最近学习Android网络编程，在AndroidStudio下无法使用HttpClient,在网上找到了答案在这里记下来；
//官方原文
Apache HTTP Client Removal
Android 6.0 release removes support for the Apache HTTP client. 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:
android {
useLibrary 'org.apache.http.legacy'
}
/*--------------------------------------------------------*/
原文地址：http://developer.android.com/intl/zh-cn/about/versions/marshmallow/android-6.0-changes.html#behavior-apache-http-client
如图项目中有有两个build.gradle，其中一个没有Android{}的标记，App文件夹下面的那个才有；
添加完成，重新编译没有错误！