Upgrading Flutter projects to build with gradle

Introduction

Prior to Pull Request 7902 -- which was merged to master on February 6th 2017 -- we used a custom build process when building for Android. We now build for Android using the same standard 'gradle-based' build process that Android Studio project uses. This makes it easier to edit the native Android code, as you can simply open the android folder in Android Studio.

If you have a project that was created prior to this date, please follow these steps to switch to building with gradle. This is required as we will be removing the custom build support shortly.

Upgrading an existing project

Step 1: Move AndroidManifest.xml

cd <root dir of your project>
mkdir android/app
mkdir android/app/src
mkdir android/app/src/main
mv android/AndroidManifest.xml android/app/src/main/

Step 3: Add gradle.properties

Create a new file gradle.properties in <app root dir>/android/ with the following contents:

org.gradle.jvmargs=-Xmx1536M

Step 4: Add build.gradle for the project

Create a new file build.gradle in <app root dir>/android/ with the following contents:

buildscript {
    repositories {
        jcenter()
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:2.2.3'
    }
}

allprojects {
    repositories {
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

task wrapper(type: Wrapper) {
    gradleVersion = '2.14.1'
}

Step 5: Add build.gradle for the main module

Create a new file build.gradle in <app root dir>/android/app/ with the following contents:

def localProperties = new Properties()
def localPropertiesFile = rootProject.file('local.properties')
if (localPropertiesFile.exists()) {
    localPropertiesFile.withInputStream { stream ->
        localProperties.load(stream)
    }
}

def flutterRoot = localProperties.getProperty('flutter.sdk')
if (flutterRoot == null) {
    throw new GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
}

apply plugin: 'com.android.application'
apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"

android {
    compileSdkVersion 25
    buildToolsVersion '25.0.2'

    lintOptions {
        disable 'InvalidPackage'
    }

    defaultConfig {
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            // TODO: Add your own signing config for the release build.
            // Signing with the debug keys for now, so `flutter run --release` works.
            signingConfig signingConfigs.debug
        }
    }
}

flutter {
    source '../..'
}

dependencies {
    androidTestCompile 'com.android.support:support-annotations:25.0.0'
    androidTestCompile 'com.android.support.test:runner:0.5'
    androidTestCompile 'com.android.support.test:rules:0.5'
}

Notes

For a concrete example of this, see this commit that performed this upgrade on the /examples/hello_world/ project.

Working with the project after upgrading

After upgrading you can build with flutter build apk and run with flutter run. The first build will take a little longer (as it will download and then cache a few gradle files).

In addition, you should now be able to edit and build from Android Studio:

1. Start Android Studio
2. Invoke File > Open...
3. Select the android folder inside your main app folder, and press OK
4. Press the Run button, or use the Run > Run menu item to build and run the app