简介

您好，我正在尝试删除应用程序settings.gradle中的重复代码。以下是我的文件当前的样子：

pluginManagement {
    def localPropertiesFile = new File(rootProject.projectDir, "local.properties")
    def properties = new Properties()
    assert localPropertiesFile.exists()
    localPropertiesFile.withReader("UTF-8") { reader -> properties.load(reader) }
    def flutterSdkPath = properties.getProperty("flutter.sdk")
    assert flutterSdkPath != null, "flutter.sdk not set in local.properties"

    includeBuild("$flutterSdkPath/packages/flutter_tools/gradle")

    plugins {
        id "dev.flutter.flutter-gradle-plugin" version "1.0.0" apply false
    }
}

include ':app'

def localPropertiesFile = new File(rootProject.projectDir, "local.properties")
def properties = new Properties()
assert localPropertiesFile.exists()
localPropertiesFile.withReader("UTF-8") { reader -> properties.load(reader) }
def flutterSdkPath = properties.getProperty("flutter.sdk")
assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
apply from: "$flutterSdkPath/packages/flutter_tools/gradle/app_plugin_loader.gradle"

(You我可以忽略特定于技术的事情以及为什么必须这样做-让我们假设 * 必须这样做 *。如果您对更多细节感兴趣，请参阅this PR to Flutter）
很容易看出，负责从local.properties文件中加载flutter.sdk属性的代码重复了两次，因此我着手删除这种重复。

尝试1（变量）

起初，我尝试了下面的代码，但Gradle很快提醒我“pluginManagement {}块必须出现在脚本中的任何其他语句之前”。

def localPropertiesFile = new File(rootProject.projectDir, "local.properties")
def properties = new Properties()
assert localPropertiesFile.exists()
localPropertiesFile.withReader("UTF-8") { reader -> properties.load(reader) }
def flutterSdkPath = properties.getProperty("flutter.sdk")
assert flutterSdkPath != null, "flutter.sdk not set in local.properties"

pluginManagement {
    includeBuild("$flutterSdkPath/packages/flutter_tools/gradle")

    plugins {
        id "dev.flutter.flutter-gradle-plugin" version "1.0.0" apply false
    }
}

include ':app'

apply from: "$flutterSdkPath/packages/flutter_tools/gradle/app_plugin_loader.gradle"

尝试2（函数）

在前面的尝试中，错误消息说在pluginManagement {}块之前不允许有 * 语句 *。我考虑过将代码移到一个单独的函数中，因为，在我（适度）的理解中，函数不是Groovy中的语句：

String flutterSdkPath() {
    def localPropertiesFile = new File(rootProject.projectDir, "local.properties")
    def properties = new Properties()
    assert localPropertiesFile.exists()
    localPropertiesFile.withReader("UTF-8") { reader -> properties.load(reader) }
    def flutterSdkPath = properties.getProperty("flutter.sdk")
    assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
    return flutterSdkPath
}

pluginManagement {
    includeBuild("$flutterSdkPath/packages/flutter_tools/gradle")

    plugins {
        id "dev.flutter.flutter-gradle-plugin" version "1.0.0" apply false
    }
}

include ':app'

apply from: "$flutterSdkPath/packages/flutter_tools/gradle/app_plugin_loader.gradle"

不幸的是，它仍然不起作用，并且错误只会变得不那么有用：

FAILURE: Build failed with an exception.

* Where:
Settings file '/Users/bartek/fvm/versions/master/examples/hello_world/android/settings.gradle' line: 20

* What went wrong:
A problem occurred evaluating settings 'android'.
> Could not get unknown property 'flutterSdkPath' for object of type org.gradle.plugin.management.internal.DefaultPluginManagementSpec.

我很确定它必须做一些关于如何pluginManagement {}块被Gradle以特殊的方式处理的事情（也就是说，在settings.gradle中的其余代码被评估之前，它首先被评估）

尝试3（类中的静态方法）

我想也许所有在pluginManagement {}块之前的代码都被剥离了（？），所以我尝试创建一个包含静态方法的类：

pluginManagement {
    includeBuild("${Flutter.flutterSdkPath}/packages/flutter_tools/gradle")

    plugins {
        id "dev.flutter.flutter-gradle-plugin" version "1.0.0" apply false
    }
}

include ':app'

apply from: "${Flutter.flutterSdkPath}/packages/flutter_tools/gradle/app_plugin_loader.gradle"

class Flutter {
    String flutterSdkPath() {
        def localPropertiesFile = new File(rootProject.projectDir, "local.properties")
        def properties = new Properties()
        assert localPropertiesFile.exists()
        localPropertiesFile.withReader("UTF-8") { reader -> properties.load(reader) }
        def flutterSdkPath = properties.getProperty("flutter.sdk")
        assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
        return flutterSdkPath
    }
}

这一次，错误消息甚至更没有帮助：

* Where:
Settings file '/Users/bartek/fvm/versions/master/examples/hello_world/android/settings.gradle' line: 11

* What went wrong:
A problem occurred evaluating settings 'android'.
> Flutter

* 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.

在使用--stracktrace标志运行Gradle后，我注意到这行：

... (<very long stack trace>)
Caused by: java.lang.NoClassDefFoundError: Flutter
...

这和我在第二次尝试中遇到的问题是一样的。
我不知道如何将属性加载代码移到一个地方，并从pluginManagement {}块的内部和外部调用它。
我认为Gradle设置插件可以在这里工作，但我宁愿不这样做，除非必要。