inital login activity

app/build.gradle

@@ -47,6 +47,9 @@ dependencies {
 
     testImplementation "com.github.tomakehurst:wiremock-jre8:2.26.2"
     testImplementation "com.nhaarman.mockitokotlin2:mockito-kotlin:2.2.0"
+    implementation 'com.google.android.material:material:1.1.0'
+    implementation 'androidx.annotation:annotation:1.1.0'
+    implementation 'androidx.lifecycle:lifecycle-extensions:2.2.0'
     testImplementation 'junit:junit:4.13'
     androidTestImplementation 'androidx.test.ext:junit:1.1.1'
     androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'

app/src/main/AndroidManifest.xml

@@ -9,6 +9,9 @@
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
         android:theme="@style/AppTheme">
+        <activity
+            android:name=".ui.login.LoginActivity"
+            android:label="@string/title_activity_login"></activity>
         <activity android:name=".MainActivity">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />

app/src/main/java/com/h/pixeldroid/data/LoginDataSource.kt

@@ -0,0 +1,25 @@
+package com.h.pixeldroid.data
+
+import com.h.pixeldroid.data.model.LoggedInUser
+import java.io.IOException
+
+/**
+ * Class that handles authentication w/ login credentials and retrieves user information.
+ */
+class LoginDataSource {
+
+    fun login(username: String, password: String): Result<LoggedInUser> {
+        try {
+            // TODO: handle loggedInUser authentication
+            val fakeUser = LoggedInUser(java.util.UUID.randomUUID().toString(), "Jane Doe")
+            return Result.Success(fakeUser)
+        } catch (e: Throwable) {
+            return Result.Error(IOException("Error logging in", e))
+        }
+    }
+
+    fun logout() {
+        // TODO: revoke authentication
+    }
+}
+

app/src/main/java/com/h/pixeldroid/data/LoginRepository.kt

@@ -0,0 +1,46 @@
+package com.h.pixeldroid.data
+
+import com.h.pixeldroid.data.model.LoggedInUser
+
+/**
+ * Class that requests authentication and user information from the remote data source and
+ * maintains an in-memory cache of login status and user credentials information.
+ */
+
+class LoginRepository(val dataSource: LoginDataSource) {
+
+    // in-memory cache of the loggedInUser object
+    var user: LoggedInUser? = null
+        private set
+
+    val isLoggedIn: Boolean
+        get() = user != null
+
+    init {
+        // If user credentials will be cached in local storage, it is recommended it be encrypted
+        // @see https://developer.android.com/training/articles/keystore
+        user = null
+    }
+
+    fun logout() {
+        user = null
+        dataSource.logout()
+    }
+
+    fun login(username: String, password: String): Result<LoggedInUser> {
+        // handle login
+        val result = dataSource.login(username, password)
+
+        if (result is Result.Success) {
+            setLoggedInUser(result.data)
+        }
+
+        return result
+    }
+
+    private fun setLoggedInUser(loggedInUser: LoggedInUser) {
+        this.user = loggedInUser
+        // If user credentials will be cached in local storage, it is recommended it be encrypted
+        // @see https://developer.android.com/training/articles/keystore
+    }
+}

app/src/main/java/com/h/pixeldroid/data/Result.kt

@@ -0,0 +1,18 @@
+package com.h.pixeldroid.data
+
+/**
+ * A generic class that holds a value with its loading status.
+ * @param <T>
+ */
+sealed class Result<out T : Any> {
+
+    data class Success<out T : Any>(val data: T) : Result<T>()
+    data class Error(val exception: Exception) : Result<Nothing>()
+
+    override fun toString(): String {
+        return when (this) {
+            is Success<*> -> "Success[data=$data]"
+            is Error -> "Error[exception=$exception]"
+        }
+    }
+}

app/src/main/java/com/h/pixeldroid/data/model/LoggedInUser.kt

@@ -0,0 +1,9 @@
+package com.h.pixeldroid.data.model
+
+/**
+ * Data class that captures user information for logged in users retrieved from LoginRepository
+ */
+data class LoggedInUser(
+    val userId: String,
+    val displayName: String
+)

app/src/main/java/com/h/pixeldroid/ui/login/LoggedInUserView.kt

@@ -0,0 +1,9 @@
+package com.h.pixeldroid.ui.login
+
+/**
+ * User details post authentication that is exposed to the UI
+ */
+data class LoggedInUserView(
+    val displayName: String
+    //... other data fields that may be accessible to the UI
+)

app/src/main/java/com/h/pixeldroid/ui/login/LoginActivity.kt

@@ -0,0 +1,129 @@
+package com.h.pixeldroid.ui.login
+
+import android.app.Activity
+import androidx.lifecycle.Observer
+import androidx.lifecycle.ViewModelProviders
+import android.os.Bundle
+import androidx.annotation.StringRes
+import androidx.appcompat.app.AppCompatActivity
+import android.text.Editable
+import android.text.TextWatcher
+import android.view.View
+import android.view.inputmethod.EditorInfo
+import android.widget.Button
+import android.widget.EditText
+import android.widget.ProgressBar
+import android.widget.Toast
+
+import com.h.pixeldroid.R
+
+class LoginActivity : AppCompatActivity() {
+
+    private lateinit var loginViewModel: LoginViewModel
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+
+        setContentView(R.layout.activity_login)
+
+        val username = findViewById<EditText>(R.id.username)
+        val password = findViewById<EditText>(R.id.password)
+        val login = findViewById<Button>(R.id.login)
+        val loading = findViewById<ProgressBar>(R.id.loading)
+
+        loginViewModel = ViewModelProviders.of(this, LoginViewModelFactory())
+            .get(LoginViewModel::class.java)
+
+        loginViewModel.loginFormState.observe(this@LoginActivity, Observer {
+            val loginState = it ?: return@Observer
+
+            // disable login button unless both username / password is valid
+            login.isEnabled = loginState.isDataValid
+
+            if (loginState.usernameError != null) {
+                username.error = getString(loginState.usernameError)
+            }
+            if (loginState.passwordError != null) {
+                password.error = getString(loginState.passwordError)
+            }
+        })
+
+        loginViewModel.loginResult.observe(this@LoginActivity, Observer {
+            val loginResult = it ?: return@Observer
+
+            loading.visibility = View.GONE
+            if (loginResult.error != null) {
+                showLoginFailed(loginResult.error)
+            }
+            if (loginResult.success != null) {
+                updateUiWithUser(loginResult.success)
+            }
+            setResult(Activity.RESULT_OK)
+
+            //Complete and destroy login activity once successful
+            finish()
+        })
+
+        username.afterTextChanged {
+            loginViewModel.loginDataChanged(
+                username.text.toString(),
+                password.text.toString()
+            )
+        }
+
+        password.apply {
+            afterTextChanged {
+                loginViewModel.loginDataChanged(
+                    username.text.toString(),
+                    password.text.toString()
+                )
+            }
+
+            setOnEditorActionListener { _, actionId, _ ->
+                when (actionId) {
+                    EditorInfo.IME_ACTION_DONE ->
+                        loginViewModel.login(
+                            username.text.toString(),
+                            password.text.toString()
+                        )
+                }
+                false
+            }
+
+            login.setOnClickListener {
+                loading.visibility = View.VISIBLE
+                loginViewModel.login(username.text.toString(), password.text.toString())
+            }
+        }
+    }
+
+    private fun updateUiWithUser(model: LoggedInUserView) {
+        val welcome = getString(R.string.welcome)
+        val displayName = model.displayName
+        // TODO : initiate successful logged in experience
+        Toast.makeText(
+            applicationContext,
+            "$welcome $displayName",
+            Toast.LENGTH_LONG
+        ).show()
+    }
+
+    private fun showLoginFailed(@StringRes errorString: Int) {
+        Toast.makeText(applicationContext, errorString, Toast.LENGTH_SHORT).show()
+    }
+}
+
+/**
+ * Extension function to simplify setting an afterTextChanged action to EditText components.
+ */
+fun EditText.afterTextChanged(afterTextChanged: (String) -> Unit) {
+    this.addTextChangedListener(object : TextWatcher {
+        override fun afterTextChanged(editable: Editable?) {
+            afterTextChanged.invoke(editable.toString())
+        }
+
+        override fun beforeTextChanged(s: CharSequence, start: Int, count: Int, after: Int) {}
+
+        override fun onTextChanged(s: CharSequence, start: Int, before: Int, count: Int) {}
+    })
+}

app/src/main/java/com/h/pixeldroid/ui/login/LoginFormState.kt

@@ -0,0 +1,10 @@
+package com.h.pixeldroid.ui.login
+
+/**
+ * Data validation state of the login form.
+ */
+data class LoginFormState(
+    val usernameError: Int? = null,
+    val passwordError: Int? = null,
+    val isDataValid: Boolean = false
+)

app/src/main/java/com/h/pixeldroid/ui/login/LoginResult.kt

@@ -0,0 +1,9 @@
+package com.h.pixeldroid.ui.login
+
+/**
+ * Authentication result : success (user details) or error message.
+ */
+data class LoginResult(
+    val success: LoggedInUserView? = null,
+    val error: Int? = null
+)

app/src/main/java/com/h/pixeldroid/ui/login/LoginViewModel.kt

@@ -0,0 +1,55 @@
+package com.h.pixeldroid.ui.login
+
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.MutableLiveData
+import androidx.lifecycle.ViewModel
+import android.util.Patterns
+import com.h.pixeldroid.data.LoginRepository
+import com.h.pixeldroid.data.Result
+
+import com.h.pixeldroid.R
+
+class LoginViewModel(private val loginRepository: LoginRepository) : ViewModel() {
+
+    private val _loginForm = MutableLiveData<LoginFormState>()
+    val loginFormState: LiveData<LoginFormState> = _loginForm
+
+    private val _loginResult = MutableLiveData<LoginResult>()
+    val loginResult: LiveData<LoginResult> = _loginResult
+
+    fun login(username: String, password: String) {
+        // can be launched in a separate asynchronous job
+        val result = loginRepository.login(username, password)
+
+        if (result is Result.Success) {
+            _loginResult.value =
+                LoginResult(success = LoggedInUserView(displayName = result.data.displayName))
+        } else {
+            _loginResult.value = LoginResult(error = R.string.login_failed)
+        }
+    }
+
+    fun loginDataChanged(username: String, password: String) {
+        if (!isUserNameValid(username)) {
+            _loginForm.value = LoginFormState(usernameError = R.string.invalid_username)
+        } else if (!isPasswordValid(password)) {
+            _loginForm.value = LoginFormState(passwordError = R.string.invalid_password)
+        } else {
+            _loginForm.value = LoginFormState(isDataValid = true)
+        }
+    }
+
+    // A placeholder username validation check
+    private fun isUserNameValid(username: String): Boolean {
+        return if (username.contains('@')) {
+            Patterns.EMAIL_ADDRESS.matcher(username).matches()
+        } else {
+            username.isNotBlank()
+        }
+    }
+
+    // A placeholder password validation check
+    private fun isPasswordValid(password: String): Boolean {
+        return password.length > 5
+    }
+}

app/src/main/java/com/h/pixeldroid/ui/login/LoginViewModelFactory.kt

@@ -0,0 +1,25 @@
+package com.h.pixeldroid.ui.login
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.ViewModelProvider
+import com.h.pixeldroid.data.LoginDataSource
+import com.h.pixeldroid.data.LoginRepository
+
+/**
+ * ViewModel provider factory to instantiate LoginViewModel.
+ * Required given LoginViewModel has a non-empty constructor
+ */
+class LoginViewModelFactory : ViewModelProvider.Factory {
+
+    @Suppress("UNCHECKED_CAST")
+    override fun <T : ViewModel> create(modelClass: Class<T>): T {
+        if (modelClass.isAssignableFrom(LoginViewModel::class.java)) {
+            return LoginViewModel(
+                loginRepository = LoginRepository(
+                    dataSource = LoginDataSource()
+                )
+            ) as T
+        }
+        throw IllegalArgumentException("Unknown ViewModel class")
+    }
+}

app/src/main/res/layout/activity_login.xml

@@ -0,0 +1,78 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:id="@+id/container"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:paddingLeft="@dimen/activity_horizontal_margin"
+    android:paddingTop="@dimen/activity_vertical_margin"
+    android:paddingRight="@dimen/activity_horizontal_margin"
+    android:paddingBottom="@dimen/activity_vertical_margin"
+    tools:context=".ui.login.LoginActivity">
+
+    <EditText
+        android:id="@+id/username"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_marginStart="24dp"
+        android:layout_marginTop="96dp"
+        android:layout_marginEnd="24dp"
+
+        android:hint="@string/prompt_email"
+        android:inputType="textEmailAddress"
+        android:selectAllOnFocus="true"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
+
+    <EditText
+        android:id="@+id/password"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_marginStart="24dp"
+        android:layout_marginTop="8dp"
+        android:layout_marginEnd="24dp"
+
+        android:hint="@string/prompt_password"
+        android:imeActionLabel="@string/action_sign_in_short"
+        android:imeOptions="actionDone"
+        android:inputType="textPassword"
+        android:selectAllOnFocus="true"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/username" />
+
+    <Button
+        android:id="@+id/login"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="start"
+        android:layout_marginStart="48dp"
+        android:layout_marginTop="16dp"
+        android:layout_marginEnd="48dp"
+        android:layout_marginBottom="64dp"
+        android:enabled="false"
+        android:text="@string/action_sign_in"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/password"
+        app:layout_constraintVertical_bias="0.2" />
+
+    <ProgressBar
+        android:id="@+id/loading"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        android:layout_marginStart="32dp"
+        android:layout_marginTop="64dp"
+        android:layout_marginEnd="32dp"
+        android:layout_marginBottom="64dp"
+        android:visibility="gone"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="@+id/password"
+        app:layout_constraintStart_toStartOf="@+id/password"
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintVertical_bias="0.3" />
+</androidx.constraintlayout.widget.ConstraintLayout>

app/src/main/res/values/dimens.xml

@@ -0,0 +1,5 @@
+<resources>
+    <!-- Default screen margins, per the Android Design guidelines. -->
+    <dimen name="activity_horizontal_margin">16dp</dimen>
+    <dimen name="activity_vertical_margin">16dp</dimen>
+</resources>

app/src/main/res/values/strings.xml

@@ -1,3 +1,12 @@
 <resources>
     <string name="app_name">PixelDroid</string>
+    <string name="title_activity_login">Sign in</string>
+    <string name="prompt_email">Email</string>
+    <string name="prompt_password">Password</string>
+    <string name="action_sign_in">Sign in or register</string>
+    <string name="action_sign_in_short">Sign in</string>
+    <string name="welcome">"Welcome !"</string>
+    <string name="invalid_username">Not a valid username</string>
+    <string name="invalid_password">Password must be >5 characters</string>
+    <string name="login_failed">"Login failed"</string>
 </resources>