随着 Flutter 的逐漸發展與完善，與 Native 結合使用的場景越來越多；小菜今天嘗試将一個曆史的 Android Native 項目接入 Flutter Module；
AndroidX
Flutter 的發展很迅速，大部分插件均适配 AndroidX，為了今後開發的便利性，小菜優先由如下版本更新适配 AndroidX；
minSdkVersion 17
targetSdkVersion 26
compileSdkVersion 28
buildToolsVersion "28.0.3" 小菜以前嘗試過
Flutter 更新适配 AndroidX，Android 的處理類似，小菜以實際項目嘗試适配；
1. 添加 AndroidX 配置
在 android/gradle.properties 檔案中添加如下配置：
android.useAndroidX=true
android.enableJetifier=true 2. Migrate to AndroidX
小菜通過 Android Studio 中的 Migrate to AndroidX 來配合更新(純手動更新需要修改巨多的檔案)，選擇本工程 -> Refactor -> Migrate to Androidx；但小菜目前 Gradle 版本是 3.0.0，此時提示 Gradle 需 >= 3.2.0，故小菜需要先更新 Gradle；
3. Gradle 更新
更新 android/build.gradle 檔案中 Gradle 版本；此時 Sync 同步時會由如下兩個提示；
classpath 'com.android.tools.build:gradle:3.2.0' 3.1 compile 已經不建議使用，小菜把各個 Module 中 compile 替換為 api / implementation；
Configuration 'compile' is obsolete and has been replaced with 'implementation' and 'api'.
It will be removed at the end of 2018. For more information see: http://d.android.com/r/tools/update-dependency-configurations.html 
3.2 小菜的項目中在之前通過 retrolambda 支援 Java8，在 Gradle > 3.0.0 之後預設支援 Java8，小菜将引入去掉即可；
One of the plugins you are using supports Java 8 language features. To try the support built into the Android plugin, remove the following from your build.gradle:
apply plugin: 'me.tatarka.retrolambda'
To learn more, go to https://d.android.com/r/tools/java-8-support-message.html 4. 重複第二步驟，Migrate to AndroidX
注意要選擇底部 Do Refactor，會幫我們節省巨大的工作量，隻需要個别的檔案引入或 xml 需要更改，否則需要我們手動修改大量的檔案引入等；
| android.support | androidx |
|---|---|
| android.support.annotation.NonNull; | androidx.annotation.NonNull; |
| android.support.annotation.Nullable; | androidx.annotation.Nullable; |
| android.support.annotation.IntRange; | androidx.annotation.IntRange; |
| android.support.design.widget.CoordinatorLayout; | androidx.coordinatorlayout.widget.CoordinatorLayout; |
| android.support.v4.content.ContextCompat; | androidx.core.content.ContextCompat; |
| android.support.v4.widget.DrawerLayout; | androidx.drawerlayout.widget.DrawerLayout; |
| android.support.v4.app.Fragment; | androidx.fragment.app.Fragment; |
| android.support.v4.graphics.drawable.RoundedBitmapDrawable; | androidx.core.graphics.drawable.RoundedBitmapDrawable; |
| android.support.v4.graphics.drawable.RoundedBitmapDrawableFactory; | androidx.core.graphics.drawable.RoundedBitmapDrawableFactory; |
| android.support.v7.widget.RecyclerView; | androidx.recyclerview.widget.RecyclerView; |
| android.support.v7.app.AlertDialog; | androidx.appcompat.app.AlertDialog; |
| ... |
5. Sync 同步打包檢驗
若有個别 xml 檔案需要調整，按照提示微調即可；debug / release 均需要打包檢驗；到此更新适配 AndroidX 工作基本完成；
Flutter Module
小菜之前也嘗試過
Android 原生內建 Flutter Module，小菜組内已有相關的 Flutter 工程，是以不再建立，內建方法很簡單；
1. setting.gradle 中引入 Flutter Module 路徑
setBinding(new Binding([gradle: this]))
evaluate(new File(
'/Users/user/Documents/workspace/flutter_module02/.android/include_flutter.groovy'
)) 2. app/build.project 中引入 Flutter 依賴
implementation project(':flutter') 3. Sync 同步後檢驗
小菜以前整理過
Flutter 與 Android 原生互動，但為了驗證友善小菜僅提供一個 FlutterActivity 供頁面跳轉即可；
public class FlutterMainActivity extends FlutterActivity {
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
} 小菜未使用 FlutterApplication，此時提示如下問題；
Caused by: java.lang.IllegalStateException: ensureInitializationComplete must be called after startInitialization
at io.flutter.embedding.engine.loader.FlutterLoader.ensureInitializationComplete(FlutterLoader.java:153)
at io.flutter.view.FlutterMain.ensureInitializationComplete(FlutterMain.java:80)
at io.flutter.app.FlutterActivityDelegate.onCreate(FlutterActivityDelegate.java:144)
at io.flutter.app.FlutterActivity.onCreate(FlutterActivity.java:89)
at com.test.FlutterMainActivity.onCreate(FlutterMainActivity.java:13)
at android.app.Activity.performCreate(Activity.java:6367)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1110)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2397) 在 FlutterMainActivity 中提前初始化後，又提示新的問題；
protected void onCreate(@Nullable Bundle savedInstanceState) {
FlutterMain.startInitialization(this);
super.onCreate(savedInstanceState);
}
UncaughtException detected: java.lang.UnsatisfiedLinkError: dalvik.system.PathClassLoader[DexPathList[[zip file "/data/app/com.test-2/base.apk", zip file "/data/app/com.test-2/split_lib_dependencies_apk.apk", zip file "/data/app/com.test-2/split_lib_slice_0_apk.apk", zip file "/data/app/com.test-2/split_lib_slice_1_apk.apk"],nativeLibraryDirectories=[/data/app/com.test-2/lib/arm, /data/app/com.test-2/base.apk!/lib/armeabi, /data/app/com.test-2/split_lib_dependencies_apk.apk!/lib/armeabi, .../split_lib_slice_8_apk.apk!/lib/armeabi, /data/app/com.test-2/split_lib_slice_9_apk.apk!/lib/armeabi, /vendor/lib, /system/lib]]] couldn't find "libflutter.so"
at java.lang.Runtime.loadLibrary(Runtime.java:379)
at java.lang.System.loadLibrary(System.java:1086)
at io.flutter.embedding.engine.loader.FlutterLoader.startInitialization(FlutterLoader.java:122)
at io.flutter.embedding.engine.loader.FlutterLoader.startInitialization(FlutterLoader.java:93)
at io.flutter.view.FlutterMain.startInitialization(FlutterMain.java:45)
at com.test.FlutterMainActivity.onCreate(FlutterMainActivity.java:14) 小菜查詢後發現目前項目 NDK 隻支援 armeabi 架構，而 Flutter 支援的時 armeabi-v7a，加入之後檢驗；若項目有特殊要求 NDK 必須是 armeabi 時，可考慮将 armeabi-v7a 的 flutter.so 拷貝到項目中；
ndk {
abiFilters "armeabi", "armeabi-v7a", "x86"
} 小擴充
小菜在适配 AndroidX 過程中還遇到如下問題，并非所有項目涉及，記錄僅供參考；
Q1：All flavors must now belong to a named flavor dimension.
小菜更新 Gradle 之後進行多管道打包時會提示如下錯誤；
FAILURE: Build failed with an exception.
* What went wrong:
A problem occurred configuring project ':app'.
> All flavors must now belong to a named flavor dimension. Learn more at https://d.android.com/r/tools/flavorDimensions-missing-error-message.html
* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.
* Get more help at https://help.gradle.org
BUILD FAILED in 0s A1：
Gradle > 3.0 時多管道打包需要指定一種 flavor dimensions；其中建議不要直接使用 main 的名稱，否則容易出現新的重複鍵問題；com.android.build.gradle.internal.api.artifact.BuildableArtifactImpl
// 修改前
productFlavors {
test1 {}
test2 {}
main {}
}
// 修改後
flavorDimensions "main"
productFlavors {
test1 { dimension "main" }
test2 { dimension "main" }
main0 { dimension "main" }
} Q2：com.android.builder.dexing.DexArchiveBuilderException
小菜在運作過程中還提示 DexArchiveBuilderException 錯誤；
com.android.builder.dexing.DexArchiveBuilderException A2：
小菜查閱是未指定 Java8 的問題，添加指定 1.8 即可；
compileOptions {
sourceCompatibility 1.8
targetCompatibility 1.8
} Q3：Unable to find method '...getOutputs()Ljava/util/List'
Error:Unable to find method 'com.android.build.gradle.api.BaseVariant.getOutputs()Ljava/util/List;'.
Possible causes for this unexpected error include:<ul><li>Gradle's dependency cache may be corrupt (this sometimes occurs after a network connection timeout.)
<a href="syncProject">Re-download dependencies and sync project (requires network)</a></li><li>The state of a Gradle build process (daemon) may be corrupt. Stopping all Gradle daemons may solve this problem. A3：
小菜幾經查證後發現是 ButterKinfe 版本較低，是以更新至支援 AndroidX 的 10.2.1 的最新版本即可；注意，此時需要 Java8 環境；
dependencies {
implementation 'com.jakewharton:butterknife:10.2.1'
annotationProcessor 'com.jakewharton:butterknife-compiler:10.2.1'
} 至此，小菜的曆史項目更新适配 AndroidX 并接入 Flutter Module 基本完成，下一步是兩者之間的互動；更新适配是一個艱難複雜的過程，可能會有很多意想不到的問題，希望可以沉下心來慢慢解決；如有問題請多多指導！
來源： 阿策小和尚