I have :
Android SDK Tools, Revision 22
Android SDK Platform, API 18
I go to <android-sdk>/tools/ , I see there is one file named "uiautomatorviewer",
I execute command uiautomatorviewer from terminal under the above path, however I got the following message:
uiautomatorviewer: command not found
why?
Because your tools/ directory is not in your PATH. Either use ./uiautomatorviewer or add tools/ (and probably platform-tools/ to your PATH. Note that this has nothing to do with programming and everything to do with your *nix-style OS (Linux, OS X, etc.).
Please note that uiautomatorviewer executable has been moved in SDK Tools Revision 25.3.0 (Feb 2017) update to new location under <android-sdk>\tools\bin
Navigate to tools folder, then launch terminal, launch monitor(Android Device Monitor) using ./monitor command.
ADM will get launched, left side of the window you may find 
.
Just follow these steps,
Open command prompt,Go to your bin folder inside tools folder of sdk location.
Example: C:\android-sdk\android-sdk\tools\bin.
Then in cmd type uiautomatorviewer and hit enter. It would immedialy open UI Automator Viewer.
C:\android-sdk\android-sdk\tools\bin>uiautomatorviewer
Refer screenshot
来源：https://stackoverflow.com/questions/18658322/unable-to-start-uiautomatorviewer