Kotlin实现Android顶部导航栏与模块联动

下面代码的实现效果就是下面那个截图，无任何其他功能，很单纯，就是Kotilin实现Android顶部导航栏与模块联动~~~

项目目录： 

实现效果：

MainActivity：

package com.lgz.kotlinstudy.activity

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.fragment.app.Fragment
import androidx.fragment.app.FragmentManager
import androidx.fragment.app.FragmentPagerAdapter
import androidx.viewpager.widget.ViewPager
import com.google.android.material.tabs.TabLayout
import com.lgz.kotlinstudy.R
import com.lgz.kotlinstudy.fragment.GoodsFragment

class MainActivity : AppCompatActivity() {

    private val goodsTypeList = listOf("推荐", "百货", "食品","男装","女装","鞋包","手机")

    private val fragmentList = ArrayList()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val tableLayout = findViewById(R.id.tab_layout)
        val viewPager = findViewById(R.id.view_pager)

        for (goodsType in goodsTypeList) {
            fragmentList.add(GoodsFragment(goodsType))
        }

        viewPager.adapter = ViewPagerAdapter(supportFragmentManager)
        tableLayout.setupWithViewPager(viewPager)

    }


    // BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT ----> Indicates that only the current fragment will be in the {@link Lifecycle.State#RESUMED}
    inner class ViewPagerAdapter(fm: FragmentManager) : FragmentPagerAdapter(fm, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {

        override fun getItem(position: Int): Fragment {
            return fragmentList[position]
        }

        override fun getCount(): Int {
            return fragmentList.size
        }

//        展示顶部导航栏标题
        override fun getPageTitle(position: Int): CharSequence? {
            return goodsTypeList[position]
        }

    }
}

GoodsAdapter：

package com.lgz.kotlinstudy.adapter

import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
import com.lgz.kotlinstudy.R
import com.lgz.kotlinstudy.model.GoodsItemOne

class GoodsAdapter(private val goodsItemOneList: List) : RecyclerView.Adapter() {
    inner class GoodsViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        val pic: TextView = itemView.findViewById(R.id.pic)
        val description: TextView = itemView.findViewById(R.id.description)
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): GoodsViewHolder {
        val itemView = LayoutInflater.from(parent.context).inflate(R.layout.goods_item_one, parent,false)
        return GoodsViewHolder(itemView)
    }

    override fun getItemCount(): Int {
        return goodsItemOneList.size
    }

    override fun onBindViewHolder(holder: GoodsViewHolder, position: Int) {
        val goodsItemOne = goodsItemOneList[position]
        holder.pic.text = goodsItemOne.pic;
        holder.description.text = goodsItemOne.description
    }

}

GoodsFragment：

package com.lgz.kotlinstudy.fragment

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.lgz.kotlinstudy.KotlinStudyApplication
import com.lgz.kotlinstudy.R
import com.lgz.kotlinstudy.adapter.GoodsAdapter
import com.lgz.kotlinstudy.model.GoodsItemOne

class GoodsFragment(val title: String) : Fragment() {

    private lateinit var goodsRecyclerView: RecyclerView

    private val goodsItemOneList = listOf(
            GoodsItemOne(
                    "image1",
                    "image1dec"
            ),
            GoodsItemOne(
                    "image2",
                    "image2dec"
            )
    )

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        val view = inflater.inflate(R.layout.fragment_goods, container, false)
        goodsRecyclerView = view.findViewById(R.id.goods_recycler_view)
        return view
    }

    override fun onActivityCreated(savedInstanceState: Bundle?) {
        super.onActivityCreated(savedInstanceState)
        goodsRecyclerView.layoutManager = LinearLayoutManager(KotlinStudyApplication.context)
        goodsRecyclerView.adapter = GoodsAdapter(goodsItemOneList)
    }
}

GoodsItemOneModel.kt：

package com.lgz.kotlinstudy.model

data class GoodsItemOne(val pic: String, val description: String)

ToastUtil.kt：

package com.lgz.kotlinstudy.util

import android.widget.Toast
import com.lgz.kotlinstudy.KotlinStudyApplication

// 设置String的扩展函数
fun String.showToast(){
    Toast.makeText(KotlinStudyApplication.context,this,Toast.LENGTH_SHORT).show()
}

KotlinStudyApplication：

package com.lgz.kotlinstudy

import android.app.Application
import android.content.Context

class KotlinStudyApplication: Application(){
    companion object{
        lateinit var context: Context
    }

    override fun onCreate() {
        super.onCreate()
        context = baseContext
    }
}

activity_main.xml：

fragment_goods.xml：

goods_item_one.xml：

记住在AndroidManifest.xml里面注明，下面指示的那句话。values文件夹下的东西就不展示了~~