发生于编译时：错误: 程序包androidx.lifecycle不存在

先贴一段报错log，让你更加准确的匹配问题所在，对症下药，药，切克闹。

D:\study\flutter\flutter\.pub-cache\hosted\pub.flutter-io.cn\flutter_plugin_android_lifecycle-1.0.8\android\src\main\java\io\flutter\embedding\engine\plugins\lifecycle\FlutterLifecycleAdapter.java:8: 错误: 程序包androidx.lifecycle不存在
import androidx.lifecycle.Lifecycle;
                         ^
D:\study\flutter\flutter\.pub-cache\hosted\pub.flutter-io.cn\flutter_plugin_android_lifecycle-1.0.8\android\src\main\java\io\flutter\embedding\engine\plugins\lifecycle\FlutterLifecycleAdapter.java:22: 错误: 找不到符 
号
  public static Lifecycle getActivityLifecycle(
  符号:   类 Lifecycle
  位置: 类 FlutterLifecycleAdapter
2 个错误

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':compileReleaseJavaWithJavac'.
> Compilation failed; see the compiler error output for details.

* 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 1s


Exception: The plugin flutter_plugin_android_lifecycle could not be built due to the issue above.

既然问题已经匹配上了，那就说下我下面的解决实践吧。
上面的问题其实就是Androidx引用库兼容问题，当某些插件升级到一定版本时就会出现这个问题。

首先升级下sdk

实际上到这里就已经解决了，但是可能有些包被墙了，下载不了，导致还是没解决，则需要使用阿里云的代理了

到这里应该是完全解决了，但是不排除个别钉子户，根据github issure给出的解决方案就是需要升级一下
gradle的版本了


方便复制：

maven{ url 'https://maven.aliyun.com/repository/google'}
maven{ url 'https://maven.aliyun.com/repository/gradle-plugin'}
maven{ url 'https://maven.aliyun.com/repository/public'}
maven{ url 'https://maven.aliyun.com/repository/jcenter'}

distributionUrl = https://services.gradle.org/distributions/gradle-4.10.2-all.zip # 手动更新Gradle版本

以上就是我实践出来的解决方法，如果能帮到你，那真的是太好了。