让UIWebView中实现并控制弹出窗口

UIWebView本身不支持弹出窗口，然而有需求要用，不仅需要弹出窗口，而且需要在用户关闭窗口时触发一个javascript函数。研究了一下，没有使用任何第三方库实现了。
基本的思路是在UIWebView中拦截window.open和window.close的调用。这里有2个技术问题：
1.如何在objective-c中改变javascript的行为？
我的思路是在页面加载完之后注入javascript。简单的说就是webViewDidFinishLoad中使用UIWebView 的stringByEvaluatingJavaScriptFromString注入javascript代码。
2.如何用javasript调用objective-c代码？
我使用URLScheme的方式来做。简单的来说，就是让定义2个URLScheme:
open://:用来出发弹出窗口；
back://:用来关闭窗口；后面可以跟一个参数，触发window.close之后需要回调的javascript函数;
然后在- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType中拦截URL请求就可以调用objective-c代码了。
具体的相关代码如下：
1.ViewController实现UIWebViewDelegate，在ViewDidLoad中将UIWebView的delegate设为自己:

_browser.delegate = self;

2.webViewDidFinishLoad中注入javascript

-(void) webViewDidFinishLoad:(UIWebView*)webView {
   // this is a pop-up window
   if (wvPopUp)
   {
       
       NSString *js = @"window.close = function () {window.location.assign(\"back://\" + window.location);};";
       __unused NSString *jsOverrides = [webView
                                         stringByEvaluatingJavaScriptFromString:js];
   }else {
     ///其他处理
           
           NSString *js = @"window.open = function (url, d1, d2) { window.location = \"open://\" + url;        }";
           __unused NSString *jsOverrides = [webView
                                             stringByEvaluatingJavaScriptFromString:js];
       }
   }
}

3.在shouldStartLoadWithRequest中拦截URL请求

- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType{
    NSString* requestURL = request.URL.absoluteString;
    
    if ([requestURL rangeOfString:@"back://"].location == 0)
        {
            [self closePopup];
            return NO;
        } else if  ([requestURL hasPrefix: @"open://"]){

            NSString *newUrl = [requestURL stringByReplacingOccurrencesOfString:@"open://" withString:@""];
            
            NSURLRequest *newRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:newUrl]];
            UIWebView *wv = [self popUpWebview];
            [wv loadRequest:newRequest];
            return NO;
        }
    return YES;
    
}

4.弹出窗口的objectie-c代码

- (UIWebView *) popUpWebview
{
    // Create a web view that fills the entire window, minus the toolbar height
    CGRect rect = CGRectMake(_browser.frame.origin.x+20,_browser.frame.origin.y+20,
                             _browser.frame.size.width-40,_browser.frame.size.height-40);
    
    vwPopUpContainer = [[UIView alloc] initWithFrame: rect];
    vwPopUpContainer.backgroundColor = [UIColor grayColor];
    [self.view addSubview:vwPopUpContainer];
    
    CGRect rectBtn = CGRectMake(10, 10, 60, 20);
    btnClosePopup = [[UIButton alloc] initWithFrame:rectBtn];

     [btnClosePopup setTitle:@"Close" forState:UIControlStateNormal];
    [btnClosePopup addTarget:self action:@selector(closePopup) forControlEvents:UIControlEventTouchUpInside];
    [vwPopUpContainer addSubview:btnClosePopup];
    
    CGRect rectWeb = CGRectMake(10, 40, rect.size.width - 20, rect.size.height - 50);
    
    UIWebView *webView = [[UIWebView alloc]
                          initWithFrame: rectWeb];
    
    webView.scalesPageToFit = YES;
    webView.delegate = self;
    
    wvPopUp = webView;
   [vwPopUpContainer addSubview:wvPopUp];
    return webView;
}

5.关闭窗口处理包括回调触发带参数的javascript函数,这里函数名为onClosePopo

- (void) closePopup {
    if (wvPopUp) {
        NSURL *url = wvPopUp.request.URL;
        NSString *surl = url.absoluteString;
        NSUInteger pos = [surl rangeOfString:@"?"].location;
        NSString *paras = @"";
        if (pos != NSNotFound && pos < [surl length]-1) {
            paras = [surl substringFromIndex:pos + 1];
        }
        NSString *js = [NSString stringWithFormat: @"onClosePopo('%@');",paras ];
        __unused NSString *jsOverrides = [_browser
                                          stringByEvaluatingJavaScriptFromString:js];
        
        [wvPopUp removeFromSuperview];
        wvPopUp = nil;
    }
    if(btnClosePopup){
        [btnClosePopup removeFromSuperview];
        btnClosePopup = nil;
    }
    
    if(vwPopUpContainer){
        [vwPopUpContainer removeFromSuperview];
        vwPopUpContainer = nil;
    }
}

2017年2月27日更新

完整的演示例子已经上传到 github