Flutter项目运行异常解决方案

Android Studio成功集成Flutter插件以后，就可以新建一个Flutter项目了。创建Flutter项目成功之后，运行Flutter项目出现如下异常：
* Where:
Build file ‘/Users/guotianhui/Downloads/flutter_app2/flutter_appw2/android/app/build.gradle’ line: 25
* What went wrong:
A problem occurred evaluating project ‘:app’.
> Could not resolve all artifacts for configuration ‘classpath’.
> Could not download guava.jar (com.google.guava:guava:23.0)
> Could not get resource ‘https://jcenter.bintray.com/com/google/guava/guava/23.0/guava-23.0.jar’.
> Could not GET ‘https://d29vzk4ow07wi7.cloudfront.net/7baa80df284117e5b945b19b98d367a85ea7b7801bd358ff657946c3bd1b6596?response-content-disposition=attachment%3Bfilename%3D%22guava-23.0.jar%22&Policy=eyJTdGF0ZW1lbnQiOiBbeyJSZXNvdXJjZSI6Imh0dHAqOi8vZDI5dnprNG93MDd3aTcuY2xvdWRmcm9udC5uZXQvN2JhYTgwZGYyODQxMTdlNWI5NDViMTliOThkMzY3YTg1ZWE3Yjc4MDFiZDM1OGZmNjU3OTQ2YzNiZDFiNjU5Nj9yZXNwb25zZS1jb250ZW50LWRpc3Bvc2l0aW9uPWF0dGFjaG1lbnQlM0JmaWxlbmFtZSUzRCUyMmd1YXZhLTIzLjAuamFyJTIyIiwiQ29uZGl0aW9uIjp7IkRhdGVMZXNzVGhhbiI6eyJBV1M6RXBvY2hUaW1lIjoxNTYwNzUwMTk3fSwiSXBBZGRyZXNzIjp7IkFXUzpTb3VyY2VJcCI6IjAuMC4wLjAvMCJ9fX1dfQ__&Signature=BoSQcFEL3Wy5BF-bG56IkHfoEYKYHwgjjlfYH9mJ-fZtvTZeigVj9CtP01QtxQJHQsCsNeiFKD2j7SuxOupMU7zjaiG4xrk2-0f-xpFJo~dto51u3n~kmRXqZEBjDZcFUch3LAusdsMbP1p-EOoZvmv9E6VjVeVkc-zR-JMuTpPYuy0TTDGEc2JfhSwVa0JE75yy1ikrlOlqAoH3JGMZjcUhQYeiCe56LKlX5f5QEFsU-aMQhuAwe12bco5~XuSf4IzdFRr~iUQ-n10e8OBykoV7ke9apVI45DMAVALTSozU0ZwyyFPvnFWO8LLNhRjdvY65RAE6mfE8RSRJFZSZMA__&Key-Pair-Id=APKAIFKFWOMXM2UMTSFA’.
> Connect to d29vzk4ow07wi7.cloudfront.net:443 [d29vzk4ow07wi7.cloudfront.net/99.84.231.221, d29vzk4ow07wi7.cloudfront.net/99.84.231.76, d29vzk4ow07wi7.cloudfront.net/99.84.231.93, d29vzk4ow07wi7.cloudfront.net/99.84.231.174] failed: Read timed out
* 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 6m 26s
Command: /Users/guotianhui/Downloads/flutter_app2/flutter_appw2/android/gradlew app:properties
Finished with error: Please review your Gradle project setup in the android/ folder.
这里提示在Android目录找不到Guava包，并提示错误在app bulid.gradle文件的第25行：
apply from: “$flutterRoot/packages/flutter_tools/gradle/flutter.gradle”
定位到flutterRoot指向的是flutter.sdk的配置。
def flutterRoot = localProperties.getProperty(‘flutter.sdk’)
if (flutterRoot == null) {
throw new GradleException(“Flutter SDK not found. Define location with flutter.sdk in the local.properties file.”)
}
我们在local.properties文件里面可以查看到flutter sdk的路径：
flutter.sdk=/Users/guotianhui/Android/flutter
目前除了找不到GradleException这个异常类之外，其他都没有发现异常问题。然后百度了通过dependencies依赖类库的方式：
testImplementation ‘com.google.guava:guava:24.0-android’
testImplementation ‘com.google.guava:guava:24.0-jre’
集成到项目里面，但是依然没有解决问题。还是报下面的错误：
* Error running Gradle:
ProcessException: Process “/Users/guotianhui/Downloads/flutter_app2/flutter_appw2/android/gradlew” exited abnormally:
Command: /Users/guotianhui/Downloads/flutter_app2/flutter_appw2/android/gradlew app:properties
Finished with error: Please review your Gradle project setup in the android/ folder.
使用Android studio 集成Flutter插件，除了在Android Studio IDE里面通过File–>Settings–>
Plugins–>下载Flutter插件，下载Flutter插件时会提示你是否下载Dart插件，点击确认下载就行。
到这里我们就在Android Studio IDE里面集成了Flutter插件，但是我们还是不能直接开发Flutter项目，在我们启动Studio的时候，我们发现多了一个可以新建Flutter项目选项。但是我们并没有配置好Flutter的开发环境，也就是Flutter的Sdk。类似与Java Sdk，我们需要配置Flutter Sdk的绝对路径到Path环境变量。
Winddows用户操作比较简单，选中电脑–>属性–>高级选项–>环境变量–>新建一个FLUTTER_PATH环境变量，设置值为你直接从Flutter官网下载的SDK绝对路径。下载完Flutter文件之后，我们就不需要再去Dart官网下载Dart Sdk文件了，因为Fluter Sdk的bin/cache/目录下就包含了dart-sdk文件。
那么我们说一些Mac用户如何配置Flutter Sdk环境变量，当然你也可以查看官网的配置教程：
open .bash_profile
这个是本人比较喜欢的Mac添加环境变量的命令，直接打开环境变量文件，然后更改里面的环境变量，添加下面配置：
export PATH=安装路径/flutter/bin:$PATH
最后更改好之后，直接关闭文件，默认就保存了。但是还要记得执行下面的命令来保存你更改的环境变量配置：
source .bash_profile
最后我们可以运行下面的命令查看Flutter Sdk有没有保存成功：
flutter doctor
如果出现下面的界面，说明你的Flutter Sdk安装成功了。
成功安装Flutter插件和Dart插件，还有配置好Flutter 和Dart的绝对路径之后，我们再去新建一个Flutter项目发现并没有报错。但是运行之后报下面的错：
What went wrong:
A problem occurred configuring root project ‘android’.
> Could not resolve all artifacts for configuration ‘:classpath’.
> Could not download kotlin-gradle-plugin.jar (org.jetbrains.kotlin:kotlin-gradle-plugin:1.2.71)
> Could not get resource ‘https://jcenter.bintray.com/org/jetbrains/kotlin/kotlin-gradle-plugin/1.2.71/kotlin-gradle-plugin-1.2.71.jar’….
这是因为我们升级了kotlin的版本导致的，项目找不到1.2.71的kotlin jar包。我们打开android项目配置里面的build.gradle文件成和你项目一致的kotlin版本和android studio版本就可以了。
buildscript {
ext.kotlin_version = ‘1.3.31’
repositories {
google()
jcenter()
}
dependencies {
classpath ‘com.android.tools.build:gradle:3.4.1’
classpath “org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version”
}
}
这里我们的android studio 的版本是3.4.1，对应的最新的kotlin版本是1.3.31，如果你不知道你的studio版本，可以查看IDE的导航栏，查看help->搜索about studio 查看版本，查看kotlin的最新版本可以查看Tools->kotlin->Configeru Kotlin Plugin Updates。需要查看kotlin版本对应的android studio版本，可以前往Kotlin Plugin官网。
但是现在虽然我的项目可以单独运行android项目了，但是直接在Flutter项目里面运行还是会报下面的错：
* What went wrong:
A problem occurred configuring root project ‘android’.
> Could not resolve all artifacts for configuration ‘:classpath’.
> Could not download kotlin-compiler-embeddable.jar (org.jetbrains.kotlin:kotlin-compiler-embeddable:1.3.31)
> Could not get resource ‘https://jcenter.bintray.com/org/jetbrains/kotlin/kotlin-compiler-embeddable/1.3.31/kotlin-compiler-embeddable-1.3.31.jar’.
> Could not GET ‘https://jcenter.bintray.com/org/jetbrains/kotlin/kotlin-compiler-embeddable/1.3.31/kotlin-compiler-embeddable-1.3.31.jar’.
> Read timed out
> Could not download kotlin-build-common.jar (org.jetbrains.kotlin:kotlin-build-common:1.3.31)
> Could not get resource ‘https://jcenter.bintray.com/org/jetbrains/kotlin/kotlin-build-common/1.3.31/kotlin-build-common-1.3.31.jar’.
> Could not GET ‘https://jcenter.bintray.com/org/jetbrains/kotlin/kotlin-build-common/1.3.31/kotlin-build-common-1.3.31.jar’.
> Read timed out
> Could not download kotlin-daemon-client.jar (org.jetbrains.kotlin:kotlin-daemon-client:1.3.31)
> Could not get resource ‘https://jcenter.bintray.com/org/jetbrains/kotlin/kotlin-daemon-client/1.3.31/kotlin-daemon-client-1.3.31.jar’.
> Could not GET ‘https://jcenter.bintray.com/org/jetbrains/kotlin/kotlin-daemon-client/1.3.31/kotlin-daemon-client-1.3.31.jar’.
> Read timed out
这里提示我下载不了kotlin compiler编译器读取超时，百度了一下说是链接链接超时的问题，需要替换成阿里的链接。把google() 和 jcenter()这两行去掉。改为阿里的链接：
maven { url ‘https://maven.aliyun.com/repository/google’ }
maven { url ‘https://maven.aliyun.com/repository/jcenter’ }
maven { url ‘http://maven.aliyun.com/nexus/content/groups/public’ }
替换成功之后，再次运行就可以成功运行了。
总结一下遇到的问题：
如果你下载了Flutter插件和Dart插件之后，新建Flutter项目之后；
第一，如果你的项目报编译错误，那么可能是你没有正确的配置好Flutter和Dart Sdk的路径。
第二，如果你配置好了Flutter和Dart 插件的Sdk路径，但是运行时报Kotlin jar包找不到，需要检查你的kotlin版本和android studio版本是否配对，然后在确认respositorier的路径是否改成阿里的地址。
以上就是全部坑，希望对大家有用！