LoginActivity

.idea/misc.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_7" project-jdk-name="1.8" project-jdk-type="JavaSDK">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_7" project-jdk-name="JDK" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/build/classes" />
   </component>
 </project>

app/build.gradle

@@ -28,6 +28,9 @@ dependencies {
 
     implementation 'androidx.appcompat:appcompat:1.1.0'
     implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
+    implementation 'com.google.android.material:material:1.0.0'
+    implementation 'androidx.annotation:annotation:1.1.0'
+    implementation 'androidx.lifecycle:lifecycle-extensions:2.0.0'
     testImplementation 'junit:junit:4.12'
     androidTestImplementation 'androidx.test.ext:junit:1.1.1'
     androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'

app/src/main/AndroidManifest.xml

@@ -9,13 +9,18 @@
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
         android:theme="@style/AppTheme">
-        <activity android:name=".MainActivity">
+        <activity
+            android:name=".ui.login.LoginActivity"
+            android:label="@string/title_activity_login">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />
 
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
         </activity>
+        <activity android:name=".MainActivity">
+
+        </activity>
     </application>
 
 </manifest>

app/src/main/java/com/yuxihan/sdu/data/LoginDataSource.java

@@ -0,0 +1,29 @@
+package com.yuxihan.sdu.data;
+
+import com.yuxihan.sdu.data.model.LoggedInUser;
+
+import java.io.IOException;
+
+/**
+ * Class that handles authentication w/ login credentials and retrieves user information.
+ */
+public class LoginDataSource {
+
+    public Result<LoggedInUser> login(String username, String password) {
+
+        try {
+            // TODO: handle loggedInUser authentication
+            LoggedInUser fakeUser =
+                    new LoggedInUser(
+                            java.util.UUID.randomUUID().toString(),
+                            "Jane Doe");
+            return new Result.Success<>(fakeUser);
+        } catch (Exception e) {
+            return new Result.Error(new IOException("Error logging in", e));
+        }
+    }
+
+    public void logout() {
+        // TODO: revoke authentication
+    }
+}

app/src/main/java/com/yuxihan/sdu/data/LoginRepository.java

@@ -0,0 +1,54 @@
+package com.yuxihan.sdu.data;
+
+import com.yuxihan.sdu.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.
+ */
+public class LoginRepository {
+
+    private static volatile LoginRepository instance;
+
+    private LoginDataSource dataSource;
+
+    // If user credentials will be cached in local storage, it is recommended it be encrypted
+    // @see https://developer.android.com/training/articles/keystore
+    private LoggedInUser user = null;
+
+    // private constructor : singleton access
+    private LoginRepository(LoginDataSource dataSource) {
+        this.dataSource = dataSource;
+    }
+
+    public static LoginRepository getInstance(LoginDataSource dataSource) {
+        if (instance == null) {
+            instance = new LoginRepository(dataSource);
+        }
+        return instance;
+    }
+
+    public boolean isLoggedIn() {
+        return user != null;
+    }
+
+    public void logout() {
+        user = null;
+        dataSource.logout();
+    }
+
+    private void setLoggedInUser(LoggedInUser user) {
+        this.user = user;
+        // If user credentials will be cached in local storage, it is recommended it be encrypted
+        // @see https://developer.android.com/training/articles/keystore
+    }
+
+    public Result<LoggedInUser> login(String username, String password) {
+        // handle login
+        Result<LoggedInUser> result = dataSource.login(username, password);
+        if (result instanceof Result.Success) {
+            setLoggedInUser(((Result.Success<LoggedInUser>) result).getData());
+        }
+        return result;
+    }
+}

app/src/main/java/com/yuxihan/sdu/data/Result.java

@@ -0,0 +1,48 @@
+package com.yuxihan.sdu.data;
+
+/**
+ * A generic class that holds a result success w/ data or an error exception.
+ */
+public class Result<T> {
+    // hide the private constructor to limit subclass types (Success, Error)
+    private Result() {
+    }
+
+    @Override
+    public String toString() {
+        if (this instanceof Result.Success) {
+            Result.Success success = (Result.Success) this;
+            return "Success[data=" + success.getData().toString() + "]";
+        } else if (this instanceof Result.Error) {
+            Result.Error error = (Result.Error) this;
+            return "Error[exception=" + error.getError().toString() + "]";
+        }
+        return "";
+    }
+
+    // Success sub-class
+    public final static class Success<T> extends Result {
+        private T data;
+
+        public Success(T data) {
+            this.data = data;
+        }
+
+        public T getData() {
+            return this.data;
+        }
+    }
+
+    // Error sub-class
+    public final static class Error extends Result {
+        private Exception error;
+
+        public Error(Exception error) {
+            this.error = error;
+        }
+
+        public Exception getError() {
+            return this.error;
+        }
+    }
+}

app/src/main/java/com/yuxihan/sdu/data/model/LoggedInUser.java

@@ -0,0 +1,23 @@
+package com.yuxihan.sdu.data.model;
+
+/**
+ * Data class that captures user information for logged in users retrieved from LoginRepository
+ */
+public class LoggedInUser {
+
+    private String userId;
+    private String displayName;
+
+    public LoggedInUser(String userId, String displayName) {
+        this.userId = userId;
+        this.displayName = displayName;
+    }
+
+    public String getUserId() {
+        return userId;
+    }
+
+    public String getDisplayName() {
+        return displayName;
+    }
+}

app/src/main/java/com/yuxihan/sdu/ui/login/LoggedInUserView.java

@@ -0,0 +1,17 @@
+package com.yuxihan.sdu.ui.login;
+
+/**
+ * Class exposing authenticated user details to the UI.
+ */
+class LoggedInUserView {
+    private String displayName;
+    //... other data fields that may be accessible to the UI
+
+    LoggedInUserView(String displayName) {
+        this.displayName = displayName;
+    }
+
+    String getDisplayName() {
+        return displayName;
+    }
+}

app/src/main/java/com/yuxihan/sdu/ui/login/LoginActivity.java

@@ -0,0 +1,131 @@
+package com.yuxihan.sdu.ui.login;
+
+import android.app.Activity;
+
+import androidx.lifecycle.Observer;
+import androidx.lifecycle.ViewModelProviders;
+
+import android.os.Bundle;
+
+import androidx.annotation.Nullable;
+import androidx.annotation.StringRes;
+import androidx.appcompat.app.AppCompatActivity;
+
+import android.text.Editable;
+import android.text.TextWatcher;
+import android.view.KeyEvent;
+import android.view.View;
+import android.view.inputmethod.EditorInfo;
+import android.widget.Button;
+import android.widget.EditText;
+import android.widget.ProgressBar;
+import android.widget.TextView;
+import android.widget.Toast;
+
+import com.yuxihan.sdu.R;
+import com.yuxihan.sdu.ui.login.LoginViewModel;
+import com.yuxihan.sdu.ui.login.LoginViewModelFactory;
+
+public class LoginActivity extends AppCompatActivity {
+
+    private LoginViewModel loginViewModel;
+
+    @Override
+    public void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_login);
+        loginViewModel = ViewModelProviders.of(this, new LoginViewModelFactory())
+                .get(LoginViewModel.class);
+
+        final EditText usernameEditText = findViewById(R.id.username);
+        final EditText passwordEditText = findViewById(R.id.password);
+        final Button loginButton = findViewById(R.id.login);
+        final ProgressBar loadingProgressBar = findViewById(R.id.loading);
+
+        loginViewModel.getLoginFormState().observe(this, new Observer<LoginFormState>() {
+            @Override
+            public void onChanged(@Nullable LoginFormState loginFormState) {
+                if (loginFormState == null) {
+                    return;
+                }
+                loginButton.setEnabled(loginFormState.isDataValid());
+                if (loginFormState.getUsernameError() != null) {
+                    usernameEditText.setError(getString(loginFormState.getUsernameError()));
+                }
+                if (loginFormState.getPasswordError() != null) {
+                    passwordEditText.setError(getString(loginFormState.getPasswordError()));
+                }
+            }
+        });
+
+        loginViewModel.getLoginResult().observe(this, new Observer<LoginResult>() {
+            @Override
+            public void onChanged(@Nullable LoginResult loginResult) {
+                if (loginResult == null) {
+                    return;
+                }
+                loadingProgressBar.setVisibility(View.GONE);
+                if (loginResult.getError() != null) {
+                    showLoginFailed(loginResult.getError());
+                }
+                if (loginResult.getSuccess() != null) {
+                    updateUiWithUser(loginResult.getSuccess());
+                }
+                setResult(Activity.RESULT_OK);
+
+                //Complete and destroy login activity once successful
+                finish();
+            }
+        });
+
+        TextWatcher afterTextChangedListener = new TextWatcher() {
+            @Override
+            public void beforeTextChanged(CharSequence s, int start, int count, int after) {
+                // ignore
+            }
+
+            @Override
+            public void onTextChanged(CharSequence s, int start, int before, int count) {
+                // ignore
+            }
+
+            @Override
+            public void afterTextChanged(Editable s) {
+                loginViewModel.loginDataChanged(usernameEditText.getText().toString(),
+                        passwordEditText.getText().toString());
+            }
+        };
+        usernameEditText.addTextChangedListener(afterTextChangedListener);
+        passwordEditText.addTextChangedListener(afterTextChangedListener);
+        passwordEditText.setOnEditorActionListener(new TextView.OnEditorActionListener() {
+
+            @Override
+            public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
+                if (actionId == EditorInfo.IME_ACTION_DONE) {
+                    loginViewModel.login(usernameEditText.getText().toString(),
+                            passwordEditText.getText().toString());
+                }
+                return false;
+            }
+        });
+
+        loginButton.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                loadingProgressBar.setVisibility(View.VISIBLE);
+                loginViewModel.login(usernameEditText.getText().toString(),
+                        passwordEditText.getText().toString());
+            }
+        });
+    }
+
+    private void updateUiWithUser(LoggedInUserView model) {
+        String welcome = getString(R.string.welcome) + model.getDisplayName();
+        // TODO : initiate successful logged in experience
+        Toast.makeText(getApplicationContext(), welcome, Toast.LENGTH_LONG).show();
+    }
+
+    private void showLoginFailed(@StringRes Integer errorString) {
+        Toast.makeText(getApplicationContext(), errorString, Toast.LENGTH_SHORT).show();
+    }
+}

app/src/main/java/com/yuxihan/sdu/ui/login/LoginFormState.java

@@ -0,0 +1,40 @@
+package com.yuxihan.sdu.ui.login;
+
+import androidx.annotation.Nullable;
+
+/**
+ * Data validation state of the login form.
+ */
+class LoginFormState {
+    @Nullable
+    private Integer usernameError;
+    @Nullable
+    private Integer passwordError;
+    private boolean isDataValid;
+
+    LoginFormState(@Nullable Integer usernameError, @Nullable Integer passwordError) {
+        this.usernameError = usernameError;
+        this.passwordError = passwordError;
+        this.isDataValid = false;
+    }
+
+    LoginFormState(boolean isDataValid) {
+        this.usernameError = null;
+        this.passwordError = null;
+        this.isDataValid = isDataValid;
+    }
+
+    @Nullable
+    Integer getUsernameError() {
+        return usernameError;
+    }
+
+    @Nullable
+    Integer getPasswordError() {
+        return passwordError;
+    }
+
+    boolean isDataValid() {
+        return isDataValid;
+    }
+}

app/src/main/java/com/yuxihan/sdu/ui/login/LoginResult.java

@@ -0,0 +1,31 @@
+package com.yuxihan.sdu.ui.login;
+
+import androidx.annotation.Nullable;
+
+/**
+ * Authentication result : success (user details) or error message.
+ */
+class LoginResult {
+    @Nullable
+    private LoggedInUserView success;
+    @Nullable
+    private Integer error;
+
+    LoginResult(@Nullable Integer error) {
+        this.error = error;
+    }
+
+    LoginResult(@Nullable LoggedInUserView success) {
+        this.success = success;
+    }
+
+    @Nullable
+    LoggedInUserView getSuccess() {
+        return success;
+    }
+
+    @Nullable
+    Integer getError() {
+        return error;
+    }
+}

app/src/main/java/com/yuxihan/sdu/ui/login/LoginViewModel.java

@@ -0,0 +1,70 @@
+package com.yuxihan.sdu.ui.login;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+import androidx.lifecycle.ViewModel;
+
+import android.util.Patterns;
+
+import com.yuxihan.sdu.data.LoginRepository;
+import com.yuxihan.sdu.data.Result;
+import com.yuxihan.sdu.data.model.LoggedInUser;
+import com.yuxihan.sdu.R;
+
+public class LoginViewModel extends ViewModel {
+
+    private MutableLiveData<LoginFormState> loginFormState = new MutableLiveData<>();
+    private MutableLiveData<LoginResult> loginResult = new MutableLiveData<>();
+    private LoginRepository loginRepository;
+
+    LoginViewModel(LoginRepository loginRepository) {
+        this.loginRepository = loginRepository;
+    }
+
+    LiveData<LoginFormState> getLoginFormState() {
+        return loginFormState;
+    }
+
+    LiveData<LoginResult> getLoginResult() {
+        return loginResult;
+    }
+
+    public void login(String username, String password) {
+        // can be launched in a separate asynchronous job
+        Result<LoggedInUser> result = loginRepository.login(username, password);
+
+        if (result instanceof Result.Success) {
+            LoggedInUser data = ((Result.Success<LoggedInUser>) result).getData();
+            loginResult.setValue(new LoginResult(new LoggedInUserView(data.getDisplayName())));
+        } else {
+            loginResult.setValue(new LoginResult(R.string.login_failed));
+        }
+    }
+
+    public void loginDataChanged(String username, String password) {
+        if (!isUserNameValid(username)) {
+            loginFormState.setValue(new LoginFormState(R.string.invalid_username, null));
+        } else if (!isPasswordValid(password)) {
+            loginFormState.setValue(new LoginFormState(null, R.string.invalid_password));
+        } else {
+            loginFormState.setValue(new LoginFormState(true));
+        }
+    }
+
+    // A placeholder username validation check
+    private boolean isUserNameValid(String username) {
+        if (username == null) {
+            return false;
+        }
+        if (username.contains("@")) {
+            return Patterns.EMAIL_ADDRESS.matcher(username).matches();
+        } else {
+            return !username.trim().isEmpty();
+        }
+    }
+
+    // A placeholder password validation check
+    private boolean isPasswordValid(String password) {
+        return password != null && password.trim().length() > 5;
+    }
+}

app/src/main/java/com/yuxihan/sdu/ui/login/LoginViewModelFactory.java

@@ -0,0 +1,26 @@
+package com.yuxihan.sdu.ui.login;
+
+import androidx.lifecycle.ViewModel;
+import androidx.lifecycle.ViewModelProvider;
+import androidx.annotation.NonNull;
+
+import com.yuxihan.sdu.data.LoginDataSource;
+import com.yuxihan.sdu.data.LoginRepository;
+
+/**
+ * ViewModel provider factory to instantiate LoginViewModel.
+ * Required given LoginViewModel has a non-empty constructor
+ */
+public class LoginViewModelFactory implements ViewModelProvider.Factory {
+
+    @NonNull
+    @Override
+    @SuppressWarnings("unchecked")
+    public <T extends ViewModel> T create(@NonNull Class<T> modelClass) {
+        if (modelClass.isAssignableFrom(LoginViewModel.class)) {
+            return (T) new LoginViewModel(LoginRepository.getInstance(new LoginDataSource()));
+        } else {
+            throw new 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">SDU</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>