Merge pull request #50 from MihaiCristianCondrea/codex/ensure-app-follows-recommended-architecture

Implement domain use cases for all screens

Author: MihaiCristianCondrea

README.md

@@ -41,6 +41,16 @@ Our app is designed to be easy to use and lightweight. Plus, it's free and open
 
 Download Android Studio Tutorials: Java Edition from the Google Play Store and begin your Android development journey today. It's free, easy to use, and perfect for beginners.
 
+## Architecture
+
+The app follows the modern layered architecture recommended by Google. The UI layer observes
+immutable state from ViewModels. Business logic is encapsulated in use case classes within the
+domain layer, which interact with repositories in the data layer. Each screen now exposes its
+operations through a small set of use cases. This pattern was inspired by the
+[Android Clean Architecture](https://github.com/android10/Android-CleanArchitecture) sample but
+implemented in a simplified form to avoid adding heavy dependencies. The result keeps the UI
+simple and ensures a clear separation of concerns across the whole app.
+
 ## Feedback
 
 We are constantly updating and improving Android Studio Tutorials: Java Edition to give you the best possible experience. If you have suggested features or improvements, please leave a review. If something isn't working correctly, let us know so we can fix it.

app/src/main/java/com/d4rk/androidtutorials/java/domain/about/GetCurrentYearUseCase.java

@@ -0,0 +1,16 @@
+package com.d4rk.androidtutorials.java.domain.about;
+
+import com.d4rk.androidtutorials.java.ui.screens.about.repository.AboutRepository;
+
+/** Provides current year as a string. */
+public class GetCurrentYearUseCase {
+    private final AboutRepository repository;
+
+    public GetCurrentYearUseCase(AboutRepository repository) {
+        this.repository = repository;
+    }
+
+    public String invoke() {
+        return repository.getCurrentYear();
+    }
+}

app/src/main/java/com/d4rk/androidtutorials/java/domain/about/GetVersionStringUseCase.java

@@ -0,0 +1,16 @@
+package com.d4rk.androidtutorials.java.domain.about;
+
+import com.d4rk.androidtutorials.java.ui.screens.about.repository.AboutRepository;
+
+/** Returns the formatted app version string. */
+public class GetVersionStringUseCase {
+    private final AboutRepository repository;
+
+    public GetVersionStringUseCase(AboutRepository repository) {
+        this.repository = repository;
+    }
+
+    public String invoke() {
+        return repository.getVersionString();
+    }
+}

app/src/main/java/com/d4rk/androidtutorials/java/domain/android/GetLessonUseCase.java

@@ -0,0 +1,16 @@
+package com.d4rk.androidtutorials.java.domain.android;
+
+import com.d4rk.androidtutorials.java.ui.screens.android.repository.LessonRepository;
+
+/** Retrieves lesson data by name. */
+public class GetLessonUseCase {
+    private final LessonRepository repository;
+
+    public GetLessonUseCase(LessonRepository repository) {
+        this.repository = repository;
+    }
+
+    public LessonRepository.Lesson invoke(String lessonName) {
+        return repository.getLesson(lessonName);
+    }
+}

app/src/main/java/com/d4rk/androidtutorials/java/domain/help/LaunchReviewFlowUseCase.java

@@ -0,0 +1,18 @@
+package com.d4rk.androidtutorials.java.domain.help;
+
+import android.app.Activity;
+import com.d4rk.androidtutorials.java.ui.screens.help.repository.HelpRepository;
+import com.google.android.play.core.review.ReviewInfo;
+
+/** Launches the in-app review flow. */
+public class LaunchReviewFlowUseCase {
+    private final HelpRepository repository;
+
+    public LaunchReviewFlowUseCase(HelpRepository repository) {
+        this.repository = repository;
+    }
+
+    public void invoke(Activity activity, ReviewInfo info) {
+        repository.launchReviewFlow(activity, info);
+    }
+}

app/src/main/java/com/d4rk/androidtutorials/java/domain/help/RequestReviewFlowUseCase.java

@@ -0,0 +1,16 @@
+package com.d4rk.androidtutorials.java.domain.help;
+
+import com.d4rk.androidtutorials.java.ui.screens.help.repository.HelpRepository;
+
+/** Requests the Google Play review flow. */
+public class RequestReviewFlowUseCase {
+    private final HelpRepository repository;
+
+    public RequestReviewFlowUseCase(HelpRepository repository) {
+        this.repository = repository;
+    }
+
+    public void invoke(HelpRepository.OnReviewInfoListener listener) {
+        repository.requestReviewFlow(listener);
+    }
+}

app/src/main/java/com/d4rk/androidtutorials/java/domain/home/GetDailyTipUseCase.java

@@ -0,0 +1,19 @@
+package com.d4rk.androidtutorials.java.domain.home;
+
+import com.d4rk.androidtutorials.java.ui.screens.home.repository.HomeRepository;
+
+/** Use case that provides the daily tip text. */
+public class GetDailyTipUseCase {
+    private final HomeRepository repository;
+
+    public GetDailyTipUseCase(HomeRepository repository) {
+        this.repository = repository;
+    }
+
+    /**
+     * Returns today's tip string.
+     */
+    public String invoke() {
+        return repository.getDailyTip();
+    }
+}

app/src/main/java/com/d4rk/androidtutorials/java/domain/home/GetPromotedAppsUseCase.java

@@ -0,0 +1,26 @@
+package com.d4rk.androidtutorials.java.domain.home;
+
+import com.d4rk.androidtutorials.java.data.model.PromotedApp;
+import com.d4rk.androidtutorials.java.ui.screens.home.repository.HomeRepository;
+
+import java.util.List;
+
+/** Use case that fetches promoted apps from the repository. */
+public class GetPromotedAppsUseCase {
+    private final HomeRepository repository;
+
+    public interface Callback {
+        void onResult(List<PromotedApp> apps);
+    }
+
+    public GetPromotedAppsUseCase(HomeRepository repository) {
+        this.repository = repository;
+    }
+
+    /**
+     * Fetches the promoted apps and returns them via the callback.
+     */
+    public void invoke(Callback callback) {
+        repository.fetchPromotedApps(callback::onResult);
+    }
+}

app/src/main/java/com/d4rk/androidtutorials/java/domain/main/ApplyLanguageSettingsUseCase.java

@@ -0,0 +1,16 @@
+package com.d4rk.androidtutorials.java.domain.main;
+
+import com.d4rk.androidtutorials.java.ui.screens.main.repository.MainRepository;
+
+/** Applies the saved language preference. */
+public class ApplyLanguageSettingsUseCase {
+    private final MainRepository repository;
+
+    public ApplyLanguageSettingsUseCase(MainRepository repository) {
+        this.repository = repository;
+    }
+
+    public void invoke() {
+        repository.applyLanguageSettings();
+    }
+}

app/src/main/java/com/d4rk/androidtutorials/java/domain/main/ApplyThemeSettingsUseCase.java

@@ -0,0 +1,16 @@
+package com.d4rk.androidtutorials.java.domain.main;
+
+import com.d4rk.androidtutorials.java.ui.screens.main.repository.MainRepository;
+
+/** Applies theme preference and returns true if changed. */
+public class ApplyThemeSettingsUseCase {
+    private final MainRepository repository;
+
+    public ApplyThemeSettingsUseCase(MainRepository repository) {
+        this.repository = repository;
+    }
+
+    public boolean invoke(String[] darkModeValues) {
+        return repository.applyThemeSettings(darkModeValues);
+    }
+}