iOS js调webview的alert 为什么弹出来点击不了

NSString* methodNameStr=[NSString stringWithFormat:@"device_callback(%d,\"%@\")",[@"6001" isEqualToString:@"6001"]?-1:-2,[@"6001" isEqualToString:@"6001"]?@"支付取消":@"支付失败"];

如果在通知方法里直接调用

[weakSelf.webView stringByEvaluatingJavaScriptFromString:methodNameStr];

会弹出alert  但是点击不了

所以不能这样写

NSString *jsMyAlert =[NSString stringWithFormat:@"setTimeout(function(){%@;},1)",methodNameStr];

[weakSelf.webView stringByEvaluatingJavaScriptFromString:jsMyAlert];