Android之BaseFragment的封装（第一篇）

Fragment的生命周期:

onCreateView是创建的时候调用，onViewCreated是在onCreateView后被触发的事件(重点)

BaseFragment封装的Demo:

package com.example.shoppingmall.base;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
作用:基类Fragment
//  首页:HomeFragment
//  分类：TypeFragment
//  发现：CommunityFragment
//  购物车:ShoppingCartFragment
//用户中心:UserFragment
//等都要继承该类

public abstract class BaseFragment extends Fragment {
    //上下文对象
    public Context mContext;
    //当该类被系统创建的时候被回调
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mContext = getActivity();
    }

    @Nullable
    @Override
    //子Fragment的UI创建
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        return initView();
    }

    //抽象类，由孩子实现，实现不同效果
    protected abstract View initView();

    //当Activity被创建了的时候回调这个方法
    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        initData();
    }

    //当子类需要联网请求数据的时候，可以重写该方法，在该方法中联网请求
    public void initData() {
    }
}

其中关于上下文对象获取getActivity()[mContext = getActivity()]源代码解释:

一个Fragment必须被嵌入到一个Activity中，它的生命周期直接受其所属的宿主Activity的生命周期影响

/**
     * Return the {@link FragmentActivity} this fragment is currently associated with.
     * May return {@code null} if the fragment is associated with a {@link Context}
     * instead.
     *
     * @see #requireActivity()
     */
    @Nullable
    final public FragmentActivity getActivity() {
        return mHost == null ? null : (FragmentActivity) mHost.getActivity();
    }

    /**
     * Return the {@link FragmentActivity} this fragment is currently associated with.
     *
     * @throws IllegalStateException if not currently associated with an activity or if associated
     * only with a context.
     * @see #getActivity()
     */
    @NonNull
    public final FragmentActivity requireActivity() {
        FragmentActivity activity = getActivity();
        if (activity == null) {
            throw new IllegalStateException("Fragment " + this + " not attached to an activity.");
        }
        return activity;
    }