Develop Reference

Undo migration to AndroidX

I've refactored my Android Studio codebase to AndroidX successfully. But it is causing a few problems with some of my libraries.
I need to revert it since the app is going into production soon. How can I do it?

I had gone through the same, Follow the steps to undo the AndroidX Migration:
Remove following lines in gradle.properties:
android.enableJetifier=true
android.useAndroidX=true
Remove AndroidX dependencies in build.gradle of your app and replace them with their equivalent Non AndroidX dependencies:
e.g.
implementation 'androidx.core:core:1.0.0-beta01'
implementation 'androidx.appcompat:appcompat:1.0.0-beta01'
Sync Project with Gradle Files
After syncing you may have import errors in java files, you can remove the androidx imports and re add the equivalent non androidx imports
I hope it will help everyone facing migration rollback problem. If you get any conflict issues while performing above steps in Android Studio, try to clean and rebuild the project.

You can simply choose Migrate App to appCompat from Refactor menu in Android Studio.
Also, don't forget to delete these lines from gradle.properties:
android.useAndroidX=true
android.enableJetifier=true

I couldn't simply roll back in version control, because the app I wanted to roll back was androidx from its initial commit, but I was tasked with integrating the app module into a larger project without androidx.
Here's what I did:
Try syncing gradle and inevitably you'll get some kind of error. Here is the first error I saw:
Error: Attribute application#appComponentFactory
value=(androidx.core.app.CoreComponentFactory) from
[androidx.core:core:1.1.0] AndroidManifest.xml:24:18-86 is also
present at [com.android.support:support-compat:28.0.0]
AndroidManifest.xml:22:18-91
value=(android.support.v4.app.CoreComponentFactory)
Take note of the androidx package in the above error.
Run gradlew dependencies inside the module you're trying to migrate back.
Search the output for the androidx package mentioned in the above error. Figure out which of your dependencies from your build.gradle file is bringing in that package, then revert that package to its equivalent support library mapping.
Repeat steps 1-4 until Gradle sync finishes successfully.
Now you need to search all your .java files for androidx and replace each import statement with its support library package name. Tip for this step: turn on "Add unambiguous imports on the fly" in Android Studio preferences and just delete all the androidx imports. Most of them will auto-repopulate with the correct support packages.
Now your project should build successfully, but you'll likely run into runtime crashes due to androidx view components used in layout files.
Search all xml files for androidx and com.google.android.material, and replace each view with its support equivalent name.
Don't forget to fix any compilation issues in your tests, and re-run them to make sure they still all pass.

Do a hard reset on repository which was working before migration to android x.
Delete the node_modules folder, and type npm install.

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.

Android Studio 3 and Gradle 4.3 -> Library modules no longer process local JARs -> how to handle this?

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

Many troubles importing a library into AndroidStudio

So I'd like to import the "apache commons ftp" libraries for use in my project. I got as far as the importing the modules, and am including a pic just to show that they're in there.
But when I try to use the import statements
(i.e.) import org.apache.commons.net.ftp.FTP;
they fail.
So am curious if I am missing a step, or am missing something.

Please add below dependency in your gradle:
// https://mvnrepository.com/artifact/commons-net/commons-net
compile group: 'commons-net', name: 'commons-net', version: '3.5'
For any dependency to import in Android Studio through gradle use below reference:
https://mvnrepository.com/
This will save your time from importing module and solving gradle errors :)
Thank You

I would recommand AndiGeeky's answer if you don't modify so you have a custom library.
Meanwhile if you really want to use the library as a module, you can add this line in your build.gradle in your module app
compile project(':NAME_OF_YOUR_MODULE') << should be commons-net-3.5
Hope that will help you :)

Error when adding libraries on Android Studio

I'm trying to create an app for android (google Tango) that uses thrift to send some information to a client. I take a sample Tango app which runs without Thrift. Then when I add try to add some of the Thrift dependencies (like slf4j-log4j12-1.7.12.jar) I suddenly get errors like
error: package com.google.atap.tangoservice does not exist
I don't get what's wrong, it worked before...
Why does this happen, and how can I fix it?
Thank you
UPDATE
The way I added the library was by clicking right on App>new>module then I chose import jar, and selected the jar. Then I went to project structure and in dependencies I added the module of the jar I imported.
Adding it like this did not help me resolve the conflicts I had before:
import org.slf4j.Logger;
giving me the error "cannot resolve symbol 'Logger'".
And it also introduced the errors previously mentioned.

Have you tried adding a dependency to your build.gradle file like this:
dependencies {
compile 'com.google.atap.tangoservice'
}

If you are using local jar dependency then add it like this to the build.gradle:
dependencies {
compile files('libs/something_local.jar')
}