• 环境：

  win10专业版（创意者），Android studio 2.3.1

• 问题描述:

  安装玩Android studio之后创建一个项目，建立AVD之后，运行程序时一直不能启动AVD，具体描述为：”Waiting for target device to come online”。即“等待目标设备在线”。

• 问题分析：

  分析1：此处参考了Android 中 adb 相关问题一文，出现此问题的原因大多是因为adb的端口被占用（eclipse，模拟器等）。

  分析2：也可能有这种问题，博主就是这种问题，参考了 “waiting for target device to come online” in Android Studio 2.3 一文

• 问题解决：

  分析1：命令行（win+r–cmd）定位到android_sdk/platform-tools/目录下,执行”adb kill-server”

  分析2：I was also having the same issue 2 days ago when i update my android studio, today I solve my issue when I was playing around with settings then I saw that in my SDK tools setting Android Emulator is uncheck so I simply checked that box and now emulator is working fine. 
  Try this steps may work for you also: 
  Go to SDK tools > SDK Tools 
  Check Android Emulator and click Apply 
  

【Android】[Problem]-"Waiting for target device to come online".