简单的子程序生成失败，因为‘包.不存在

Question

一个使用外部图书馆的简单的初学者项目，由于缺少一些基本的东西，我无法构建这个项目。谢谢你的帮助。

build.gradle

plugins {
  id 'java'
  id 'maven'
}

repositories {
  mavenCentral()
}

dependencies {
  compile 'com.pi4j:pi4j-parent:1.2'
}

sourceSets {
  main {
    java {
      srcDir 'src'
    }
  }
  test {
    java {
      srcDir 'test'
    }
  }
}

在./src/main/java/JavaMotor.java中，我有导入语句：

import com.pi4j.io.gpio.GpioController;
import com.pi4j.io.gpio.GpioFactory;
import com.pi4j.io.gpio.GpioPinDigitalOutput;
import com.pi4j.io.gpio.PinState;
import com.pi4j.io.gpio.RaspiPin;

所有这些在gradle build上都失败了

:compileJava/home/pi/workspaces/javamotor/src/main/java/JavaMotor.java:1: error: package com.pi4j.io.gpio does not exist
import com.pi4j.io.gpio.GpioController;
                       ^
/home/pi/workspaces/javamotor/src/main/java/JavaMotor.java:2: error: package com.pi4j.io.gpio does not exist
import com.pi4j.io.gpio.GpioFactory;
                       ^
/home/pi/workspaces/javamotor/src/main/java/JavaMotor.java:3: error: package com.pi4j.io.gpio does not exist
import com.pi4j.io.gpio.GpioPinDigitalOutput;
                       ^
/home/pi/workspaces/javamotor/src/main/java/JavaMotor.java:4: error: package com.pi4j.io.gpio does not exist
import com.pi4j.io.gpio.PinState;
                       ^
/home/pi/workspaces/javamotor/src/main/java/JavaMotor.java:5: error: package com.pi4j.io.gpio does not exist
import com.pi4j.io.gpio.RaspiPin;
                       ^
5 errors
 FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':compileJava'.
> Compilation failed; see the compiler error output for details.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

BUILD FAILED

Total time: 3.107 secs

我在Ubuntu上运行Gradle 3.2.1。爱德是活力和巴什。

Answer 1

您声明的com.pi4j:pi4j-parent依赖项不是您所期望的典型依赖项。它是Pi4J项目的父Maven POM。

如果您查看此依赖项的内容，则可以看到没有已发布的*.jar工件：https://repo1.maven.org/maven2/com/pi4j/pi4j-parent/1.2/。

因为没有发布的JAR工件，所以您的类路径上没有任何东西。您需要做的是声明所需的依赖关系：

• https://github.com/Pi4J/pi4j
• https://mvnrepository.com/artifact/com.pi4j

基于您的导入，您将希望使用pi4j-core包。因此，将其声明为依赖项：

dependencies {
    // This dependency is used by the application.
    implementation("com.pi4j:pi4j-core:1.2")
}

不建议使用compile配置。有关详细信息，请参阅这。

这应该足以解决你的进口问题。

我看到您还在重新声明Java源代码集。这是不必要的，因为java插件已经不适合你了。建议您熟悉Gradle：started.html

一个完整的例子：

plugins {
    // Apply the application plugin to add support for building a CLI application.
    // The application plugin implicitly applies the Java plugin
    id("application")
}

repositories {
    // Use central for resolving dependencies.
    // You can declare any Maven/Ivy/file repository here.
    mavenCentral()
}

dependencies {
    // This dependency is used by the application.
    implementation("com.pi4j:pi4j-parent:1.2")
}

application {
    // Define the main class for the application.
    mainClassName = "io.mateo.MyApplication"
}

• plugin.html