fixed autofocus on droid

Author: f1nzer

Source/ZXing.Net.Mobile.Android/ZXingSurfaceView.cs

@@ -181,10 +181,13 @@ async Task SetupCamera ()
 
             // First try continuous video, then auto focus, then fixed
             var supportedFocusModes = parameters.SupportedFocusModes;
-            if (supportedFocusModes.Contains (Camera.Parameters.FocusModeAuto))
-                parameters.FocusMode = Camera.Parameters.FocusModeAuto;
+            if (Build.VERSION.SdkInt >= BuildVersionCodes.IceCreamSandwich && 
+                supportedFocusModes.Contains (Camera.Parameters.FocusModeContinuousPicture))
+                parameters.FocusMode = Camera.Parameters.FocusModeContinuousPicture;
             else if (supportedFocusModes.Contains (Camera.Parameters.FocusModeContinuousVideo))
                 parameters.FocusMode = Camera.Parameters.FocusModeContinuousVideo;
+            else if (supportedFocusModes.Contains(Camera.Parameters.FocusModeAuto))
+                parameters.FocusMode = Camera.Parameters.FocusModeAuto;
             else if (supportedFocusModes.Contains (Camera.Parameters.FocusModeFixed))
                 parameters.FocusMode = Camera.Parameters.FocusModeFixed;