We know how frustrating it can be when a completely random dog approaches yours off lead, out of the blue. You will usually be greeted with the delightful saying (or something along these lines) "don't worry, he is friendly, he only wants to say hello". This is fine - if your dog is willing to say hello back.
The main issues here are that the dog (majority of the time) will have poor recall, is usually too far away from the owner to notice and the owner does not know the nature of your dog. By the time that this situation arises, it is usually too late for the owner to do anything to prevent any form of interaction.
From someone who has a dog whom isn't interested in the slightest in any interaction with any other dog, it is extremely annoying when you are trying to keep your dog focused on you and there is a rogue one jumping around you. Strangers do not know that your dog is reactive, in heat or generally dog aggressive, so it is your job to let them know. Do not worry about seeming 'too forward' or 'bitchy' when doing this. If it means that you have prevented an unnecessary situation from escalating, you are completely in order. In situations like this, the last thing you want to do is people please.
There are plenty of things you may have seen people do to attempt at preventing unwanted interactions with other dogs such as 'not friendly' dog harnesses or dog leads, or the simple action of putting your dog on its lead as soon as another dog is in sight, however, when you are in the event that a dog comes out of no-where and is quite keen to approach, the owner clearly would not know to prevent the dog from greeting yours.
There are a few things you can do to try to keep your dog from either a) running away or b) reacting. They are as follows;
Ensure your dog has a standard recall. Whether it is their name, a whistle or a word, ensuring your dogs recall is good will actively prevent them from wandering in the way of others. You can then give your self time to think about where you are going to position yourself and your dog.
If you have enough time, think about changing your path. If you can see a dog and owner walking towards you across the field, it might be more worthwhile to just make that left instead of straight on.
Teach the dog 'Middle' . This is where you teach your dog to stand or sit between your legs and wait there. Their full attention will be on you and the other dog will not get the interaction they were hoping for and will most likely move on. If you would like some more information on how to teach your dog to middle, get in touch.
Simply ask the person to recall their dog or come and put it on their lead. If they really ask for an explanation- give it to them plain and simple. You are your dogs voice, if it is really against socialising and is more interested in its ball, or is resource guarding, tell them that it's not aggressive, it just doesn't want to say hello.
Do not worry if your dog is not a fan of meeting others. It does not have an issue as such, it simply doesn't want anyone else in its personal space.
If you feel as though there may be a deeper behavioural issue, seek behavioural or veterinary advice, otherwise, listen to your dog and act accordingly. They do not have to like other dogs or like to play so do not try to force them.