MVP
for
Listing Templates
-nihal111
Nihal Singh
Why?
- To showcase my work (more technical depth)
- To share knowledge about existence of a feature in our codebase that follows MVP pattern (the
re-architectured"right" way)
Overview
- The Listing Templates Feature
- How did I make it?
- Some MVP Tips
- Recreating a Screen Together
- Android Studio walkthrough
Demo Video
Listing Templates
How did I do it?
Step 1: Understand the SPEC
Understanding the spec and being able to picture the flow of the feature is crucial for efficient implementation.
Step 2: Sketch out the flow
Have a design/flow-diagram to work with.
Make a rough one by hand if you don't get one from the designer. It helps.
Design Blueprint
Step 3: Sign the contract
Once the first two steps are done, it's time to create a Contract for the ViewProxy, Presenter and Model layers.
This does not have to be final. It just serves as a great starting point and allows you to get some clarity.
Make an architectural design doc, using the template.
Step 3: Sign the contract
The doc should essentially contain the following-
- Breakdown/Decomposition of the feature in ViewProxy, Model and Presenter layers
- (Having a draft contract for each screen works well)
- List of classes with brief distribution of responsibilities.
Step 4: Dive into implementation
Once you've signed the Contract,
it's time to commit.
Keep writing tests as you go, or at least keep thinking about how you'll write them. This should keep the code testable.
MVP tips
Activity
Keep the activities lean
Delegate lifecycle events to the Presenter
To call super methods in the Activity, use a custom interface, that gets called by the presenter
MVP tips
Presenter
It's a good idea to have the Presenter extend from the LifecycleAwarePresenter (com.kouzoh.mercari.common.presenter)
The lifecycle (FragmentActivity.getLifecycle()) can be passed to the Presenter during construction
This allows for clearing the disposables at the right lifecycle events.
MVP tips
ViewProxy
The ViewProxy should be initialized inside the Activity and passed on to the presenter during it's construction.
The ViewProxy can take in the activity as parameter during construction. This allows for obtaining the context and finding views by ID.
Let's do it together!
Template Create and Edit Screen
TemplateCreateEditActivity
SPEC Breakdown
Create Screen
- Set Toolbar Title and Button text
- Setup onClickListener for the Create button
- On Click of the Create Button-
- If entered title and description are non-empty, make the API request to create a new template
- Else show a dialog alert
SPEC Breakdown
Edit Screen
- Set Toolbar Title and Button text
- Fill fields with selected template
- Setup onClickListener for the Edit button
- On Click of the Edit Button-
- If entered title and description are non-empty, make the API request to edit the opened template
- Else show a dialog alert
Set Toolbar Title and Button text
When?
onCreate
How?
Activity
Presenter
ViewProxy
Activity delegates onCreate to Presenter
Presenter calls view to update UI, based on intent received
Depends on?
intent.getStringExtra(S.MODE)
Set onClickListeners for the Button
When?
onCreate
How?
Activity
Presenter
ViewProxy
Activity delegates onCreate to Presenter
Presenter defines the onClickListener and passes it to the ViewProxy
Depends on?
intent.getStringExtra(S.MODE)
What does the contract look like?
Presenter
-
onCreate
- createTemplate
- editTemplate
Repository
-
createTemplate(title, description): Observable
- editTemplate(id, title, description): Observable
ViewProxy
- setTitleForCreate()
- setTitleForEdit()
- setTextForSaveButton()
-
setOnClickListenerForSave
Button(listener)
-
fillFields(title, description)
- getTitleText()
-
getDescriptionText()
- displayErrorMessage()