Android Cloud Development Part 2: Android Registration &. Firebase Email Response

17 min readNov 13, 2020

In part 2, I’ll get in touch with Bluetooth On/Off switch on the Android phone. For the most part of the story, I focus on Client-Server communication. I will use more commonly with the function ejection. The task is simple: Register a customer and send he/she an email response, like this:

The customer needs to enter the product ID to download its operational code in the app.
The server searches product ID and returns one if it is found.
The customer fills out the registration form and sends it to the server. Or just an email if he/she is a return customer, he/she needs to transfer the app to a new phone.
The server saves the data into the online database and sends a welcome email to the customer’s email. We need a cloud function in this section.

Part 2 will end at the registration activity, and the backend service will send a welcome email to the customer’s email address.

— === Menu === —

Frontend ==>

Backend ==>

👾7. Google Cloud Functions: HelloWorld
📡8. HTTP functions in VS Code
🐱‍🏍9. Snippet in VS Code
🏄‍♀️10. Realtime Database Functions in VS Code
🏵🏵🏵🏵 SendGrid Email Service

🐬1. Android-Client Design

< === Menu

Pseudocode:

MainActivity (Part 2)→ Cache: Registered? → WelcomeFragment: Yes: ControlPanel || No: → Registration

ControlPanel (Part 3) → ControlActivity → Bluetooth Detection → Bluetooth Socket

Registration (Part 2) → RegistrationActivity → SearchProductFragment → RegistrationActivity → Found: RegistrationForm || Not Found: SearchProductFragment

File Pattern: MVVM

Gradle:

Project:

buildscript {
    ext.kotlin_version = "1.4.10"
    repositories {
        google()
        jcenter()
        mavenCentral()
        maven { url "https://oss.jfrog.org/libs-snapshot" }
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:4.2.0-alpha14'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
        // Hilt
        classpath 'com.google.dagger:hilt-android-gradle-plugin:2.28-alpha'
        // google service
        classpath 'com.google.gms:google-services:4.3.4'
    }
}
...

Module:

plugins {
    id 'com.android.application'
    id 'kotlin-android'
    id 'kotlin-android-extensions'
    id 'kotlin-kapt'
    id 'dagger.hilt.android.plugin'
    id 'com.google.gms.google-services'
}

android {
    ...
    buildFeatures {
        dataBinding true
        viewBinding true
    }
}

dependencies {
    // STD
    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
    implementation 'androidx.core:core-ktx:1.3.2'
    implementation 'androidx.appcompat:appcompat:1.2.0'
    implementation 'androidx.legacy:legacy-support-v4:1.0.0'
        // Design
    implementation 'com.google.android.material:material:1.2.1'
        // Layout
    implementation 'androidx.constraintlayout:constraintlayout:2.0.3'

    // Activity and Fragment
    def activity_version = "1.2.0-beta01"
    def fragment_version = "1.3.0-beta01"
    implementation "androidx.activity:activity-ktx:$activity_version"
    implementation "androidx.fragment:fragment-ktx:$fragment_version"
        // Testing Fragments in Isolation
    debugImplementation "androidx.fragment:fragment-testing:$fragment_version"

    // Test
    testImplementation 'junit:junit:4.13'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
        // Assertions
    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
    androidTestImplementation 'androidx.test.ext:truth:1.3.0'
    androidTestImplementation 'com.google.truth:truth:1.0'

    // Kotlin coroutines
    def coroutines_version = "1.3.9"
    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:$coroutines_version"
    testImplementation "org.jetbrains.kotlinx:kotlinx-coroutines-test:$coroutines_version"
    testImplementation 'org.hamcrest:hamcrest-library:1.3'
        // Test: Kotlin coroutines
    testImplementation 'org.jetbrains.kotlinx:kotlinx-coroutines-test:1.3.9'
    testImplementation 'org.hamcrest:hamcrest-library:1.3'

    // Hilt
    def hilt_version = '2.28-alpha'
    def hilt_lifecycle_version = '1.0.0-alpha02'
    implementation "com.google.dagger:hilt-android:$hilt_version"
    kapt "com.google.dagger:hilt-android-compiler:$hilt_version"
    implementation "androidx.hilt:hilt-lifecycle-viewmodel:$hilt_lifecycle_version"
    kapt "androidx.hilt:hilt-compiler:$hilt_lifecycle_version"
        // Tests
    androidTestImplementation "com.google.dagger:hilt-android-testing:$hilt_version"
    kaptAndroidTest "com.google.dagger:hilt-android-compiler:$hilt_version"

    // Firebase platform
    implementation platform('com.google.firebase:firebase-bom:25.12.0')
    implementation 'com.google.firebase:firebase-database-ktx'

    // Lifecycle
    def lifecycle_version = "2.2.0"
        // ViewModel
    implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:$lifecycle_version"
    implementation "androidx.lifecycle:lifecycle-extensions:$lifecycle_version"
        // LiveData
    implementation "androidx.lifecycle:lifecycle-livedata-ktx:$lifecycle_version"
        // Lifecycles only (without ViewModel or LiveData)
    implementation "androidx.lifecycle:lifecycle-runtime-ktx:$lifecycle_version"
    implementation "androidx.lifecycle:lifecycle-common-java8:$lifecycle_version"
        // Test helpers for LiveData
    def arch_version = "2.1.0"
    testImplementation "androidx.arch.core:core-testing:$arch_version"
}

👐🏻2. Global Helpers

< === Menu

ConfigHelper: Serve constant variables for all files

// System
const val REQUEST_SEARCH = "Request Key"
const val SEARCH_KEY = "Search Key"
const val REGISTERED = "Registered"

// Error
const val ERROR = "ERROR"
const val INVALID_EMAIL = "Invalid Email"
const val INVALID_PHONE = "Invalid Phone#"
const val TOO_SHORT = "Too short"
const val UNKNOWN = "UNKNOWN"
const val INTERNAL_CACHE_ERROR = "Internal cache error!"
...

FirebaseHelper: Serve functions for Firebase Realtime database

searchEmail():

fun searchEmail(
    regRef:DatabaseReference, // Firebase
    email: String, // email key
    refTrue: KFunction2<String, Customer, Unit>, // True
    refFalse: KFunction2<String, Customer?, Unit> // False
) {
    val tag = "FirebaseHelper: searchEmail():\n"
    var fKey = ""
    var fCustomer:Customer? = null
    val EMAIL_NF = "Email Not Found!"

    // search
    regRef
        .orderByChild("email")
        .endAt(email)
        .addListenerForSingleValueEvent(
            object : ValueEventListener {
                override fun onDataChange(
                    snapshot: DataSnapshot
                ) {
                    val children = snapshot.children
                    lgd(tag+"Done gathering children.")

                    var result = false
                    for (child in children) {
                        val data =
                            child.getValue(Customer::class.java)

                        lgd(tag+"${child.key} ==> $data ")
                        if (data?.email == email) {
                            fKey = child.key!!
                            fCustomer = data
                            result = true
                            break
                        }
                    }

                    if (result) {
                        lgd(tag+"Work on True Function.")
                        refTrue(fKey, fCustomer!!)
                    } else {
                        lgd(tag+"Work on False Function.")
                        refFalse(EMAIL_NF, fCustomer)
                    }
                }

                override fun onCancelled(error: DatabaseError) {
                    refFalse(EMAIL_NF, fCustomer)
                }
            })
}

SearchEmail eject the result to refTrue and refFalse fucntion.

saveCustomerCache():

// Save customer info into cache
fun saveCustomerCache(storage: Storage, customer: Customer) {
    storage.setString(CUSTOMER_ID, customer.customerId)
    storage.setString(FIRST_NAME, customer.firstName)
    storage.setString(LAST_NAME, customer.lastName)
    storage.setString(EMAIL_KEY, customer.email)
    storage.setString(ADDRESS, customer.address)
    storage.setString(CITY, customer.city)
    storage.setString(STATE, customer.state)
    storage.setInt(Zip, customer.zip)

    val tag = "FirebaseHelper: saveCustomerCache():\n"
    lgd(tag+"Customer: $customer")
}

LogHelper: Help with Logcat

const val TAG = "MLOG"
fun lgd(s:String) = Log.d(TAG, s)
fun lgi(s:String) = Log.i(TAG, s)
fun lge(s:String) = Log.e(TAG, s)

I use “MLOG” to track the debug process.

UiHelper: Help UI to process the user input.

// Toast: len: 0-short, 1-long
fun msg(context: Context, s: String, len: Int) =
    if (len > 0) Toast.makeText(context, s, LENGTH_LONG).show()
    else Toast.makeText(context, s, LENGTH_SHORT).show()

// Flash error for 15 times.
fun flashError(
    viewLifecycleOwner: LifecycleOwner,
    errorTV: TextView,
    duration: Long, // second
    delay: Long, // ms
) {...}// Gather UI data from keyboard, Edittext + rootView
fun isKeyboardShown(
    rootView: View,
    mEt: EditText,
    refSave: KFunction2<Int, Boolean, Unit>
): Boolean {...}

Please check Android: Bottom Side EditText Position Shifting and Android: Coroutines with Blinking TextView for their usages.

ValidateForm.kt: Validate the EditText

private val numRegex = "-?\\d+(\\.\\d+)?".toRegex()
private val hexRegex = "\\p{XDigit}+".toRegex()

class ValidateForm {
...
}

Go ahead, DIY yourself. It’s contains isEtEmplty(), isEtHex(), isEtNum(), isEtEmail(), isEtPhone(), chkMac(), chkLen() and View.OnFocusChangeListener. I just unite all the validations into one class.

➽3. Direct Inject SharedPreference: Storage

< === Menu

Nothing new is in the package. I copy the function from the Dagger-Hilt Codelab and expand the code usage.

Storage.kt

interface Storage {
    fun setString(key: String, value: String)
    fun getString(key: String): String

    fun setBoolean(key: String, value: Boolean)
    fun getBoolean(key: String): Boolean

    fun setInt(key: String, value: Int)
    fun getInt(key: String): Int

    fun delKey(key: String): Boolean
    fun clear()
}

SharedPreferenceStorage.kt:

// @Inject tells Dagger how to provide instances of this type
class SharedPreferencesStorage @Inject constructor(
    @ApplicationContext context: Context,
    private val fileName: String
) : Storage {

    private val sharedPreferences = context
        .getSharedPreferences(fileName, Context.MODE_PRIVATE)

    // String Value
    override fun setString(key: String, value: String) {
        with(sharedPreferences.edit()) {
            putString(key, value)
            apply()
        }
    }

    override fun getString(key: String): String {
        return sharedPreferences.getString(key, UNKNOWN)!!
    }

    // Boolean Value
    override fun setBoolean(key: String, value: Boolean) {
        with(sharedPreferences.edit()) {
            putBoolean(key, value)
            apply()
        }
    }

    override fun getBoolean(key: String): Boolean {
        return sharedPreferences.getBoolean(key, false)
    }

    // Integer Value
    override fun setInt(key: String, value: Int) {
        with(sharedPreferences.edit()) {
            putInt(key, value)
            apply()
        }
    }

    override fun getInt(key: String): Int {
        return sharedPreferences.getInt(key, 0)
    }

    // Remove value
    override fun delKey(key: String): Boolean {
        with(sharedPreferences.edit()) {
            remove(key)
            apply()
        }
        return !sharedPreferences.contains(key)
    }

    // Clear all data
    override fun clear() {
        with(sharedPreferences.edit()) {
            clear()
            apply()
        }
    }
}

BluetoothAppModule.kt:

@Module
@InstallIn(ApplicationComponent::class)
class BluetoothAppModule {

    @Provides
    fun provideFileName(): String = "bleDevice"
}

StorageModule.kt:

@InstallIn(ApplicationComponent::class)
@Module
abstract class StorageModule {

    @Binds abstract fun provideStorage(
         storage: SharedPreferencesStorage): Storage

}

🐙4. Android: MainActivity & ViewModel

< === Menu

A: What?! It looks pretty empty.
Homan: The UI depends on everntContainer to dispatch the fragment.

Coding Path

MainActivity detects new user and old user.

New user => WelcomeFragment

Old user => ControlFragment

Contracts

In the client app, I need to deal with permissions and BluetoothOnOff. So I need two contracts.

1. Permission Contract:

AndroidManifest.xml:

<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<uses-permission android:name="com.google.android.things.permission.MANAGE_BLUETOOTH" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

<uses-feature
    android:name="android.hardware.bluetooth_le"
    android:required="true" />

MainActivity.kt:

private val REQUIRED_PERMISSIONS = arrayOf(
        BLUETOOTH,
        BLUETOOTH_ADMIN,
        ACCESS_FINE_LOCATION,
        ACCESS_COARSE_LOCATION
)

private const val BLUETOOTH_REQUEST_CODE = 9191

@AndroidEntryPoint
class MainActivity : AppCompatActivity() {    private lateinit var bluetoothHelper: BluetoothHelper    private val reqMultiplePermissions = registerForActivityResult(
        RequestMultiplePermissions()
    ) { permissions ->
        permissions.entries.forEach {
            lgd("Permission: ${it.key} = ${it.value}")
        }
        checkBluetoothStatus()
    }    @RequiresApi(Build.VERSION_CODES.O)
    override fun onCreate(savedInstanceState: Bundle?) {
        ...        // check permission
        reqMultiplePermissions.launch(REQUIRED_PERMISSIONS)
        // load bluetooth functions
        bluetoothHelper = BluetoothHelper()
        ...
    }
    ...    companion object {
        const val tag = "MainAct: "
    }
}

After the app gets permission from the owner, it will detect Bluetooth On/Off status.

Bluetooth OnOff Contract

BluetoothHelper.kt: My Bluetooth library

class BluetoothHelper {
    private var bluetoothAdapter = 
        BluetoothAdapter.getDefaultAdapter()

    // check bluetooth switch
    fun isEnabled(): Boolean {
        return !bluetoothAdapter.isEnabled
    }
}

BluetoothOnOffContract.kt: It contols Bluetooth switch on the cell phone.

class BluetoothOnOffContract: 
        ActivityResultContract<Int, String?>() {
    
    override fun createIntent(p0: Context, p1: Int?): 
            Intent {
        return Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE)
    }

    override fun parseResult(resultCode: Int, intent: Intent?):
            String? {
        return if (resultCode == RESULT_OK)
            BLUETOOTH_ON
        else
            BLUETOOTH_OFF
    }
}

MainActivity.kt: bluetoothContract

private val bluetoothContract = registerForActivityResult(
    BluetoothOnOffContract()
) { result ->
    if (result.equals(BLUETOOTH_ON)) {
        lgd(tag+BLUETOOTH_ON)
        msg(this, BLUETOOTH_READY, 1)
    }
    else {
        lgd(tag+BLUETOOTH_OFF)
        msg(this, BLUETOOTH_NOT_ON, 0)
        finish()
    }
}

After the permission check, the app will check the Bluetooth switch.

private fun checkBluetoothStatus() {
    lgd(tag+"check bluetooth status")
    if (bluetoothHelper.isEnabled()) {
        lgd(tag+"Turning Bluetooth ON...")
        bluetoothContract.launch(BLUETOOTH_REQUEST_CODE)
    }
}

MainViewModel: Check cache and offer registration

MainViewModel.kt:

class MainViewModel @ViewModelInject constructor(
    private val storage: Storage
) : ViewModel()  {

    // Registration control
    val regControls = MutableLiveData<Int>()
    // Cache var
    var registered = false

    init {
        //storage.clear() // test purpose
        // Check cache
        registered = storage.getBoolean(REGISTERED)

        if (registered)
            regControls.value = -1
        else
            regControls.value = storage.getInt(CTRL_COUNT)
        lgd(tag+"Controls count: ${regControls.value}")
    }

    companion object {
        const val tag = "MainVM: "
    }
}

Monitor the registration control at MainActivity.kt:

override fun onCreate(savedInstanceState: Bundle?) {
    ...
    // Welcome
    mainViewModel.regControls.observe(
        this,
        { controlCount ->
            if (controlCount < 1) {
                showWelcomeFragment()
            } else {
                //showControlPanel()
            }
        }
    )
}fun showWelcomeFragment() {
    val fragment = WelcomeFragment.newInstance()
    lgd(tag+"Show Welcome Fragment.")
    val mTransaction = fragmentManager.beginTransaction()
    mTransaction.add(R.id.eventContainer, fragment)
    mTransaction.commit()
}

🎉5. WelcomeFragemnt and ViewModel

< === Menu

WelcomeFragement and its ViewModel serves for MainActivity. So it stays in the same package.

fragment_welcome.xml

WelcomeFragment.kt:

The fragment manages the new customer and returned customer.

New customer => RegistrationActivity => RegisterControlActivity
Return customer => RegisterControlActivity

Vars

private var diffGap = 0
private var adjustEditText = false
private var mGlobalLayoutListener: OnGlobalLayoutListener? = null

UI

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)

    welcomeCL = view.findViewById(R.id.welcomeCL)

    // EditText
    customerEmailEt = view.findViewById(R.id.customerEmailEt)
    customerEmailEt.setOnEditorActionListener { _, actionId, _ ->
        if (actionId == EditorInfo.IME_ACTION_DONE) {
            checkCustomer()
        }
        false
    }

    // Search indicator
    progressBar = view.findViewById(R.id.progressBar)
    progressBar.visibility = View.GONE
    lgd(ftag+"ProgressBar is GONE.")

    // EditText adjustment
    mGlobalLayoutListener = OnGlobalLayoutListener {
        resolvePosition()
    }
    rootView = view.findViewById(R.id.rootFL)
    rootView // check keyboard and editText distance
        .viewTreeObserver
        .addOnGlobalLayoutListener(mGlobalLayoutListener)

    // Registration FAB
    regFab = view.findViewById(R.id.regFab)
    regFab.setOnClickListener {
        progressBar.visibility = View.GONE
        val intent = Intent(activity, 
            RegistrationActivity::class.java)
        startActivity(intent)
    }

    // Email FAB
    emailFab = view.findViewById(R.id.emailFab)
    emailFab.setOnClickListener {
        checkCustomer()
    }

    // Email error
    emailNotFoundTV = view.findViewById(R.id.emailNotFoundTV)
    emailNotFoundTV.visibility = View.GONE

    // ImageButton
    clearIB = view.findViewById(R.id.clearIBT)
    clearIB.setOnClickListener{
        customerEmailEt.setText("")
        emailNotFoundTV.visibility = View.GONE
    }

    // LiveData
    welcomeVM.emailError.observe(
        viewLifecycleOwner,
        { message ->
            if (message != UNKNOWN)
                showErrorMsg(message)
        }
    )

    // LiveData
    welcomeVM.emailKeyFound.observe(
        viewLifecycleOwner,
        { customerKey ->
            lgd(ftag+"emailKeyFound: $customerKey")
            if (customerKey != UNKNOWN)
                toRegisteredControl(customerKey)
        }
    )
}

SoftKeyboard

fun resolvePosition() {
    // achieve keyboard and UI ratio
    val kbStatus = isKeyboardShown(
        customerEmailEt.rootView,
        customerEmailEt,
        ::getKeyboardData
    )

    if (kbStatus) {
        if (adjustEditText)
            welcomeCL.translationY = diffGap.toFloat()
    } else {
        welcomeCL.translationY = 0f
    }
}

private fun getKeyboardData(
    diffGap: Int, adjustEditText: Boolean
) {
    this.diffGap = diffGap
    this.adjustEditText = adjustEditText
}override fun onDestroy() {
    super.onDestroy()
    rootView.viewTreeObserver
        .removeOnGlobalLayoutListener(mGlobalLayoutListener)
}

Email Form Check

private fun checkCustomer() {
    if (!validateForm()) return
    lgd(ftag + "Data passed")

    val email = customerEmailEt.text.toString()
    progressBar.visibility = View.VISIBLE
    welcomeVM.searchCustomer(email)
}

private fun validateForm(): Boolean {
    var emailVf = vf.isEtEmpty(customerEmailEt)
    if (emailVf) {
        if (!vf.isEtEmail(customerEmailEt)) {
            customerEmailEt.error = "Invalid Email"
            customerEmailEt.requestFocus()
            emailVf = false
        }
        customerEmailEt.error = null
    }

    return emailVf
}

// Blink the error message
private fun showErrorMsg(message: String) {
    customerEmailEt.requestFocus()
    progressBar.visibility = View.GONE
    emailNotFoundTV.text = message

    flashError(
        viewLifecycleOwner,
        emailNotFoundTV,
        10,
        300
    )
}

To RegisterControlActivity

fun toRegisterControl(emailKey: String) {
    progressBar.visibility = View.GONE
    val intent = Intent(
        activity,
        RegisterControlActivity::class.java
    )
    startActivity(intent)
}

👨‍💻6. Registration and ViewModel

< === Menu

This activity will save the user data on the Firebase.

activity_registration.xml

RegistartionActivity.kt

onCreate(): If email is detected, the activity will redirect to RegisterControlActivity.

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_registration)

    // verified form for empty
    lastNameEt.onFocusChangeListener = vf.mFocusChangeListener
    firstNameEt.onFocusChangeListener = vf.mFocusChangeListener
    emailEt.onFocusChangeListener = vf.mFocusChangeListener
    phoneEt.onFocusChangeListener = vf.mFocusChangeListener
    addrEt.onFocusChangeListener = vf.mFocusChangeListener
    cityEt.onFocusChangeListener = vf.mFocusChangeListener
    stateEt.onFocusChangeListener = vf.mFocusChangeListener
    zipEt.onFocusChangeListener = vf.mFocusChangeListener

    //fillTestData()

    // Search Actions
    registrationVM.emailKeyFound.observe(
            this, { addRegisterControl() })
}

submitData():

fun submitData(view: View) {
    if (!validateForm()) return
    lgd(tag + "Data passed")

    // Combine data to form a customer
    val customer = Customer(
            "",
            firstNameEt.text.toString(),
            lastNameEt.text.toString(),
            emailEt.text.toString(),
            phoneEt.text.toString(),
            addrEt.text.toString(),
            cityEt.text.toString(),
            stateEt.text.toString(),
            zipEt.text.toString().toInt()
    )

    registrationVM.saveRgistrationData(customer)
}

validateFrom():

private var click = 1 //click effect
private fun validateForm() : Boolean {
    lgd(tag + "validate form...")
    click = if (click == 1) {
        submit.setBackgroundResource(R.drawable.frame_red_filled)
        submitTV.setTextColor(Color.parseColor(M_RED))
        0
    } else {
        submit.setBackgroundResource(R.drawable.frame_green_filled)
        submitTV.setTextColor(Color.parseColor(M_GREEN))
        1
    }

    val fnameVf = vf.isEtEmpty(firstNameEt)
    if (fnameVf) firstNameEt.error = null

    val lnameVf = vf.isEtEmpty(lastNameEt)
    if (lnameVf) lastNameEt.error = null

    var emailVf = vf.isEtEmpty(emailEt)
    if (emailVf) {
        if (!vf.isEtEmail(emailEt)) {
            emailEt.error = INVALID_EMAIL
            emailVf = false
        }
        emailEt.error = null
    }

    var phoneVf = vf.isEtEmpty(phoneEt)
    if (phoneVf) {
        if (vf.chkLen(phoneEt, 10)) {
            if (!vf.isEtPhone(phoneEt)) {
                phoneEt.error = INVALID_PHONE
                phoneVf = false
            }
            phoneEt.error = null
        } else {
            phoneEt.error = TOO_SHORT
            phoneVf = false
        }
    }

    val addrVf = vf.isEtEmpty(addrEt)
    if (lnameVf) addrEt.error = null

    val cityVf = vf.isEtEmpty(cityEt)
    if (lnameVf) cityEt.error = null

    val stateVf = vf.isEtEmpty(stateEt)
    if (lnameVf) stateEt.error = null

    var zipVf = vf.isEtEmpty(zipEt)
    if (zipVf)  {
        if (vf.chkLen(zipEt, 5)) {
            if (!vf.isEtNum(zipEt)) {
                zipEt.error = "Invalid Zipcode"
                zipVf = false
            }
            zipEt.error = null
        } else {
            zipEt.error = "Too short"
            zipVf = false
        }
    }

    return fnameVf && lnameVf && emailVf && phoneVf
            && addrVf && cityVf && stateVf && zipVf
}

addRegisterControl():

fun addRegisterControl() {
    val intent = Intent(this,
            RegisterControlActivity::class.java)
    startActivity(intent)
}

ValidateFrom.kt:

val mFocusChangeListener = View.OnFocusChangeListener {
        v, hasFocus ->
    val et = v as EditText
    if (!hasFocus) {
        isEtEmpty(et)
    }
}

RegistrationViewModel.kt

class RegistrationViewModel@ViewModelInject constructor(
    private val storage: Storage
) : ViewModel()  {

    // customer exist?
    val emailKeyFound = MutableLiveData<String>()
    // firebase
    private val dbRef = Firebase.database.reference
    private var fCustomer: Customer? = null


    companion object {
        const val tag = "RegVM:"
    }
}

saveRegistrationData():

fun saveRgistrationData(customer: Customer) {
    lgd(tag+"Register customer's info on Firebase.")
    fCustomer = customer

    // Search existed customer
    val regRef = dbRef.child("registration")
    searchEmail(
        regRef,
        customer.email,
        ::showProductList, // true
        ::saveCustomer // false
    )
}

True function — showProductList():

// Shows the control list
// refTrue: KFunction1<String, Customer?, Unit>
fun showProductList(customerKey: String, customer: Customer) {
    lgd(tag+"Save customer($customerKey) to cache: $customer")
    saveCustomerCache(storage, customer)
    emailKeyFound.postValue(customerKey)
}

False function — saveCustomer():

// Register a new customer (parameters useless)
// refFalse: KFunction2<String, Customer?, Unit>
// extra is null
// customer is null
private fun saveCustomer(extra: String, customer: Customer?) {
    val regRef = dbRef.child("registration")

    val customerKey = regRef.push().key
    fCustomer!!.customerId = customerKey!!
    regRef.child(customerKey)
        .setValue(fCustomer)
        .addOnSuccessListener {
            lgd(tag+"Saved the data.")
            saveCustomerCache(storage, fCustomer!!)
            showProductList(fCustomer!!.email, fCustomer!!)
        }
        .addOnFailureListener {
            lge(tag+"Save Customer Error: ${it.message}")
        }
}

Firebase Realtime Database Rule

I need to change the rule to accept the new data category.

{
  "rules": {
    "product": {
      ".read": true,
        ".write": "auth != null && auth.uid == 'YOUR USER ID'"
    },
      
    "registration": {
      ".read": true,
      ".write": true
    }
  }
}

The “registration” sector allows customer registration.

👾7. Google Cloud Functions: HelloWorld

< === Backend Menu

At the backend, I can create a GCF to respond to the new registration. If you have a RestAPI server, you can do it, too. This is a serverless example.

In Google Cloud Platform, you need to enable Cloud Functions API.

Install Firebase CLI

New Folder

I will put everything in a folder for local editing.

Open a CMD,

> d:
> md firebase

Or you can do it in the windows.

Firebase-tools

> npm install -g firebase-tools

> firebase login

You’d better logout and login back in because your login authentication may be outdated.

> firebase logout
+  Logged out from homanhuang@gmail.com> firebase login
i  Firebase optionally collects CLI usage and error reporting information to help improve our products. Data is collected in accordance with Google's privacy policy (https://policies.google.com/privacy) and is not used to identify you.? Allow Firebase to collect CLI usage and error reporting information? (Y/n) yVisit this URL on this device to log in:
https://accounts.google.com/...Waiting for authentication...

A browser will ask you to login like this:

Close the browser and go back to CLI:

+  Success! Logged in as YOUR@EMAIL.COM

Now, you can check your projects in Firebase.

> firebase projects:list

This is mine.

It’s ready to input.

D:\firebase\firebase init

“init” parameter will automatically create some function file for you.

####### ### #######  ####### #######     ##     #####  #######
#        #  #     ## #       #     ##  #   ##  #       #
#####    #  #######  #####   #######  ########  #####  #####
#        #  #    ##  #       #     ## #     ##       # #
#       ### #     ## ####### #######  #     ##  #####  #######You're about to initialize a Firebase project in this directory:D:\firebase\? Are you ready to proceed? Yes
? Which Firebase CLI features do you want to set up for this folder? Press Space to select features, then Enter to confirm your choices.
(space & enter)
(*) Functions: Configure and deploy Cloud Functions=== Project SetupFirst, let's associate this project directory with a Firebase project. You can create multiple project aliases by running firebase use --add, but for now we'll just set up a default project.? Please select an option: Use an existing project
? Select a default Firebase project for this directory: 
(*) bluetoothfirebase-27440 (BluetoothFirebase)
i  Using project bluetoothfirebase-27440 (BluetoothFirebase)=== Functions SetupA functions directory will be created in your project with a Node.js
package pre-configured. Functions can be deployed with firebase deploy.? What language would you like to use to write Cloud Functions? TypeScript
? Do you want to use ESLint to catch probable bugs and enforce style? Yes
+  Wrote functions/package.json
+  Wrote functions/.eslintrc.js
+  Wrote functions/tsconfig.json
+  Wrote functions/src/index.ts
+  Wrote functions/.gitignore
? Do you want to install dependencies with npm now? Yes> protobufjs@6.10.1 postinstall D:\firebase\email\functions\node_modules\protobufjs
> node scripts/postinstallnpm notice created a lockfile as package-lock.json. You should commit this file.
added 417 packages from 274 contributors and audited 417 packages in 12.626s38 packages are looking for funding
  run `npm fund` for detailsfound 0 vulnerabilitiesi  Writing configuration info to firebase.json...
i  Writing project information to .firebaserc...
i  Writing gitignore file to .gitignore...+  Firebase initialization complete!

📡8. HTTP functions in VS Code

< === Backend Menu

index.ts

functions.https: helloWorld

Ctrl + S and deploy:

D:\firebase>firebase deploy...
+  functions[helloWorld(us-central1)]: Successful create operation.
Function URL (helloWorld): https://us-central1-bluetoothfirebase-27440.cloudfunctions.net/helloWorld+  Deploy complete!...D:\firebase>

It takes 3 to 5 minutes to upload. Slow, be patient. The server will give you a link to run this function.

functions.https: Query Test

Remove helloWorld; let’s test HTTP query.

export const stringLength = functions.https.onRequest(
        (request, response) => {
    var text = request.query.text;
    var textLength = text?.length;    response.send(textLength+"");    //attach with null
});

Ctrl + S and deploy:

+  functions[stringLength(us-central1)]: Successful create operation.
Function URL (stringLength): https://us-central1-bluetoothfirebase-27440.cloudfunctions.net/stringLength+  Deploy complete!...D:\firebase>

Nothing at the end:

?text=HelloWorld

Passed.

🐱‍🏍9. Snippet in VS Code

< === Backend Menu

functions.database: sample

export const myDbFun = functions.database.ref('PATH')
    .onCreate((snapshot, context) => {});

Create Live Template or Snippet.

VS Code:

Open your browser; enter: snippet-generator.app

Right Hand Side:

VS Code:

You can save multiple snippets in typescript.json separated by “{} , {}”, for example:

{
    "Firebase Realtime Database Function onCreate": {
        ...
      },
    "HTTPS Query text": {
        ...
      }
}

Let’s use the snippet in index.ts:

🏄‍♀️10. Realtime Database Functions in VS Code

< === Backend Menu

**https://firebase.google.com/docs/functions/database-events**

functions.database: onCreate Trigger

export const newRegistrationDetected = functions
    .region('europe-west2')
    .database.ref('registration/{$regId}/email')
    .onCreate((snapshot, context) => {});

Before I input more code, I need a domain service and email service to deliver emails.

Domain Service

You can get any Domain service within $12/year. Some domains even provide free email accounts, except Google.

Email Service

Email Delivery Service

Delivering your transactional and marketing emails through the world's largest cloud-based email delivery platform…

sendgrid.com

I choose SendGrid. It’s basically free for everyone. After I registered an account, I need to add an API key.

Next,

Next,

Click the “Create Key” button, you’ll have your password.

Don’t verify yet, it has a time limit!

VC Code:

const mailOptions = {
  from: 'manager@homanandroidworld.com', 
  to: regEmail, 
  subject: 'Welcome to Homan Wifi Control Service.',
  html: '<b>Our company will help you to manage all of your wireless controls.!</b>' 
};const transporter = nodeMailer.createTransport({
  host: "smtp.sendgrid.net",
  port: 465,
  secure: true,
  auth: {
  user: "apikey", 
    pass: "YOUR PASSWORD FROM SendGrid"
  }
});try {
  transporter.sendMail(mailOptions)
  console.log("email sent")
} catch(e) {
  console.log("Something broke!"+e)
}

Now, deploy the function:

>firebase deploy
...
+  functions: Finished running predeploy script.
i  functions: ensuring required API cloudfunctions.googleapis.com is enabled...
i  functions: ensuring required API cloudbuild.googleapis.com is enabled...
+  functions: required API cloudbuild.googleapis.com is enabled
+  functions: required API cloudfunctions.googleapis.com is enabled
i  functions: preparing functions directory for uploading...
i  functions: packaged functions (45.08 KB) for uploading
+  functions: functions folder uploaded successfully
i  functions: creating Node.js 12 function newRegistrationDetected(europe-west2)...
+  functions[newRegistrationDetected(europe-west2)]: Successful create operation.+  Deploy complete!Project Console: https://console.firebase.google.com/project/bluetoothfirebase-27440/overview

My bad: I sent my function to the European region. My region is “us-west2”. So I delete the old one and deploy again.