안드로이드 버튼 중복 클릭 방지

https://stackoverflow.com/questions/5608720/android-preventing-double-click-on-a-button

findViewById(R.id.button).setOnClickListener(new OnClickListener() {
    @Override
    public void onClick(View v) {
        // mis-clicking prevention, using threshold of 1000 ms
        if (SystemClock.elapsedRealtime() - mLastClickTime < 1000){
            return;
        }
        mLastClickTime = SystemClock.elapsedRealtime();

        // do your magic here
    }
}