package com.tejia.lijin.app.ui.BrandRebate;
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import android.os.Bundle;
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import androidx.fragment.app.Fragment;
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import android.view.LayoutInflater;
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import android.view.View;
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import android.view.ViewGroup;
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/**
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* Fragment 懒加载
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*/
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public abstract class RetainView_LJZFragment extends Fragment {
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/**
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* 标记已加载完成，保证懒加载只能加载一次
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*/
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private boolean hasLoaded = false;
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/**
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* 标记Fragment是否已经onCreate
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*/
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private boolean isCreated = false;
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/**
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* 界面对于用户是否可见
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*/
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private boolean isVisibleToUser = false;
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private View view;
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public RetainView_LJZFragment() {
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// Required empty public constructor
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}
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@Override
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public View onCreateView(LayoutInflater inflater, ViewGroup container,
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Bundle savedInstanceState) {
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if (view != null) {
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ViewGroup parent = (ViewGroup) view.getParent();
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if (parent != null) {
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parent.removeView(view);
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}
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} else {
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init(getView(inflater, getContentResource(), container), savedInstanceState);
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}
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return view;
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}
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private View getView(LayoutInflater inflater, int layoutId, ViewGroup container) {
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return inflater.inflate(layoutId, container, false);
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}
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public void init(View view, Bundle savedInstanceState) {
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isCreated = true;
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this.view = view;
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onCreateView(this.view, savedInstanceState);
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lazyLoad(this.view, savedInstanceState);
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}
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/**
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* 监听界面是否展示给用户，实现懒加载
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* 这个方法也是网上的一些方法用的最多的一个，我的思路也是这个，不过把整体思路完善了一下
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*/
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@Override
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public void setUserVisibleHint(boolean isVisibleToUser) {
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//注：关键步骤
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this.isVisibleToUser = isVisibleToUser;
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lazyLoad(view, null);
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}
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public abstract void onCreateView(View view, Bundle savedInstanceState);
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/**
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* 懒加载方法，获取数据什么的放到这边来使用，在切换到这个界面时才进行网络请求
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*/
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private void lazyLoad(View view, Bundle savedInstanceState) {
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//如果该界面不对用户显示、已经加载、fragment还没有创建，
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//三种情况任意一种，不获取数据
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if (!isVisibleToUser || hasLoaded || !isCreated) {
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return;
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}
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lazyInit(view, savedInstanceState);
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//注：关键步骤，确保数据只加载一次
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hasLoaded = true;
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}
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/**
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* 子类必须实现的方法，这个方法里面的操作都是需要懒加载的
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*/
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public abstract void lazyInit(View view, Bundle savedInstanceState);
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public abstract int getContentResource();
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@Override
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public void onDestroyView() {
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super.onDestroyView();
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isCreated = false;
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hasLoaded = false;
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}
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}
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