Anyone know a good and complete resource about Dagger 2? i want to inject various thing, like context or retrofit interface in my view module and other stuff like that

Many of the example git repositories and tutorials don't show newest features. Official documentation would be your best bet, or try looking for a relatively new or recently updated examples. If you don't care about using the latest features, one or both of the mentioned at the top is a good starting point.

It's big topic and really depends on your use case. It's easy for Retrofit (no dependency on context), more tricky for activity/fragment/view contexts, you need separate scope that reapects lifecycle of those components