@Override

    public void onBackPressed() {

        // TODO 退出提示

        if (System.currentTimeMillis() - mExitTime > 1000) {

            if (mDrawerLayout.isDrawerOpen(GravityCompat.START)) {

                mDrawerLayout.closeDrawer(GravityCompat.START);

            }

            //点击间隔大于2s

            Toast.makeText(this, getResources().getString(R.string.exit_app), Toast.LENGTH_SHORT).show();

            mExitTime = System.currentTimeMillis();

        } else {

            //连续点击2次退出应用

            finish();

        }

        return;

    }