In the app module I added baseLayerCore module as a dependency and both app and baseLayerCore modules need core module as their dependency so I defined core in app but baseLayerCore dose not resolve it and needs to be defined in its own build.gradle too.
I believe baseLayerCore does not need core since it has defined in app.
Am I wrong?! Why is this happening?
app build.gradle:
According to this link, I finally recognized that this error occurs on compile time not run time so I should use compileOnly dependancy for baseLayerCore and implementation for app module.These way I can compile the project to see the result but there is no need to have the dependency on run time.
Related
Unable to understand the latest gradle dependency configurations which are introduced in Android Studio 3.0 i.e. implementation, api , compileonly and runtimeonly.
Please refer the link : Android Studio 3.0 New Gradle Configuration available at android developers official site.
Based on description mentioned in above link:
implementation: When your module configures an implementation dependency, it's letting Gradle know that the module does not want to
leak the dependency to other modules at compile time. That is, the
dependency is available to other modules only at runtime. Using this
dependency configuration instead of api or compile can result in
significant build time improvements because it reduces the amount of
projects that the build system needs to recompile. For example, if an
implementation dependency changes its API, Gradle recompiles only that
dependency and the modules that directly depend on it. Most app and
test modules should use this configuration.
api: When a module includes an api dependency, it's letting Gradle know that the module wants to transitively export that
dependency to other modules, so that it's available to them at both
runtime and compile time. This configuration behaves just like compile
(which is now deprecated), and you should typically use this only in
library modules. That's because, if an api dependency changes its
external API, Gradle recompiles all modules that have access to that
dependency at compile time. So, having a large number of api
dependencies can significantly increase build times. Unless you want
to expose a dependency's API to a separate test module, app modules
should instead use implementation dependencies.
compileOnly: Gradle adds the dependency to the compilation classpath only (it is not added to the build output). This is useful
when you're creating an Android library module and you need the
dependency during compilation, but it's optional to have present at
runtime. That is, if you use this configuration, then your library
module must include a runtime condition to check whether the
dependency is available, and then gracefully change its behavior so it
can still function if it's not provided. This helps reduce the size of
the final APK by not adding transient dependencies that aren't
critical. This configuration behaves just like provided (which is now
deprecated).
runtimeonly: Gradle adds the dependency to the build output only, for use during runtime. That is, it is not added to the compile
classpath. This configuration behaves just like apk (which is now
deprecated).
Upgrade to Android Studio 3.0.0 mentions this, and doesn't elaborate on how to handle it:
Library modules no longer process local JARs. This is to speed up incremental builds that are caused by changes to a library module's code.
So I have a project with a library project in it. In my library project's build.gradle file I have this:
compile files('libs/com.somelib.somepackage.jar')
I changed compile to implementation and when I tried to run my app, all my classes that tried to access the import com.somelib.somepackage.SomeClass import statement threw an error that this package didnt exist.
I changed back to compile and I was able to build and run my app.
I want to comply to the new rules since compile is deprecated and will be removed with the next Gradle release, so how do I go about doing that?
If you are trying to access classes from the .jar that is included in the library project from the app project, you will have to use api instead of implementation otherwise the classes will only be accessible in the library project:
implementation files('libs/com.somelib.somepackage.jar')
should be
api files('libs/com.somelib/somepackage.jar')
As said by the documentation:
... When a module includes an api dependency, it's letting Gradle know
that the module wants to transitively export that dependency to other
modules, so that it's available to them at both runtime and compile
time ...
Reference:
https://developer.android.com/studio/build/gradle-plugin-3-0-0-migration.html#new_configurations
I have an Android project with the following dependencies:
-- Android App
---> MySDK.Jar
------> 'org.apache.commons:commons-lang3:3.5'
This is MySDK.jar that has a dependency on commons-lang3.
I'm working on Android Studio and I'm thus using Gradle.
Here is my problem:
I have shared "MySDK.Jar" to someone and he has built his own Android App on top of it.
It works but we have seen that the compiler doesn't notice the missing dependency on 'org.apache.commons:commons-lang3:3.5'. At run-time there will be a crash if the code using 'org.apache.commons:commons-lang3:3.5' is called. One may not notice the problem if he doesn't call the code using this library.
I know that we can solve this issue by adding the following line to Android App build.gradle file:
compile 'org.apache.commons:commons-lang3:3.5'
I'm wondering if there is a way to get a compile error indicating such missing dependencies? It is indeed better to see the dependency problem at compilation time rather than at runtime.
What are the recommended good practices for this?
Thanks!
commons-lang3 is a transitive dependency of Android App. As such, it is often not needed for compilation - there are exceptions, especially regarding multiple levels of inheritance. So at compile time you (usually) do not know whether you miss a transitive dependency that you need at runtime.
This is where Gradle comes in. Gradle can (as Maven) resolve dependencies transitively from a Maven repository (as MavenCentral). If you put MySDK into a Maven repository (like Nexus or Artifactory, which have open source versions), everyone using MySDK will automatically draw commons-lang3 so you will not miss anything at runtime.
If you are just adding the jar file in your project you can't warning about the missing dependencies.
To do it you have to publish the jar file in a maven repo.
In this way you have a pom file which describes the dependencies that gradle has to download.
Provide a method like MySDK.init() int your MySDK.jar,call a method whe is belong to org.apache.commons:commons-lang3:3.5' in the MySDK.init() method, then put init() into onCreate() of your Application,
Another way is，putorg.apache.commons:commons-lang3:3.5 into MySDK.jar，
Hope it helps you :)
I'm trying to figure out what is the difference between api and implementation configuration while building my dependencies.
In the documentation, it says that implementation has better build time, but, seeing this comment in a similar question I got to wonder if is it true.
Since I'm no expert in Gradle, I hope someone can help. I've read the documentation already but I was wondering about an easy-to-understand explanation.
Gradle compile keyword was deprecated in favor of the api and implementation keywords to configure dependencies.
Using api is the equivalent of using the deprecated compile, so if you replace all compile with api everything will works as always.
To understand the implementation keyword consider the following example.
EXAMPLE
Suppose you have a library called MyLibrary that internally uses another library called InternalLibrary. Something like this:
// 'InternalLibrary' module
public class InternalLibrary {
public static String giveMeAString(){
return "hello";
}
}
// 'MyLibrary' module
public class MyLibrary {
public String myString(){
return InternalLibrary.giveMeAString();
}
}
Suppose the MyLibrary build.gradle uses api configuration in dependencies{} like this:
dependencies {
api(project(":InternalLibrary"))
}
You want to use MyLibrary in your code so in your app's build.gradle you add this dependency:
dependencies {
implementation(project(":MyLibrary"))
}
Using the api configuration (or deprecated compile) you can access InternalLibrary in your application code:
// Access 'MyLibrary' (granted)
MyLibrary myLib = new MyLibrary();
System.out.println(myLib.myString());
// Can ALSO access the internal library too (but you shouldn't)
System.out.println(InternalLibrary.giveMeAString());
In this way the module MyLibrary is potentially "leaking" the internal implementation of something. You shouldn't (be able to) use that because it's not directly imported by you.
The implementation configuration was introduced to prevent this.
So now if you use implementation instead of api in MyLibrary:
dependencies {
implementation(project(":InternalLibrary"))
}
you won't be able to call InternalLibrary.giveMeAString() in your app code anymore.
This sort of boxing strategy allows Android Gradle plugin to know that if you edit something in InternalLibrary, it must only trigger the recompilation of MyLibrary and not the recompilation of your entire app, because you don't have access to InternalLibrary.
When you have a lot of nested dependencies this mechanism can speed up the build a lot. (Watch the video linked at the end for a full understanding of this)
CONCLUSIONS
When you switch to the new Android Gradle plugin 3.X.X, you should replace all your compile with the implementation keyword *(1). Then try to compile and test your app. If everything it's ok leave the code as is, if you have problems you probably have something wrong with your dependencies or you used something that now is private and not more accessible. *Suggestion by Android Gradle plugin engineer Jerome Dochez (1))
If you are a library mantainer you should use api for every dependency which is needed for the public API of your library, while use implementation for test dependencies or dependencies which must not be used by the final users.
Useful article Showcasing the difference between implementation and api
REFERENCES
(This is the same video splitted up for time saving)
Google I/O 2017 - How speed up Gradle builds (FULL VIDEO)
Google I/O 2017 - How speed up Gradle builds (NEW GRADLE PLUGIN 3.0.0 PART ONLY)
Google I/O 2017 - How speed up Gradle builds (reference to 1*)
Android documentation
I like to think about an api dependency as public (seen by other modules) while implementation dependency as private (only seen by this module).
Note, that unlike public/private variables and methods, api/implementation dependencies are not enforced by the runtime. This is merely a build-time optimization, that allows Gradle to know which modules it needs to recompile when one of the dependencies changes its API.
Consider you have app module which uses lib1 as a library and lib1 uses lib2 as a library. Something like this: app -> lib1 -> lib2.
Now when using api lib2 in lib1, then app can see lib2 code when using: api lib1 or implementation lib1 in the app module.
BUT when using implementation lib2 in lib1, then app can not see the lib2 code.
Please refer the link: Android Studio Dependency Configuration available at android developers' official site.
Inside the dependencies block, you can declare a library dependency using one of several different dependency configurations (such as implementation shown above). Each dependency configuration provides Gradle with different instructions about how to use the dependency.
implementation
Gradle adds the dependency to the compile classpath and packages the dependency to the build output. However, when your module configures an implementation dependency, it's letting Gradle know that you do not want the module to leak the dependency to other modules at compile time. That is, the dependency is available to other modules only at runtime.
Using this dependency configuration instead of api or compile (deprecated) can result in significant build time improvements because it reduces the number of modules that the build system needs to recompile. For example, if an implementation dependency changes its API, Gradle recompiles only that dependency and the modules that directly depend on it. Most app and test modules should use this configuration.
api
Gradle adds the dependency to the compile classpath and build output. When a module includes an api dependency, it's letting Gradle know that the module wants to transitively export that dependency to other modules, so that it's available to them at both runtime and compile time.
This configuration behaves just like compile (which is now deprecated), but you should use it with caution and only with dependencies that you need to transitively export to other upstream consumers. That's because, if an api dependency changes its external API, Gradle recompiles all modules that have access to that dependency at compile time. So, having a large number of api dependencies can significantly increase build time. Unless you want to expose a dependency's API to a separate module, library modules should instead use implementation dependencies.
From gradle documentation:
Let’s have a look at a very simple build script for a JVM-based project.
plugins {
id 'java-library'
}
repositories {
mavenCentral()
}
dependencies {
implementation 'org.hibernate:hibernate-core:3.6.7.Final'
api 'com.google.guava:guava:23.0'
testImplementation 'junit:junit:4.+'
}
implementation
The dependencies required to compile the production source of the project which are not part of the API exposed by the project. For example the project uses Hibernate for its internal persistence layer implementation.
api
The dependencies required to compile the production source of the project which are part of the API exposed by the project. For example the project uses Guava and exposes public interfaces with Guava classes in their method signatures.
Answers from #matpag and #dev-bmax are clear enough to make people understand different usages between implementation and api. I just want to make an extra explaination from another angle, hopes to help for peoples that have the same question.
I created two projects for testing :
project A as a java library project named 'frameworks-web-gradle-plugin' depends on 'org.springframework.boot:spring-boot-gradle-plugin:1.5.20.RELEASE'
project B depends on project A by implementation 'com.example.frameworks.gradle:frameworks-web-gradle-plugin:0.0.1-SNAPSHOT'
The dependencies hierarchy descripted above looks like:
[project-b] -> [project-a] -> [spring-boot-gradle-plugin]
Then I tested following scenarios:
Make project A depends on 'org.springframework.boot:spring-boot-gradle-plugin:1.5.20.RELEASE' by implementation .
Run gradle dependencies command in a terminal in poject B root dir，with following screenshot of output we can see that 'spring-boot-gradle-plugin' appears in runtimeClasspath dependencies tree, but not in compileClasspath's, I think that's exactly why we can't make use of library that declared using implementation, it just won't through compilation.
Make project A depends on 'org.springframework.boot:spring-boot-gradle-plugin:1.5.20.RELEASE' by api
Run gradle dependencies command in a terminal in poject B root dir again.
Now 'spring-boot-gradle-plugin' appears both in compileClasspath and runtimeClasspath dependencies tree.
A significant difference I noticed is that the dependency in producer/library project declared in implementation way won't appear in compileClasspath of consumer projects, so that we can't make use of corresponding lib in the consumer projects.
One more technical note regarding api vs implementation. Suppose you have following dependencies:
dependencies {
api "com.example:foo:1.0"
implementation "com.example:bar:1.0"
}
If you install a generated jar file in your local Maven repository (with help of maven-publish plugin) you will see that generated pom.xml file will look like this:
<dependency>
<groupId>com.example</groupId>
<artifactId>foo</artifactId>
<version>1.0</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>com.example</groupId>
<artifactId>bar</artifactId>
<version>1.0</version>
<scope>runtime</scope>
</dependency>
Note: api was converted to compile scope and implementation - to runtime scope.
That allows for consumers of this library to avoid having runtime dependencies in their compile classpath.
Now there is good explanation in the documentation
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.
An Android app uses a library (aar module) that uses "com.google.gson.Gson". The library has the following in its build.gradle:
compile 'com.google.code.gson:gson:2.6.2'
The app builds fine, but generates the following error when it starts:
Failed resolution of: Lcom/google/gson/Gson;
The only way to solve it is adding the same compile line to the app's build.gradle:
compile 'com.google.code.gson:gson:2.6.2'
Could anyone shed some light on this?
[Edit]
The library was added with the standard procedure that created a folder under the app called "androidLibrary-release". The following line has been added to the build.gradle of the app:
compile project(':androidLibrary-release')
Libraries don't include their dependencies. It is up to the developer to include them as necessary in the app modules that implement them. However, if this library comes from a Maven repo, it is possible to include the information about which dependencies the library uses and they will be fetched when your project is built.