Develop Reference

AndroidX migrate dependency / libraries

I have successfully migrated my project to AndroidX. App is running perfectly, but I am getting compile time errors, because my dependencies use support package.
Reason of this error
Because PhotoView is a dependency class, which uses android.support.v7.widget.AppCompatImageView which is no more available in my project. Because it is now androidx.appcompat.widget.AppCompatImageView
Project still run?
Yes, android.enableJetifier convert this dependency to AndroidX at runtime, but I want to get rid of compile time errors.
Is there a quick fix for now?

If you depend on a library that references the older Support Library, Android Studio will update that library to reference androidx instead via dependency translation. Dependency translation is automatically applied by the Android Gradle Plugin 3.2.0-alpha14, which rewrites bytecode and resources of JAR and AAR dependencies (and transitive dependencies) to reference the new androidx-packaged classes and artifacts. We will also provide a standalone translation tool as a JAR.
I see (using ./gradlew app:dependencies) that rxbinding's design dependency is updated to the new com.google.android.material dependency. Passing com.google.android.material.snackbar.Snackbar to a library function that references android.support.design.widget.Snackbar themselves makes Android Studio show a compiler error, but actually compiling and running the app works. I assume AS can't really handle these changes yet.
It seems there are some caching issues, removing .idea/libraries and performing a Gradle sync makes the errors disappear.

I solved this issue by deleting .idea folder and syncing project again.
This seems a bug of IDE not Jetifier, it does not re-sync dependencies after migrating.
Jetifier does its work well. It converts all dependencies support libraries into androidx at building time. See #this post for good explaination.

My fix for this was converting the library with the compile time error to AndroidX and submitting a pull request to the library.

Library not adding its dependencies when used

I made a library, but when I tried to use it with implementation 'com.example:mylibrary:1.3.0' in my app's build.gradle, I keep getting an error saying the ConstraintLayout dependency (which the library uses but not the app) is not found. However it was explicitly defined in the library's build.gradle with implementation.
When I ran gradlew app:dependencies on the terminal, it shows that the library has no dependencies, even though it actually has 2. This seems to be the source of the problem, Gradle can't detect the dependencies of the library.
I didn't run into this problem for a while but when I decided to remove the ConstraintLayout dependency from my app an error appears during build.

When you're using implementation for the dependencies in your library, the project which is dependent with it will not see the dependencies. You need to use api instead of implementation.

Failed resolution of: Lcom/google/android/gms/location/LocationRequest

I am using gradle dependency of
implementation 'com.google.android.gms:play-services-location:15.0.1'
at runtime I get below error
java.lang.NoClassDefFoundError: Failed resolution of: Lcom/google/android/gms/location/LocationRequest;
I am trying to fetch lat long using LocationRequest and when I am using this code in a standalone project it works. And when I am trying to build a library with same code I get above error.
I have checked, both standalone project and library project have same dependencies and versions.

This maybe because of 2 reasons
1st possible reason
When you used this library directly you used implementation method in build.gradle.
So you can use it directly in simple app module.
When you move it to your library and use that location library using same implementation option that location library can be only used by your library. and can't be used by app module in which you have used your library
Try by replacing that implementation by api for location library like this
api 'com.google.android.gms:play-services-location:15.0.1'
For more details refer this post for implementation vs api - Here
2nd possible reason
As you mentioned in comments, its a runtime error
As per my opinion it maybe because of obfuscation by ProGuard
add that class to keep ProGuard rule like this
-keep class com.google.android.gms.location.** { *; }
So this will stop obfuscation of that Location Request class

The code is working now with below changes (I am still looking for an explnation)
in the library gradle edited to below dependency
compileOnly "com.google.android.gms:play-services-location:15.0.1"
and in the app's gradle file added below dependency
runtimeOnly 'com.google.android.gms:play-services-location:11.6.0'
my guess is, since "compileOnly" takes care of adding the dependency in library and "runtimeOnly" takes care of using that dependency the code works and is able to find LocationRequest class.
P.S adityakamble49 's answer in the thread also helped. Please try that as well as it might work for your case.

AsyncTask.java cannot resolve symbol for Nullable, Mainthread, WorkerThread

I'm pretty new to android studio, but i got this error and i can't run my project. I saw a lot of answers which suggest to add the support-annotations dependency, but I'm using appcompat so i don't need that. Any thoughts?

Do you have the Android Support Library?
To do it add this to your build.gradle file of the "app" module:
dependencies {
...
implementation "com.android.support:support-annotations:27.1.0"
}
Then sync the project.
Sometimes you can do this automatically by pressing Alt+Enter over the error message and selecting the solution.

You need to fetch the libraries that contain the imports, in your build gradle file of your module add the line inside dependencies tag:
api 'com.android.support:support-annotations:X.X.X'
or
implementation 'com.android.support:support-annotations:X.X.X'
Where X.X.X is the version of the rest of your support libraries.
You should read this article that explains how to implement this with more detail.

How to get a compile error if a JAR dependency is missing?

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 :)