?active agreement vs. AI attack?

Does anyone know how much effect does an active trade or gift have on the likelyhood the AI will attack you?
The situation is I had a city on a small island with Germany(who is polite with me). My city is guarded by a spearman which I can upgrade to a musketman next turn when I get my barrack. But Germany attacked me the turn before my barrack is done. So I loaded the game and offered them 200gpt for their 300 gold lump sum. I was hoping that the fact that they are getting 200gpt from me would stop them from attacking me, but it didn't.

I don't see any strategic advantage of them attacking me for that one city and losing 200gpt, but they attacked anyways. Is there any way to prevent them from attacking?

 

If they had already made the choice they will attack, there is little, if anything you can do about it.

Once they decided they will declare war, and started moving it's troops towards you, they won't re-consider any other circumstances between the time they made that choice, and the time they actually did declare war.

From a previous game I played like a year ago, the Germans sneak attacked me. I reloaded 1 turn, and tried to change their minds like you did, but they still declared war. Reloaded to 5 turns ago, and they did not attack. I think if they are too far into your territory (or landed on your island that you completely control), they won't ever change their mind.