我有一個使用NavigationComponentswith的應用程式ViewPager 2。
我想ViewPager用于在片段之間切換。我做了我ActivityMain的 as FragmentContainerView，我想ViewPager在我的一個片段中實作。
問題是，ViewPager它根本不起作用。它不改變碎片，不知道為什么。我應該在代碼中更改什么？
活動主
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
tools:context=".MainActivity">
<androidx.fragment.app.FragmentContainerView
android:id="@ id/fragmentContainerView"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
app:navGraph="@navigation/nav_graph" />
</androidx.constraintlayout.widget.ConstraintLayout>
第一個片段
class BlankFragment : Fragment() {
private var mPag: ViewPager2? = null
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.fragment_blank, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
mPag = view.findViewById(R.id.pager123)
val adapter = PagerAdapter(this)
val list = mutableListOf<Fragment>()
list.add(BlankFragment())
list.add(BlankFragment2())
mPag?.adapter = adapter
}
}
.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".BlankFragment"
android:orientation="vertical">
<TextView
android:id="@ id/test123"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="111111111" />
<androidx.viewpager2.widget.ViewPager2
android:id="@ id/pager123"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#a1a1"/>
</LinearLayout>
第二個片段
class BlankFragment2 : Fragment() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_blank2, container, false)
}
}
.xml
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".BlankFragment2">
<TextView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="222222222222222" />
</FrameLayout>
導航圖
<?xml version="1.0" encoding="utf-8"?>
<navigation 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:id="@ id/nav_graph"
app:startDestination="@id/blankFragment">
<fragment
android:id="@ id/blankFragment"
android:name="com.example.myapplication.BlankFragment"
android:label="fragment_blank"
tools:layout="@layout/fragment_blank" />
<fragment
android:id="@ id/blankFragment2"
android:name="com.example.myapplication.BlankFragment2"
android:label="fragment_blank2"
tools:layout="@layout/fragment_blank2" />
</navigation>
尋呼機配接器
class PagerAdapter(fragment: Fragment) : FragmentStateAdapter(fragment) {
val mFragments = mutableListOf<Fragment>()
override fun getItemCount(): Int {
return mFragments.size
}
override fun createFragment(position: Int): Fragment {
when (position){
0 -> return BlankFragment()
1 -> return BlankFragment2()
}
return mFragments[position]
}
}
uj5u.com熱心網友回復：
您基本上缺少的是我在上一個問題中試圖解釋的內容。
您需要使用Navigation componentandViewPager2作為兩個獨立的物體。
你的也有問題PagerAdapter。片段配接器與您可能使用過的其他配接器不同（mFragments）。他們不應該持有對這些片段的參考。有兩個主要的片段配接器（更多here）。
class PagerAdapter(fragment: Fragment) : FragmentStateAdapter(fragment) {
override fun getItemCount(): Int = 2
override fun createFragment(position: Int): Fragment {
return when (position){
0 -> BlankFragment1()
1 -> BlankFragment2()
else -> throw IllegalArgumentException("Out of fragments, will depend on getItemCount")
}
}
}
您需要Fragments僅在 Navigation 組件中（例如FirstFragment& SecondFragment）并且Fragments屬于ViewPager2（例如BlankFragment1& BlankFragment2）
<?xml version="1.0" encoding="utf-8"?>
<navigation android:id="@ id/nav_graph"
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"
app:startDestination="@id/FirstFragment">
<fragment
android:id="@ id/FirstFragment"
android:name="com.example.myapplication.FirstFragment"
android:label="@string/first_fragment_label"
tools:layout="@layout/fragment_first" >
<action
android:id="@ id/action_FirstFragment_to_SecondFragment"
app:destination="@id/SecondFragment" />
</fragment>
<fragment
android:id="@ id/SecondFragment"
android:name="com.example.myapplication.SecondFragment"
android:label="@string/second_fragment_label"
tools:layout="@layout/fragment_second" />
</navigation>
ViewPager2 的片段：
class BlankFragment1: Fragment() {
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
return inflater.inflate(R.layout.fragment_blank_1, container, false)
}
}
class BlankFragment2: Fragment() {
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
return inflater.inflate(R.layout.fragment_blank_2, container, false)
}
}
將FirstFragment托管ViewPager2將允許您在BlankFragment1和之間滑動BlankFragment2。
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,savedInstanceState: Bundle?): View? {
val view = inflater.inflate(R.layout.fragment_first, container, false)
view.findViewById<ViewPager2>(R.id.vp2)?.let { viewPager2 ->
val pagerAdapter = PagerAdapter(this)
viewPager2.adapter = pagerAdapter
}
return view
}
現在，您需要在任何要使用的片段中做的唯一事情Navigation component就是簡單地和findNavControler您想要的。navigatedestination
class BlankFragment1: Fragment() {
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
val view = inflater.inflate(R.layout.fragment_blank_1, container, false)
view.findViewById<MaterialButton>(R.id.blank_1_button).setOnClickListener {
findNavController().navigate(R.id.action_FirstFragment_to_SecondFragment)
}
return view
}
}
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