Code Implementation

Step 1. Login Contract

• Defines the interface between the View (Activity) and Presenter.
• View interface defines methods for UI updates (e.g., show/hide dialogue, etc).
• Presenter interface defines methods for business logic (e.g., signInWithInternet).

interface LoginContract {
   interface View : BaseView {
       fun dismissDialog()
       fun setCampaignAdapter()
       fun showLoginAlertDialog(message: String)
       fun showProgressDialog()
       fun showBiometricDialog(user: User)
       fun startHomeScreen(user: User)
       fun startMetadataService()
       fun showSnackBarLong(msg: String)
   }

interface Presenter : BasePresenter<View> {
       fun doSync()
     fun signInWithInternet(username: String, password: String, versionName: String)
       fun signInOffline(username: String, password: String)

       fun saveUser(user: User)
       fun getUserByUsername(username: String): User?
       fun rememberUser(remember: Boolean)
       fun isUserRemembered(): Boolean
       fun getLastUser(): User?
       fun removeUser()
       fun getCampaigns(): List<Campaign>
       fun downloadCampaigns()
       fun setVaccinatorType(vaccinatorType: String)
       fun removeVaccinatorType()
       fun getVaccinatorType(): String
       fun isVaccinatorTypeCampaign(): Boolean
       fun getCampaignByName(name: String): Campaign
       fun saveCampaign(campaign: Campaign)
       fun requestForMetadataService()
       fun isLocationsPresent(): Boolean
 }
}

Step 2. Presenter

The LoginPresenterImpl contains the business logic for handling user login. It interacts with the model and updates the LoginView.

class LoginPresenterImpl : LoginContract.Presenter {

   private var view: LoginContract.View? = null

   override fun doSync() {
       ApiService.getMetadata(object : OnResponseReceivedListener {
           override fun onSuccessReceived(response: Any?) {
               val isSaved = Utils.saveMetadata((response as BaseResponse).params.metadata)
               if (isSaved)
                   view?.showToast(view?.getResource(R.string.app_synced))
               else
                   view?.showToast(view?.getResource(R.string.metadata_error))
               view?.dismissDialog()
           }

           override fun onFailureReceived(errorMessage: String?, responseCode: Int) {
               view?.showToast(view?.getResource(R.string.app_sync_failed))
               view?.dismissDialog()
           }
       })
   }
   override fun signInOffline(username: String, password: String) {
       val user = getUserByUsername(username)
       if (user != null) {
           val decryptedPassword = SecurityUtils.decrypt(user.password, user.username)
           if (decryptedPassword.equals(password, ignoreCase = false)) {
               user.username = username
               if (isPrivileged(BIOMETRIC_VERIFICATION,user))
                   view?.showBiometricDialog(user)
               else
                   view?.startHomeScreen(user)
           } else
               view?.showLoginAlertDialog(view?.getResource(R.string.login_username_password_invalid)!!)
       } else
           view?.showLoginAlertDialog(view?.getResource(R.string.login_username_password_invalid)!!)
   }
 override fun signInWithInternet(username: String, password: String, versionName: String) {
       ApiService.doLogin(
           getPayload(username, password, versionName),
           object : OnResponseReceivedListener {
               override fun onSuccessReceived(response: Any?) {
                   view?.dismissDialog()
                   syncMetadataAfterSignInWithInternet(username)
               }

               override fun onFailureReceived(errorMessage: String?, responseCode: Int) {
                   view?.dismissDialog()
                   view?.showToast(errorMessage)
               }
           })
   }
   override fun isLocationsPresent(): Boolean = !LocationDbHelper.isEmpty()
   override fun getUserByUsername(username: String): User? =
       UserDBHelper.getUserByUsername(username)
   override fun saveUser(user: User) = DevicePreferences.saveUser(user)

   override fun rememberUser(remember: Boolean) =      DevicePreferences.rememberUser(remember)

   override fun isUserRemembered(): Boolean = DevicePreferences.isUserRemembered()
   override fun getLastUser(): User? = DevicePreferences.getLastUser()
   override fun removeUser() = DevicePreferences.removeUser()
   override fun takeView(view: LoginContract.View) {
       this.view = view
   }

   override fun dropView() {
       view = null   }}

Step 3.Implement the Activity

The Activity serves as the concrete implementation of the View interface and integrates with the Presenter.

class LoginActivity : BaseActivity(), LoginContract.View, BiometricCallback {

   @Inject
   lateinit var presenter: LoginContract.Presenter
   var username = ""
   var password = ""
   lateinit var user: User

   override fun onCreate(savedInstanceState: Bundle?) {
       super.onCreate(savedInstanceState)
       setContentView(R.layout.activity_login)
       (application as Application).component.inject(this)
       presenter.takeView(this)
       init()
       setListeners()
   }
 btnSignIn.setOnClickListener {
       Utils.hideKeyboard(this)

       username = etUserName.text!!.trim().toString()
       password = etPassword.text!!.trim().toString()
       if (presenter.getVaccinatorType().isNotEmpty())
           if (presenter.isVaccinatorTypeCampaign())
               if (campaignDropdown.text.toString().isNotEmpty())
                   presenter.signInOffline(username, password)
               else
                   showToast(getResource(R.string.login_no_campaigns_found))
           else
               presenter.signInOffline(username, password)
       else
           showSnackBarLong(getResource(R.string.login_select_activity_type))
   }
}

override fun showLoginAlertDialog(message: String) {
   dialog.showAlertDialogYesNo(
       this,
       null,
       message,
       getString(R.string.yes),
       getString(R.string.no),
       object : DialogListener {
           override fun onPositiveButtonClick() {
               if (isInternetAvailable(this@LoginActivity)) {
                   dialog.showProgressAlertDialog(
                       this@LoginActivity,
                       getResource(R.string.dialog_please_wait)
                   )
                   presenter.signInWithInternet(
                       username,
                       password,
                       packageManager.getPackageInfo(packageName, 0).versionName
                   )
               } else
                   showToast(getResource(R.string.no_internet))
           }

           override fun onNegativeButtonClick() {}
       })
}

override fun showProgressDialog() {
   dialog.showProgressAlertDialog(this, getResource(R.string.dialog_please_wait))
}
override fun dismissDialog() = dialog.dismiss()

override fun showToast(message: String?) =
   Toast.makeText(this, message, Toast.LENGTH_SHORT).show()
override fun showSnackBarLong(msg: String) =
   Snackbar.make(mainLayout, msg, Snackbar.LENGTH_LONG).show()

override fun onDestroy() {
   presenter.dropView()
   super.onDestroy()
}