@Override
 public void onBackPressed() {
   long t = System.currentTimeMillis();
   if (t - mPrevbackPress <= 1000) {
     super.onBackPressed();
   } else {
     Toast.makeText(this, "再按一次返回退出", Toast.LENGTH_SHORT).show();
   }
   mPrevbackPress = t;
 }
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_list);

    cid = getIntent().getData().getQueryParameter("id");

    ListView listView = (ListView) findViewById(R.id.listView);
    adapter = new Adapter(StudentDetailActivity.this);
    listView.setAdapter(adapter);
    listView.setOnItemClickListener(this);

    requestData();
  }
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_root);

    tabHost = (FragmentTabHost) findViewById(android.R.id.tabhost);
    tabHost.setup(this, getSupportFragmentManager(), R.id.realtabcontent);
    tabHost.addTab(
        tabHost
            .newTabSpec("manager")
            .setIndicator(createTabItem("课程管理", R.drawable.ic_tab_manager)),
        CourseManagerFragment.class,
        null);

    View groupTabItem = createTabItem("学生群组", R.drawable.ic_tab_group);
    groupDot = groupTabItem.findViewById(R.id.dot);
    tabHost.addTab(
        tabHost.newTabSpec("chatlist").setIndicator(groupTabItem), ChatListFragment.class, null);
    tabHost.addTab(
        tabHost
            .newTabSpec("material")
            .setIndicator(createTabItem("教材教具", R.drawable.ic_tab_material)),
        TeachMaterialFragment.class,
        null);

    View mineTabItem = createTabItem("我的", R.drawable.ic_tab_mine);
    mineDot = mineTabItem.findViewById(R.id.dot);
    tabHost.addTab(tabHost.newTabSpec("mine").setIndicator(mineTabItem), MineFragment.class, null);

    tabHost.setOnTabChangedListener(this);

    // Umeng
    MobclickAgent.updateOnlineConfig(this);
    UmengUpdateAgent.silentUpdate(this);

    // RongCloud
    doRCIMConnect(3);

    isFirstLogin = Boolean.valueOf(getIntent().getData().getQueryParameter("isFirstLogin"));
    if (isFirstLogin) {
      startActivity("sgteacher://applyteacher?fromLogin=true");
    }

    RongIM.setOnReceiveMessageListener(this);

    setSwipeBackEnable(false);
  }
 @Override
 public void onResume() {
   super.onResume();
   refreshDot();
 }