Question

Programming an iPhone App, I need to use Google Maps api to get directions and routes. Unfortunatelly, Google Maps works around javascript.

Any idea how to do this?

Answer 1

You can implement this by using a UIWebView. When it comes to using JavaScript to access the Google Maps service through its Google Maps APIs, you simply take advantage of the UIWebView method:

- (NSString *)stringByEvaluatingJavaScriptFromString:(NSString *)script

Note that you will need to escape in the string representing your script, all of the occurrences of double quotes as needed.

As an example, the following method, needed to center a map, is taken from chapter 12 of iPhone SDK programming, by Maher Ali:

-(void) centerMap:(NSUInteger) index{
    CLLocation *loc = [locations objectAtIndex:index];
    NSString *js = 
    [NSString stringWithFormat:
     @"var map = new GMap2(document.getElementById(\"map_canvas\"));"
     "map.setMapType(G_HYBRID_MAP);"
     "map.setCenter(new GLatLng(%lf, %lf), 18);"
     "map.panTo(map.getCenter());"  
     "map.openInfoWindow(map.getCenter(),"
     "document.createTextNode(\"Loc: (%i/%i), Time: %@\"));", 
     [loc coordinate].latitude, [loc coordinate].longitude,
     index+1, [locations count], 
     [loc timestamp]];
    [webView stringByEvaluatingJavaScriptFromString:js];
}

Also, bear in mind the following from the Apple documentation:

JavaScript execution time is limited to 10 seconds for each top-level entry point. If your script executes for more than 10 seconds, Safari stops executing the script. This is likely to occur at a random place in your code, so unintended consequences may result. This limit is imposed because JavaScript execution may cause the main thread to block, so when scripts are running, the user is not able to interact with the webpage.

JavaScript allocations are also limited to 10 MB. Safari raises an exception if you exceed this limit on the total memory allocation for JavaScript.