docs/contributing/Android-API-And-Related-Versions.md

# Android Api and Related versions

Picking the full suite of android versions can be difficult if you are not a full time android developer.
This document is for contributors to understand what versions of common android tooling should be used in the flutter/flutter codebase.

## Overview

**The most important thing is for any test, project, or app to have compatible versions. **

If versions need to be different then a comment explaining why and what is being evaluated should be included.
All chosen versions should pass the minimum versions checks defined in [DependencyVersionChecker](https://github.com/flutter/flutter/blob/main/packages/flutter_tools/gradle/src/main/kotlin/DependencyVersionChecker.kt)

If the versions chosen are not known by [gradle_utils.dart](https://github.com/flutter/flutter/blob/a16c447abcb695b4ca907d59e66dc87f4f7178d3/packages/flutter_tools/lib/src/android/gradle_utils.dart#L63) then update gradle_utils.dart.

## Specifics

### compileSdk

- Must be higher then or equal to `targetSdk`.
- Should be `compileSdk` instead of `compileSdkVersion`.
- Should be the max stable value available in CIPD if not `flutter.compileSdkVersion`.
- Must have a comment if an api level lower than max is chosen intentionally.

```
// OK
android {
  compileSdk = flutter.compileSdkVersion
}
```

```
// OK if flutter.compileSdkVersion is not available like in an add to app example.
android {
  compileSdk = 35
}
```

```
// NOT OK
android {
  compileSdk 28
}
```

### targetSdk

- Must be higher then or equal to `minSdk`.
- Should be `targetSdk` instead of `targetSdkVersion`.
- `targetSdk` takes human level effort to update. This is a design decision by the AGP team.
- `targetSdk` may lag behind compile sdk because of the effort to update.
- If the `targetSdk` version is intentionally different there should be a comment explaining why.

```
// OK
defaultConfig {
  targetSdk = flutter.targetSdkVersion
}
```

```
// OK if flutter.compileSdkVersion is not available like in an add to app example.
defaultConfig {
  targetSdk = 35
}
```

```
// NOT OK
defaultConfig {
  targetSdk 28
}
```

### AGP
AKA `com.android.application`, `com.android.tools.build:gradle` `com.android.library`

- "AGP" version should be the version set in flutter templates or newer.
- If the version is intentionally different there should be a comment explaining why.


```
// OK
dependencies {
    classpath "com.android.tools.build:gradle:8.8.1"
}
```

```
// OK
dependencies {
    // Testing backwards compatibility of feature XYZ
    classpath "com.android.tools.build:gradle:7.5.2"
}
```

### gradle

Gradle versions are the least likely to break across minor version updates.

- In new code the "gradle" version should be the version set in flutter templates or newer.
- In older code any gradle version that works with the other version constraints is ok.
- In practice our customers use a large variety of gradle versions.
- If the version is intentionally different there should be a comment explaining why.

```
// OK
distributionUrl=https\://services.gradle.org/distributions/gradle-8.12.1-bin.zip
```

### Kotlin

Changing kotlin versions is most likely to have an issue with another dependency and not the code under test.

- "kotlin" version should be the version set in flutter templates or newer.
- If the version is intentionally different there should be a comment explaining why.

```
// Ok
ext.kotlin_version = "1.7.10"
...
classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
```

### compileOptions and kotlinOptions

- sourceCompatibility must use JavaVersion.*
- targetCompatibility must use JavaVersion.*
- kotlinOptions jvmTarget should match the versions used by compileOptions or there should be a comment explaining why.
- jvmTarget should use JavaVersion.<SOMEVERSION>.toString() or there should be a comment explaining why.

```
// Correct configuration
compileOptions {
    sourceCompatibility = JavaVersion.VERSION_17
    targetCompatibility = JavaVersion.VERSION_17
}

kotlinOptions {
    jvmTarget = JavaVersion.VERSION_17.toString()
}
```

```
// Not ok, kotlinOptions uses a string.
compileOptions {
    sourceCompatibility = JavaVersion.VERSION_17
    targetCompatibility = JavaVersion.VERSION_17
}

kotlinOptions {
    jvmTarget = "17"
}
```

```
// Not ok, different versions of java
compileOptions {
    sourceCompatibility = JavaVersion.VERSION_11
    targetCompatibility = JavaVersion.VERSION_11
}

kotlinOptions {
    jvmTarget = JavaVersion.VERSION_17.toString()
}
```