In order to display a loading bar you have to make some kind of workaround, because you are not able to know the progress of the resources that are being downloaded.
Many apps use tricks, to simulate that there is a loading ongoing.
Here is a simple example to ilustrate the idea:
- Display loading bar with progress 30% for 1 second.
- If the request did not finish, display progress 90% until the progress finishes
- When the request finishes, animate progress to 100%.
You can have a look on this open source library to see how it's done. You can do it in a similar way.
https://github.com/ninjinkun/NJKWebViewProgress