Windows下Flutter开发AR应用报错：Cannot invoke method afterEvaluate() on null object

错误现象 #

Plugin project :permission_handler_android not found. Please update settings.gradle.
Plugin project :geolocator_android not found. Please update settings.gradle.
Plugin project :path_provider_android not found. Please update settings.gradle.
Plugin project :ar_flutter_plugin not found. Please update settings.gradle.

FAILURE: Build failed with an exception.

### 出错原因：
配置项目':app'时出现问题。
Cannot invoke method afterEvaluate() on null object

问题根源 #

1. settings.gradle未配置Flutter插件自动加载逻辑，导致依赖的Android端插件无法被Gradle识别
2. 可能存在Flutter SDK路径配置异常或项目结构不匹配的情况

解决方案 #

1. 修正settings.gradle配置 #

替换现有内容为以下代码，确保Flutter自动引入所有依赖插件：

pluginManagement {
    def flutterSdkPath = {
        def properties = new Properties()
        file("local.properties").withInputStream { properties.load(it) }
        def flutterSdkPath = properties.getProperty("flutter.sdk")
        assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
        return flutterSdkPath
    }
    settings.ext.flutterSdkPath = flutterSdkPath()

    includeBuild("${settings.ext.flutterSdkPath}/packages/flutter_tools/gradle")

    repositories {
        google()
        mavenCentral()
        gradlePluginPortal()
    }
}

// 新增：让Flutter自动加载所有插件项目
apply from: "${settings.ext.flutterSdkPath}/packages/flutter_tools/gradle/app_plugin_loader.gradle"

include ':app'

2. 检查local.properties中的Flutter SDK路径 #

打开local.properties文件，确认flutter.sdk指向正确的本地路径（Windows系统路径用双反斜杠或斜杠）：

flutter.sdk=C:\\flutter

3. 验证app/build.gradle中的Flutter源路径 #

检查flutter块的source路径是否匹配项目结构，标准Flutter项目中应为：

flutter {
    source '../' // 指向Flutter项目根目录
}

若你的android文件夹在更深层级，需调整路径确保指向正确的Flutter根目录。

4. 清理缓存并重新构建 #

依次执行以下命令：

flutter clean
flutter pub get
cd android
gradlew clean
gradlew build

5. 检查ar_flutter_plugin兼容性 #

确认pubspec.yaml中ar_flutter_plugin版本与你的Flutter版本兼容，建议使用最新稳定版，同时保证minSdkVersion≥24（你的配置已满足）。

内容的提问来源于stack exchange，提问作者Md. Asad Mondall