[移动开发]Flutter Module Android的构建流程

? 对于目前市场上的集成方式来说最常用的就是原生工程+Flutter Module实现部分业务逻辑的跨平台开发，这里我们一起来分析一下Flutter Module是如何参与到Android的构建流程当中的；

首先如果对Flutter APP构建流程不熟悉的可以先熟悉：“深度了解Flutter APP的构建流程”

我们分一下几个步骤了解

1. settings.gradle
2. include_flutter.groovy
3. module_plugin_loader.gradle
4. build.gradle

对于第3，4点，与Flutter APP构建流程相似，在"深度了解Flutter APP的构建流程"文中有解析，这里不再重复，重点看前两个步骤

1. settings.gradle核心部分

//导入配置.android/include_flutter.groovy
// inculde_flutter.groovy内部会引入":flutter"
rootProject.name = 'android_generated'
setBinding(new Binding([gradle: this]))
evaluate(new File(settingsDir, 'include_flutter.groovy'))

2. include_flutter.groovy核心部分

include_flutter.groovy是创建flutter module是自动生成，一帮情况下无需手动修改

// 查找项目根路径
def scriptFile = getClass().protectionDomain.codeSource.location.toURI()
def flutterProjectRoot = new File(scriptFile).parentFile.parentFile

// 导入flutter module名称为相对当前目录的flutter
gradle.include ":flutter"
// flutter module android真正的实现位于.android/Flutter目录下
gradle.project(":flutter").projectDir = new File(flutterProjectRoot, ".android/Flutter")

// 获取 配置文件.android/local.properties
def localPropertiesFile = new File(flutterProjectRoot, ".android/local.properties")
def properties = new Properties()

assert localPropertiesFile.exists(), "??The Flutter module doesn't have a `$localPropertiesFile` file." +
                                     "\nYou must run `flutter pub get` in `$flutterProjectRoot`."
localPropertiesFile.withReader("UTF-8") { reader -> properties.load(reader) }

// 获取flutter sdk路径，导入module_plugin_loader.gradle
def flutterSdkPath = properties.getProperty("flutter.sdk")
assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
gradle.apply from: "$flutterSdkPath/packages/flutter_tools/gradle/module_plugin_loader.gradle"

? 到了这里，整个流程比较简单，后续的module_plugin_loader.gradle, app/build.gradle，flutter.gradle都在上一篇文中"深度了解Flutter APP的构建流程"有做分析，这里不再阐述。