Android 中基于TabLayout+ViewPager实现标签卡效果

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:orientation="vertical"
  tools:context="com.plbear.yyj.myapplication.MainActivity">
  <android.support.design.widget.TabLayout
    android:id="@+id/tab"
    android:layout_width="match_parent"
    android:layout_height="40dp"
    app:tabGravity="fill"
    app:tabIndicatorColor="#4978ef"
    app:tabIndicatorHeight="2dp"
    app:tabMode="scrollable"
    app:tabSelectedTextColor="#4978ef"
    app:tabTextColor="#222222"></android.support.design.widget.TabLayout>
  <android.support.v4.view.ViewPager
    android:id="@+id/view_pager"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"></android.support.v4.view.ViewPager>
</LinearLayout>

package com.plbear.yyj.myapplication
import android.os.Bundle
import android.support.design.widget.Snackbar
import android.support.design.widget.TabLayout
import android.support.v4.app.Fragment
import android.support.v4.app.FragmentPagerAdapter
import android.support.v7.app.AppCompatActivity
import android.view.Menu
import android.view.MenuItem
import kotlinx.android.synthetic.main.activity_main.*
class MainActivity : AppCompatActivity() {
  var mFragList = ArrayList<Fragment>()
  var adapter = object:FragmentPagerAdapter(supportFragmentManager){
    override fun getItem(position: Int): Fragment {
      return mFragList[position]
    }
    override fun getCount(): Int {
      return 2
    }
  }
  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    initViewPager() //先将各个fragment加入到viewpager中
    initTabLayout(); //初始化tablayout
  }
  fun initTabLayout(){
    tab.setupWithViewPager(view_pager)
    tab.setTabsFromPagerAdapter(adapter)
    tab.tabMode = TabLayout.MODE_FIXED
    tab.getTabAt(0)?.setText("第一页")
    tab.getTabAt(1)?.setText("第二页")
  }
  fun initViewPager(){
    mFragList.add(Fragment1())
    mFragList.add(Fragment2())
    view_pager.adapter = adapter
  }
}