不講原理，不花里胡哨，直接說咋用

一般在做項(xiàng)目時(shí) 會(huì)碰見這種界面,上面有tab指示器下面可以滑動(dòng),一般的做法是tablayout+viewpager+fragment去實(shí)現(xiàn),但是如果需要展示的tab很多的話,那么所有的fragment會(huì)直接加載完,這樣的話不僅影響性能,而且也是耗流量的.如同uc瀏覽器的新聞分類一樣,它是當(dāng)你去滑倒這個(gè)tab的時(shí)候才去加載數(shù)據(jù),這個(gè)時(shí)候就需要對(duì)fragment進(jìn)行懶加載配置了.

   /**
     * @return The current value of the user-visible hint on this fragment.
     * @see #setUserVisibleHint(boolean)
     */
    public boolean getUserVisibleHint() {
        return mUserVisibleHint;
    }

這個(gè)方法會(huì)在當(dāng)前界面用戶可見的時(shí)候調(diào)用,執(zhí)行順序在createview之前.返回值mUserVisibleHint為true代表當(dāng)前界面可見
定義兩個(gè)參數(shù)

    protected boolean mIsInitView = false;//是否初始化視圖
    protected boolean mIsVisible = false;//是否可見

然后再在方法中判斷是否去加載數(shù)據(jù)

    @Override
    public void setUserVisibleHint(boolean isVisibleToUser) {
        super.setUserVisibleHint(isVisibleToUser);
        if (isVisibleToUser) {
            mIsVisible = true;
            isCanLoadData();
        } else {
            mIsVisible = false;
        }
    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {

        //復(fù)用mView
        if (mView == null) {
            mView = inflater.inflate(getLayoutId(), container, false);
        }

        initView(mView);

        mIsInitView = true;

        isCanLoadData();

        return mView;
    }

   /**
    *是否可以加載數(shù)據(jù)
    */
   private void isCanLoadData() {
        //所以條件是view初始化完成并且對(duì)用戶可見
        if (mIsInitView && mIsVisible) {
            initData();
            //防止重復(fù)加載數(shù)據(jù)
            mIsInitView = false;
            mIsVisible = false;
        }
    }

我自己的baselazy基類代碼

public abstract class LazyLoadFragment<T extends IBasePresenter> extends Fragment
        implements IBaseView, SwipeRefreshLayout.OnRefreshListener {

    protected Context mContext;
    protected Activity mActivity;
    protected T mPresenter;

    protected Unbinder unbinder;

    protected View mView;

    private AlertDialog mDialog;

    protected boolean mIsInitView = false;
    protected boolean mIsVisible = false;

    /**
     * 獲取fragment的布局id
     *
     * @return
     */
    protected abstract @LayoutRes
    int getLayoutId();

    /**
     * 創(chuàng)建Presenter
     *
     * @return
     */
    protected abstract T createPresenter();

    /**
     * view的一些初始化操作
     *
     * @param mView
     */
    protected abstract void initView(View mView);

    /**
     * 數(shù)據(jù)的初始化，包括網(wǎng)絡(luò)請(qǐng)求
     */
    protected abstract void initData();

    @Override
    public void setUserVisibleHint(boolean isVisibleToUser) {
        super.setUserVisibleHint(isVisibleToUser);
        if (isVisibleToUser) {
            mIsVisible = true;
            isCanLoadData();
        } else {
            mIsVisible = false;
        }
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        mContext = getContext();
        mActivity = getActivity();

        mPresenter = createPresenter();

    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {

        //復(fù)用mView
        if (mView == null) {
            mView = inflater.inflate(getLayoutId(), container, false);
        }

        unbinder = ButterKnife.bind(this, mView);

        initView(mView);

        mIsInitView = true;

        isCanLoadData();

        return mView;
    }

    private void isCanLoadData() {
        //所以條件是view初始化完成并且對(duì)用戶可見
        if (mIsInitView && mIsVisible) {
            initData();
            //防止重復(fù)加載數(shù)據(jù)
            mIsInitView = false;
            mIsVisible = false;
        }
    }

    @Override
    public void onDestroyView() {
        if (mPresenter != null) {
            mPresenter.dispose();
        }
        if (unbinder != null) {
            unbinder.unbind();
        }
        super.onDestroyView();
    }

    @Override
    public void onDestroy() {
        if (mPresenter != null) {
            mPresenter.detachView();          //解除presenter與view的綁定
        }
        super.onDestroy();
    }

    @Override
    public Context provideContext() {
        return mContext;
    }

    @Override
    public void showLoading() {
        if (mActivity instanceof BaseActivity) {
            ((BaseActivity) mActivity).showLoading();
        }
    }

    @Override
    public void dismissLoading() {
        if (mActivity instanceof BaseActivity) {
            ((BaseActivity) mActivity).dismissLoading();
        }
    }

    @Override
    public void requestFail(String message) {
        dismissLoading();
    }


}