如何在原生项目中集成flutter

两个前提条件：

从flutter v1.17版本开始，flutter module仅支持AndroidX的应用
在release模式下flutter仅支持一下架构：x84_64、armeabi-v7a、arm6f4-v8a,不支持mips和x86;所以引入flutter前需要在app/build.gradle下配置flutter支持的架构

android {
    
    defaultConfig {

        ndk {
            // armeabi：已经淘汰（0%）
            // armeabi-v7a：曾经主流的架构平台（20%）
            // arm64-v8a：目前主流架构平台（80%）
            abiFilters "armeabi-v7a", "arm64-v8a"
        }
    }
}

1、源代码集成

将flutter集成到现有的Android应用中主要步骤如下：

创建flutter module
为已存在的Android应用添加flutter module依赖(setting.gradle中加入代码)
在需要的module引入
添加Java 8编译选项
在kotlin中调用flutter module
编写dart代码

创建flutter module

//--org后面为域名 flutter_module为module名称

flutter create -t module --org com.example.module flutter_module

生成module的目录结构：

为已存在的Android应用添加flutter module依赖：

打开Android项目的setting.gradle添加如下代码：

setBinding(new Binding([gradle: this]))
evaluate(new File(
        settingsDir.parentFile,
        'flutter_module/.android/include_flutter.groovy'
))

//可选，作用：可以在当前AS的project下显示flutter_module以方便查看和编写Dart代码
include ':flutter_module'
project(':flutter_module').projectDir = new File('../flutter_module')

在需要的module引入

//asproj/app/build.gradle
implementation project(':flutter')

添加Java 8编译选项

因为flutter的Android engine是用来Java8的特性，所以在引入flutter时需要配置你的项目都Java8编译选项（app/build.gradle）

android {
    compileOptions {
        sourceCompatibility = 1.8
        targetCompatibility = 1.8
    }
}

在kotlin中调用flutter module，抽取一个基类HiFlutterFragment如下代码：

package org.devio.`as`.proj.common.flutter

import android.content.Context
import android.os.Bundle
import android.view.View
import android.view.ViewGroup
import io.flutter.embedding.android.FlutterTextureView
import io.flutter.embedding.android.FlutterView
import io.flutter.embedding.engine.FlutterEngine
import io.flutter.embedding.engine.dart.DartExecutor
import kotlinx.android.synthetic.main.fragment_flutter.title
import org.devio.`as`.proj.common.R
import org.devio.`as`.proj.common.ui.component.HiBaseFragment

abstract class HiFlutterFragment : HiBaseFragment() {

    private lateinit var flutterEngine: FlutterEngine

    protected var flutterView: FlutterView? = null

    override fun onAttach(context: Context) {
        super.onAttach(context)
        flutterEngine = FlutterEngine(context)

        flutterEngine.dartExecutor.executeDartEntrypoint(DartExecutor.DartEntrypoint.createDefault())
    }

    override fun getLayoutId(): Int {
        return R.layout.fragment_flutter
    }

    fun setTitle(titleStr: String) {
        title.text = titleStr
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        (layoutView as ViewGroup).addView(createFlutterView(activity!!))
    }

    override fun onStart() {
        flutterView!!.attachToFlutterEngine(flutterEngine!!)
        super.onStart()
    }

    override fun onResume() {
        super.onResume()
        //for flutter >= v1.17
        flutterEngine.lifecycleChannel.appIsResumed()
    }

    override fun onPause() {
        super.onPause()
        flutterEngine.lifecycleChannel.appIsInactive()
    }

    override fun onStop() {
        super.onStop()
        flutterEngine.lifecycleChannel.appIsPaused()
    }

    override fun onDetach() {
        super.onDetach()
        flutterEngine.lifecycleChannel.appIsDetached()
    }

    private fun createFlutterView(context: Context): FlutterView {
        //使用FlutterTextureView来进行渲染，以规避fluttersurfaceview压后台回来后界面被复用的问题
        val flutterTextureView = FlutterTextureView(activity!!)
        flutterView = FlutterView(context, flutterTextureView)
        return flutterView!!
    }


}