KMMT : Kotlin Multiplatform Mobile Template

Kotlin Multiplatform Mobile Development Simplified

KMMT is a KMM based project template designed to simplify the KMM development. It uses a simplified approach that can be shared both in android and iOS easily.

Primary objective of this project is to help KMM Developers & promote KMM technology

Credits : KaMP Kit

Android.mp4

iOS.mp4

IDE Requirements

IntelliJ/Android Studio - Android & Shared Module

Xcode - iOS Project

✨Features ✨

1. Simple Networking API ( Ktor )

Create API Services using BaseAPI class. All network responses are wrapped in Either data type

class JsonPlaceHolderServiceAPI : BaseAPI() {

    override val baseUrl: String
        get() = "https://jsonplaceholder.typicode.com/"

    suspend fun getPosts(postId: Int): Either<List<PostModel>, NetworkFailure> {
        return doGet {
            apiPath("comments?postId=$postId")
        }
    }

    suspend fun setPost(post: PostModel): Either<PostModel, NetworkFailure> {
        return doPost(post) {
            apiPath("comments")
        }
    }
}

class BreedServiceAPI : BaseAPI() {
    override val baseUrl: String
        get() = "https://dog.ceo/"

    suspend fun getBreeds(): Either<List<TBreed>, NetworkFailure> {
        return doGet<BreedResult> {
            apiPath("api/breeds/list/all")
        }.flatMap { breedResult ->
            //Converting BreedResult to List<TBreed>
            Either.Success(
                breedResult.message.keys
                    .sorted().toList()
                    .map { TBreed(0L, name = it.toWordCaps(), false) }
            )
        }
    }
}

2. Async Task Helper ( Kotlinx.Coroutines )

Run code (Networking calls, Heavy calculations, Large dataSets from local DB, etc..) in Background thread and get the result in UI thread.

runOnBackground {
    //Code to execute in background
}

Return value from background

runOnBackgroundWithResult {
    //Code to execute in background with return
}.resultOnUI { result ->

}

or

runOnBackgroundWithResult {
    //Code to execute in background with return
}.resultOnBackground { result ->

}

class PostViewModel(view: LoginView) : BaseViewModel<LoginView>(view) {

    fun getPostsFromAPI() {

        runOnBackgroundWithResult {
            JsonPlaceHolderServiceAPI().getPosts(1)    //getPost returns data so return statement is not needed
            //or 
            // return@runOnBackgroundWithResult JsonPlaceHolderServiceAPI().getPosts(1)
        }.resultOnUI {
            getView()?.showPopUpMessage(
                "First Post Details",
                "Username : ${it.first().name}\n email : ${it.first().email}"
            )
        }
    }

    fun savePost() {

        val post = PostModel("Post Body", "[email protected]", 100, "Jitty", 6)

        runOnBackgroundWithResult {
            JsonPlaceHolderServiceAPI().setPost(post)
        }.resultOnUI {
            getView()?.showPopUpMessage("Saved Post Details", "Name : ${it.name}\n email : ${it.email}")
        }
    }
}

3. Multiplatform Bundle : Object Passing B/W Activities or ViewControllers

View Model can pass objects & values from Activity to Activity (Android) or ViewController to ViewController (iOS)

Send Values From 1st View Model

   // 1st View Model 

var userModel = UserModel("[email protected]", "Jitty", "Andiyan")

var bundle = Bundle {
    putStringExtra(HomeViewModel.USER_NAME, username.toString())
    putSerializableExtra(HomeViewModel.USER_OBJECT, userModel, UserModel.serializer())
}

getView()?.navigateToHomePage(bundle)


// 1st View 

fun navigateToHomePage(bundle: BundleX)


// 1st Activity : Android

override fun navigateToHomePage(bundle: BundleX) {
    openActivity(HomeActivity::class.java, bundle)
    finish()
}

// 1st ViewContoller : iOS

func navigateToHomePage (bundle: BundleX) {
    openViewController(newViewControllerName: "HomeViewController", bundle: bundle)
}

Retrieve Values From 2nd View Model

   // 2nd View Model 

class HomeViewModel(view: HomeView) : BaseViewModel<HomeView>(view) {

    companion object BundleKeys {
        const val USER_NAME = "USERNAME"
        const val USER_OBJECT = "USEROBJ"
    }

    override fun onStartViewModel() {

        getBundleValue<String>(USER_NAME)?.let { username ->

        }
        getBundleValue<UserModel>(USER_OBJECT)?.let { userModel ->

        }
    }
}

4. Platform Blocks

Execute anything specific to a particular platform using Platform Blocks

runOnAndroid {

}

runOniOS {

}

5. Object Serialization Helper ( Kotlinx.Serialization )

Use toJsonString and toObject functions for instant serialization.

Objects to String Serialization

        var userModel = UserModel("[email protected]", "Jitty", "Andiyan")
        
        var jsonString = userModel.toJsonString(UserModel.serializer())

String to Object Serialization

        var userModel = jsonString.toObject<UserModel>()
        
        or
        
        var userModel:UserModel = jsonString.toObject()
        
        or
        
        var userModel = jsonString.toObject(UserModel.serializer())

6. Key Value Store ( Multiplatform Settings )

Use storeValue and getStoreValue functions for storing and retrieving Key-Value respectively

Storing Key-Value pair

        var userModel = UserModel("[email protected]", "Jitty", "Andiyan")
        
        storeValue { 
            putString("Key1","Value")
            putBoolean("Key2",false)
            putSerializable("Key3",userModel,UserModel.serializer())
        }

Retrieve Value using Key

        var stringValue = getStoreValue<String>("Key1")
        
        or
        
        var stringValue:String? = getStoreValue("Key1")
        
        var boolValue = getStoreValue<Boolean>("Key2")
        
        var userModel = getStoreValue<UserModel>("Key3",UserModel.serializer())

7. LiveData & LiveDataObservable ( LiveData )

LiveData follows the observer pattern. LiveData notifies Observer objects when underlying data changes. You can consolidate your code to update the UI in these Observer objects. That way, you don't need to update the UI every time the app data changes because the observer does it for you.

        //Sources
        var premiumManager = PremiumManager()
        var premiumManagerBoolean = PremiumManagerBoolean()

        //Create Observer & Observe
        var subscriptionLiveDataObservable = observe<String> {
           getView()?.setSubscriptionLabel(it)
        }
        
        //Adding Sources
        subscriptionLiveDataObservable.addSource(premiumManager.premium())

        or
        
        //Adding Sources with converter (Boolean to String)
        subscriptionLiveDataObservable.addSource(premiumManagerBoolean.isPremium()){
            if (it)
            {
                return@addSource "Premium"
            }else{
                return@addSource "Free"
            }

        }

        //Update source states
        premiumManager.becomePremium()

        premiumManagerBoolean.becomeFree()

        premiumManager.becomeFree()

        premiumManagerBoolean.becomePremium()

class PremiumManager {
    private val premium = MutableLiveDataX<String>()
    fun premium(): LiveDataX<String> {
        return premium
    }

    fun becomePremium() {
        premium.value = "premium"
    }

    fun becomeFree() {
        premium.value = "free"
    }

}

class PremiumManagerBoolean {
    private val premium = MutableLiveDataX<Boolean>()
    fun isPremium(): LiveDataX<Boolean> {
        return premium
    }

    fun becomePremium() {
        premium.value = true
    }

    fun becomeFree() {
        premium.value = false
    }

}

8. Observe with DBHelper ( Local Database : SQLite - SQLDelight )

Use 'asFlow()' extension from DBHelper class to observe a query data

class BreedTableHelper : DBHelper() {

    fun getAllBreeds(): Flow<List<TBreed>> =
        localDB.tBreedQueries
            .selectAll()
            .asFlow()
            .mapToList()
            .flowOn(Dispatchers_Default)


    suspend fun insertBreeds(breeds: List<TBreed>) {
        ...
    }

    fun selectById(id: Long): Flow<List<TBreed>> =
        localDB.tBreedQueries
            .selectById(id)
            .asFlow()
            .mapToList()
            .flowOn(Dispatchers_Default)

    suspend fun deleteAll() {
        ...
    }

    suspend fun updateFavorite(breedId: Long, favorite: Boolean) {
        localDB.transactionWithContext(Dispatchers_Default) {
            localDB.tBreedQueries.updateFavorite(favorite, breedId)
        }
    }

}

class BreedViewModel(view: BreedView) : BaseViewModel<BreedView>(view) {

    private lateinit var breedTableHelper: BreedTableHelper
    private lateinit var breedLiveDataObservable: LiveDataObservable<Either<List<TBreed>, Failure>>
    private lateinit var breedListCache: BreedListCache

    override fun onStartViewModel() {

        breedTableHelper = BreedTableHelper()
        breedListCache = BreedListCache(getBackgroundCoroutineScope())

        breedLiveDataObservable = observe { breedList ->
            breedList.either({
                getView()?.showPopUpMessage(it.message)
                getView()?.stopRefreshing()
            }, {
                getView()?.refreshBreedList(it)
                getView()?.stopRefreshing()
            })

        }

        refreshBreedListCache(forceRefresh = false)

        observeBreedsTable()

    }

    private fun observeBreedsTable() {
        //get Data from db with observe (Flow)
        runOnBackground {
            //Each refreshBreedListCache will trigger collect 
            breedTableHelper.getAllBreeds().collect {
                breedLiveDataObservable.setValue(Either.Success(it))
            }
        }
    }

    private fun refreshBreedListCache(forceRefresh: Boolean) {
        breedListCache.cacheData(Unit, forceRefresh)
        { cachedResult ->
            cachedResult.either({
                breedLiveDataObservable.setValue(Either.Failure(it))
            }, {
                println("Cache Table updated : $it")
            })
        }
    }
}

9. Useful Functional Programming

use Either data type to represent a value of one of two possible types (a disjoint union). Instances of Either are either an instance of Failure or Success

 Either<SuccessType, FailureType>

convert or map SuccessType using flatMap or map

var result = doGet<List<UserModel>> {
    apiPath("jittya/jsonserver/users?username=${credentails.username}&password=${credentails.password}")
}

return result.flatMap {
    // convert List to Boolean
    Either.Success(it.any { it.username == credentails.username && it.password == credentails.password })
}

use either blocks( either or eitherAsync [for suspended method support] ) to define failure & success functionalities

 authenticatedResult.either({
    //Failure
    getView()?.showPopUpMessage(it.message)

}, { isAuthenticated ->
    //Success
    if (isAuthenticated) {

        var userModel = UserModel("[email protected]", "Jitty", "Andiyan")

        var bundle = Bundle {
            putStringExtra(HomeViewModel.USER_NAME, username.toString())
            putSerializableExtra(HomeViewModel.USER_OBJECT, userModel, UserModel.serializer())
        }

        getView()?.navigateToHomePage(bundle)
    } else {
        getView()?.showPopUpMessage("Login Failed")
    }
})

10. Data Cache Helper

Use BaseDataCache<RequestParamType, DataType> to implement data caching (remote to local). call cacheData function to get and save data

class BreedListCache(backgroundCoroutineScope: CoroutineScope) :
    BaseDataCache<Unit, List<TBreed>>(backgroundCoroutineScope, "BREED_SYNC_TIME") {
    
    override suspend fun getData(param: Unit): Either<List<TBreed>, Failure> {
        //get data from remote (using api)
        return BreedServiceAPI().getBreeds()
    }

    override suspend fun saveData(data: List<TBreed>): Either<Boolean, Failure> {
        //save remote data in Local database
        return try {
            BreedTableHelper().insertBreeds(data)
            Either.Success(true)
        } catch (e: Exception) {
            Either.Failure(DataBaseFailure(e))
        }
    }
}

var breedListCache = BreedListCache(getBackgroundCoroutineScope())

private fun refreshBreedListCache(forceRefresh: Boolean) {
    
//    breedListCache.cacheData(Unit, forceRefresh)
//                or
    breedListCache.cacheData(Unit, forceRefresh)
    { cachedResult ->
        cachedResult.either({ failure ->
            println("Cache failed : $failure")
        }, { success ->
            println("Cache updated : $success")
        })
    }
}

How to use

Shared Module (Business Logics & UI Binding Methods) :

Step 1 : Define View

Create a View interface by extending from BaseView.
Define UI binding functions in View interface.

interface LoginView : BaseView {

    fun setLoginPageLabel(msg: String)
    fun setUsernameLabel(usernameLabel: String)
    fun setPasswordLabel(passwordLabel: String)
    fun setLoginButtonLabel(loginLabel: String)

    fun getEnteredUsername(): String
    fun getEnteredPassword(): String

    fun setLoginButtonClickAction(onLoginClick: KFunction0<Unit>)

    fun navigateToHomePage(bundle: BundleX)
}

Step 2 : Define ViewModel

Create a ViewModel class by extending from BaseViewModel with View as Type.
Define your business logic in ViewModel class.

class LoginViewModel(view: LoginView) : BaseViewModel<LoginView>(view) {
    override fun onStartViewModel() {
        getView()?.setLoginPageLabel("Login : ${Platform().platform}")
        getView()?.setUsernameLabel("Enter Username")
        getView()?.setPasswordLabel("Enter Password")
        getView()?.setLoginButtonLabel("Login")
        getView()?.setLoginButtonClickAction(this::onLoginButtonClick)
    }

    fun onLoginButtonClick() {
        getView()?.showLoading("authenticating...")
        val username = getView()?.getEnteredUsername()
        val password = getView()?.getEnteredPassword()
        checkValidation(username, password)
    }

    fun checkValidation(username: String?, password: String?) {
        if (username.isNullOrBlank().not() && password.isNullOrBlank().not()) {
            val credentials = CredentialsModel(username.toString(), password.toString())

            runOnBackgroundWithResult {
                JsonPlaceHolderServiceAPI().authenticate(credentials)
            }.resultOnUI { authenticatedResult ->
                getView()?.dismissLoading()
                authenticatedResult.either({
                    getView()?.showPopUpMessage(it.message)
                }, { isAuthenticated ->
                    if (isAuthenticated) {
                        var bundle = Bundle {
                            putStringExtra(HomeViewModel.USER_NAME, username.toString())
                        }
                        getView()?.navigateToHomePage(bundle)
                    } else {
                        getView()?.showPopUpMessage(
                            "Login Failed"
                        )
                    }
                })

            }
        } else {
            getView()?.showPopUpMessage("Validation Failed", "Username or Password is empty")
        }
    }
}

Android Module UI Binding :

Step 3 : Define Android View

Create new activity by extending from KMMActivity with ViewModel as Type.
Implement created View interface in activity.
Implement all necessary methods from View & KMMActivity.

Implement LoginView & Bind UI Controls

class LoginActivity : KMMActivity<LoginViewModel, ActivityMainBinding>(), LoginView {

    //Generated Methods from KMMActivity based on LoginViewModel
    override fun initializeViewModel(): LoginViewModel {
        return LoginViewModel(this)
    }

    override fun viewBindingInflate(): ActivityMainBinding {
        return ActivityMainBinding.inflate(layoutInflater)
    }

    //Generated Methods from LoginView
    override fun setLoginPageLabel(msg: String) {
        binding.textView.text = msg
    }

    override fun setUsernameLabel(usernameLabel: String) {
        binding.usernameET.hint = usernameLabel
    }

    override fun setPasswordLabel(passwordLabel: String) {
        binding.passwordET.hint = passwordLabel
    }

    override fun getEnteredUsername(): String {
        return binding.usernameET.text.toString()
    }

    override fun getEnteredPassword(): String {
        return binding.passwordET.text.toString()
    }

    override fun setLoginButtonClickAction(onLoginClick: KFunction0<Unit>) {
        binding.loginBtn.setClickAction(onLoginClick)
    }

    override fun setLoginButtonLabel(loginLabel: String) {
        binding.loginBtn.text = loginLabel
    }

    override fun navigateToHomePage(bundle: BundleX) {
        openActivity(HomeActivity::class.java, bundle)
        finish()
    }
}

iOS Module UI Binding (Xcode) :

Step 4 : Define iOS View

Create new viewcontroller by extending from KMMUIViewController.
Implement created View interface in viewcontroller.
Implement all necessary methods from View & KMMUIViewController.