The Objective-C interface in the JavascriptCore framework introduced with iOS 7 permits calling Objective-C methods from Javascript. For a great intro to these features, check out the 2013 WWDC introduction "Integrating JavaScript into Native Apps" session on Apple's developer network: https://developer.apple.com/videos/wwdc/2013/?id=615
It does have a brief section towards the end on WebView (MacOs only not iOS)
The sample code below shows how to implement what you want for iOS.
- (void)viewDidLoad
{
[super viewDidLoad];
UIWebView *webView = [[UIWebView alloc] initWithFrame:CGRectMake(0,40,320,320)];
webView.delegate = self;
[self.view addSubview:webView];
NSString *pageSource = @"<!DOCTYPE html> <html> <head> </head> <body> <h1>My Mobile App</h1> <p>Please enter the Details</p> <form name=\"feedback\" method=\"post\" action=\"mailto:[email protected]\"> <!-- Form elements will go in here --> </form> <form name=\"inputform\"> <input type=\"button\" onClick=\"submitButton('My Test Parameter')\" value=\"submit\"> </form> </body> </html>";
[webView loadHTMLString:pageSource baseURL:nil];
}
- (void)webViewDidFinishLoad:(UIWebView *)webView
{
JSContext *context = [webView valueForKeyPath:@"documentView.webView.mainFrame.javaScriptContext"]; // Undocumented access
context[@"submitButton"] = ^(NSString *param1) {
[self yourObjectiveCMethod:param1];
};
}
- (void)yourObjectiveCMethod:(NSString *)param1 {
NSLog(@"User clicked submit. param1=%@", param1);
}
Things to note:
- Accessing the JSContext of a UIWebView is undocumented. Two techniques are known (see Access the JavaScriptCore engine of a UIWebView). The first technique is used here.
- You don't need to define the javascript function "submitButton" inside the page, you will define the function from Objective-C using the webView's JSContext
- A page load in a webview causes its JSContext to get replaced, hence you should implement a delegate for the UIWebView and define your Objective-C callback in your implementation of the selector for -webViewDidFinishLoad:
- I've assumed you will want to pass parameters to this callback, so I've shown a sample parameter. Although this is not covered in the video tutorial mentioned above (or the PDF equivalent), looking at JSValue.h shows that JavascriptCore offers built-in conversion between the following Objective-C and Javascript types:
.
Objective-C type | JavaScript type
--------------------+---------------------
nil | undefined
NSNull | null
NSString | string
NSNumber | number, boolean
NSDictionary | Object object
NSArray | Array object
NSDate | Date object
NSBlock * | Function object *
id ** | Wrapper object **
Class *** | Constructor object ***
* Instances of NSBlock with supported arguments types will be presented to
JavaScript as a callable Function object. For more information on supported
argument types see JSExport.h. If a JavaScript Function originating from an
Objective-C block is converted back to an Objective-C object the block will
be returned. All other JavaScript functions will be converted in the same
manner as a JavaScript object of type Object.
** For Objective-C instances that do not derive from the set of types listed
above, a wrapper object to provide a retaining handle to the Objective-C
instance from JavaScript. For more information on these wrapper objects, see
JSExport.h. When a JavaScript wrapper object is converted back to Objective-C
the Objective-C instance being retained by the wrapper is returned.
*** For Objective-C Class objects a constructor object containing exported
class methods will be returned. See JSExport.h for more information on
constructor objects.
