Flutter：打包apk，详细图文介绍

困扰了一天，终于能正常打包apk安装了，记录下打包的流程。建议参考我这篇文章时，同时看下官网的构建说明。
官网构建并发布 Android 应用详情

1、AS创建Flutter项目

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2、cmd执行命令
生成一个sunluyi.jks的文件，可以自行把sunluyi替换)
-alias sunluyi（别名），方便管理都用一个名字

keytool -genkey -v -keystore sunluyi.jks -keyalg RSA -keysize 2048 -validity 10000 -alias sunluyi

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然后你会得到一个命名sunluyi.jks的文件

3、cmd执行命令，查看文件详情

keytool -list -v -keystore sunluyi.jks

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4、把生成好的.jks文件放在Flutter项目android/app目录下
并在android目录下手动创建key.properties文件

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key.properties文件内容就是第二步自己设置的口令密码和别名storeFile对应的文件路径./sunluyi.jks(app目录)

storePassword=sunluyi
keyPassword=sunluyi
keyAlias=sunluyi
storeFile=./sunluyi.jks

5、修改/android/app/build.gradle文件
下边代码中我标注了哪些是新增的内容，哪些是修改的内容

plugins {
    id "com.android.application"
    id "kotlin-android"
    // The Flutter Gradle Plugin must be applied after the Android and Kotlin Gradle plugins.
    id "dev.flutter.flutter-gradle-plugin"
}

// 新增内容 ↓
def localProperties = new Properties()
def localPropertiesFile = rootProject.file("local.properties")
if (localPropertiesFile.exists()) {
    localPropertiesFile.withReader("UTF-8") { reader ->
        localProperties.load(reader)
    }
}

def flutterVersionCode = localProperties.getProperty("flutter.versionCode")
if (flutterVersionCode == null) {
    flutterVersionCode = "1"
}

def flutterVersionName = localProperties.getProperty("flutter.versionName")
if (flutterVersionName == null) {
    flutterVersionName = "1.0"
}

def keystoreProperties = new Properties()
def keystorePropertiesFile = rootProject.file('key.properties')
if (keystorePropertiesFile.exists()) {
    keystoreProperties.load(new FileInputStream(keystorePropertiesFile))
}

// 新增内容↑

android {
    namespace = "com.sunluyi.app.flutter_sunluyi"
    compileSdk = flutter.compileSdkVersion
    ndkVersion = flutter.ndkVersion

    compileOptions {
        sourceCompatibility = JavaVersion.VERSION_1_8
        targetCompatibility = JavaVersion.VERSION_1_8
    }

    kotlinOptions {
        jvmTarget = JavaVersion.VERSION_1_8
    }

    defaultConfig {
        // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
        applicationId = "com.sunluyi.app.flutter_sunluyi"
        // You can update the following values to match your application needs.
        // For more information, see: https://flutter.dev/to/review-gradle-config.
        minSdk = flutter.minSdkVersion
        targetSdk = flutter.targetSdkVersion
        // 修改内容 ↓
        versionCode = flutterVersionCode.toInteger()
        versionName = flutterVersionName
        // 修改内容 ↑
    }

    // 新增内容 ↓
    signingConfigs {
        release {
            keyAlias = keystoreProperties['keyAlias']
            keyPassword = keystoreProperties['keyPassword']
            storeFile = keystoreProperties['storeFile'] ? file(keystoreProperties['storeFile']) : null
            storePassword = keystoreProperties['storePassword']
        }
    }

    // 新增内容 ↑

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

flutter {
    source = "../.."
}

6、最后你可能还需要配置应用的权限
/android/app/src/main/AndroidManifest.xml目录

<manifest xmlns:android="http://schemas.android.com/apk/res/android">
    <application
        android:label="[project]"
        ...
    </application>
    ...
    // 这里是新增的权限
    <uses-permission android:name="android.permission.INTERNET"/>
</manifest>

最后根目录执行flutter build apk打包成apk文件。

打包时有个提示警告：

Warning: SDK processing. This version only understands SDK XML versions up to 3 but an SDK XML file of version 4 was encountered. This can happen if you use versions of Android Studio and the command-line tools that were released at different times.
记录下如何解决。

1、cmd执行：flutter doctor -v

下图是我解决过警告的，最开始是Platform android-35, build-tools 34.0.0
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百度了下解决方案：
在设置/Android SDK中最开始我是勾选的35，换成下方的勾选之后，再次执行
flutter doctor -v得到：Platform android-35, build-tools 34.0.0

重新执行flutter build apk后没有警告，完成了打包流程。
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