package com.wangsz.myapplication.fragment;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

/**
 * Created by admin on 2017/7/5.
 */
public abstract class BaseFragment extends Fragment {

    protected String TAG = "BaseFragment";

    protected View mView;

    private boolean hasLoadData = false; // 是否已加載數(shù)據(jù)

    protected abstract void inflateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState);

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d(TAG, "onCreate()");
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        Log.d(TAG, "onCreateView()");
        if (mView == null) {
            inflateView(inflater, container, savedInstanceState);
        }

        return mView;
    }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        //如果setUserVisibleHint()在mView 創(chuàng)建前調(diào)用時(shí)涣旨，那么
        //就等到rootView創(chuàng)建完后才回調(diào)onFragmentVisibleChange(true)
        //保證onFragmentVisibleChange()的回調(diào)發(fā)生在mView 創(chuàng)建完成之后，防止mView == null
        if (getUserVisibleHint()) {
            if (!hasLoadData) {
                // 一般是第一次打開TabActivity頁面時(shí)浑测，當(dāng)前Fragment會(huì)走這里
                loadData();
                hasLoadData = true;
            }
            onFragmentVisibleChange(true);
        }
        super.onViewCreated(view, savedInstanceState);
    }

    @Override
    public void setUserVisibleHint(boolean isVisibleToUser) {
        super.setUserVisibleHint(isVisibleToUser);
        // setUserVisibleHint在初始化Fragment的時(shí)候也會(huì)調(diào)用杠输，且在onCreateView之前赎败，所以mView會(huì)為null
        // mView是否初始化標(biāo)志，防止回調(diào)函數(shù)在mView為空的時(shí)候觸發(fā)
        if (mView == null) {
            return;
        }

        if (!hasLoadData && isVisibleToUser) {
            loadData();
            hasLoadData = false;
        }

        onFragmentVisibleChange(isVisibleToUser);

    }


    /**
     * fragment可見狀態(tài)發(fā)生變化時(shí)的回調(diào)蠢甲。處理一些UI變化等僵刮？
     *
     * @param isVisible true  不可見 -> 可見
     *                  false 可見  -> 不可見
     */
    protected void onFragmentVisibleChange(boolean isVisible) {
        Log.d(TAG, "頁面可見切換 onFragmentVisibleChange = " + isVisible);

    }

    /**
     * 在fragment首次可見時(shí)回調(diào)，可在這里進(jìn)行加載數(shù)據(jù)峡钓，
     * 用hasLoadData保證只在Fragment第一次可見時(shí)才會(huì)加載數(shù)據(jù)妓笙，
     * 這樣就可以防止每次進(jìn)入都重復(fù)加載數(shù)據(jù)
     */
    protected void loadData() {
        Log.d(TAG, "頁面第一次可見，loadData");

    }

}