Enhance Todo App: Validation, UI, and Architecture Improvements

.gitignore

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+# Android Studio
+.idea/
+*.iml
+.gradle/
+build/
+captures/
+
+# Kotlin and Java
+*.class
+*.kotlin_module
+*.log
+*.ctxt
+*.jar
+*.war
+*.nar
+*.ear
+*.zip
+*.tar.gz
+*.rar
+
+# Gradle
+local.properties
+/out/
+/node_modules/
+node_modules/
+kotlin-js-store/
+
+# Development Environments
+.DS_Store
+.env
+.mtj.tmp/
+.externalNativeBuild
+.cxx
+
+# Compiled Outputs
+/build
+/captures
+__pycache__/
+
+# Virtual Machine Crash Logs
+hs_err_pid*

app/build.gradle

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+plugins {
+    id 'com.android.application'
+    id 'kotlin-android'
+    id 'kotlin-kapt'
+}
+
+dependencies {
+    // Kotlin standard library
+    implementation "org.jetbrains.kotlin:kotlin-stdlib:1.8.0"
+
+    // AndroidX
+    implementation 'androidx.core:core-ktx:1.10.1'
+    implementation 'androidx.appcompat:appcompat:1.6.1'
+    implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.6.1'
+
+    // Room Database
+    implementation 'androidx.room:room-runtime:2.5.2'
+    implementation 'androidx.room:room-ktx:2.5.2'
+    kapt 'androidx.room:room-compiler:2.5.2'
+
+    // Test dependencies
+    testImplementation 'junit:junit:4.13.2'
+    testImplementation 'org.robolectric:robolectric:4.10.3'
+    testImplementation 'androidx.test:core:1.5.0'
+    testImplementation 'androidx.test.ext:junit:1.1.5'
+}

app/src/main/java/com/example/todoapp/ui/CreateTodoItemActivity.kt

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+package com.example.todoapp.ui
+
+import android.content.Intent
+import android.os.Bundle
+import android.widget.Button
+import android.widget.EditText
+import androidx.appcompat.app.AppCompatActivity
+import androidx.lifecycle.lifecycleScope
+import com.example.todoapp.R
+import com.example.todoapp.data.TodoItem
+import com.example.todoapp.data.TodoRepository
+import kotlinx.coroutines.launch
+
+class CreateTodoItemActivity : AppCompatActivity() {
+
+    private lateinit var titleEditText: EditText
+    private lateinit var descriptionEditText: EditText
+    private lateinit var saveButton: Button
+    private lateinit var todoRepository: TodoRepository
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        setContentView(R.layout.activity_create_todo_item)
+
+        // Initialize views
+        titleEditText = findViewById(R.id.edit_text_todo_title)
+        descriptionEditText = findViewById(R.id.edit_text_todo_description)
+        saveButton = findViewById(R.id.button_save_todo)
+
+        // Initialize repository (assumes dependency injection or manual initialization)
+        todoRepository = TodoRepository(application)
+
+        saveButton.setOnClickListener {
+            saveTodoItem()
+        }
+    }
+
+    private fun saveTodoItem() {
+        val title = titleEditText.text.toString().trim()
+        val description = descriptionEditText.text.toString().trim()
+
+        // Basic validation
+        if (title.isEmpty()) {
+            titleEditText.error = "Title cannot be empty"
+            return
+        }
+
+        // Create todo item
+        val todoItem = TodoItem(
+            title = title,
+            description = description,
+            isCompleted = false
+        )
+
+        // Save todo item using coroutines
+        lifecycleScope.launch {
+            todoRepository.insert(todoItem)
+            // Navigate back to main activity
+            navigateToMainActivity()
+        }
+    }
+
+    private fun navigateToMainActivity() {
+        val intent = Intent(this, MainActivity::class.java)
+        // Clear the back stack so user can't navigate back to create todo screen
+        intent.flags = Intent.FLAG_ACTIVITY_CLEAR_TOP or Intent.FLAG_ACTIVITY_NEW_TASK
+        startActivity(intent)
+        // Finish current activity
+        finish()
+    }
+}

app/src/test/java/com/example/todoapp/CreateTodoItemActivityTest.kt

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+package com.example.todoapp
+
+import android.content.Intent
+import androidx.test.core.app.ActivityScenario
+import androidx.test.core.app.ApplicationProvider
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import com.example.todoapp.ui.CreateTodoItemActivity
+import com.example.todoapp.ui.MainActivity
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.Robolectric
+import org.robolectric.Shadows.shadowOf
+
+@RunWith(AndroidJUnit4::class)
+class CreateTodoItemActivityTest {
+
+    @Test
+    fun `test navigation to main activity after saving todo item`() {
+        // Create an activity scenario
+        val scenario = ActivityScenario.launch(CreateTodoItemActivity::class.java)
+
+        scenario.onActivity { activity ->
+            // Mock saving a todo item by directly calling private method
+            val method = activity.javaClass.getDeclaredMethod("navigateToMainActivity")
+            method.isAccessible = true
+            method.invoke(activity)
+
+            // Get the next started intent
+            val shadowActivity = Robolectric.shadowOf(activity)
+            val startedIntent = shadowActivity.nextStartedActivity
+
+            // Verify intent navigation
+            assertEquals(MainActivity::class.java.name, 
+                         startedIntent.component?.className)
+
+            // Verify intent flags
+            assertEquals(
+                Intent.FLAG_ACTIVITY_CLEAR_TOP or Intent.FLAG_ACTIVITY_NEW_TASK, 
+                startedIntent.flags
+            )
+        }
+    }
+}

build.gradle

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+plugins {
+    id 'org.jetbrains.kotlin.jvm' version '1.9.0'
+}
+
+dependencies {
+    testImplementation 'junit:junit:4.13.2'
+    testImplementation "org.jetbrains.kotlin:kotlin-test-junit"
+}
+
+repositories {
+    mavenCentral()
+}
+
+test {
+    useJUnit()
+}

build.gradle.kts

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+plugins {
+    kotlin("jvm") version "1.9.0"
+    kotlin("plugin.serialization") version "1.9.0"
+}
+
+dependencies {
+    implementation("org.jetbrains.kotlin:kotlin-stdlib")
+    implementation("org.jetbrains.kotlinx:kotlinx-serialization-json:1.5.1")
+
+    testImplementation("junit:junit:4.13.2")
+    testImplementation(kotlin("test"))
+    testImplementation("org.jetbrains.kotlinx:kotlinx-coroutines-test:1.7.3")
+}
+
+repositories {
+    mavenCentral()
+    google()
+}
+
+tasks.test {
+    useJUnitPlatform()
+}
+
+kotlin {
+    jvmToolchain(17)
+}

src/main/kotlin/com/todoapp/validation/TodoValidation.kt

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+package com.todoapp.validation
+
+/**
+ * Provides validation methods for Todo items
+ */
+object TodoValidation {
+    /**
+     * Validates the title of a todo item
+     * 
+     * @param title The title to validate
+     * @return Boolean indicating if the title is valid
+     */
+    fun isValidTitle(title: String?): Boolean {
+        // Check if title is null or empty after trimming whitespace
+        return !title.isNullOrBlank()
+    }
+
+    /**
+     * Throws an exception if the title is invalid
+     * 
+     * @param title The title to validate
+     * @throws IllegalArgumentException if title is invalid
+     */
+    fun validateTitle(title: String?) {
+        require(isValidTitle(title)) { "Todo item title cannot be empty" }
+    }
+}

src/test/kotlin/com/todoapp/validation/TodoValidationTest.kt

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+package com.todoapp.validation
+
+import org.junit.Assert.*
+import org.junit.Test
+
+class TodoValidationTest {
+    @Test
+    fun `test valid title returns true`() {
+        // Arrange
+        val validTitle = "Buy groceries"
+
+        // Act
+        val result = TodoValidation.isValidTitle(validTitle)
+
+        // Assert
+        assertTrue("Valid title should return true", result)
+    }
+
+    @Test
+    fun `test empty title returns false`() {
+        // Arrange
+        val emptyTitle = ""
+
+        // Act
+        val result = TodoValidation.isValidTitle(emptyTitle)
+
+        // Assert
+        assertFalse("Empty title should return false", result)
+    }
+
+    @Test
+    fun `test null title returns false`() {
+        // Arrange
+        val nullTitle: String? = null
+
+        // Act
+        val result = TodoValidation.isValidTitle(nullTitle)
+
+        // Assert
+        assertFalse("Null title should return false", result)
+    }
+
+    @Test
+    fun `test whitespace-only title returns false`() {
+        // Arrange
+        val whitespaceTitle = "   "
+
+        // Act
+        val result = TodoValidation.isValidTitle(whitespaceTitle)
+
+        // Assert
+        assertFalse("Whitespace-only title should return false", result)
+    }
+
+    @Test(expected = IllegalArgumentException::class)
+    fun `test validateTitle throws exception for invalid title`() {
+        // Act
+        TodoValidation.validateTitle("")
+    }
+
+    @Test
+    fun `test validateTitle does not throw for valid title`() {
+        // Act
+        TodoValidation.validateTitle("Valid Title")
+        // Assert (no exception thrown)
+    }
+}