iOS 微信支付，顯示一個確定按鈕的坑

這兩天在項目里面接入了微信支付，剛開始在項目里面引入了官方提供的sdk，這是下載地址https://pay.weixin.qq.com/wiki/doc/api/app/app.php?chapter=11_1，填入了在微信開發平台申請的，應用的APP_ID APP_SECRET已經PARTNER_ID，自己生成一個訂單，發現可以跳轉到微信進行支付，但是和后台調試的時候，拿到后台給我的訂單信息，進入微信，發現只有一個確定按鈕，

當時在網上搜了不少文章，但是沒有符合自己情況的，和后台一起按照步奏調試了好幾天，好在問題最后解決了，分享一下給遇到同樣問題的同學看看，也避免以后自己踩到同樣的坑，下面，我盡可能用通俗的語言，說一下我遇到問題的原因和解決方法。

3，首先看一下在客戶端，選擇一個要買的商品以后，點擊去微信支付，在沒有進入微信前經歷了什么

3 .1 下單 這里面呢需要提供三個參數，orderid是要買商品的id，ordertitle是在跳轉到微信支付里面，展示給用戶的訂單標題，orderprice是商品的價錢了，iOS里面對應下訂單的方法如下

     - ( NSMutableDictionary *)sendPay_demo:(NSString *)orderid title:(NSString *)ordertitle price:(NSString *)orderprice
{
//訂單標題，展示給用戶
NSString *order_name    = ordertitle;
//訂單金額,單位（分）
NSString *order_price   = orderprice;//1分錢測試
//================================
//預付單參數訂單設置
//================================
srand( (unsigned)time(0) );
NSString *noncestr  = [NSString stringWithFormat:@"%d", rand()];
NSMutableDictionary *packageParams = [NSMutableDictionary dictionary];
NSString *ii=@"079d9a74b95f41c58e636e344109ee1f";
[packageParams setObject: appid             forKey:@"appid"];       //開放平台appid
[packageParams setObject: mchid             forKey:@"mch_id"];      //商戶號
[packageParams setObject: @"APP-001"        forKey:@"device_info"]; //支付設備號或門店號
NSLog(@"第一次noncestr %@",noncestr);
[packageParams setObject: noncestr          forKey:@"nonce_str"];   //隨機串
[packageParams setObject: @"APP"            forKey:@"trade_type"];  //支付類型，固定為APP
[packageParams setObject: order_name        forKey:@"body"];        //訂單描述，展示給用戶
[packageParams setObject: NOTIFY_URL        forKey:@"notify_url"];  //支付結果異步通知
[packageParams setObject: orderid           forKey:@"out_trade_no"];//商戶訂單號
[packageParams setObject: @"196.168.1.1"    forKey:@"spbill_create_ip"];//發器支付的機器ip
[packageParams setObject: order_price       forKey:@"total_fee"];       //訂單金額，單位為分

//獲取prepayId（預支付交易會話標識）
NSString *prePayid;
prePayid            = [self sendPrepay:packageParams];
NSLog(@"獲取prepayId %@",prePayid);

if ( prePayid != nil) {
    //獲取到prepayid后進行第二次簽名
    
    NSString    *package, *time_stamp, *nonce_str;
    //設置支付參數
    time_t now;
    time(&now);
    time_stamp  = [NSString stringWithFormat:@"%ld", now];
    nonce_str	= [WXUtil md5:time_stamp];
    //重新按提交格式組包，微信客戶端暫只支持package=Sign=WXPay格式，須考慮升級后支持攜帶package具體參數的情況
    //package       = [NSString stringWithFormat:@"Sign=%@",package];
    package         = @"Sign=WXPay";
    //第二次簽名參數列表
    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"];
    //生成簽名
    NSString *sign  = [self createMd5Sign:signParams];
    //添加簽名
    [signParams setObject: sign         forKey:@"sign"];
    [debugInfo appendFormat:@"第二步簽名成功，sign＝%@\n",sign];
    
    //返回參數列表
    return signParams;
    
}else{
    [debugInfo appendFormat:@"獲取prepayid失敗！\n"];
}
return nil;
 }

3.2這里面非常重要的一步是提交預支付獲取prepayid，我們的錯誤就出在這里，獲取prepayid的方法如下

    //提交預支付
   -(NSString *)sendPrepay:(NSMutableDictionary *)prePayParams
 {
NSString *prepayid = nil;
NSLog(@"提交預支付發送的數據%@",prePayParams);
//獲取提交支付
NSString *send      = [self genPackage:prePayParams];
NSLog(@"獲取提交支付 send %@",send);
//輸出Debug Info
[debugInfo appendFormat:@"API鏈接:%@\n", payUrl];
[debugInfo appendFormat:@"發送的xml:%@\n", send];
//發送請求post xml數據
NSData *res = [WXUtil httpSend:payUrl method:@"POST" data:send];
//輸出Debug Info
[debugInfo appendFormat:@"服務器返回：\n%@\n\n",[[NSString alloc] initWithData:res encoding:NSUTF8StringEncoding]];
XMLHelper *xml  = [[XMLHelper alloc] init];
//開始解析
[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"] )
{
    //生成返回數據的簽名
    NSString *sign      = [self createMd5Sign:resParams ];
    NSString *send_sign =[resParams objectForKey:@"sign"] ;
    //驗證簽名正確性
    if( [sign isEqualToString:send_sign]){
        if( [result_code isEqualToString:@"SUCCESS"]) {
            //驗證業務處理狀態
            prepayid    = [resParams objectForKey:@"prepay_id"];
            return_code = 0;
            [debugInfo appendFormat:@"獲取預支付交易標示成功！\n"];
        }
    }else{
        last_errcode = 1;
        [debugInfo appendFormat:@"gen_sign=%@\n   _sign=%@\n",sign,send_sign];
        [debugInfo appendFormat:@"服務器返回簽名驗證錯誤！！！\n"];
    }
}else{
    last_errcode = 2;
    [debugInfo appendFormat:@"接口返回錯誤！！！\n"];
}
return prepayid;
 }

3.3 這個方法進行了第一次MD5的加密，

 //獲取package帶參數的簽名包
-(NSString *)genPackage:(NSMutableDictionary*)packageParams
{
NSString *sign;
NSMutableString *reqPars=[NSMutableString string];
//生成簽名
sign        = [self createMd5Sign:packageParams];
//生成xml的package
NSArray *keys = [packageParams allKeys];
[reqPars appendString:@"<xml>\n"];
for (NSString *categoryId in keys) {
    [reqPars appendFormat:@"<%@>%@</%@>\n", categoryId, [packageParams objectForKey:categoryId],categoryId];
}
[reqPars appendFormat:@"<sign>%@</sign>\n</xml>", sign];

return [NSString stringWithString:reqPars];
}

就是通過上面的這個方法，獲得了向微信發送的生成訂單xml的內容，我們后台剛開始的錯誤是生成sign簽名的時候，他沒有找到系統提供給后台的生成簽名的方法，就自己寫了一個方法進行簽名，然后他把所有的參數，包括key進行ASCII碼從小到大排序，事實上應該把除key以外的參數進行排序，且參數名要區分大小寫，排序后，在得到的字符串后面在追加key.

在微信簽名的文檔規則在這里https://pay.weixin.qq.com/wiki/doc/api/app/app.php?chapter=4_3,

iOS里面簽名的方法是下面這個

-(NSString*) createMd5Sign:(NSMutableDictionary*)dict
{
NSMutableString *contentString  =[NSMutableString string];
NSArray *keys = [dict allKeys];
//按字母順序排序
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(@"數據排序前 %@ 數據排序后sortedArray %@ 先把參數排序后追加一個key后得到 %@",keys,sortedArray,contentString);
NSLog(@"添加key字段 %@",spkey);
//得到MD5 sign簽名
NSString *md5Sign =[WXUtil md5:contentString]; 
//輸出Debug Info
[debugInfo appendFormat:@"MD5簽名字符串：\n%@\n\n",contentString];
return md5Sign;
}

3.4在獲得prepayid以后，還要在進行第二次簽名 ios里面對應的方法是這個

if ( prePayid != nil) {
    //獲取到prepayid后進行第二次簽名
    
    NSString    *package, *time_stamp, *nonce_str;
    //設置支付參數
    time_t now;
    time(&now);
    time_stamp  = [NSString stringWithFormat:@"%ld", now];
    nonce_str	= [WXUtil md5:time_stamp];
    //重新按提交格式組包，微信客戶端暫只支持package=Sign=WXPay格式，須考慮升級后支持攜帶package具體參數的情況
    //package       = [NSString stringWithFormat:@"Sign=%@",package];
    package         = @"Sign=WXPay";
    //第二次簽名參數列表
    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"];
    //生成簽名
    NSString *sign  = [self createMd5Sign:signParams];
    //添加簽名
    [signParams setObject: sign         forKey:@"sign"];
    [debugInfo appendFormat:@"第二步簽名成功，sign＝%@\n",sign];
    //返回參數列表
    return signParams;
}

3.5 這時候就生成了跳轉到微信所需要的signParams ，然后在iOS客戶端里面調用下面的方法就可以發起支付了

     NSMutableString *stamp  = [dict objectForKey:@"timestamp"];
    
    //調起微信支付
    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];

總結一下，我開始遇到跳轉微信只有一個確定按鈕，就是因為服務器那邊在進行簽名的時候，出錯了，微信支付流程就服務器在下訂單前要進行一次簽名，拿到prepayid以后要再進行一次簽名，不知道大家遇到的問題是否和我一樣，如果不一樣，你剛好也解決了，歡迎補充。