android再按一次退出程序

	private static Boolean isExit = false;

	@Override
	public void finish()
	{
		if (isExit == false)
		{
			isExit = true;//
			Toast.makeText(this, "再按一次退出程序", Toast.LENGTH_SHORT).show();
			new Timer().schedule(new TimerTask()
			{
				@Override
				public void run()
				{
					isExit = false;
				}
			}, 2000);
		} else
		{
			MainActivity.super.finish();
		}
	}
上面个这个放在主Activity中就行

  @Override

    public boolean onKeyDown(int keyCode, KeyEvent event) {

        if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {

            finish();

            return false;

        }

        return false;

    }