简单的懒加载实现

public abstract class LazyFragment extends Fragment {

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.lazyfragment, container, false);
    return view ;
}

@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    isViewCreated = true;
    lazyLoad();
}
//Fragment的View加载完毕的标记
private boolean isViewCreated;

//Fragment对用户可见的标记
private boolean isUIVisible;
@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
    if (isVisibleToUser) {
        isUIVisible = true;
        lazyLoad();
    } else {
        isUIVisible = false;
    }

}

private void lazyLoad() {
    //这里进行双重标记判断,是因为setUserVisibleHint会多次回调,并且会在onCreateView执行前回调,必须确保onCreateView加载完毕且页面可见,才加载数据
    if (isViewCreated && isUIVisible) {
        loadData();
        //数据加载完毕,恢复标记,防止重复加载
        isViewCreated = false;
        isUIVisible = false;
    }

}

protected abstract void loadData();

}