title: Emulator doesn't work: Apps can't be executed
body: <p>I'm new in android studio. There is a problem: I cannot execute my app in emulator. When I create a new project, I choose Basic Activity. As you know, there is text 'hello world' and I also can exec that without any code changed. But when emulator exec, didn't show anything! </p>
  
  <ol>
  <li>No USB devices or running emulators detected: I'm googled about that. But another people said that problem could ignore.</li>
  </ol>
  
  <p>2.May I change build types variable in Open Module settings?</p>
  
  <p>Here is emulator executing. Nothing happened!
  <a href="https://i.stack.imgur.com/c03UM.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/c03UM.png" alt="enter image description here"></a></p>
  
  <p>Please help me! Thank you!</p>