title: How to work out the time a user has opened the app for in android?
body: <p>I am trying to implement something that allows me to caluclate the time a user has used the application for, but it seems quite difficult or at least complicated to code. I tried several attempts and logics but failed.</p>
  
  <p>I am not sure whether this is write, but I create two variables as below</p>
  
  <pre><code>    static Date startTime = new Date();
  The startTime variable goes in the main activity and it notes the time user launched the app.
  
  
       static Date endTime = new Date();
  The endTime goes in the onDestroy method and takes the time when the user closes the app.
  
  If this approach is write, I understand I would need to find out the different between the two times but I am not sure how to attempt something like this. Could someone please help, what I want to be able to do is get a final value and pass it to the code below and send it over to Google Analyst for Android;
  
  /*
   * Called after a list of high scores finishes loading.
   *
   * @param loadTime The time it takes, in milliseconds, to load a resource.
   */
  public void onLoad(long loadTime) { // I need to put my value instead of loadTime, but I cannot figure out how to find the difference between two times.
  
    // May return null if EasyTracker has not been initialized with a property
    // ID.
    Tracker easyTracker = EasyTracker.getInstance(this);
  
    easyTracker.send(MapBuilder
        .createTiming("resources",    // Timing category (required)
                      loadTime,       // Timing interval in milliseconds (required)
                      "high scores",  // Timing name
                      null)           // Timing label
        .build()
    );
  }
  </code></pre>
  
  <p>Thanks and I would really appreciate any help.</p>