Android org.apache.http包下的类找不到

原因：

由于Android6.0 之后的sdk不在包含org.apache.http包。所以编译版本为6.0之后就会报错。

官方文档

If your app is using this client and targets Android 2.3 (API level 9) or higher, use the HttpURLConnection class instead. This API is more efficient because it reduces network use through transparent compression and response caching, and minimizes power consumption. To continue using the Apache HTTP APIs, you must first declare the following compile-time dependency in your build.gradle file:

解决方案：

自己加入org.apache.http包内容。
在moudle的build.gradle中android中加入useLibrary 'org.apache.http.legacy'

android {
    useLibrary 'org.apache.http.legacy'
// ...
}