Android仿今日头条多个fragment懒加载的实现

public abstract class LazyloadFragment extends Fragment {
 protected View rootView;
 private boolean isInitView = false;
 private boolean isVisible = false;

 @Nullable
 @Override
 public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
  rootView = inflater.inflate(setContentView(), container, false);
  init();
  isInitView = true;
  isCanLoadData();
  return rootView;
 }

 @Override
 public void setUserVisibleHint(boolean isVisibleToUser) {
  super.setUserVisibleHint(isVisibleToUser);

  //isVisibleToUser这个boolean值表示:该Fragment的UI 用户是否可见，获取该标志记录下来
  if(isVisibleToUser){
   isVisible = true;
   isCanLoadData();
  }else{
   isVisible = false;
  }
 }

 private void isCanLoadData(){
  //所以条件是view初始化完成并且对用户可见
  if(isInitView && isVisible ){
   lazyLoad();

   //防止重复加载数据
   isInitView = false;
   isVisible = false;
  }
 }

 /**
  * 加载页面布局文件
  * @return
  */
 protected abstract int setContentView();

 /**
  * 让布局中的view与fragment中的变量建立起映射
  */
 protected abstract void init();

 /**
  * 加载要显示的数据
  */
 protected abstract void lazyLoad();

}

public class PageFragment extends LazyloadFragment implements XRecyclerView.LoadingListener {
 private CommonAdapter adapter;
 private ArrayList datas = new ArrayList<>();
 private XRecyclerView recyclerView;
 private Handler handler = new Handler();

 @Override
 public int setContentView() {
  return R.layout.fragment_page;
 }


 @Override
 public void init() {
  recyclerView = rootView.findViewById(R.id.recyclerview);
  recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
  adapter = new CommonAdapter(getActivity(),R.layout.item,datas) {
   @Override
   protected void convert(ViewHolder holder, String s, int position) {

   }
  };
  recyclerView.setAdapter(adapter);
  recyclerView.setPullRefreshEnabled(true);
  recyclerView.setLoadingListener(this);

 }

 @Override
 public void lazyLoad() {
  recyclerView.refresh();
 }

 @Override
 public void onRefresh() {
  handler.postDelayed(new Runnable() {
   @Override
   public void run() {
    recyclerView.refreshComplete();
    for(int i=0;i<10;i++){
     datas.add("");
    }
    adapter.notifyDataSetChanged();
   }
  },500);
 }

 @Override
 public void onLoadMore() {

 }
}

public class MainActivity extends AppCompatActivity {
 private TabLayout tabLayout;
 private String[] topics = new String[]{"推荐","热点","北京","视频","社会","图片"};
 private ViewPager viewPager;
 private ArrayList fragments = new ArrayList<>();

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
  setContentView(R.layout.activity_main);

  init();
 }

 private void init() {
  viewPager = (ViewPager) findViewById(R.id.viewpager);
  tabLayout = (TabLayout) findViewById(R.id.tablayout);
  viewPager.setOffscreenPageLimit(3);

  for(int i=0;i