Fix Android 6 crash.

It is now required to pass Activity to the run() method to make sure the Activity is still there when starting the queue page, in the scenario where applications are storing the QueueITEngine for longer periods.
Closes #4

Author: Morten Brix Pedersen

README.md

@@ -37,7 +37,7 @@ Invoke QueueITEngine as per example below. Parameters `layoutName` and `language
       });
 
       try {
-        engine.run();
+        engine.run(YourActivity.this);
       }
       catch (QueueITException e) { } // Gets thrown when a request is already in progress.
 

demoapp/src/main/java/com/queue_it/shopdemo/MainActivity.java

@@ -108,7 +108,7 @@ public void onError(Error error, String errorMessage) {
                     }
                 });
                 try {
-                    queueITEngine.run(!enableCacheRadioButton.isChecked());
+                    queueITEngine.run(MainActivity.this, !enableCacheRadioButton.isChecked());
                 }
                 catch (QueueITException e) {
                     Toast.makeText(getApplicationContext(), "Please try again.", Toast.LENGTH_LONG).show();

library/src/main/java/com/queue_it/androidsdk/QueueITEngine.java

@@ -26,6 +26,7 @@ public class QueueITEngine {
     private QueueCache _queueCache;
     private Context _context;
 
+    private Activity _activity;
     private boolean _requestInProgress;
     private boolean _isInQueue;
 
@@ -38,12 +39,12 @@ public class QueueITEngine {
     private Handler _checkConnectionHandler;
     private int _isOnlineRetry = 0;
 
-    public QueueITEngine(Activity activity, String customerId, String eventOrAliasId, QueueListener queueListener)
+    public QueueITEngine(Context applicationContext, String customerId, String eventOrAliasId, QueueListener queueListener)
     {
-        this(activity, customerId, eventOrAliasId, "", "", queueListener);
+        this(applicationContext, customerId, eventOrAliasId, "", "", queueListener);
     }
 
-    public QueueITEngine(Activity activity, String customerId, String eventOrAliasId, String layoutName,
+    public QueueITEngine(Context applicationContext, String customerId, String eventOrAliasId, String layoutName,
                          String language, QueueListener queueListener)
     {
         if (TextUtils.isEmpty(customerId))
@@ -54,13 +55,13 @@ public QueueITEngine(Activity activity, String customerId, String eventOrAliasId
         {
             throw new IllegalArgumentException("eventOrAliasId must have a value");
         }
-        _context = activity.getApplicationContext();
+        _context = applicationContext.getApplicationContext();
         _customerId = customerId;
         _eventOrAliasId = eventOrAliasId;
         _layoutName = layoutName;
         _language = language;
         _queueListener = queueListener;
-        _queueCache = new QueueCache(activity, customerId, eventOrAliasId);
+        _queueCache = new QueueCache(_context, customerId, eventOrAliasId);
         _deltaSec = INITIAL_WAIT_RETRY_SEC;
     }
 
@@ -86,17 +87,18 @@ private boolean isOnline() {
         return netInfo != null && netInfo.isConnected();
     }
 
-    public void run(boolean clearCache) throws QueueITException
+    public void run(Activity activity, boolean clearCache) throws QueueITException
     {
         if (clearCache)
         {
             _queueCache.clear();
         }
-        run();
+        run(activity);
     }
 
-    public void run() throws QueueITException
+    public void run(Activity activity) throws QueueITException
     {
+        _activity = activity;
         registerReceivers();
 
         if (_requestInProgress)
@@ -189,7 +191,7 @@ private void showQueue(String queueUrl, final String targetUrl)
         Intent intent = new Intent(_context, QueueActivity.class);
         intent.putExtra("queueUrl", queueUrl);
         intent.putExtra("targetUrl", targetUrl);
-        _context.startActivity(intent);
+        _activity.startActivity(intent);
     }
 
     private void raiseQueueViewWillOpen()