[转]android两次按返回键退出程序实现

private static Boolean isExit = false;
    private static Boolean hasTask = false;
    Timer tExit = new Timer();
    TimerTask task = new TimerTask() {

        @Override
        public void run() {
            isExit = false;
            hasTask = true;
        }
    };


public boolean onKeyDown(int keyCode, KeyEvent event) {
                // TODO Auto-generated method stub
                if(keyCode == KeyEvent.KEYCODE_BACK){
//                        System.out.println("user back down");
                        if(isExit == false ) {
                                isExit = true;
                                Toast.makeText(this, "再按一次退出程序", Toast.LENGTH_SHORT).show();
                                if(!hasTask) {
                                        tExit.schedule(task, 2000);
                                }} else {
                                                                                }
                                finish();
                                System.exit(0);
                        }
                }
                return false;
        }