Project structure (app, gradle, manifests) in Android Kotlin

Introduction

Understanding the project structure helps you find and organize your app files easily. It makes building and running your app smoother.

When you start a new Android app project and want to know where to put your code and resources.

When you need to change app settings like app name or permissions.

When you want to add libraries or dependencies to your app.

When you want to understand how your app is built and packaged.

When you want to fix errors related to app configuration or build.

Syntax

Android Kotlin

ProjectRoot/
  app/
    src/
      main/
        java/ (Kotlin code here)
        res/ (UI resources here)
        AndroidManifest.xml
    build.gradle (Module-level)
  build.gradle (Project-level)
  settings.gradle

app/ folder contains your app code and resources.

build.gradle files control how your app is built and what libraries it uses.

Examples

This file describes your app to the system, like its name and permissions.

Android Kotlin

app/src/main/AndroidManifest.xml

This file lists dependencies and build settings specific to your app module.

Android Kotlin

app/build.gradle

This file manages settings and dependencies for the whole project.

Android Kotlin

build.gradle (Project-level)

Sample App

This shows a simple project structure with a MainActivity Kotlin file inside the app module. The AndroidManifest.xml and build.gradle files are in their usual places.

The MainActivity displays a simple text on the screen.

Android Kotlin

/*
Project structure overview:

ProjectRoot/
  app/
    src/
      main/
        java/com/example/myapp/MainActivity.kt
        res/layout/activity_main.xml
        AndroidManifest.xml
    build.gradle
  build.gradle
  settings.gradle
*/

// MainActivity.kt
package com.example.myapp

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.material3.Text

class MainActivity : ComponentActivity() {
  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContent {
      Text("Hello from MainActivity")
    }
  }
}

Important Notes

Always keep your AndroidManifest.xml inside app/src/main/.

Use the module-level build.gradle to add libraries your app needs.

The project-level build.gradle manages overall project settings and plugin versions.

Summary

The app folder holds your app code and resources.

AndroidManifest.xml describes your app to Android.

build.gradle files control building and dependencies.

Practice

1. What is the main purpose of the app folder in an Android project?

easy

A. It stores the build configuration files.

B. It contains the app's source code and resources.

C. It holds the Android system files.

D. It contains the device emulator settings.

Solution

1. Step 1: Understand the app folder role

   The app folder is where you put your app's code and resources like images and layouts.

2. Step 2: Differentiate from other folders

   Build files like build.gradle are outside or inside app but serve different purposes; system files are not in app.

3. Final Answer:

   It contains the app's source code and resources. -> Option B

4. Quick Check:

   App folder = source code and resources [OK]

Hint: App folder = your app's code and resources [OK]

Common Mistakes:

• Confusing build files with app folder contents
• Thinking system files are inside app folder
• Mixing emulator settings with project structure

2. Which file in an Android project declares the app's components and permissions?

easy

A. build.gradle

B. proguard-rules.pro

C. settings.gradle

D. AndroidManifest.xml

Solution

1. Step 1: Identify the manifest file role

   The AndroidManifest.xml file describes app components like activities and permissions.

2. Step 2: Compare with other files

   build.gradle handles build settings, settings.gradle manages modules, and proguard-rules.pro is for code shrinking rules.

3. Final Answer:

   AndroidManifest.xml -> Option D

4. Quick Check:

   Manifest = app components and permissions [OK]

Hint: Manifest file = app components and permissions [OK]

Common Mistakes:

• Confusing build.gradle with manifest
• Thinking settings.gradle declares permissions
• Mixing ProGuard rules with app declarations

3. Given this snippet from build.gradle inside the app folder, what will happen if you add a new dependency incorrectly?

dependencies {
    implementation 'androidx.core:core-ktx:1.9.0'
    implementation 'com.google.android.material:material:1.7.0'
}

medium

A. The app will build successfully with all dependencies.

B. The app will run but crash at runtime due to missing classes.

C. The build will fail due to a syntax error in dependencies.

D. The build will ignore the incorrect dependency and continue.

Solution

1. Step 1: Understand dependency syntax

   Dependencies must be declared with correct syntax like implementation 'group:name:version'. Any syntax error causes build failure.

2. Step 2: Consequence of incorrect dependency

   If a dependency line is malformed, Gradle will fail to build and show an error, not ignore it or allow runtime crashes.

3. Final Answer:

   The build will fail due to a syntax error in dependencies. -> Option C

4. Quick Check:

   Incorrect dependency syntax = build failure [OK]

Hint: Syntax errors in build.gradle cause build failure [OK]

Common Mistakes:

• Assuming build ignores syntax errors
• Thinking runtime crashes happen from build errors
• Confusing dependency syntax with code syntax

4. You added a new permission in AndroidManifest.xml but the app crashes on launch. What is a likely cause?

medium

A. The permission tag is outside the manifest root element.

B. The build.gradle file is missing the permission.

C. The app folder is empty.

D. The emulator does not support permissions.

Solution

1. Step 1: Check manifest XML structure

   All permission tags must be inside the root <manifest> element. Placing them outside causes XML errors and app crashes.

2. Step 2: Understand build.gradle and emulator roles

   Permissions are declared only in manifest, not build.gradle. Emulators support permissions normally.

3. Final Answer:

   The permission tag is outside the <manifest> root element. -> Option A

4. Quick Check:

   Permissions must be inside manifest root [OK]

Hint: Permission tags must be inside <manifest> root [OK]

Common Mistakes:

• Adding permissions in build.gradle
• Ignoring XML structure errors
• Blaming emulator for permission issues

5. You want to add a new module to your Android project. Which files/folders must you update or create to integrate it properly?

hard

A. Create a new folder for the module, add a build.gradle for it, and update settings.gradle to include it.

B. Add the module folder inside app and update AndroidManifest.xml only.

C. Create a new folder and add dependencies in app/build.gradle only.

D. Add the module folder anywhere and no other changes are needed.

Solution

1. Step 1: Create module folder and build file

   Each module needs its own folder and build.gradle to define its build settings.

2. Step 2: Update settings.gradle

   The settings.gradle file must include the new module so Gradle knows to build it.

3. Final Answer:

   Create a new folder for the module, add a build.gradle for it, and update settings.gradle to include it. -> Option A

4. Quick Check:

   New module = folder + build.gradle + settings.gradle update [OK]

Hint: New module needs folder, build.gradle, and settings.gradle update [OK]

Common Mistakes:

• Only updating AndroidManifest.xml
• Adding module inside app folder incorrectly
• Forgetting to update settings.gradle