title: Android Studio: Application Installation Failed
body: <p>I've been trying to learn how to use Android Studio but when I attempted to run one of the sample programs I get this error message:</p>
  
  <blockquote>
    <p>Installation failed with message null.
        It is possible that this issue is resolved by uninstalling an existing version of the apk if it is present, and then re-installing.</p>
    
    <p>WARNING: Uninstalling will remove the application data!</p>
    
    <p>Do you want to uninstall the existing application?</p>
  </blockquote>
  
  <p>I've tried to do this on 5 more sample programs and all of them give me this error. Does anyone know how to solve this?</p>