title: ionic 2 - Error Could not find an installed version of Gradle either in Android Studio
body: <p>I create ionic 2 project and add diagnostic cordova plugin like this :</p>
  
  <pre><code>ionic plugin add cordova.plugins.diagnostic
  
  npm install --save @ionic-native/diagnostic
  </code></pre>
  
  <p>and add android platform like this :</p>
  
  <pre><code>ionic platform add android@latest
  </code></pre>
  
  <p>but when build with <code>ionic build android</code> console give me this error :</p>
  
  <pre><code>Error: Could not find an installed version of Gradle either in Android Studio,
  or on your system to install the gradle wrapper. Please include gradle 
  in your path, or install Android Studio
  </code></pre>
  
  <p>and I try to download manualy gradle.3.3-all.zip and change this  distributionUrl var in platform/android/cordova/lib/builders/GradleBuilder.js</p>
  
  <pre><code> var distributionUrl = process.env['CORDOVA_ANDROID_GRADLE_DISTRIBUTION_URL'] || 'https\\://services.gradle.org/distributions/gradle-3.3-all.zip'
  </code></pre>
  
  <p>to:</p>
  
  <pre><code>var distributionUrl = process.env['CORDOVA_ANDROID_GRADLE_DISTRIBUTION_URL'] || 'file:///E:/gradles/gradle-3.3-all.zip';
  </code></pre>
  
  <p>but not working and console give me last error.</p>
  
  <p>I dont know how to add gradle for android@latest version</p>