1."Your project contains error(s)，please fix them before running your application"问题
解决方法:：工程文件右键->Properties->Java Editor->Run/Debug settings ->删除所有configurations;
project--clean.
2.[2018-08-05 21:26:54 - HelloWorld] Failed to install HelloWorld.apk on device 'emulator-5554': timeout [2018-08-05 21:26:54 - HelloWorld] Launch canceled!
解决方法：Window -> Preferences -> Android->DDMS ->ADB connection time out ->修改成大一点，如10000.