android 再按一次后退键退出应用程序

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;

		}

	};

	

	@Override

	public boolean onKeyDown(int keyCode, KeyEvent event) {

		System.out.println("TabHost_Index.java onKeyDown");

		if (keyCode == KeyEvent.KEYCODE_BACK) {

			if(isExit == false ) {

				isExit = true;

				Toast.makeText(this, "再按一次后退键退出应用程序", Toast.LENGTH_SHORT).show();

				if(!hasTask) {

					tExit.schedule(task, 2000);

				}

			} else {

				finish();

				System.exit(0);

			}

		}

		return false;

	}

public boolean onKeyDown(int keyCode, KeyEvent event) {

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

			if ((System.currentTimeMillis() - exitTime) > 2000) {

				Toast.makeText(this, "再按一次退出程序", Toast.LENGTH_SHORT).show();

				exitTime = System.currentTimeMillis();

			} else {

				finish();

			}

		}

		return false;

	}