I have a webpage. I have a javascript file that does a whole lot of stuff. In the app I have an NSString with some crucial data that needs to be processed in the javascript file. How do I get my string value into a certain place in my html so my javascript can read it?
Also, the javascript will produce certain data when actions are performed (like pressing a button), how do I retrieve the data from the webview/javascript so it can be stored in the app?
You can call a javascript method and pass the value by using this
NSString *selectedValue = [webViewInstance stringByEvaluatingJavaScriptFromString:[NSString stringWithFormat:@"getAndReturnRadioValue(%d)", questionCounterIntValue]];
But to trigger back from javascript you need to use a workaround method,
Implement the following webViewDelegate method
- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType{
NSLog(@"passed data from web view : %@",[[request URL] query]);
if([[[request URL] query] isEqualToString:@"clickedOnLineNo"])
{
//Do your action here
}
}
You have to navigate to a fake URL from your javascript method like,
window.location = "someLink://yourApp/form_Submitted:param1:param2:param3";
on a button click or your required action.
You could take a look at my answer for this question Submit a form in UIWebView
- (NSString *)stringByEvaluatingJavaScriptFromString:(NSString *)script
sounds like exactly the method you need. If, for example, the input and output need to interact with the JavaScript can be done with a single method, you can pass a value into JavaScript and get the results with something like the following code:
NSString* jsCode = [NSString stringWithFormat:@"doSomething('%@')", dataToPass];
NSString* resultFromJavaScript = [webView stringByEvaluatingJavaScriptFromString:jsCode];
Hi we can send the data from objective c to javascript and can callback from javascript easily
Objective-C --> javaScript
In Objective-C class
NSData *locationCountData = [NSJSONSerialization dataWithJSONObject:locationCount options:NSJSONWritingPrettyPrinted error:nil];
NSString *locationCountString = [[NSString alloc] initWithData:locationCountData encoding:NSUTF8StringEncoding];
NSData *locationCountData = [NSJSONSerialization dataWithJSONObject:locationCount options:NSJSONWritingPrettyPrinted error:nil];
NSString *locationCountString = [[NSString alloc] initWithData:locationCountData encoding:NSUTF8StringEncoding];
NSString *str = [NSString stringWithFormat:@"testFunction(%@,%@)",locationCountString, locationsListString];
[self.myWebView stringByEvaluatingJavaScriptFromString: str];
in JavaScript file
<script type="text/javascript">
function testFunction(locationCount,locationList)
{
alert(locationCount + locationList);
}
</Script>
