title: Could not find property 'xxxx' on com.android.build.gradle.AppExtension_Decorated
body: <p>I got this error after I added these lines to my gradle file:</p>
  
  <pre><code>buildTypes.each {
          it.buildConfigField 'String', 'OPEN_WEATHER_MAP_API_KEY', MyOpenWeatherMapApiKey
      }
  </code></pre>
  
  <p>then the log show: </p>
  
  <pre><code>Could not find property 'MyOpenWeatherMapApiKey' on com.android.build.gradle.AppExtension_Decorated@c3b784
  </code></pre>
  
  <p>The solutions on google that I searched cannot solve my problem. Please show me where I was wrong?</p>