Iso8601Parser improved to be able to parse timestamp offsets from UTC

library/dash/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaSource.java

@@ -962,19 +962,39 @@ public final class DashMediaSource implements MediaSource {
 
   private static final class Iso8601Parser implements ParsingLoadable.Parser<Long> {
 
+    private static final String ISO_8601_FORMAT = "yyyy-MM-dd'T'HH:mm:ss'Z'";
+    private static final String ISO_8601_FORMAT_2 = "yyyy-MM-dd'T'HH:mm:ssZ";
+    private static final String ISO_8601_FORMAT_3 = "yyyy-MM-dd'T'HH:mm:ssZ";
+    private static final String ISO_8601_FORMAT_2_REGEX_PATTERN = ".*[+\\-]\\d{2}:\\d{2}$";
+    private static final String ISO_8601_FORMAT_3_REGEX_PATTERN = ".*[+\\-]\\d{4}$";
+
     @Override
     public Long parse(Uri uri, InputStream inputStream) throws IOException {
       String firstLine = new BufferedReader(new InputStreamReader(inputStream)).readLine();
-      try {
-        // TODO: It may be necessary to handle timestamp offsets from UTC.
-        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.US);
-        format.setTimeZone(TimeZone.getTimeZone("UTC"));
-        return format.parse(firstLine).getTime();
-      } catch (ParseException e) {
-        throw new ParserException(e);
+
+      if (firstLine != null) {
+        //determine format pattern
+        String formatPattern;
+        if (firstLine.matches(ISO_8601_FORMAT_2_REGEX_PATTERN)) {
+          formatPattern = ISO_8601_FORMAT_2;
+        } else if (firstLine.matches(ISO_8601_FORMAT_3_REGEX_PATTERN)) {
+          formatPattern = ISO_8601_FORMAT_3;
+        } else {
+          formatPattern = ISO_8601_FORMAT;
+        }
+        //parse
+        try {
+          SimpleDateFormat format = new SimpleDateFormat(formatPattern, Locale.US);
+          format.setTimeZone(TimeZone.getTimeZone("UTC"));
+          return format.parse(firstLine).getTime();
+        } catch (ParseException e) {
+          throw new ParserException(e);
+        }
+
+      } else {
+        throw new ParserException("Unable to parse ISO 8601. Input value is null");
       }
     }
-
   }
 
 }