Kotlin高效实现 Android ViewPager2 顶部导航之动态配置与性能优化指南(推荐)

dependencies {
    implementation 'androidx.viewpager2:viewpager2:1.0.0'
    implementation 'com.google.android.material:material:1.4.0'
}

// Page.kt
sealed class Page(val title: String, val icon: Int) {
    object Home : Page("Home", R.drawable.ic_home)
    object Dashboard : Page("Dashboard", R.drawable.ic_dashboard)
    object Notifications : Page("Notifications", R.drawable.ic_notifications)
    companion object {
        val pages = listOf(Home, Dashboard, Notifications)
    }
}

// Fragment1.kt
class Fragment1 : Fragment() {
    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        return inflater.inflate(R.layout.fragment_1, container, false)
    }
}
// Fragment2.kt
class Fragment2 : Fragment() {
    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        return inflater.inflate(R.layout.fragment_2, container, false)
    }
}
// Fragment3.kt
class Fragment3 : Fragment() {
    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        return inflater.inflate(R.layout.fragment_3, container, false)
    }
}

class ViewPagerAdapter(fragmentActivity: FragmentActivity) : FragmentStateAdapter(fragmentActivity) {
    override fun getItemCount(): Int = Page.pages.size
    override fun createFragment(position: Int): Fragment {
        return when (Page.pages[position]) {
            is Page.Home -> Fragment1()
            is Page.Dashboard -> Fragment2()
            is Page.Notifications -> Fragment3()
        }
    }
}

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val viewPager = findViewById<ViewPager2>(R.id.viewPager)
        val tabLayout = findViewById<TabLayout>(R.id.tabLayout)
        // 设置 ViewPager2 适配器
        viewPager.adapter = ViewPagerAdapter(this)
        // 将 TabLayout 与 ViewPager2 联动
        TabLayoutMediator(tabLayout, viewPager) { tab, position ->
            tab.text = Page.pages[position].title
            tab.icon = ContextCompat.getDrawable(this, Page.pages[position].icon)
        }.attach()
    }
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
    <!-- 顶部导航 -->
    <com.google.android.material.tabs.TabLayout
        android:id="@+id/tabLayout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:tabMode="fixed"
        app:tabGravity="fill"/>
    <!-- ViewPager2 -->
    <androidx.viewpager2.widget.ViewPager2
        android:id="@+id/viewPager"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"/>
</LinearLayout>

// TabLayoutExtensions.kt
fun TabLayout.setupWithViewPager(viewPager: ViewPager2, pages: List<Page>) {
    TabLayoutMediator(this, viewPager) { tab, position ->
        tab.text = pages[position].title
        tab.icon = ContextCompat.getDrawable(context, pages[position].icon)
    }.attach()
}

tabLayout.setupWithViewPager(viewPager, Page.pages)

object Profile : Page("Profile", R.drawable.ic_profile)

override fun createFragment(position: Int): Fragment {
    return when (Page.pages[position]) {
        is Page.Home -> Fragment1()
        is Page.Dashboard -> Fragment2()
        is Page.Notifications -> Fragment3()
        is Page.Profile -> Fragment4() // 新增页面
    }
}