if (matcher.find())
        return [matcher.group(1).toLowerCase(), matcher.group(2).toLowerCase()]
    else {
        println "NO MATCH FOUND"
        return ["", ""];
    }
}