Android studio启动 Flutter 启动报错：Operation timed out

第一次搭建Flutter项目，启动后报错连接超时，似乎是下载什么东西没ok....

详细报错信息：

event sent after app closed: {id: 0, progressId: null, message: Running "flutter pub get" in flutter_app...}
event sent after app closed: {id: 0, progressId: null, finished: true}
Launching lib/main.dart on Android SDK built for x86 in debug mode...
Running Gradle task 'assembleDebug'...
Exception in thread "main" java.net.ConnectException: Operation timed out (Connection timed out)
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    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.SocksSocketImpl.connect(SocksSocketImpl.java:392)
    at java.net.Socket.connect(Socket.java:607)
    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:1162)
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1056)
    at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:177)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1570)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1498)
    at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:268)
    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)
Exception: Gradle task assembleDebug failed with exit code 1

解决方法（本地尝试可行）：

　　项目结构

　　1.通过配置文件 gradle-wrapper.properties 查看项目所需的gradlew版本（上图所示为 gradle-5.6.2-all.zip）。通过浏览器下载到本地解压，将压缩包放入到与配置文件gradle-wrapper.properties同级目录下。入上图所示，我下载的是：

gradle-5.6.2-bin.zip

　　2.修改gradlw.bat文件，在 APP_HOME下面添加一行代码，指定到gradlew目录（根据个人目录配置）：/Library/profiles/gradle-5.6.2/.gradle

　

set APP_BASE_NAME=%~n0
set APP_HOME=%DIRNAME%
set GRADLE_OPTS="-Dgradle.user.home=/Library/profiles/gradle-5.6.2/.gradle"

set GRADLE_OPTS="-Dgradle.user.home=/Library/profiles/gradle-5.6.2/.gradle"

　　3.修改 Flutter sdk中的gradle工具配置文件(根据自己的路径配置) ： /Library/profiles/Flutter/sdk/flutter/packages/flutter_tools/gradle/flutter.gradle，添加国内的仓库镜像地址，指定到aliyun上：

buildscript {
    repositories {
        // google()
        // jcenter()
        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'}
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.5.0'
    }
}
......
......
......
......

　　4.重新启动运行，正常：