Dependency injection is an important technique that helps us write testable Android apps. For large apps with complex requirements, powerful frameworks like Dagger centralize and organize our dependency relationships and lifecycles and automate injection. However, many applications are simple enough that manual dependency injection provides all the benefits of Dagger with few of the costs (e.g. a steep learning curve; slower build times). In this beginner-friendly talk, we’ll learn how to identify, extract, and inject dependencies by hand in several common Android architectures. Attendees will leave with a solid grasp of dependency injection fundamentals and the ability (and desire!) to introduce manual dependency injection into their own codebases.