This document discusses design patterns used in Android development. It defines design patterns as reusable object-oriented code between projects. The most common patterns used in Android are MVC, MVP, and MVVM. MVC separates an app into a model, view, and controller. MVP is similar but the presenter updates the passive view. MVVM uses a view model to send data streams between the model and view. Design patterns help make code more maintainable, manage complexity, and improve readability and testability.

1. Design Patterns in
Android
A guide by Zahra Heydari

2. What are Design Patterns?
A Design Pattern is just a convenient way of reusing
object-oriented(OO) code between projects and
programmers.
A common pattern in early literature on programming
frameworks is MVC for smalltalk, which divides user
interface problem into three parts.

3. Why we use Design Patterns?
There are many reasons that we use the Design Patterns but most important of
them:
➔ Make our code
more
maintainable
➔ To manage an
app`s
complexity
➔ Make our code
more readable &
testable

4. Design pattern use in Android
Three most common Design
Patterns use? 1.MVC(Model View
Controller)
2.MVP(Model View
Presenter)
3.MVVM(Model
View ViewModel)

5. 1.MVC (Model View Controller)
Model The data layer,
responsible for managing the
business logic and handling
network or database API.
View The UI layer, a
visualisation of the data from
the model.
Controller The logic layer,
get notified of the user`s
behavior and updates the
model as needed.

6. 2.MVP (Model View
Presenter)
MVP(Model View
Presenter)
The MVP pattern allows
separating the
presentation layer from
the logic.

7. Notice:
In the MVP pattern, the View is completely
passive and Data is always delivered to the
View by the Presenter.
➔ The View cannot access the Model.
➔ The Presenter is tied to a single
View.
➔ The View is completely passive in the
MVP pattern.

8. 3.MVVM(Model View
ViewModel)
This pattern allows fast reaction to
design changes!

9. MVVM is Not a Framework,
class(Android Architecture
Component Class) or API!
It`s for modeling
applications that have a
User Interface.

10. The difference between
MVVM & MVP?
● ViewModel replaces the Presenter in the Middle
Layer.
● The Presenter holds references to the View. The
ViewModel doesn’t.
● The Presenter updates the View using the
classical way (triggering methods).
● The ViewModel sends data streams.
● The Presenter and View are in a 1 to 1 relationship.
● The View and the ViewModel are in a 1 to many
relationship.
Singleton
The Singleton Pattern
specifies that only a single
instance of a class should
exist with a global point of
access. This works well
when modeling real-world
objects only having one
instance.

12. Good luck!
We hope you’ll use these tips to find out more
about Design Patterns and use them to
implement the structure of your projects!
For more (free) information and tips relevant
to these concepts, go to
medium.com
For more about making
your ideas stick with
others, check out Design
Patterns book!