iphone - 在 UIWebView 中从 JS 返回一个 var

Question

我很困惑如何在 UIWebView 中执行的 js 中提取 var 的值，我的代码是:

NSString * js = [NSString stringWithFormat:@"var script = document.createElement('script');"  
                     "script.type = 'text/javascript';"  
                     "script.text = \"function getTopLeftCorner() { "  
                        "var el = document.elementFromPoint(%f, %f);"
                        "var pos = [el.offsetLeft, el.offsetTop];"
                        "var parent = el.offsetParent;"
                        "if (parent != el) {" 
                            "while (parent) {"  
                             "pos[0] += parent.offsetLeft;" 
                             "pos[1] += parent.offsetTop;" 
                             "parent = parent.offsetParent;"
                            "}"
                        "}"
                        "return pos;"
                      "}\";"  
                      "document.getElementsByTagName('head')[0].appendChild(script);"
                     , pt.x, pt.y];  

    [self stringByEvaluatingJavaScriptFromString:js];
    NSString * result = [self stringByEvaluatingJavaScriptFromString:@"getTopLeftCorner()"];

    NSLog(@"RESULT IS %@", result);

知道为什么结果是空的吗？

Answer 1

你的第一个语句 NSString * js = [NSString stringWithFormat:@"var script 关闭了行尾的字符串，然后是几个 C 字符串。你应该从 Objective-C 编译器中得到一个语法错误。

连接字符串使用[NSString stringWithFormat:@"%@/%@/%@", three, two, one];。通读 class reference以获得对该方法的更多解释。