[[UIPasteboard generalPasteboard] setString:@"1234"];  

dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1.5f * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{          

 if ([WXApi isWXAppInstalled]) {

 [WXApi openWXApp];  

}

});

手动打开微信，能获取到剪贴板的内容；但是使用openWXApp 这个方法就只有扫描文档