Fix a bug that the application crashes when the browser opens.

labelImg.py

@@ -1,7 +1,9 @@
 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
 import codecs
+import distutils.spawn
 import os.path
+import platform
 import re
 import sys
 import subprocess
@@ -112,7 +114,7 @@ class MainWindow(QMainWindow, WindowMixin):
 
         self._noSelectionSlot = False
         self._beginner = True
-        self.screencastViewer = "firefox"
+        self.screencastViewer = self.getAvailableScreencastViewer()
         self.screencast = "https://youtu.be/p0nR2YsCY_U"
 
         # Load predefined classes to the list
@@ -577,9 +579,19 @@ class MainWindow(QMainWindow, WindowMixin):
     def advanced(self):
         return not self.beginner()
 
+    def getAvailableScreencastViewer(self):
+        osName = platform.system()
+
+        if osName == 'Windows':
+            return ['C:\\Program Files\\Internet Explorer\\iexplore.exe']
+        elif osName == 'Linux':
+            return ['xdg-open']
+        elif osName == 'Darwin':
+            return ['open', '-a', 'Safari']
+
     ## Callbacks ##
     def showTutorialDialog(self):
-        subprocess.Popen([self.screencastViewer, self.screencast])
+        subprocess.Popen(self.screencastViewer + [self.screencast])
 
     def showInfoDialog(self):
         msg = u'Name:{0} \nApp Version:{1} \n{2} '.format(__appname__, __version__, sys.version_info)