doubletap cannot be triggered

[StringKe]

maybe check doubletap failed excute tap?

hammerjs failure check

[StringKe]

          case Recognizer.FailedDSTap:
            hammer.add(new Hammer.Tap({event: 'doubletap', taps: 2}));
            hammer.add(new Hammer.Tap({event: 'singletap'}));
            hammer.get('doubletap').recognizeWith('singletap');
            hammer.get('singletap').requireFailure('doubletap');
            hammer.on("singletap doubletap", listener);
            break;