在更新到Android Studio 3.0并创建一个新项目后，我注意到在构建中。gradle有一种新方法来添加新的依赖项，而不是compile，而是implementation，而不是testCompile，而是testimplemimplementation。
例子:
implementation 'com.android.support:appcompat-v7:25.0.0'
testImplementation 'junit:junit:4.12'
而不是
compile 'com.android.support:appcompat-v7:25.0.0'
testCompile 'junit:junit:4.12'
它们之间的区别是什么，我应该用什么?
当前回答
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| Name | Role | Consumable? | Resolveable? | Description |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| api | Declaring | no | no | This is where you should declare |
| | API | | | dependencies which are transitively |
| | dependencies | | | exported to consumers, for compile. |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| implementation | Declaring | no | no | This is where you should |
| | implementation | | | declare dependencies which are |
| | dependencies | | | purely internal and not |
| | | | | meant to be exposed to consumers. |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| compileOnly | Declaring compile | yes | yes | This is where you should |
| | only | | | declare dependencies |
| | dependencies | | | which are only required |
| | | | | at compile time, but should |
| | | | | not leak into the runtime. |
| | | | | This typically includes dependencies |
| | | | | which are shaded when found at runtime. |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| runtimeOnly | Declaring | no | no | This is where you should |
| | runtime | | | declare dependencies which |
| | dependencies | | | are only required at runtime, |
| | | | | and not at compile time. |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| testImplementation | Test dependencies | no | no | This is where you |
| | | | | should declare dependencies |
| | | | | which are used to compile tests. |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| testCompileOnly | Declaring test | yes | yes | This is where you should |
| | compile only | | | declare dependencies |
| | dependencies | | | which are only required |
| | | | | at test compile time, |
| | | | | but should not leak into the runtime. |
| | | | | This typically includes dependencies |
| | | | | which are shaded when found at runtime. |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| testRuntimeOnly | Declaring test | no | no | This is where you should |
| | runtime dependencies | | | declare dependencies which |
| | | | | are only required at test |
| | | | | runtime, and not at test compile time. |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
其他回答
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| Name | Role | Consumable? | Resolveable? | Description |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| api | Declaring | no | no | This is where you should declare |
| | API | | | dependencies which are transitively |
| | dependencies | | | exported to consumers, for compile. |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| implementation | Declaring | no | no | This is where you should |
| | implementation | | | declare dependencies which are |
| | dependencies | | | purely internal and not |
| | | | | meant to be exposed to consumers. |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| compileOnly | Declaring compile | yes | yes | This is where you should |
| | only | | | declare dependencies |
| | dependencies | | | which are only required |
| | | | | at compile time, but should |
| | | | | not leak into the runtime. |
| | | | | This typically includes dependencies |
| | | | | which are shaded when found at runtime. |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| runtimeOnly | Declaring | no | no | This is where you should |
| | runtime | | | declare dependencies which |
| | dependencies | | | are only required at runtime, |
| | | | | and not at compile time. |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| testImplementation | Test dependencies | no | no | This is where you |
| | | | | should declare dependencies |
| | | | | which are used to compile tests. |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| testCompileOnly | Declaring test | yes | yes | This is where you should |
| | compile only | | | declare dependencies |
| | dependencies | | | which are only required |
| | | | | at test compile time, |
| | | | | but should not leak into the runtime. |
| | | | | This typically includes dependencies |
| | | | | which are shaded when found at runtime. |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| testRuntimeOnly | Declaring test | no | no | This is where you should |
| | runtime dependencies | | | declare dependencies which |
| | | | | are only required at test |
| | | | | runtime, and not at test compile time. |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
这个答案将演示项目中的实现、api和编译之间的区别。
假设我有一个有三个Gradle模块的项目:
app (Android应用程序) myandroidlibrary(一个Android库) myjavalibrary(一个Java库)
应用程序有myandroidlibrary作为依赖项。Myandroidlibrary有myjavlibrary作为依赖项。
myjavlibrary有一个MySecret类
public class MySecret {
public static String getSecret() {
return "Money";
}
}
myandroidlibrary中有MyAndroidComponent类，用于操作MySecret类的值。
public class MyAndroidComponent {
private static String component = MySecret.getSecret();
public static String getComponent() {
return "My component: " + component;
}
}
最后，app只对myandroidlibrary的值感兴趣
TextView tvHelloWorld = findViewById(R.id.tv_hello_world);
tvHelloWorld.setText(MyAndroidComponent.getComponent());
现在，让我们谈谈依赖关系……
应用需要消耗:myandroidlibrary，所以在应用构建中。Gradle使用实现。
(注意:你也可以使用api/compile。但请稍等片刻。)
dependencies {
implementation project(':myandroidlibrary')
}
你认为myandroidlibrary构建了什么?Gradle应该是什么样子?我们应该使用哪个作用域?
我们有三个选择:
dependencies {
// Option #1
implementation project(':myjavalibrary')
// Option #2
compile project(':myjavalibrary')
// Option #3
api project(':myjavalibrary')
}
它们之间的区别是什么，我应该用什么?
编译或Api(选项#2或#3)
如果你使用的是编译器或者api。我们的Android应用现在可以访问myandroidcomponent依赖，这是一个MySecret类。
TextView textView = findViewById(R.id.text_view);
textView.setText(MyAndroidComponent.getComponent());
// You can access MySecret
textView.setText(MySecret.getSecret());
实现(选项#1)
如果您正在使用实现配置，MySecret将不会公开。
TextView textView = findViewById(R.id.text_view);
textView.setText(MyAndroidComponent.getComponent());
// You can NOT access MySecret
textView.setText(MySecret.getSecret()); // Won't even compile
那么，应该选择哪种配置呢?那要看你的要求了。
如果你想公开依赖关系，请使用api或compile。
如果你不想公开依赖关系(隐藏你的内部模块)，那么使用实现。
注意:
这只是Gradle配置的一个要点，参见表49.1。Java库插件-用于声明依赖关系的配置，以获得更详细的解释。
这个答案的示例项目可以在https://github.com/aldoKelvianto/ImplementationVsCompile上找到
编译配置已弃用，应由实现或api取代。
你可以在API和实现分离部分阅读文档。
简短的部分是
The key difference between the standard Java plugin and the Java Library plugin is that the latter introduces the concept of an API exposed to consumers. A library is a Java component meant to be consumed by other components. It's a very common use case in multi-project builds, but also as soon as you have external dependencies. The plugin exposes two configurations that can be used to declare dependencies: api and implementation. The api configuration should be used to declare dependencies which are exported by the library API, whereas the implementation configuration should be used to declare dependencies which are internal to the component.
进一步的解释请参考这张图片。
在继续之前先做一些笔记;compile已弃用，并且文档声明您应该使用implementation，因为compile将在Gradle 7.0版本中被删除。 如果你使用——warning-mode运行Gradle构建，你会看到以下消息:
对于依赖项声明，compile配置已弃用。这将失败，并在Gradle 7.0中出现错误。请改用实现配置。
只要看看帮助页上的图片，就很有意义了。
你有蓝色框compileClasspath和runtimeClassPath。 当运行gradle build时，compileClasspath是成功构建所必需的。编译时将出现在类路径上的库将是在gradle构建中使用compileOnly或implementation配置的所有库。
然后我们有runtimeClasspath，这些都是使用实现或runtimeOnly添加的包。所有这些库都将添加到您部署到服务器上的最终构建文件中。
如图所示，如果您希望一个库既用于编译，又希望将它添加到构建文件中，那么应该使用实现。
runtimeOnly的示例可以是数据库驱动程序。 compileOnly的一个例子可以是servlet-api。 实现的一个例子是spring-core。
implementation: mostly we use implementation configuration. It hides the internal dependency of the module to its consumer to avoid accidental use of any transitive dependency, hence faster compilation and less recompilation. api: must be used very carefully, since it leaks the to consumer’s compile classpath, hence misusing of api could lead to dependency pollution. compileOnly: when we don’t need any dependency at runtime, since compileOnly dependency won’t become the part of the final build. we will get a smaller build size. runtimeOnly: when we want to change or swap the behaviour of the library at runtime (in final build).
我已经创建了一个深入了解每个工作示例的帖子:源代码
https://medium.com/@gauraw.negi/how-gradle-dependency-configurations-work-underhood-e934906752e5
