为什么我不能在UIWebView中关闭或关闭Javascript警报？

Question

Situation: I invoke a Javascript alert through the UIWebView method stringByEvaluatingJavaScriptFromString: like this...

[myWebView stringByEvaluatingJavaScriptFromString:@"alert('FOOBAR');"];

Problem: iOS displays an alert saying "FOOBAR" as expected, but tapping on the "Close" button does not dismiss the alert.

Why can't I close the Javascript alert? How do I get it to close?

Answer 1

This question gave me the most insight to the problem...

Deadlock with GCD and webView

The gist is that the thread handling the JS from the stringByEvaluatingJavaScriptFromString: method and the thread handling the iOS alert view are probably blocking each other, making the "Close" button unresponsive.

My workaround is to defer the JS alert with a setTimeout , something like this...

NSString *jsMyAlert = @"setTimeout(function(){alert('FOOBAR');}, 1);";

[myWebView stringByEvaluatingJavaScriptFromString:jsMyAlert];

To avoid any risk of deadlock, it might be better to have the UIWebView trigger an UIAlertView rather than rely on UIWebView to handle the JS alert . The workaround above would be suitable for most debugging purposes though.