我开始了解ViewPager2并尝试实现它,但没有找到任何合适的示例。
谁能告诉我如何使用它。
我正在寻找正确的用法,而不是示例。
如果您想使用 View Pager2 实现 Carousel,请查看我的答案
如何在 ViewPager2 中使用 TabLayout
示例代码
下面使用dependencies
implementation 'com.google.android.material:material:1.1.0-alpha08'
implementation 'androidx.viewpager2:viewpager2:1.0.0-beta02'
示例代码
XML 布局
<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout
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">
<com.google.android.material.appbar.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">
<androidx.appcompat.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:layout_scrollFlags="scroll|enterAlways"
app:popupTheme="@style/ThemeOverlay.AppCompat.Light"/>
<com.google.android.material.tabs.TabLayout
android:id="@+id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
</com.google.android.material.appbar.AppBarLayout>
<androidx.viewpager2.widget.ViewPager2
android:id="@+id/viewpager"
app:layout_anchor="@id/tabs"
app:layout_anchorGravity="bottom"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
</androidx.coordinatorlayout.widget.CoordinatorLayout>
活动
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import kotlinx.android.synthetic.main.activity_main.*
import com.google.android.material.tabs.TabLayoutMediator
import com.google.android.material.tabs.TabLayout
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
// setSupportActionBar(toolbar)
viewpager.adapter = AppViewPagerAdapter(supportFragmentManager, lifecycle)
TabLayoutMediator(tabs, viewpager, object : TabLayoutMediator.OnConfigureTabCallback {
override fun onConfigureTab(tab: TabLayout.Tab, position: Int) {
// Styling each tab here
tab.text = "Tab $position"
}
}).attach()
}
}
输出
来自文档
新功能
API 更改
FragmentStateAdapter
替换FragmentStatePagerAdapter
RecyclerView.Adapter
替换PagerAdapter
registerOnPageChangeCallback
替换addPageChangeListener
示例代码
添加最新
dependencies
的ViewPager2
implementation 'androidx.viewpager2:viewpager2:1.0.0-alpha01'
布局
<?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"
android:orientation="vertical"
tools:context=".MainActivity">
<androidx.viewpager2.widget.ViewPager2
android:id="@+id/view_pager"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
活动
import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager2.widget.ViewPager2;
import java.util.ArrayList;
public class MyActivity extends AppCompatActivity {
ViewPager2 myViewPager2;
MyAdapter MyAdapter;
private ArrayList<String> arrayList = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my);
myViewPager2 = findViewById(R.id.view_pager);
arrayList.add("Item 1");
arrayList.add("Item 2");
arrayList.add("Item 3");
arrayList.add("Item 4");
arrayList.add("Item 5");
MyAdapter = new MyAdapter(this, arrayList);
myViewPager2.setOrientation(ViewPager2.ORIENTATION_VERTICAL);
myViewPager2.setAdapter(MyAdapter);
}
}
我的适配器
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import java.util.ArrayList;
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {
private Context context;
private ArrayList<String> arrayList = new ArrayList<>();
public MyAdapter(Context context, ArrayList<String> arrayList) {
this.context = context;
this.arrayList = arrayList;
}
@NonNull
@Override
public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(context).inflate(R.layout.list_item, parent, false);
return new MyViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
holder.tvName.setText(arrayList.get(position));
}
@Override
public int getItemCount() {
return arrayList.size();
}
public class MyViewHolder extends RecyclerView.ViewHolder {
TextView tvName;
public MyViewHolder(@NonNull View itemView) {
super(itemView);
tvName = itemView.findViewById(R.id.tvName);
}
}
}
现在我们需要使用
ViewPager2.OnPageChangeCallback()
来获取 Swipe 事件ViewPager2
示例代码
myViewPager2.registerOnPageChangeCallback(new ViewPager2.OnPageChangeCallback() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
super.onPageScrolled(position, positionOffset, positionOffsetPixels);
}
@Override
public void onPageSelected(int position) {
super.onPageSelected(position);
Log.e("Selected_Page", String.valueOf(position));
}
@Override
public void onPageScrollStateChanged(int state) {
super.onPageScrollStateChanged(state);
}
});
我们可以使用设置方向
myViewPager2.setOrientation()
示例代码
供HORIZONTAL Orientation
使用
myViewPager2.setOrientation(ViewPager2.ORIENTATION_HORIZONTAL);
供VERTICAL Orientation
使用
myViewPager2.setOrientation(ViewPager2.ORIENTATION_VERTICAL);
我们可以使用
notifyDataSetChanged
与我们在RecyclerView.Adapter
添加新项目的示例代码
btnAdd.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
arrayList.add("New ITEM ADDED");
MyAdapter.notifyDataSetChanged();
}
});
删除新项目的示例代码
btnRemove.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
arrayList.remove(3);
MyAdapter.notifyItemRemoved(3);
}
});
Fragment
与ViewPager2
首先创建一个
ViewPagerFragmentAdapter
扩展类FragmentStateAdapter
import java.util.ArrayList;
import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.viewpager2.adapter.FragmentStateAdapter;
public class ViewPagerFragmentAdapter extends FragmentStateAdapter {
private ArrayList<Fragment> arrayList = new ArrayList<>();
public ViewPagerFragmentAdapter(@NonNull FragmentManager fragmentManager) {
super(fragmentManager);
}
@NonNull
@Override
public Fragment getItem(int position) {
return arrayList.get(position);
}
public void addFragment(Fragment fragment) {
arrayList.add(fragment);
}
@Override
public int getItemCount() {
return arrayList.size();
}
}
现在在你的活动中像这样使用
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager2.widget.ViewPager2;
import neel.com.bottomappbar.R;
public class MainActivity extends AppCompatActivity {
ViewPager2 myViewPager2;
ViewPagerFragmentAdapter myAdapter;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
myViewPager2 = findViewById(R.id.view_pager);
myAdapter = new ViewPagerFragmentAdapter(getSupportFragmentManager());
// add Fragments in your ViewPagerFragmentAdapter class
myAdapter.addFragment(new FragmentOne());
myAdapter.addFragment(new Fragmenttwo());
myAdapter.addFragment(new FragmentThree());
// set Orientation in your ViewPager2
myViewPager2.setOrientation(ViewPager2.ORIENTATION_VERTICAL);
myViewPager2.setAdapter(myAdapter);
}
}
有关更多信息,请查看此
新功能
setUserInputEnabled
, isUserInputEnabled
)API 更改
ViewPager2
班级决赛Bug修复
FragmentStateAdapter
稳定性修复在 viewpager2 中禁用滑动的示例代码
myViewPager2.setUserInputEnabled(false);// SAMPLE CODE to disable swiping in viewpager2
myViewPager2.setUserInputEnabled(true);//SAMPLE CODE to enable swiping in viewpager2
新功能
API 更改
FragmentStateAdapter
现在需要一个Lifecycle
对象。FragmentActivity
添加了两个实用程序构造函数以从主机或主机 Fragment获取它示例代码
ViewPagerFragmentAdapter
import java.util.ArrayList;
import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.lifecycle.Lifecycle;
import androidx.viewpager2.adapter.FragmentStateAdapter;
public class ViewPagerFragmentAdapter extends FragmentStateAdapter {
private ArrayList<Fragment> arrayList = new ArrayList<>();
public ViewPagerFragmentAdapter(@NonNull FragmentManager fragmentManager, @NonNull Lifecycle lifecycle) {
super(fragmentManager, lifecycle);
}
@NonNull
@Override
public Fragment getItem(int position) {
return arrayList.get(position);
}
public void addFragment(Fragment fragment) {
arrayList.add(fragment);
}
@Override
public int getItemCount() {
return arrayList.size();
}
}
MainActivity 代码
import android.os.Bundle;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager2.widget.ViewPager2;
import neel.com.bottomappbar.R;
public class MainActivity extends AppCompatActivity {
ViewPager2 myViewPager2;
ViewPagerFragmentAdapter myAdapter;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
myViewPager2=findViewById(R.id.view_pager);
myAdapter = new ViewPagerFragmentAdapter(getSupportFragmentManager(), getLifecycle());
// add Fragments in your ViewPagerFragmentAdapter class
myAdapter.addFragment(new FragmentOne());
myAdapter.addFragment(new Fragmenttwo());
myAdapter.addFragment(new FragmentThree());
myViewPager2.setOrientation(ViewPager2.ORIENTATION_VERTICAL);
myViewPager2.setAdapter(myAdapter);
}
}
ItemDecorator
引入了与 一致的行为RecyclerView
。MarginPageTransformer
引入以提供在页面之间(页面插图之外)创建空间的能力。CompositePageTransformer
引入以提供组合多个的能力PageTransformers
API 更改
FragmentStateAdapter#getItem
方法重命名为FragmentStateAdapter#createFragment
- 过去的方法名称已被证明是错误的来源。OFFSCREEN_PAGE_LIMIT_DEFAULT
值从 0 变为 -1。如果使用,则无需更改客户端代码OFFSCREEN_PAGE_LIMIT_DEFAULTconstant
。示例代码
活动代码
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;
import androidx.recyclerview.widget.RecyclerView;
import androidx.viewpager2.widget.MarginPageTransformer;
import androidx.viewpager2.widget.ViewPager2;
import neel.com.bottomappbar.R;
public class MainActivity extends AppCompatActivity {
ViewPager2 myViewPager2;
ViewPagerFragmentAdapter myAdapter;
private ArrayList<Fragment> arrayList = new ArrayList<>();
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
myViewPager2 = findViewById(R.id.myViewPager2);
// add Fragments in your ViewPagerFragmentAdapter class
arrayList.add(new FragmentOne());
arrayList.add(new Fragmenttwo());
arrayList.add(new FragmentThree());
myAdapter = new ViewPagerFragmentAdapter(getSupportFragmentManager(), getLifecycle());
// set Orientation in your ViewPager2
myViewPager2.setOrientation(ViewPager2.ORIENTATION_HORIZONTAL);
myViewPager2.setAdapter(myAdapter);
myViewPager2.setPageTransformer(new MarginPageTransformer(1500));
}
}
ViewPagerFragmentAdapter
import java.util.ArrayList;
import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.lifecycle.Lifecycle;
import androidx.viewpager2.adapter.FragmentStateAdapter;
public class ViewPagerFragmentAdapter extends FragmentStateAdapter {
private ArrayList<Fragment> arrayList = new ArrayList<>();
public ViewPagerFragmentAdapter(@NonNull FragmentManager fragmentManager, @NonNull Lifecycle lifecycle) {
super(fragmentManager, lifecycle);
}
@NonNull
@Override
public Fragment createFragment(int position) {
switch (position) {
case 0:
return new FragmentOne();
case 1:
return new Fragmenttwo();
case 2:
return new FragmentThree();
}
return null;
}
@Override
public int getItemCount() {
return 3;
}
}
实际上现在有一个 ViewPager2 的官方示例 repo(链接如下)
回购包含以下示例(引用下面的回购自述文件)
样品
- ViewPager2 with Views - 展示如何设置 ViewPager2 与 Views 作为页面
- ViewPager2 with Fragments - 展示如何设置 ViewPager2 与 Fragments 作为页面
- ViewPager2 with a Mutable Collection (Views) - 演示 ViewPager2 与 Views 作为页面的用法和页面适配器中的突变
- ViewPager2 with a Mutable Collection (Fragments) - 演示 ViewPager2 与 Fragments 作为页面的用法,以及页面适配器中的突变
- ViewPager2 with a TabLayout (Views) - 展示如何设置 ViewPager2 与 Views 作为页面,并将其链接到 TabLayout
Kotlin 中带有 Fragments 的 ViewPager2 的简单示例
activity_main.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"
android:orientation="vertical"
xmlns:app="http://schemas.android.com/apk/res-auto"
tools:context=".MainActivity">
<androidx.viewpager2.widget.ViewPager2
android:id="@+id/pager2_container"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"/>
</LinearLayout>
MainActivity.kt
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val viewPager2 = findViewById<ViewPager2>(R.id.pager2_container)
val fragmentList = arrayListOf(
FirstFragment.newInstance(),
SecondFragment.newInstance(),
ThirdFragment.newInstance()
)
viewPager2.adapter = ViewPagerAdapter(this, fragmentList)
}
}
FirstFragment.kt(SecondFragment.kt
和ThirdFragment.kt
看起来相似FirstFragment.kt
)
class FirstFragment : Fragment() {
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.fragment_first, container, false)
}
companion object{
fun newInstance() = FirstFragment()
}
}
ViewPagerAdapter.kt
class ViewPagerAdapter(fa:FragmentActivity, private val fragments:ArrayList<Fragment>): FragmentStateAdapter(fa) {
override fun getItemCount(): Int = fragments.size
override fun createFragment(position: Int): Fragment = fragments[position]
}
其他一些有用的资源:
Android中ViewPager2的使用
API 更改
FragmentStateAdapter 替换 FragmentStatePagerAdapter
RecyclerView.Adapter 替换 PagerAdapter
registerOnPageChangeCallback 替换 addPageChangeListener
简而言之,他们使 View Pager 适配器像 Recycle View Adapter 一样工作。
注意:- 我们不需要在 View Pager 2 中使用片段。它完全依赖于 RecyclerView.Adapter 膨胀布局。
这是示例 gitHub 回购链接
例子:-
MainActivity.class
public class MainActivity extends AppCompatActivity {
private ViewPager2 mPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
getSupportActionBar().setTitle("View Pager 2");
mPager = findViewById(R.id.pager);
mPager.setAdapter(new MyViewPagerAdapter(this));
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if (R.id.change == item.getItemId()) {
mPager.setOrientation(mPager.getOrientation() != ViewPager2.ORIENTATION_VERTICAL ? ViewPager2.ORIENTATION_VERTICAL : ViewPager2.ORIENTATION_HORIZONTAL);
}
return super.onOptionsItemSelected(item);
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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.viewpager2.widget.ViewPager2
android:id="@+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</android.support.constraint.ConstraintLayout>
MyViewPagerAdapter.class
public class MyViewPagerAdapter extends RecyclerView.Adapter<MyHolder> {
private Context context;
public MyViewPagerAdapter(Context context) {
this.context=context;
}
@NonNull
@Override
public MyHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
return new MyHolder(LayoutInflater.from(context).inflate(R.layout.cell_item, parent, false));
}
@Override
public void onBindViewHolder(@NonNull MyHolder holder, int position) {
holder.mText.setText("Page "+(position+1));
}
@Override
public int getItemCount() {
return 10;
}
}
cell_item.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="@+id/text"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:text="Page 1"
android:textSize="20sp" />
</android.support.constraint.ConstraintLayout>
MyHolder.class
class MyHolder extends RecyclerView.ViewHolder {
public TextView mText;
public MyHolder(@NonNull View itemView) {
super(itemView);
mText = itemView.findViewById(R.id.text);
}
}
输出:
这是我用 TabLayout 和 3 Fragment full Examble 实现 ViewPager2 所做的:
布局ViewPager2
包含TabLayout
:
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="0dp"
android:layout_height="0dp"
android:orientation="vertical"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/include3">
<com.google.android.material.tabs.TabLayout
android:id="@+id/tab_layout"
android:layout_width="match_parent"
android:background="@color/colorPrimary"
app:tabTextColor="@color/tab_dismiss_color"
app:tabSelectedTextColor="@color/green"
android:layout_height="wrap_content" />
<View
android:layout_width="match_parent"
android:layout_height="1dp"
android:layout_gravity="bottom"
android:background="#e4e4e4" />
<androidx.viewpager2.widget.ViewPager2
android:id="@+id/pager"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1" />
</LinearLayout>
初始化 ViewPager2 并设置选项卡名称:
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_report);
ButterKnife.bind(this);
actionBarTitleId.setText(R.string.reports);
viewPager.setAdapter(new ViewPagerAdapter(this));
new TabLayoutMediator(tabLayout, viewPager, (tab, position) -> {
switch (position) {
case 0:
tab.setText(R.string.financial_duty_str);
break;
case 1:
tab.setText(R.string.financial_unpaid_str);
break;
case 2:
tab.setText(R.string.financial_paid_str);
break;
}
}).attach();
}
ViewPager2
适配器 :
public class ViewPagerAdapter extends FragmentStateAdapter {
public ViewPagerAdapter(@NonNull FragmentActivity fragmentActivity) {
super(fragmentActivity);
}
@NonNull
@Override
public Fragment createFragment(int position) {
switch (position) {
case 0:
return new FinancialFragment();
case 1:
return new FinancialUnPaidFragment();
case 2:
return new FinancialPaidFragment();
default:
return null;
}
}
@Override
public int getItemCount() {
return 3;
}
使用的依赖:
implementation "androidx.viewpager2:viewpager2:1.0.0"
implementation 'com.google.android.material:material:1.1.0-alpha10'
如何使用它解释得很清楚。让我给出关于 ViewPager2 的小但非常重要的提示和详细信息,特别是如果它位于有关如何防止内存泄漏的片段中
不要使用带有片段的构造函数,尤其是在使用TabLayout
.
public FragmentStateAdapter(@NonNull Fragment fragment) {
this(fragment.getChildFragmentManager(), fragment.getLifecycle());
}
因为它有内存泄漏的风险,如此处所述
而是使用 FragmentManager 和 LifeCycle。并且不要将lifeCycle
片段作为参数发送,使用viewLifeCycleOwner
' 生命周期,因为 viewLifeCycleOwner 代表片段的生命周期view
。
class NavigableFragmentStateAdapter(
fragmentManager: FragmentManager,
lifecycle: Lifecycle
) : FragmentStateAdapter(fragmentManager, lifecycle) {
}
并使用 in 设置适配器onCreateView
viewPager.adapter =
NavigableFragmentStateAdapter(childFragmentManager, viewLifecycleOwner.lifecycle)
TabLayout
在 ViewPager2 位于片段内时使用,请不要忘记分离 TabLayout 并将 ViewPager2 的适配器设置为分离 TabLayoutMediator,因为它在片段中时会导致内存泄漏
用导航组件导航替换片段后,片段内的 ViewPager2 泄漏
TabLayoutMediator(tabLayout, viewPager2, tabConfigurationStrategy).detach()
viewPager2.adapter = null
onDestroyView
Fragment的内部方法
如果您希望将 ViewPager 页面navHostFragment
与导航组件一起使用以导航回子片段,请将 FragmentTransactionCallback 注册FragmentStateAdapter
为
private val fragmentTransactionCallback =
object : FragmentStateAdapter.FragmentTransactionCallback() {
override fun onFragmentMaxLifecyclePreUpdated(
fragment: Fragment,
maxLifecycleState: Lifecycle.State
) = if (maxLifecycleState == Lifecycle.State.RESUMED) {
// This fragment is becoming the active Fragment - set it to
// the primary navigation fragment in the OnPostEventListener
OnPostEventListener {
fragment.parentFragmentManager.commitNow {
setPrimaryNavigationFragment(fragment)
}
}
} else {
super.onFragmentMaxLifecyclePreUpdated(fragment, maxLifecycleState)
}
}
init {
// Add a FragmentTransactionCallback to handle changing
// the primary navigation fragment
registerFragmentTransactionCallback(fragmentTransactionCallback)
}
此外,如果您希望查看一些示例,如何将 ViewPager2 与导航组件、动态功能模块以及与 BottomNavigationView 结合使用,您可以查看此 github 存储库中的教程。
这是 Kotlin 中 @sushildlh 答案的 kotlin 版本实现。
在这段代码中,我正在使用 recyclerview 实现 viewpager2 来查看图像。我也在使用视图绑定
food_details.xml
<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=".presentation.recipeitem.RecipeDetailsFragment">
<androidx.viewpager2.widget.ViewPager2
android:id="@+id/viewPager2"
android:layout_width="0dp"
android:layout_height="300dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:src="@tools:sample/avatars" />
...
膨胀这个 xml 的片段
@AndroidEntryPoint
class RecipeDetailsFragment : Fragment(R.layout.fragment_recipe_details) {
private val viewModel: RecipeItemViewModel by viewModels()
private val viewBinding: FragmentRecipeDetailsBinding by viewBinding()
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
bindRecipeData(//object of data that is to be desplayed)
}
private fun bindRecipeData(recipeDetailedInfo: RecipeDetailedInfo?) {
recipeDetailedInfo?.let {
with(viewBinding) {
viewPager2.adapter = ViewPagerAdapter(it.images)
viewPager2.setPageTransformer(ZoomOutPageTransformer())
lifecycleScope.launchWhenCreated {
delay(500)
viewPager2.setCurrentItem(if (it.images.size >= 2) 1 else 0, true)
}
}
}
}....
在片段中,我正在创建适配器的对象并直接发送包含图像 URL 的字符串列表
这是 viewpager 适配器,它基本上是一个普通的 recyclerview 适配器
import android.view.LayoutInflater
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
import com.blogspot.soyamr.recipes2.databinding.ImageviewBinding
import com.squareup.picasso.Picasso
class ViewPagerAdapter(private val images: List<String>) :
RecyclerView.Adapter<ViewPagerAdapter.ImageViewHolder>() {
class ImageViewHolder(private val imageViewBinding: ImageviewBinding) :
RecyclerView.ViewHolder(imageViewBinding.root) {
fun bind(imageLink: String) {
Picasso.get().load(imageLink).into(imageViewBinding.root)
}
companion object {
fun from(parent: ViewGroup): ImageViewHolder {
val itemBinding =
ImageviewBinding.inflate(LayoutInflater.from(parent.context), parent, false)
return ImageViewHolder(itemBinding)
}
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ImageViewHolder {
return ImageViewHolder.from(parent)
}
override fun onBindViewHolder(holder: ImageViewHolder, position: Int) {
holder.bind(images[position])
}
override fun getItemCount(): Int = images.size
}
在 recyclerview 我膨胀这个 imageview.xml
<?xml version="1.0" encoding="utf-8"?>
<com.google.android.material.imageview.ShapeableImageView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent" android:layout_height="match_parent"
android:scaleType="centerCrop"
android:theme="@style/roundedImageView"
/>
如果需要,您可以使用复杂的 xml 视图
这是我的解决方案(Android Studio 3.6):
在 app/build.gradle 中:
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation('com.crashlytics.sdk.android:crashlytics:2.10.1@aar') { transitive = true; }
implementation 'androidx.appcompat:appcompat:1.1.0'
implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
implementation 'com.google.android.material:material:1.1.0-beta01'
implementation 'org.altbeacon:android-beacon-library:2.16.3'
implementation 'androidx.localbroadcastmanager:localbroadcastmanager:1.0.0'
implementation 'androidx.viewpager2:viewpager2:1.0.0-beta05'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'androidx.test.ext:junit:1.1.1'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
implementation "androidx.core:core-ktx:+"
implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
}
这是我的活动:
import android.os.Bundle;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;
import androidx.viewpager2.widget.ViewPager2;
import java.util.ArrayList;
import java.util.List;
import com.myproject.android.R;
import com.myproject.android.adapter.CustomFragmentStateAdapter;
import com.myproject.android.ui.fragment.BluetoothPageFragment;
import com.myproject.android.ui.fragment.QrPageFragment;
public class QRBluetoothSwipeActivity extends AppCompatActivity {
private ViewPager2 myViewPager2;
private CustomFragmentStateAdapter myAdapter;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
// Make sure this is before calling super.onCreate
setTheme(R.style.AppTheme); // show splash screen
super.onCreate(savedInstanceState);
setContentView(R.layout.qr_bluetooth_swipe_activity);
init();
}
private void init() {
List<Fragment> fragmentList = new ArrayList<Fragment>();
QrPageFragment m1 = new QrPageFragment();
BluetoothPageFragment m2 = new BluetoothPageFragment();
myViewPager2 = findViewById(R.id.viewPager2);
fragmentList.add(m2);
fragmentList.add(m1);
myAdapter = new CustomFragmentStateAdapter(this, fragmentList);
myViewPager2.setAdapter(myAdapter);
}
}
这里布局:
<?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=".ui.actviity.SplashDelayActivity">
<androidx.viewpager2.widget.ViewPager2
android:id="@+id/viewPager2"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
这是我的CustomFragmentStateAdapter
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentActivity;
import androidx.viewpager2.adapter.FragmentStateAdapter;
import org.jetbrains.annotations.NotNull;
import java.util.ArrayList;
import java.util.List;
public class CustomFragmentStateAdapter extends FragmentStateAdapter {
private List<Fragment> listFragment = new ArrayList<>();
public CustomFragmentStateAdapter(FragmentActivity fa, List<Fragment> list) {
super(fa);
listFragment = list;
}
@NotNull
@Override
public Fragment createFragment(int position) {
return listFragment.get(position);
}
@Override
public int getItemCount() {
return 2;
}
}
这里是我的片段:
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import com.myproject.android.R;
public class BluetoothPageFragment extends Fragment {
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.bluetooth_page_fragment, container, false);
}
}
第二个片段:
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import com.myproject.android.R;
public class QrPageFragment extends Fragment {
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.qr_page_fragment, container, false);
}
}
因此,现在我使用androidx.viewpager2.widget.ViewPager2
我的自定义片段。
它的工作!
好的。
PS另一个工具:
public class CustomFragmentStateAdapter extends FragmentStateAdapter {
private ArrayList<Fragment> arrayList = new ArrayList<>();
public CustomFragmentStateAdapter (FragmentActivity fa) {
super(fa);
}
public void addFragment(Fragment fragment) {
arrayList.add(fragment);
}
@Override
public int getItemCount() {
return arrayList.size();
}
@NonNull
@Override
public Fragment createFragment(int position) {
// return your fragment that corresponds to this 'position'
return arrayList.get(position);
}
}
并像这样使用(在活动中):
myViewPager2 = findViewById(R.id.viewPager2);
myAdapter = new CustomFragmentStateAdapter (this);
myAdapter.addFragment(new QrPageFragment());
myAdapter.addFragment(new BluetoothPageFragment());
myViewPager2.setAdapter(myAdapter);
我首先创建了一个视图寻呼机,然后使用以下说明迁移到查看寻呼机 2: https ://developer.android.com/training/animation/vp2-migration
这是正确的实现!
typealias FragmentBuilder = () -> Fragment
class MyAdapter(
fragmentManager: FragmentManager,
lifecycle: Lifecycle
) : FragmentStateAdapter(fragmentManager, lifecycle) {
private val fragmentBuilders = mutableListOf<FragmentBuilder>()
fun add(fragmentBuilder: FragmentBuilder) {
fragmentBuilders.add(fragmentBuilder)
}
/**
* Dynamic replacement of fragments
*/
fun set(position: Int, fragmentBuilder: FragmentBuilder) {
fragmentBuilders[position] = fragmentBuilder
}
override fun getItemCount() = fragmentBuilders.size
override fun createFragment(position: Int) = fragmentBuilders[position].invoke()
}
连谢谢都不行)
使用标签的两个不同片段的简单示例。主要布局:
<?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:id="@+id/mainConstraintLayout"
android:layout_width="match_parent"
android:layout_height="match_parent">
<androidx.viewpager2.widget.ViewPager2
android:id="@+id/mainViewPager"
android:layout_width="match_parent"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/mainTabLayout">
</androidx.viewpager2.widget.ViewPager2>
<com.google.android.material.tabs.TabLayout
android:id="@+id/mainTabLayout"
android:layout_width="match_parent"
android:layout_height="@dimen/toolbar_height"
android:background="@color/brown_normal"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:tabIndicatorColor="@color/yellow_light"
app:tabIndicatorHeight="3dp"
app:tabSelectedTextColor="@color/yellow_light"
app:tabTextColor="@color/yellow_normal"
tools:ignore="SpeakableTextPresentCheck" />
</androidx.constraintlayout.widget.ConstraintLayout>
适配器:
public class MainToolsAdapter extends FragmentStateAdapter
{
// The quantity of tab is fixed
private static final int FRAGMENT_COUNT = 2;
// Titles for each tab
private final String[] titles = new String[FRAGMENT_COUNT];
public MainToolsAdapter(@NonNull FragmentManager fragmentManager, @NonNull Lifecycle lifecycle, Context context)
{
super(fragmentManager, lifecycle);
// Load titles for tab from resourses
titles[0] = context.getResources().getString(R.string.tab_1);
titles[1] = context.getResources().getString(R.string.tab_2);
}
@NonNull
@Override
public Fragment createFragment(int position)
{
// Create fragments according to position
if(position == 0)
{
return new FragmentTabOne();
}
return new FragmentTabTwo();
}
@Override
public int getItemCount()
{
return FRAGMENT_COUNT;
}
public String getItemTitle(int position)
{
if(position == 0)
{
return titles[0];
}
return titles[1];
}
}
主要活动 OnCreate:
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Create adapter for ViewPager
mainToolsAdapter = new MainToolsAdapter(getSupportFragmentManager(), getLifecycle(), this);
// Set adapter to the ViewPager
viewPager = findViewById(R.id.mainViewPager);
viewPager.setAdapter(mainToolsAdapter);
tabLayout = findViewById(R.id.mainTabLayout);
// Create the TabLayoutMediator to asociate ViewPager2 to TabLayout
TabLayoutMediator tabLayoutMediator = new TabLayoutMediator(tabLayout, viewPager, true, new TabLayoutMediator.TabConfigurationStrategy()
{
@Override
public void onConfigureTab(@NonNull TabLayout.Tab tab, int position)
{
// When a tab is created this is called, then we can set tab properties, in this case the text
tab.setText(mainToolsAdapter.getItemTitle(position));
}
});
// After configure we need to realice attach then Tab and ViewPager2 are asociated
tabLayoutMediator.attach();
}
毕业典礼:
plugins {
id 'com.android.application'
}
android {
compileSdk 30
defaultConfig {
applicationId "com.xxxx.yyyy"
minSdk 19
targetSdk 30
versionCode 1
versionName "1.0"
testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
}
dependencies
{
implementation fileTree(include: ['*.jar', '*.aar'], dir: 'libs')
implementation 'androidx.appcompat:appcompat:1.3.1'
implementation 'com.google.android.material:material:1.4.0'
implementation 'androidx.constraintlayout:constraintlayout:2.1.1'
testImplementation 'junit:junit:4.13.2'
androidTestImplementation 'androidx.test.ext:junit:1.1.3'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}
以防万一有人想监听ViewPager2.OnPageChangeCallback
事件:
private final ViewPager2.OnPageChangeCallback onPageChangeListener = new ViewPager2.OnPageChangeCallback() {
/**
* This method will be invoked when the current page is scrolled, either as part
* of a programmatically initiated smooth scroll or a user initiated touch scroll.
* @param position Position index of the first page currently being displayed.
* Page position+1 will be visible if positionOffset is nonzero.
* @param positionOffset Value from [0, 1) indicating the offset from the page at position.
* @param positionOffsetPixels Value in pixels indicating the offset from position.
*/
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
super.onPageScrolled(position, positionOffset, positionOffsetPixels);
}
/**
* This method will be invoked when a new page becomes selected.
* Animation is not necessarily complete.
* @param position Position index of the first page currently being displayed.
* Page position+1 will be visible if positionOffset is nonzero.
*/
@Override
public void onPageSelected (int position) {
super.onPageSelected(position);
if (position == 2) { // SomeFragment
Log.d(LOG_TAG, "ViewPager2.onPageSelected( " + position + " )");
SomePagerAdapter adapter = (SomePagerAdapter) viewpager.getAdapter();
if (adapter != null) {
SomeFragment fragment = (SomeFragment) adapter.getItem(position);
fragment.onLateInit();
}
}
}
};
适用于ViewPager2.registerOnPageChangeCallback()
:
viewpager.registerOnPageChangeCallback(this.onPageChangeListener);
FragmentStateAdapter
需要持有ArrayList<Fragment> mItems
, 以便可以访问提前构建的实例。SomeFragment
暴露方法public void onLateInit()
,因为@Override public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState)
可能无法使用(取决于Fragment
)。
public Fragment getItem(int position) {
return this.mItems.get(position);
}
与此类似,可以解决该问题,Fragment
例如,在人们能够正确初始化其视图之前很久就正在构建什么。与上一个中输入的数据Fragment
。对于大量Fragment
(...)来说,它可能不是最佳选择,但对于少数人来说,它工作得很好。