请求授权代码要写在- (void)applicationDidBecomeActive:(UIApplication*)application{ }里面才会弹出来
if (@available(iOS 14, *)) {
[ATTrackingManager requestTrackingAuthorizationWithCompletionHandler:^(ATTrackingManagerAuthorizationStatus status) {
// 获取到权限后，依然使用老方法获取idfa
switch (status) {
case ATTrackingManagerAuthorizationStatusNotDetermined:
NSLog(@"申请tracking权限，用户为做选择或未弹窗");
break;
case ATTrackingManagerAuthorizationStatusRestricted:
NSLog(@"申请tracking权限，用户为做选择或未弹窗");
break;
case ATTrackingManagerAuthorizationStatusDenied:
NSLog(@"申请tracking权限，用户拒绝");
break;
case ATTrackingManagerAuthorizationStatusAuthorized:

                      NSLog(@"用户允许广告追踪, idfa:");
                      break;
              }
          }];
   }