iOS 微信支付，显示一个确定按钮的坑

这两天在项目里面接入了微信支付，刚开始在项目里面引入了官方提供的sdk，这是下载地址https://pay.weixin.qq.com/wiki/doc/api/app/app.php?chapter=11_1，填入了在微信开发平台申请的，应用的APP_ID APP_SECRET已经PARTNER_ID，自己生成一个订单，发现可以跳转到微信进行支付，但是和后台调试的时候，拿到后台给我的订单信息，进入微信，发现只有一个确定按钮，

当时在网上搜了不少文章，但是没有符合自己情况的，和后台一起按照步奏调试了好几天，好在问题最后解决了，分享一下给遇到同样问题的同学看看，也避免以后自己踩到同样的坑，下面，我尽可能用通俗的语言，说一下我遇到问题的原因和解决方法。

3，首先看一下在客户端，选择一个要买的商品以后，点击去微信支付，在没有进入微信前经历了什么

3 .1 下单 这里面呢需要提供三个参数，orderid是要买商品的id，ordertitle是在跳转到微信支付里面，展示给用户的订单标题，orderprice是商品的价钱了，iOS里面对应下订单的方法如下

     - ( NSMutableDictionary *)sendPay_demo:(NSString *)orderid title:(NSString *)ordertitle price:(NSString *)orderprice
{
//订单标题，展示给用户
NSString *order_name    = ordertitle;
//订单金额,单位（分）
NSString *order_price   = orderprice;//1分钱测试
//================================
//预付单参数订单设置
//================================
srand( (unsigned)time(0) );
NSString *noncestr  = [NSString stringWithFormat:@"%d", rand()];
NSMutableDictionary *packageParams = [NSMutableDictionary dictionary];
NSString *ii=@"079d9a74b95f41c58e636e344109ee1f";
[packageParams setObject: appid             forKey:@"appid"];       //开放平台appid
[packageParams setObject: mchid             forKey:@"mch_id"];      //商户号
[packageParams setObject: @"APP-001"        forKey:@"device_info"]; //支付设备号或门店号
NSLog(@"第一次noncestr %@",noncestr);
[packageParams setObject: noncestr          forKey:@"nonce_str"];   //随机串
[packageParams setObject: @"APP"            forKey:@"trade_type"];  //支付类型，固定为APP
[packageParams setObject: order_name        forKey:@"body"];        //订单描述，展示给用户
[packageParams setObject: NOTIFY_URL        forKey:@"notify_url"];  //支付结果异步通知
[packageParams setObject: orderid           forKey:@"out_trade_no"];//商户订单号
[packageParams setObject: @"196.168.1.1"    forKey:@"spbill_create_ip"];//发器支付的机器ip
[packageParams setObject: order_price       forKey:@"total_fee"];       //订单金额，单位为分

//获取prepayId（预支付交易会话标识）
NSString *prePayid;
prePayid            = [self sendPrepay:packageParams];
NSLog(@"获取prepayId %@",prePayid);

if ( prePayid != nil) {
    //获取到prepayid后进行第二次签名
    
    NSString    *package, *time_stamp, *nonce_str;
    //设置支付参数
    time_t now;
    time(&now);
    time_stamp  = [NSString stringWithFormat:@"%ld", now];
    nonce_str	= [WXUtil md5:time_stamp];
    //重新按提交格式组包，微信客户端暂只支持package=Sign=WXPay格式，须考虑升级后支持携带package具体参数的情况
    //package       = [NSString stringWithFormat:@"Sign=%@",package];
    package         = @"Sign=WXPay";
    //第二次签名参数列表
    NSMutableDictionary *signParams = [NSMutableDictionary dictionary];
    [signParams setObject: appid        forKey:@"appid"];
    NSLog(@"第二次noncestr %@ %@",nonce_str,time_stamp);
    [signParams setObject: nonce_str    forKey:@"noncestr"];
    [signParams setObject: package      forKey:@"package"];
    [signParams setObject: mchid        forKey:@"partnerid"];
    [signParams setObject: time_stamp   forKey:@"timestamp"];
    [signParams setObject: prePayid     forKey:@"prepayid"];
    //[signParams setObject: @"MD5"       forKey:@"signType"];
    //生成签名
    NSString *sign  = [self createMd5Sign:signParams];
    //添加签名
    [signParams setObject: sign         forKey:@"sign"];
    [debugInfo appendFormat:@"第二步签名成功，sign＝%@
",sign];
    
    //返回参数列表
    return signParams;
    
}else{
    [debugInfo appendFormat:@"获取prepayid失败！
"];
}
return nil;
 }

3.2这里面非常重要的一步是提交预支付获取prepayid，我们的错误就出在这里，获取prepayid的方法如下

    //提交预支付
   -(NSString *)sendPrepay:(NSMutableDictionary *)prePayParams
 {
NSString *prepayid = nil;
NSLog(@"提交预支付发送的数据%@",prePayParams);
//获取提交支付
NSString *send      = [self genPackage:prePayParams];
NSLog(@"获取提交支付 send %@",send);
//输出Debug Info
[debugInfo appendFormat:@"API链接:%@
", payUrl];
[debugInfo appendFormat:@"发送的xml:%@
", send];
//发送请求post xml数据
NSData *res = [WXUtil httpSend:payUrl method:@"POST" data:send];
//输出Debug Info
[debugInfo appendFormat:@"服务器返回：
%@

",[[NSString alloc] initWithData:res encoding:NSUTF8StringEncoding]];
XMLHelper *xml  = [[XMLHelper alloc] init];
//开始解析
[xml startParse:res];
NSMutableDictionary *resParams = [xml getDict];
NSString *return_code   = [resParams objectForKey:@"return_code"];
NSString *result_code   = [resParams objectForKey:@"result_code"];
if ( [return_code isEqualToString:@"SUCCESS"] )
{
    //生成返回数据的签名
    NSString *sign      = [self createMd5Sign:resParams ];
    NSString *send_sign =[resParams objectForKey:@"sign"] ;
    //验证签名正确性
    if( [sign isEqualToString:send_sign]){
        if( [result_code isEqualToString:@"SUCCESS"]) {
            //验证业务处理状态
            prepayid    = [resParams objectForKey:@"prepay_id"];
            return_code = 0;
            [debugInfo appendFormat:@"获取预支付交易标示成功！
"];
        }
    }else{
        last_errcode = 1;
        [debugInfo appendFormat:@"gen_sign=%@
   _sign=%@
",sign,send_sign];
        [debugInfo appendFormat:@"服务器返回签名验证错误！！！
"];
    }
}else{
    last_errcode = 2;
    [debugInfo appendFormat:@"接口返回错误！！！
"];
}
return prepayid;
 }

3.3 这个方法进行了第一次MD5的加密，

 //获取package带参数的签名包
-(NSString *)genPackage:(NSMutableDictionary*)packageParams
{
NSString *sign;
NSMutableString *reqPars=[NSMutableString string];
//生成签名
sign        = [self createMd5Sign:packageParams];
//生成xml的package
NSArray *keys = [packageParams allKeys];
[reqPars appendString:@"<xml>
"];
for (NSString *categoryId in keys) {
    [reqPars appendFormat:@"<%@>%@</%@>
", categoryId, [packageParams objectForKey:categoryId],categoryId];
}
[reqPars appendFormat:@"<sign>%@</sign>
</xml>", sign];

return [NSString stringWithString:reqPars];
}

就是通过上面的这个方法，获得了向微信发送的生成订单xml的内容，我们后台刚开始的错误是生成sign签名的时候，他没有找到系统提供给后台的生成签名的方法，就自己写了一个方法进行签名，然后他把所有的参数，包括key进行ASCII码从小到大排序，事实上应该把除key以外的参数进行排序，且参数名要区分大小写，排序后，在得到的字符串后面在追加key.

在微信签名的文档规则在这里https://pay.weixin.qq.com/wiki/doc/api/app/app.php?chapter=4_3,

iOS里面签名的方法是下面这个

-(NSString*) createMd5Sign:(NSMutableDictionary*)dict
{
NSMutableString *contentString  =[NSMutableString string];
NSArray *keys = [dict allKeys];
//按字母顺序排序
NSArray *sortedArray = [keys sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
    return [obj1 compare:obj2 options:NSNumericSearch];
}];
//拼接字符串
for (NSString *categoryId in sortedArray) {
    if (   ![[dict objectForKey:categoryId] isEqualToString:@""]
        && ![categoryId isEqualToString:@"sign"]
        && ![categoryId isEqualToString:@"key"]
        )
    {
        [contentString appendFormat:@"%@=%@&", categoryId, [dict objectForKey:categoryId]];
    }
    }
//添加key字段
spkey=PARTNER_ID;
[contentString appendFormat:@"key=%@", spkey];
NSLog(@"数据排序前 %@ 数据排序后sortedArray %@ 先把参数排序后追加一个key后得到 %@",keys,sortedArray,contentString);
NSLog(@"添加key字段 %@",spkey);
//得到MD5 sign签名
NSString *md5Sign =[WXUtil md5:contentString]; 
//输出Debug Info
[debugInfo appendFormat:@"MD5签名字符串：
%@

",contentString];
return md5Sign;
}

3.4在获得prepayid以后，还要在进行第二次签名 ios里面对应的方法是这个

if ( prePayid != nil) {
    //获取到prepayid后进行第二次签名
    
    NSString    *package, *time_stamp, *nonce_str;
    //设置支付参数
    time_t now;
    time(&now);
    time_stamp  = [NSString stringWithFormat:@"%ld", now];
    nonce_str	= [WXUtil md5:time_stamp];
    //重新按提交格式组包，微信客户端暂只支持package=Sign=WXPay格式，须考虑升级后支持携带package具体参数的情况
    //package       = [NSString stringWithFormat:@"Sign=%@",package];
    package         = @"Sign=WXPay";
    //第二次签名参数列表
    NSMutableDictionary *signParams = [NSMutableDictionary dictionary];
    [signParams setObject: appid        forKey:@"appid"];
    NSLog(@"第二次noncestr %@ %@",nonce_str,time_stamp);
    [signParams setObject: nonce_str    forKey:@"noncestr"];
    [signParams setObject: package      forKey:@"package"];
    [signParams setObject: mchid        forKey:@"partnerid"];
    [signParams setObject: time_stamp   forKey:@"timestamp"];
    [signParams setObject: prePayid     forKey:@"prepayid"];
    //[signParams setObject: @"MD5"       forKey:@"signType"];
    //生成签名
    NSString *sign  = [self createMd5Sign:signParams];
    //添加签名
    [signParams setObject: sign         forKey:@"sign"];
    [debugInfo appendFormat:@"第二步签名成功，sign＝%@
",sign];
    //返回参数列表
    return signParams;
}

3.5 这时候就生成了跳转到微信所需要的signParams ，然后在iOS客户端里面调用下面的方法就可以发起支付了

     NSMutableString *stamp  = [dict objectForKey:@"timestamp"];
    
    //调起微信支付
    PayReq* req             = [[PayReq alloc] init];
    req.openID              = [dict objectForKey:@"appid"];
    req.partnerId           = [dict objectForKey:@"partnerid"];
    req.prepayId            = [dict objectForKey:@"prepayid"];
    req.nonceStr            = [dict objectForKey:@"noncestr"];
    req.timeStamp           = stamp.intValue;
    req.package             = [dict objectForKey:@"package"];
    req.sign                = [dict objectForKey:@"sign"];
    BOOL status = [WXApi sendReq:req];

总结一下，我开始遇到跳转微信只有一个确定按钮，就是因为服务器那边在进行签名的时候，出错了，微信支付流程就服务器在下订单前要进行一次签名，拿到prepayid以后要再进行一次签名，不知道大家遇到的问题是否和我一样，如果不一样，你刚好也解决了，欢迎补充。