由于"包..不存在"，简单的gradle构建失败

Question

一个使用外部库的简单初学者项目，由于我在这里缺少一些基本的东西，我无法构建。感谢您的帮助。

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'
}
}
}

./src/main/java/JavaMotor.java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;

所有这些都在gradle build上失败：

: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。IDE 是 vim 和 bash。

Answer 1

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

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

由于没有已发布的 JAR 工件，因此类路径上不会有任何内容。您需要做的是声明所需的依赖项：

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

根据您的导入，您需要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")
}

compile配置已弃用。有关详细信息，请参阅此处。

这应该足以修复您的导入。

我看到您也在重新声明 Java 源代码集。这不是必需的，因为java插件已经不适合您。建议您熟悉 Gradle： https://docs.gradle.org/current/userguide/getting_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"
}

• https://docs.gradle.org/current/userguide/application_plugin.html