Show dialog from background thread - problem

In my app while copying files I want to ask user whether he wants to overwrite the file with same name, skip, etc. Here is some code from the thread:

        if(target.exists()){
            synchronized(this){
                while(wait){
                    try{
                        popupHandler.sendMessage(popupHandler.obtainMessage(0, target));
                        wait();
                    }catch (Exception e){
                        e.printStackTrace();
                    }
                }
            }
        }

Here is my handler:

    Handler popupHandler = new Handler(){
        @Override
        public void handleMessage(Message m){
            c.showConfirmDialog("The file " + ((File)m.obj).getName() + " exists. What do you want to do?",
                    "Overwrite", "Skip", "Keep both", Explorer.PASTE_CONFIRM, null);
        }
    };

After choosing an option from dialog something like that is called:

public void resume(){
    synchronized(copyThread){
            copyThread.wait = false;
            copyThread.notify();
        }
}

And here goes the problem. The copyThread on resume() is always null. I can't find what is wrong because t开发者_运维知识库he same scheme with pausing the thread works in my other class. It looks like the thread is dying after sending the message:/ Any ideas? Thanks in advance.