Script to update Gradle, Java and other Android project settings in a Flutter project

update-android-project.sh

#!/bin/bash
# Update Gradle, Java and other Android project settings in a Flutter project
# Works with both .gradle and .gradle.kts build files

# See: https://gradle.org/releases/
# See: https://developer.android.com/build/releases/gradle-plugin#compatibility
DESIRED_GRADLE_VERSION="8.11.1"
# Build errors often show the required Java version
DESIRED_JAVA_VERSION="17"
# See: https://developer.android.com/ndk/downloads
DESIRED_NDK_VERSION="27.0.12077973"
# Google Play Stores requires a minimum target SDK version
DESIRED_TARGET_SDK="35"
# The minimum Android SDK version
DESIRED_MIN_SDK_VERSION="24"
# This should be compatible with the DESIRED_GRADLE_VERSION set above
# See: https://developer.android.com/build/releases/gradle-plugin#updating-gradle
DESIRED_ANDROID_APPLICATION_VERSION="8.9.1"


# Exit if this is not a Flutter project
if [ ! -f "pubspec.yaml" ]; then
  echo "This is not a Flutter project"
  exit 1
fi

# Exit if the Android directory does not exist
if [ ! -d "android" ]; then
  echo "The Android directory does not exist"
  exit 1
fi

# Navigate to the Android directory
cd android

# Update Gradle version (if specified)
if [ -n "$DESIRED_GRADLE_VERSION" ]; then
  sed -i '' "s/gradle-.*-all.zip/gradle-${DESIRED_GRADLE_VERSION}-all.zip/" gradle/wrapper/gradle-wrapper.properties
fi

# Detect if using Groovy or Kotlin build gradle file
if [ -f "app/build.gradle.kts" ]; then
  BUILD_GRADLE="app/build.gradle.kts"
else
  BUILD_GRADLE="app/build.gradle"
fi

# Update Java version (if specified)
if [ -n "$DESIRED_JAVA_VERSION" ]; then
  sed -i '' "s/JavaVersion.VERSION_[0-9_]*/JavaVersion.VERSION_${DESIRED_JAVA_VERSION}/" "$BUILD_GRADLE"
fi

# Update NDK version (if specified)
if [ -n "$DESIRED_NDK_VERSION" ]; then
  sed -i '' "s/ndkVersion = .*/ndkVersion = \"${DESIRED_NDK_VERSION}\"/" "$BUILD_GRADLE"
fi

# Update minSdk version (if specified)
if [ -n "$DESIRED_MIN_SDK_VERSION" ]; then
  sed -i '' "s/minSdk = .*/minSdk = ${DESIRED_MIN_SDK_VERSION}/" "$BUILD_GRADLE"
fi

# Update targetSdk version (if specified)
if [ -n "$DESIRED_TARGET_SDK" ]; then
  sed -i '' "s/targetSdk = .*/targetSdk = ${DESIRED_TARGET_SDK}/" "$BUILD_GRADLE"
fi


# Update com.android.application version in settings.gradle (if specified)
if [ -n "$DESIRED_ANDROID_APPLICATION_VERSION" ]; then
  # Detect if using Groovy or Kotlin build gradle file
  if [ -f "settings.gradle.kts" ]; then
    sed -i '' "s/id(\"com.android.application\") version \".*\" apply false/id(\"com.android.application\") version \"${DESIRED_ANDROID_APPLICATION_VERSION}\" apply false/" settings.gradle.kts
  else
    sed -i '' "s/id \"com.android.application\" version \".*\" apply false/id \"com.android.application\" version \"${DESIRED_ANDROID_APPLICATION_VERSION}\" apply false/" settings.gradle
  fi
fi

echo "Android project updated. Run 'git diff android' to see the changes."

I noticed a potential issue with this script.

if [ -n "$DESIRED_GRADLE_VERSION" ]; then
  sed -i '' "s/gradle-.*-all.zip/gradle-${DESIRED_GRADLE_VERSION}-all.zip/" gradle/wrapper/gradle-wrapper.properties
fi

Notice this replacement expression is expecting *-all.zip to be located in the distributionUrl property in the gradle-wrapper.properties file. This might work fine because flutter create defaults to using the *-all.zip gradle distribution. However, if you follow the recommended approach for updating the version of the gradle wrapper with:

./gradlew wrapper --gradle-version=<updated_gradle_version>

Then you might find that your distributionUrl no longer contains *-all.zip but instead has *-bin.zip.

*-all.zip is useful if you require all the source code and documentation in your project but its heavy. Usually (when building a flutter app) you don't need all the extra weight that comes with the all distribution, especially when you configure your build on a CI/CD server that needs to download gradle to build. You will probably benefit from using the *-bin.zip instead, which has a smaller footprint.

Anyway, I would recommend this script be modifed to use ./gradlew wrapper --gradle-version="${DESIRED_GRADLE_VERSION}" instead of the existing sed command. The advantage of doing so is that gradlew will also update the gradlew and gradlew.bat files (which are .gitignore'd) to make sure they are current for the specified version of gradle.

Anyway, thank you for your courses and content Andrea.