android实现双击back键退出

	private int mBackKeyPressedTimes = 0;



	@Override

	public void onBackPressed() {

		if (mBackKeyPressedTimes == 0) {

			Toast.makeText(this, "再次按返回键退出", Toast.LENGTH_SHORT).show();

			mBackKeyPressedTimes = 1;

			new Thread() {

				@Override

				public void run() {

					try {

						Thread.sleep(2000);

					} catch (InterruptedException e) {

						e.printStackTrace();

					} finally {

						mBackKeyPressedTimes = 0;

					}

				}

			}.start();

			return;

		}

		super.onBackPressed();

	}