I believe the Template method pattern involves encapsulating each step in the algorithm.
I think activity's life cycles (onCreate, onResume, etc) are steps that must be overridden by the concrete class.
Does this mean that the Android activity lifecycle (activity and fragment classes) conform to the template design pattern or is there a different pattern which suits it better
Thanks
The way Android framework is built is definitely following the template pattern, which is its strength but also its weakness. Because this pattern suggests to implement only some part of the module, it gets pretty easy to obtain a quick and simple result without involving too many efforts.
However, as its is based on inheritance, this can get really nasty once you start thinking about extending the framework, or deal with cross-concerns pattern. Most of android framework require to extend an Activity in order to be used, and as multi-inheritance is not an option, this limits the way you can compose your features.
An approach that favors composition over inheritance would have been more than welcome, and the only reason I can imagine why this choice has been made is performance problems.
Going through job openings, I sometimes see the phrase "design patterns" listed as a requirement. The phrase "design pattern" is rather too generalized. When I think of design patterns, I often think of something like MVC (Model View Controller) but MVC doesn't really fit in well with Android, whereas it does fit in well with web applications.
If someone in a job interview asks me what design patterns do I know of for Android, I would be stumped. Can you indicate any major design patterns that Android developers might use so that I can get familiar with them? Thanks a million!
There are couple of design patterns being used by developer weather they are aware of it or not, below is the list of the most used
Observer pattern
Singeton Pattern
Factory Pattern
State Pattern
Filter Pattern
Iterator Pattern
Template Pattern
Adapter Pattern
I would like to know if someone know some Android Framework to conventional applications. For example, a framework like rails which we can see easily the MVC pattern.
See answer here for an overview of Android's limitations, which will give you an idea of why an MVC pattern on Android has not yet emerged: http://www.quora.com/Is-there-any-standard-MVC-framework-in-Android-application-development-If-not-is-it-worth-developing-one
After having posted that answer I have gone ahead and built a fully-featured app using a single-Activity architecture. It allowed us to get past all the major UX limitations that were mentioned while being able to have arbitrary complexity in controller hierarchies (parents with children with sub-children etc.). Overall it worked out great, however you WILL have to build out specialized components (ie: custom back stack mechanism) as well as to store/restore state in a way that plays nicely with Android's own Activity/Fragment lifecycle patterns. There are also certain limitations around Fragment animations which had us pull our hair out at times, which required more custom component workarounds. ie: animations that show both an outgoing and incoming Fragment on-screen at the same time aren't supported on Android, so you will have to resort to taking screenshots of views and placing them into temporary ImageViews so that you create the appearance of transitions that show two fragments at the same time. In the end it's all possible, but you will have to be ready to work around annoying Android limitations while keeping an overall MVC architecture intact.
In summary: make your top-level component an Activity which is primarily responsible for top-level navigation (tab-based, menu-based, etc., as well as back stack and state preservation). The top-level component should not govern any particular screen of your app, instead it manages controllers for every top-level screen. The controllers are all Fragments, and can contain sub-controllers which are also Fragments. All screen transitions are performed using fragment transactions as opposed to Intents/Activities. Passing around data between Fragments is another point of contention as Android generally only supports data-passing through an Activity (ie: Fragment uses its parent Activity). But in this architecture you have need to have Fragments passing data to each other (either parent/child or sibling-sibling relationships).
I don't have this wrapped up into a framework or anything, but if your dev/arch team is sufficiently proficient the architecture is definitely worthwhile shooting for. You will come out with an app that is not subject to the traditional UX limitations of Android... something that very few Android apps can say they've achieved. Also... it generally feels awesome showing you can achieve the same level of UX that iOS apps have for years. It's about time isn't it??
Don't know about the "conventional" part - Android does not play well with MVC architecture natively (mostly because Activities and Fragments take on responsibilities of both views and controllers), and I don't know if there is a standard framework for implementing MVC in Android.
I described some of my insights in more details in this answer.
That said, I created MVC (in fact MVP) template/tutorial application which demonstrates the approach I take to enforce MVP in my apps. You can use this app as tutorial, or clone/fork it and use as Android Studio template for your own apps. The source code is here: https://github.com/techyourchance/android_mvc_template
basically android has MVC pattern, but if you need more features like .net mvc you can use com.divankits.mvc module. Just see one of samples to find out how to use it.
here is more details about module:
bind properties to view(layout) objects
you are able to create field validators
convert model to json
I come from C Background and have knowledge on C++(at least I know virtual functions, INheritance, Code -reuse and some OOPS concept), But still I am having hard time understanding the Design Patterns in C++/Java.I guess Binders Design Patterns are based on C++ Design pattern(correct me).
DO i have to understand UML as well to understand them.
Plz explain or direct a link with test source code on the above.
PS: I am trying to understand this blog by Tetsuyuki Kobayashi and i am in no way related to him.
I wouldnt say that C++ Binders are a design pattern. I put a link here explaining them.
I would also say that Design patterns arent really language specific, they can basically be implemented in any (most) programming languages. Languages that support OOP typically make implementing design patterns easier, but that could be argued.
The Gang of Four design patterns book uses UML to explain design patterns, but I wouldnt say you would have to be a UML expert to understand design patterns. If UML is bothering you, try the Head First Design Patterns book, its much easier to understand.
Closed. This question needs to be more focused. It is not currently accepting answers.
Want to improve this question? Update the question so it focuses on one problem only by editing this post.
Closed 4 years ago.
Improve this question
I'm doing a small research of mobile platforms and I would like to know which design patterns are used in Android?
e.g. in iOS Model-view-controller is very widely used together with delegation and other patterns.
What patterns and where in particular does Android use?
EDIT
I'm not asking for design patterns used deep in kernel, dalvik and so on, but about patterns which an application developer will meet while developing an application.
I tried using both the model–view–controller (MVC) and model–view–presenter architectural patterns for doing android development. My findings are model–view–controller works fine, but there are a couple of "issues". It all comes down to how you perceive the Android Activity class. Is it a controller, or is it a view?
The actual Activity class doesn't extend Android's View class, but it does, however, handle displaying a window to the user and also handle the events of that window (onCreate, onPause, etc.).
This means, that when you are using an MVC pattern, your controller will actually be a pseudo view–controller. Since it is handling displaying a window to the user, with the additional view components you have added to it with setContentView, and also handling events for at least the various activity life cycle events.
In MVC, the controller is supposed to be the main entry point. Which is a bit debatable if this is the case when applying it to Android development, since the activity is the natural entry point of most applications.
Because of this, I personally find that the model–view–presenter pattern is a perfect fit for Android development. Since the view's role in this pattern is:
Serving as a entry point
Rendering components
Routing user events to the presenter
This allows you to implement your model like so:
View - this contains your UI components, and handles events for them.
Presenter - this will handle communication between your model and your view, look at it as a gateway to your model. Meaning, if you have a complex domain model representing, God knows what, and your view only needs a very small subset of this model, the presenters job is to query the model and then update the view. For example, if you have a model containing a paragraph of text, a headline and a word-count. But in a given view, you only need to display the headline in the view. Then the presenter will read the data needed from the model, and update the view accordingly.
Model - this should basically be your full domain model. Hopefully it will help making your domain model more "tight" as well, since you won't need special methods to deal with cases as mentioned above.
By decoupling the model from the view all together (through use of the presenter), it also becomes much more intuitive to test your model. You can have unit tests for your domain model, and unit tests for your presenters.
Try it out. I personally find it a great fit for Android development.
Update November 2018
After working and blogging about MVC and MVP in Android for several years (see the body of the answer below), I decided to capture my knowledge and understanding in a more comprehensive and easily digestible form.
So, I released a full blown video course about Android applications architecture. So, if you're interested in mastering the most advanced architectural patterns in Android development, check out this comprehensive course here.
This answer was updated in order to remain relevant as of November 2016
It looks like you are seeking for architectural patterns rather than design patterns.
Design patterns aim at describing a general "trick" that programmer might implement for handling a particular set of recurring software tasks. For example: In OOP, when there is a need for an object to notify a set of other objects about some events, the observer design pattern can be employed.
Since Android applications (and most of AOSP) are written in Java, which is object-oriented, I think you'll have a hard time looking for a single OOP design pattern which is NOT used on Android.
Architectural patterns, on the other hand, do not address particular software tasks - they aim to provide templates for software organization based on the use cases of the software component in question.
It sounds a bit complicated, but I hope an example will clarify: If some application will be used to fetch data from a remote server and present it to the user in a structured manner, then MVC might be a good candidate for consideration. Note that I said nothing about software tasks and program flow of the application - I just described it from user's point of view, and a candidate for an architectural pattern emerged.
Since you mentioned MVC in your question, I'd guess that architectural patterns is what you're looking for.
Historically, there were no official guidelines by Google about applications' architectures, which (among other reasons) led to a total mess in the source code of Android apps. In fact, even today most applications that I see still do not follow OOP best practices and do not show a clear logical organization of code.
But today the situation is different - Google recently released the Data Binding library, which is fully integrated with Android Studio, and, even, rolled out a set of architecture blueprints for Android applications.
Two years ago it was very hard to find information about MVC or MVP on Android. Today, MVC, MVP and MVVM has become "buzz-words" in the Android community, and we are surrounded by countless experts which constantly try to convince us that MVx is better than MVy. In my opinion, discussing whether MVx is better than MVy is totally pointless because the terms themselves are very ambiguous - just look at the answers to this question, and you'll realize that different people can associate these abbreviations with completely different constructs.
Due to the fact that a search for a best architectural pattern for Android has officially been started, I think we are about to see several more ideas come to light. At this point, it is really impossible to predict which pattern (or patterns) will become industry standards in the future - we will need to wait and see (I guess it is matter of a year or two).
However, there is one prediction I can make with a high degree of confidence: Usage of the Data Binding library will not become an industry standard. I'm confident to say that because the Data Binding library (in its current implementation) provides short-term productivity gains and some kind of architectural guideline, but it will make the code non-maintainable in the long run. Once long-term effects of this library will surface - it will be abandoned.
Now, although we do have some sort of official guidelines and tools today, I, personally, don't think that these guidelines and tools are the best options available (and they are definitely not the only ones). In my applications I use my own implementation of an MVC architecture. It is simple, clean, readable and testable, and does not require any additional libraries.
This MVC is not just cosmetically different from others - it is based on a theory that Activities in Android are not UI Elements, which has tremendous implications on code organization.
So, if you're looking for a good architectural pattern for Android applications that follows SOLID principles, you can find a description of one in my post about MVC and MVP architectural patterns in Android.
When i reach this post it really help me to understand patterns with example so i have make below table to clearly see the Design patterns & their example in Android Framework
I hope you will find it helpful.
Some useful links for reference:
Common Design Patterns for Android with Kotlin
Introduction to Android Design Patterns
Design Patterns
There are various patterns used in Android framework like:
Broadcast receiver uses Observer pattern
Remoter service invocation uses Proxy pattern
View and view group uses Composite pattern
Media framework uses Facade pattern
Here is a great article on Common Design Patterns for Android:
Creational patterns:
Builder (e.g. AlertDialog.Builder)
Dependency Injection (e.g. Dagger 2)
Singleton
Structural patterns:
Adapter (e.g. RecyclerView.Adapter)
Facade (e.g. Retrofit)
Behavioral patterns:
Command (e.g. EventBus)
Observer (e.g. RxAndroid)
Model View Controller
Model View ViewModel (similar to the MVC pattern above)
The Following Android Classes uses Design Patterns
1) View Holder uses Singleton Design Pattern
2) Intent uses Factory Design Pattern
3) Adapter uses Adapter Design Pattern
4) Broadcast Receiver uses Observer Design Pattern
5) View uses Composite Design Pattern
6) Media FrameWork uses Façade Design Pattern
In the Notifications case, the NotificationCompat.Builder uses Builder Pattern
like,
mBuilder = new NotificationCompat.Builder(this)
.setSmallIcon(R.drawable.ic_stat_notification)
.setContentTitle(getString(R.string.notification))
.setContentText(getString(R.string.ping))
.setDefaults(Notification.DEFAULT_ALL);
Android also uses the ViewHolder design pattern.
It's used to improve performance of a ListView while scrolling it.
The ViewHolder design pattern enables you to access each list item view without the need for the look up, saving valuable processor cycles. Specifically, it avoids frequent calls of findViewById() during ListView scrolling, and that will make it smooth.
All these patterns, MVC, MVVM, MVP, and Presentation Model, can be applied to Android apps, but without a third-party framework, it is not easy to get well-organized structure and clean code.
MVVM is originated from PresentationModel. When we apply MVC, MVVM, and Presentation Model to an Android app, what we really want is to have a clear structured project and more importantly easier for unit tests.
At the moment, without an third-party framework, you usually have lots of code (like addXXListener(), findViewById(), etc.), which does not add any business value. What's more, you have to run Android unit tests instead of normal JUnit tests, which take ages to run and make unit tests somewhat impractical.
For these reasons, some years ago we started an open source project, RoboBinding - A data-binding Presentation Model framework for the Android platform. RoboBinding helps you write UI code that is easier to read, test, and maintain. RoboBinding removes the need of unnecessary code like addXXListener or so, and shifts UI logic to the Presentation Model, which is a POJO and can be tested via normal JUnit tests. RoboBinding itself comes with more than 300 JUnit tests to ensure its quality.
I would like to add a design pattern that has been applied in Android Framework. This is Half Sync Half Async pattern used in the Asynctask implementation. See my discussion at
https://docs.google.com/document/d/1_zihWXAwgTAdJc013-bOLUHPMrjeUBZnDuPkzMxEEj0/edit?usp=sharing
In Android the "work queue processor" pattern is commonly used to offload tasks from an application's main thread.
Example: The design of the IntentService class.
The IntentService receives the Intents, launch a worker thread, and stops the service as appropriate.All requests are handled on a single worker thread.
Binder uses "Observer Pattern" for Death Recipient notifications.