Display with Crystal Reports 
To display data in Crystal Reports, the user needs a local installation of the Crystal Reports Viewer. For this reason the option to display data in Crystal Reports is initially deactivated.
You can activate Crystal Reports in Customizing for SAP List Viewer (ALV) under SAP Web Application Server Customizing (transaction SIMGH). Here you can also maintain the generic Crystal Reports layout under Managing Generic Crystal Reports.
You can control the option of the display with Crystal Reports with the following method for your Web Dynpro application: IF_SALV_WD_STD_FUNCTIONS~SET_CR_INPLACE_ALLOWED
See also: List Display with Crystal Reports