viewpager2+tablayout实现页面的切换

1.布局文件

<androidx.constraintlayout.widget.ConstraintLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent">
            <com.google.android.material.tabs.TabLayout
                android:id="@+id/tabLayout"
                app:layout_constraintTop_toTopOf="parent"
                android:layout_width="match_parent"
                android:layout_height="40dp"
                app:tabGravity="start"
                app:tabBackground="@android:color/transparent"
                app:tabRippleColor="@color/white"
                app:tabUnboundedRipple="false"
                app:tabMode="scrollable"/>

            <androidx.viewpager2.widget.ViewPager2
                android:id="@+id/viewPager"
                android:layout_width="match_parent"
                android:layout_height="0dp"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintTop_toBottomOf="@+id/tabLayout"/>
        </androidx.constraintlayout.widget.ConstraintLayout>

2.子布局tab_item_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:paddingHorizontal="8dp"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical">
    <View
        android:id="@+id/tv_index"
        android:layout_width="20dp"
        android:layout_height="6dp"
        android:layout_marginTop="-6dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/tv_name"
        android:background="@drawable/shape_6ccdff_00a8ff_3r_bg"/>
    <TextView
        android:id="@+id/tv_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="14sp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:textColor="@color/black_333"
        android:gravity="center"
        android:maxLength="4"
        android:textStyle="bold"/>

</androidx.constraintlayout.widget.ConstraintLayout>

3.交互代码

private var mediator: TabLayoutMediator? = null
    private val mTitles = arrayOf("全部","待支付","已支付","已换绑","已完成","已取消")
    private fun initViewPager() {
        val fragments:MutableList<Fragment> = ArrayList()
        fragments.add(BuyRecordFragment.newInstance(null))
        fragments.add(BuyRecordFragment.newInstance("0"))
        fragments.add(BuyRecordFragment.newInstance("1"))
        fragments.add(BuyRecordFragment.newInstance("2"))
        fragments.add(BuyRecordFragment.newInstance("3"))
        fragments.add(BuyRecordFragment.newInstance("4"))
        mBinding.apply {
            //viewPager.offscreenPageLimit = fragments.size
            viewPager.adapter = object : FragmentStateAdapter(supportFragmentManager,lifecycle) {
                override fun getItemCount(): Int {
                    return fragments.size
                }
                override fun createFragment(position: Int): Fragment {
                    //FragmentStateAdapter内部自己会管理已实例化的fragment对象,所以不需要考虑复用的问题.
                    return fragments[position]
                }
            }
            //以下两种方式都可以,如果tab的点击监听不想用系统的，而是想通过自定义的tabView来实现点击事件，
//则把下面两种方式都注释掉，并且通过tabLayout.clearOnTabSelectedListeners()方法清掉tab的点击监听，然后使用tabView.setOnClickListener来实现,如下所示
            //viewPager.registerOnPageChangeCallback(changeCallback)//第一种方式
            //addTabLayoutListener()//第二种方式
            mediator = TabLayoutMediator(tabLayout, viewPager,false,false) { tab, position ->
                //这里可以自定义TabView
                val tabView = LayoutInflater.from(context).inflate(R.layout.tab_item_layout, null)
                //第三种方式
                tabView .setOnClickListener {
                    tabLayoutIndex(position)
                    //第二个参数表示去除滑动效果
                    viewPager.setCurrentItem(position,false)
                }
                val tv_name =tabView .findViewById<TextView>(R.id.tv_name)
                val tv_index =tabView .findViewById<View>(R.id.tv_index)
                tv_name.text = mTitles[position]
                tv_index.visibility=View.INVISIBLE
                tab.customView = tabView 
            }
            //要执行这一句才是真正将两者绑定起来
            mediator?.attach()
            //配合第三种方式时，需要初始化一个item
            tabLayout.clearOnTabSelectedListeners()
            tabLayoutIndex(0)
            viewPager.setCurrentItem(0,false)
        }
    }
    private val changeCallback = object : ViewPager2.OnPageChangeCallback() {
        override fun onPageSelected(position: Int) {
            tabLayoutIndex(position)
        }
    }
    private fun addTabLayoutListener(){
        mBinding.tabLayout.addOnTabSelectedListener(object : TabLayout.OnTabSelectedListener {
            override fun onTabSelected(tab: TabLayout.Tab) {
                tabLayoutIndex(tab.position)
                //Toast.makeText(mContext, "选中的" + tab.text, Toast.LENGTH_SHORT).show()
            }

            override fun onTabUnselected(tab: TabLayout.Tab) {
                //Toast.makeText(mContext, "未选中的" + tab.text, Toast.LENGTH_SHORT).show()
            }

            override fun onTabReselected(tab: TabLayout.Tab) {
                //Toast.makeText(mContext, "复选的" + tab.text, Toast.LENGTH_SHORT).show()
            }
        })
    }
private fun tabLayoutIndex(position:Int){
    //可以来设置选中时tab的大小
    val tabCount: Int = mBinding.tabLayout.tabCount
    for (i in 0 until tabCount) {
        val tab: TabLayout.Tab = mBinding.tabLayout.getTabAt(i)!!
        val tabView = tab.customView
        val tv_name = tabView?.findViewById<TextView>(R.id.tv_name)
        val tv_index = tabView?.findViewById<View>(R.id.tv_index)
        if (tab.position == position) {
            if (tv_name != null) {
                tv_name.textSize = 18f
            }
            if (tv_index != null) {
                tv_index.visibility=View.VISIBLE
            }
        } else {
            if (tv_name != null) {
                tv_name.textSize = 14f
            }
            if (tv_index != null) {
                tv_index.visibility=View.INVISIBLE
            }
        }
    }
}
    override fun onDestroy() {
        mediator?.detach()
        //mBinding.viewPager.unregisterOnPageChangeCallback(changeCallback)
        super.onDestroy()
    }
//如果页面中不需要fragment显示数据，只需要一小块地方进行内容展示时，使用tabLayout+recyclerView实现内容的切换
private fun setTabData(faqList:MutableList<Faq>){
    mBinding.apply {
        for (item in faqList){
            val tab=tabLayout.newTab()
            val view = LayoutInflater.from(mContext).inflate(R.layout.tab_item_layout, null)
            val tvName =view.findViewById<TextView>(R.id.tv_name)
            val tvIndex =view.findViewById<View>(R.id.tv_index)
            tvName.text = item.title
            tvIndex.visibility= View.INVISIBLE
            tab.customView = view
            tabLayout.addTab(tab)
        }
        tabLayout.addOnTabSelectedListener(object : TabLayout.OnTabSelectedListener {
            override fun onTabSelected(tab: TabLayout.Tab?) {
                tab?.position?.let {
                    //请求数据
                    tabLayoutIndex(it)
                    refreshData(it)
                }
            }
            override fun onTabUnselected(tab: TabLayout.Tab?) {
            }
            override fun onTabReselected(tab: TabLayout.Tab?) {
            }
        })
        val manager=LinearLayoutManager(mContext)
        recyclerView.layoutManager= manager
        mAdapter= OnlineServerAdapter()
        mAdapter?.apply {
            val emptyView = EmptyView(mContext, null)
            emptyView.changeEmptyImgTopMargin(0f)
            //emptyView.setEmptyIcon(R.mipmap.ic_empty_account_msg)
            emptyView.setEmptyDesc("暂无数据")
            setEmptyView(emptyView)
            setOnItemClickListener { adapter, view, position ->
                
            }
        }
        recyclerView.adapter=mAdapter
        //请求默认第一页数据
        tabLayoutIndex(0)
        refreshData(0)
    }
}