UIWebView取得内容的高－作出自适应高的UIWebView

- (void)webViewDidFinishLoad:(UIWebView *)webView
{    
NSString *height_str= [webView stringByEvaluatingJavaScriptFromString: @"document.body.offsetHeight"];
    int height = [height_str intValue];
    webView.frame = CGRectMake(0,0,320,height);
    NSLog(@"height: %@", [webView stringByEvaluatingJavaScriptFromString: @"document.body.offsetHeight"]);
}