Flutter 新建项目运行报错 Exception in thread "main" java.net.ConnectException: Connection timed out: connect

问题：Flutter create新建项目之后运行，一直报错显示Exception in thread "main" java.net.ConnectException: Connection timed out: connect

Exception in thread "main" java.net.ConnectException: Connection timed out: connect
        at java.net.DualStackPlainSocketImpl.connect0(Native Method)    
        at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79)
        at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)     
        at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
        at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
        at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)   
        at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
        at java.net.Socket.connect(Socket.java:589)
        at sun.security.ssl.SSLSocketImpl.connect(SSLSocketImpl.java:666)
        at sun.security.ssl.BaseSSLSocketImpl.connect(BaseSSLSocketImpl.java:173)
        at sun.net.NetworkClient.doConnect(NetworkClient.java:180)
        at sun.net.www.http.HttpClient.openServer(HttpClient.java:463)  
        at sun.net.www.http.HttpClient.openServer(HttpClient.java:558)
        at sun.net.www.protocol.https.HttpsClient.<init>(HttpsClient.java:264)
        at sun.net.www.protocol.https.HttpsClient.New(HttpsClient.java:367)
        at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(AbstractDelegateHttpsURLConnection.java:191)
        at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1156)
        at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1050)
        at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:177)
        at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1492)
        at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:263)
        at org.gradle.wrapper.Download.downloadInternal(Download.java:58)
        at org.gradle.wrapper.Download.download(Download.java:44)
        at org.gradle.wrapper.Install$1.call(Install.java:61)
        at org.gradle.wrapper.Install$1.call(Install.java:48)
        at org.gradle.wrapper.ExclusiveFileAccessManager.access(ExclusiveFileAccessManager.java:65)  
        at org.gradle.wrapper.Install.createDist(Install.java:48)
        at org.gradle.wrapper.WrapperExecutor.execute(WrapperExecutor.java:128)
        at org.gradle.wrapper.GradleWrapperMain.main(GradleWrapperMain.java:61)
Running Gradle task 'assembleDebug'...
Running Gradle task 'assembleDebug'... Done                        26.4s
Exception: Gradle task assembleDebug failed with exit code 1

其实主要估计就是网络超时问题，我上网搜了一波发现都建议
需要修改项目下 android/build.gradle 和 flutter 安装目录 flutter/packages/flutter_tools/gradle/flutter.gradle 两个文件中 buildscript 和allprojects 中的

google()
jcenter()

替换成阿里云镜像

//google() 
//jcenter()

//添加aliyun的镜像仓库
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' }

如果还是提示错误，通过查看 android 目录下的 android/gradle/wrapper/gradle-wrapper.properties 查看版本，通过 Gradle官方下载地址，下载对应的Gradle版本zip文件放到，一般C盘目录下 .gradle\wrapper\dists\对应版本目录中。

步骤一：到你项目里面的 gradle-wrapper.properties 文件里面查找到你所需要的版本，我这里是gradle-6.7-all.zip

步骤二：到这里http://services.gradle.org/distributions/找到对应的版本下载

步骤三：找到你的.grade地方，我电脑所在是 C:\Users\husk\.gradle ，然后将刚刚下载成功的zip包放在该目录下（其实你喜欢放在哪都无所谓，反正到时候引入本地这个zip就好）

步骤四：到你项目里面的gradle-wrapper.properties文件里面将原来的 distributionUrl=https\://services.gradle.org/distributions/gradle-6.7-all.zip 换乘本地的

或者将下载的 gradle-6.7-all.zip 上传到公开可读的oss上，将文件地址替换 distributionUrl={oss 文件 url}

然后运行，运行成功了！！！