Does UIGestureRecognizer work on a UIWebView?
I am attempting to get a UIGestureRecognizer working with a UIWebview which is a subview of a UIScrollView. This sounds odd but when I have the numberOfTouchesRequired set to 2 the selector fires, but when numberOfTouchesRequired is set to one the selector doesn't fire.
Here is my code:
UITapGestureRecognizer *tap1 = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(select1:)];
tap1.numberOfTouchesRequired = 2;
tap1.numberOfTapsRequired = 1;
tap1.delegate = self;
[self.ans1WebView addGestureRecognizer:tap1];
[tap1 release];
- (void) select1:(UILongPressGestureRecognizer *)sender {
//Do Stuff
}
I've confirmed this by using the Apple sample for UIGestureRecognizer and inserting a webview in their nib. Their tap code works everywhere but inside the area of the webview.
Answer
From what I have seen, UIWebView does not play well with others. For gesture recognizers, you could try returning YES from:
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer;
I had to be backwards compatible with 3.0 so I ended up doing all the gesture handling with Javascript inside the UIWebView. Not a good solution, but it worked for my needs. I was able to capture a long press on an element, as well as tap, swipe, pinch and rotate. Of course, I was using only local content.
Edit:
You can look in PhoneGap for an example of sending messages to the delegate of the UIWebView. In a nutshell, you use document.location = "myscheme:mycommand?myarguments" then parse out the command and arguments from this delegate callback:
-(BOOL) webView:(UIWebView *)inWeb shouldStartLoadWithRequest:(NSURLRequest *)inRequest navigationType:(UIWebViewNavigationType)inType {
if ( [[[inRequest URL] absoluteString] hasPrefix:@"myscheme:"] ) {
//.. parse arguments
return NO;
}
}
You can see in the PhoneGap code that they set up a queue and timer to send the messages. Depending on your usage, you may need to do the same thing. There are other questions on SO on this topic.
Here is the Event Handling documentation. In my case I added event listeners to document from <body onload="myloader();">
function myloader() {
document.addEventListener( 'touchcancel' , touch_cancel , false );
document.addEventListener( 'touchstart' , touch_start , false );
document.addEventListener( 'touchmove' , touch_move , false );
document.addEventListener( 'touchend' , touch_end , false );
};
The actual event handling depends a lot on your needs. Each event handler will receive a TouchEvent with a touches property where each item is a Touch. You can record the start time and location in your touchstart handler. If the touches move to far or the wrong amount of time passes it is not a long touch.
WebKit may try to handle a long touch to start a selection and copy. In your event handler you can use event.preventDefault(); to stop the default behavior. I also found the -webkit-user-select:none css property handy for some things.
var touch = {};
function touch_start( event /*TouchEvent*/ {
event.preventDefault();
touch = {};
touch.startX = event.touches.item(0).pageX;
touch.startY = event.touches.item(0).pageY;
touch.startT = ( new Date() ).getTime();
}
This is only the second project I have used javascript with. You can find better examples elsewhere.
As you can see this is no quick answer to your problem. I am pretty happy with the results I got. The html I was working with had no interactive elements beyond a link or two.