For projects with multiple modules, there may be several AndroidManifest files. Why is this necessary?

Each module of an Android project can have its own AndroidManifest.xml file to describe its components, such as activities, services, receivers, and providers. This is necessary for:

1. Encapsulation: The module fully describes its components, independent of other modules.
2. Reusability: The module with its manifest can be easily added to other projects.
3. Build-time reading: The build system (Gradle) merges these manifests into a single final manifest for the entire application, which is then included in the APK. The merge process considers priorities and resolves conflicts.

Example of a project structure with multiple modules:

MyApp/
├── app/
│   ├── src/
│   │   └── main/
│   │       └── AndroidManifest.xml  // Main application manifest
├── feature_a/
│   ├── src/
│   │   └── main/
│   │       └── AndroidManifest.xml  // feature_a module manifest
├── feature_b/
│   ├── src/
│   │   └── main/
│   │       └── AndroidManifest.xml  // feature_b module manifest

The manifest merging process is governed by rules that can be modified using directives within the manifests themselves (tools:merge attributes).