javascript - IOS: How do you detect user changing text on a UIWebView within a content editable div - Stack Overflow

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When using a UIWebView with editable content, the user can type their own text on the editable DIV.

Is there a way to fire an event on the ViewController every time the user changes the editable text (similar to the UITextField value change event)?

The ViewController needs to know when the user has changed to the text for two reasons; to know if the user entered any text at all, and to resize the UIWebView as the content text grows.

The UIWebView delegate doesn't seem to include this type of event. This will probably have to be done via Javascript but can't seem to find the answer out there. Help!

When using a UIWebView with editable content, the user can type their own text on the editable DIV.

Is there a way to fire an event on the ViewController every time the user changes the editable text (similar to the UITextField value change event)?

The ViewController needs to know when the user has changed to the text for two reasons; to know if the user entered any text at all, and to resize the UIWebView as the content text grows.

The UIWebView delegate doesn't seem to include this type of event. This will probably have to be done via Javascript but can't seem to find the answer out there. Help!

• javascript
• ios
• objective-c
• uiwebview

Share Improve this question Follow edited Mar 7, 2014 at 9:45 Lenny asked Mar 7, 2014 at 9:20 LennyLenny 34366 silver badges1919 bronze badges

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2 Answers 2

Sorted by: Reset to default 9

There is no direct way to listen to events from UIWebView, but you can bridge them. Since iOS7 it is pretty easy as there is JavaScriptCore.framework (you need to link it with project):

JSContext *ctx = [webView valueForKeyPath:@"documentView.webView.mainFrame.javaScriptContext"];
ctx[@"myUpdateCallback"] = ^(JSValue *msg) {
    [self fieldUpdated];
};
[ctx evaluateScript:@"document.getElementById('myEditableDiv').addEventListener('input', myUpdateCallback, false);"];

(I have no possibility at the moment to test the code, but I hope it works)

Before iOS7 (if you want to support lower version you have to use this) it was a bit more tricky. You can listen on webView delegate method webView:shouldStartLoadWithRequest:navigationType: for some custom scheme, ex:

- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType {
        if ([request.URL.scheme isEqualToString:@"divupdated"]) {
            [self fieldUpdated];
            return NO;
        }
        return YES;
}

and fire something like this on webView:

[webView stringByEvaluatingJavaScriptFromString:@"document.getElementById('myEditableDiv').addEventListener('change', function () {"
                                                @"var frame = document.createElement('iframe');"
                                                @"frame.src = 'divupdated://something';"
                                                @"document.body.appendChild(frame);"
                                                @"setTimeout(function () { document.body.removeChild(frame); }, 0);"
                                                @"}, false);"];

You need to do some JS hack in order to get this working.

First, create a JS file with a script that adds an observer that watch all the editable divs for when they start being edited (I don't know exactly how this should be done in JS, but a quick search on Google should help). The callback should then invoke a specifically crafted url, like:

textFieldBeginEditing://whateveryoulike

Inject the JS file into the UIWebView. One possible technique:

- (void)injectJavascript:(NSString *)resource {
    NSString *jsPath = [[NSBundle mainBundle] pathForResource:resource ofType:@"js"];
    NSString *js = [NSString stringWithContentsOfFile:jsPath encoding:NSUTF8StringEncoding error:NULL];

    [self.webView stringByEvaluatingJavaScriptFromString:js];
}

take from another so thread.

Finally, in the UIWebViewDelegate method shouldStartLoadingRequest

- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType
{
    // ... check the url schema
    NSURL *url = request.URL;
    if ([url.scheme isEqual:@"textFieldBeginEditing"]){
         // here you can handle the event
         return NO; // important
    }
}

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