Flutter首次初始化应用遇java.net.ConnectException连接超时问题求助

问题描述 #

初始化首个Flutter应用时，严格遵循入门步骤操作仍触发连接超时异常，错误日志如下：

Launching lib\main.dart on sdk gphone64 x86 64 in debug mode...
main.dart:1
Exception in thread "main" java.net.ConnectException: Connection timed out: connect
    at java.base/sun.nio.ch.Net.connect0(Native Method)
    at java.base/sun.nio.ch.Net.connect(Net.java:579)
    at java.base/sun.nio.ch.Net.connect(Net.java:568)
    at java.base/sun.nio.ch.NioSocketImpl.connect(NioSocketImpl.java:588)
    at java.base/java.net.Socket.connect(Socket.java:633)
    at java.base/java.net.Socket.connect(Socket.java:583)
    at java.base/sun.net.NetworkClient.doConnect(NetworkClient.java:183)
    at java.base/sun.net.www.http.HttpClient.openServer(HttpClient.java:531)
    at java.base/sun.net.www.http.HttpClient$1.run(HttpClient.java:590)
    at java.base/sun.net.www.http.HttpClient$1.run(HttpClient.java:588)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:569)
    at java.base/sun.net.www.http.HttpClient.privilegedOpenServer(HttpClient.java:587)
    at java.base/sun.net.www.http.HttpClient.openServer(HttpClient.java:631)
    at java.base/sun.net.www.protocol.https.HttpsClient.<init>(HttpsClient.java:266)
    at java.base/sun.net.www.protocol.https.HttpsClient.New(HttpsClient.java:380)
    at java.base/sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(AbstractDelegateHttpsURLConnection.java:202)
    at java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1263)
    at java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1128)
    at java.base/sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:179)
    at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1665)
    at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1589)
    at java.base/sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:224)
    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
Exited (sigterm)

已尝试的操作：

• 使用标准模拟器、冷启动模拟器
• 通过VS Code和flutter run命令启动应用
• 更换旧版Android Studio与Pixel 6模拟器

解决方案 #

1. 配置Gradle国内镜像 #

修改项目根目录下android/build.gradle文件，将仓库地址替换为国内镜像（如阿里云），加快依赖下载速度：

buildscript {
    repositories {
        maven { url 'https://maven.aliyun.com/repository/google' }
        maven { url 'https://maven.aliyun.com/repository/jcenter' }
        maven { url 'https://maven.aliyun.com/nexus/content/groups/public' }
    }
}

allprojects {
    repositories {
        maven { url 'https://maven.aliyun.com/repository/google' }
        maven { url 'https://maven.aliyun.com/repository/jcenter' }
        maven { url 'https://maven.aliyun.com/nexus/content/groups/public' }
    }
}

2. 手动下载Gradle包 #

• 查看项目android/gradle/wrapper/gradle-wrapper.properties中的distributionUrl，获取需要的Gradle版本（如gradle-7.4-all.zip）
• 手动下载对应版本的Gradle包，放置到本地Gradle缓存目录（默认路径：C:\Users\你的用户名\.gradle\wrapper\dists\gradle-x.x.x-all\随机子目录）
• 修改gradle-wrapper.properties中的distributionUrl为本地文件路径，示例：

  distributionUrl=file:///C:/Users/你的用户名/.gradle/wrapper/dists/gradle-7.4-all/gradle-7.4-all.zip
  

3. 检查代理与网络设置 #

• 关闭系统代理或VPN，避免Gradle连接外部仓库时被拦截
• 若必须使用代理，在项目根目录创建gradle.properties文件（无则新建），添加代理配置：

  systemProp.http.proxyHost=代理地址
  systemProp.http.proxyPort=代理端口
  systemProp.https.proxyHost=代理地址
  systemProp.https.proxyPort=代理端口
  

4. 清理缓存后重新构建 #

执行以下命令清理Flutter和Gradle缓存，再尝试构建：

flutter clean
flutter pub get
cd android
gradlew clean
gradlew assembleDebug

内容的提问来源于stack exchange，提问作者rustemtopcu