在已有android studio工程中添加flutter - 好文

基本介绍

flutter是google的跨平台开发框架, 他和react native及weex框架的最大差别是flutter不使用原生控件而使用gdi按帧渲染,
个人理解非常类似windows时代的DirectUI

老工程集成flutter有两大方法:

* 把老工程完全改成flutter,这种方法能实现dart代码的动态加载,但改动很大,
因为flutter引擎内部写死了android-studio里的一些路径,如果AndroidManifest.xml的路径,改造可以做,但不一定有很好的兼容性
本文就介绍此种方法
*
制作一个纯的flutter工程A,fluuter的开发调试都在这个工程进行,当需要发布到老工程B时,把A工程flutter编译后的平台相关的中间文件复制到B工程,B工程没有dart的调试功能,类似与基础了一个第三方的功能模块,
参考另一篇blog：https://blog.csdn.net/langouster/article/details/81566668
<https://blog.csdn.net/langouster/article/details/81566668>
操作过程

目录结构

一个android studio工程的目录结构是这样的
project
├─local.properties
├─build.gradle
├─settings.gradle
├─app
│ ├─build
│ ├─libs
│ └─src
└─gradle
└─wrapper

而flutter的目录结构是
flutter
├─android 对应安卓工程的project目录
├─build
├─ios
├─lib
└─pubspec.yaml

1, 所以第一步, 把project目录名改成android

工程修改

2.复制pubspec.yaml和lib文件到跟android并列
3.修改AndroidManifest.xml文件
<application android:name="io.flutter.app.FlutterApplication" 加入这行
android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label=
"@string/app_name" android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true" android:theme="@style/AppTheme"> <activity
android:name=".MainActivity"> <intent-filter> <action android:name=
"android.intent.action.MAIN" /> <category android:name=
"android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application
>
如果这边修改没成功运行时会报错如下
E/FlutterMain(13694): Flutter initialization failed. E/FlutterMain(13694):
java.lang.NullPointerException: Attemptto invoke virtual method 'void io.flutter
.view.ResourceExtractor.waitForCompletion()' on a null object reference
4.修改settings.gradle
include ':app' def flutterProjectRoot =
rootProject.projectDir.parentFile.toPath()def plugins = new Properties() def
pluginsFile = newFile(flutterProjectRoot.toFile(), '.flutter-plugins') if
(pluginsFile.exists()) { pluginsFile.withReader('UTF-8') { reader ->
plugins.load(reader) } } plugins.each { name, path ->def pluginDirectory =
flutterProjectRoot.resolve(path).resolve('android').toFile() include ":$name"
project(":$name").projectDir = pluginDirectory }
如果这步修改失败会提示GeneratedPluginRegistrant文件编译出错:
错误: 程序包io.flutter.plugins.pathprovider不存在
错误: 程序包io.flutter.plugins.sharedpreferences不存在

5.修改project的build.gradle,加入这一段
rootProject.buildDir = '../build' subprojects { project.buildDir = "
${rootProject.buildDir}/${project.name}" } subprojects {
project.evaluationDependsOn(':app') }
6.修改app的的build.gradle,加入这一段
def localProperties = new Properties() def localPropertiesFile = rootProject.
file('local.properties') if (localPropertiesFile.exists()) {
localPropertiesFile.withReader('UTF-8') { reader -> localProperties.load
(reader) } } 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 {
compileSdkVersion27 defaultConfig { applicationId
"flutter_app2.yourcompany.com.myapplication" minSdkVersion 15 targetSdkVersion
27 versionCode 1 versionName "1.0" testInstrumentationRunner
"android.support.test.runner.AndroidJUnitRunner" } buildTypes { release {
minifyEnabledfalse proguardFiles getDefaultProguardFile('proguard-android.txt'),
'proguard-rules.pro' } } } 这个别忘了 flutter { source '../..' } dependencies {
implementation fileTree(dir:'libs', include: ['*.jar']) implementation
'com.android.support:appcompat-v7:27.1.1' implementation
'com.android.support.constraint:constraint-layout:1.1.0' testImplementation
'junit:junit:4.12' androidTestImplementation
'com.android.support.test:runner:1.0.2' androidTestImplementation
'com.android.support.test.espresso:espresso-core:3.0.2' }
7.修改local.properties加入fluttersdk的路径
ndk.dir=E\:\\software\\android-sdk-windows\\ndk-bundle sdk.dir=E\:\\software\\
android-sdk-windows flutter.sdk=D:\\flutter flutter.buildMode=debug
* 修改MainActivity.java import android.os.Bundle; import
io.flutter.app.FlutterActivity;import
io.flutter.plugins.GeneratedPluginRegistrant;public class MainActivity extends
FlutterActivity { @Override protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState); GeneratedPluginRegistrant.registerWith(this
); } }
修改这8点内容后,编译运行看看,顺利的话就可以正常运行了

但是你会发现没有hot read热更新代码了, 别急, 先关闭工程
然后用android studio打开第一步中android文件夹的上层目录, 也就是pubspec.yaml所在的目录, android
stdio发现存在文件pubspec.yaml,自动识别为一个flutter工程了, 就有热更新了

官方关于这块的文档见:https://github.com/flutter/flutter/wiki/Add-Flutter-to-existing-apps
<https://github.com/flutter/flutter/wiki/Add-Flutter-to-existing-apps>

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