ViewPager2 dependency confusion

Question

I was about to try ViewPager2 but I don't understand when I saw someone add the following dependency declaration in their gradle file:

implementation 'androidx.viewpager2:viewpager2:1.0.0'

I am using AndroidX and, even without adding this in my app-level gradle file, I still have access to the ViewPager2 class and I am able to add it in my code. Is this line only needed when a project is still using legacy Android support libraries and you just want to use a specific AndroidX component such as ViewPager2?

Answer 1

If you have visibility of the ViewPager2 classes in your project without adding an explicit dependency on the androidx.viewpager2:viewpager library, then you have a transitive dependency on the androidx.viewpager2:viewpager library. It will be the case that one of the libraries which you have an explicit dependency on has a dependency on the androidx.viewpager2:viewpager library.

You can run the dependencies Gradle task to see your application's dependency graph and to work out from it which of your explicit dependencies is bringing in the androidx.viewpager2:viewpager library. In my project, when I run the gradle :app:dependencies task, I see in the dependency graph that it's my app's dependency on com.google.android.material:material which brings in the androidx.viewpager2:viewpager library.

If you prefer, you can run the dependencyInsight Gradle task instead to get a more direct answer to the question. For example, in my project, if I run gradle :app:dependencyInsight --configuration debugCompileClasspath --dependency viewpager2, then I see output as follows:

androidx.viewpager2:viewpager2:1.0.0
\--- com.google.android.material:material:1.4.0
     \--- debugCompileClasspath

Answer 2

To use ViewPager2, add the following AndroidX dependency to your project's build.gradle file:

dependencies { implementation "androidx.viewpager2:viewpager2:1.0.0" }