问题
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?
回答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.
来源：https://stackoverflow.com/questions/23833840/why-cant-i-close-or-dismiss-a-javascript-alert-in-uiwebview