Recently I published my new application in Android Market. This application contained Android Licence. This Licence was working perfectly fine, when I put my own apk on my phone, there is a dialog that will pop out saying I need to buy this application on the market. However, today I saw my application on some forum and when I tested it, the license was not working, I can get in to the application without buying it. Is there something I am doing wrong?
And also can you give me some tips that can help me to stop this hackers. I am thinking to have a Push Notification on my main activity which will pop out only when I have a new updates therefore people who are not registered can't get this new updates. But the real problem is I don't know how to accomplish this. If you have a better solution can you please tell me, I am planning to publish my new app soon but I am thinking to delay it for a while because of this kind of piracy that is going on. Please help me, I have been working on this new application for several months and I don't want this kind of piracy to happen again.
I don't think you can get your licensed application through the market without buying it. I'm not sure why you would want to, since you can just compile it and install it yourself with ADB.
However, I wouldn't worry too much about people pirating your software. Any good or even marginally skilled cracker is going to be able to remove any security you have anyway. In my experience (from both ends of the playing field), the game always comes down to cat and mouse, and you will end up wasting time instead of adding features, fixing bugs, etc.
Look into ProGuard.
It comes free with the Eclipse/Android stuff.
ProGuard presumably makes it more difficult for people to decompile and modify your application package to defeat the licensing check.
I do not know how well ProGuard actually is at discouraging piracy.
来源：https://stackoverflow.com/questions/5671722/android-licensing-issue