我开始了解ViewPager2并尝试实现它,但是没有找到合适的示例。
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。
recommend or find a book, tool, software library, tutorial or other off-site resource
请仔细阅读我所寻找的内容。
Answers:
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
样本代码
在下面使用 dependencies
implementation 'com.google.android.material:material:1.1.0-alpha08'
implementation 'androidx.viewpager2:viewpager2:1.0.0-beta02'
样本代码
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()
}
}
输出值
从文档
新的功能
API变更
FragmentStateAdapter
取代 FragmentStatePagerAdapter
RecyclerView.Adapter
取代 PagerAdapter
registerOnPageChangeCallback
取代 addPageChangeListener
样本代码
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()
来获取的Swipe事件ViewPager2
样本代码
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
myViewPager2.setOrientation()
样本代码
对于HORIZONTAL Orientation
使用
myViewPager2.setOrientation(ViewPager2.ORIENTATION_HORIZONTAL);
对于VERTICAL Orientation
使用
myViewPager2.setOrientation(ViewPager2.ORIENTATION_VERTICAL);
我们可以
notifyDataSetChanged
像在RecyclerView.Adapter
样本代码以添加新项目
btnAdd.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
arrayList.add("New ITEM ADDED");
MyAdapter.notifyDataSetChanged();
}
});
样本代码以删除新项目
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
扩展的类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();
}
}
现在在您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,请检查此
新的功能
setUserInputEnabled
,isUserInputEnabled
)API变更
ViewPager2
班级决赛Bug修复
FragmentStateAdapter
稳定性修复样本代码以禁用在viewpager2中滑动
myViewPager2.setUserInputEnabled(false);// SAMPLE CODE to disable swiping in viewpager2
myViewPager2.setUserInputEnabled(true);//SAMPLE CODE to enable swiping in viewpager2
新的功能
API变更
FragmentStateAdapter
现在需要一个Lifecycle
对象。添加了两个实用程序构造函数以从主机FragmentActivity
或主机Fragment获取它样本代码
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
引入与行为一致的行为RecyclerView
。MarginPageTransformer
引入以提供在页面之间创建空间的能力(页面插图之外)。CompositePageTransformer
引入以提供组合多个功能 PageTransformers
API变更
FragmentStateAdapter#getItem
方法重命名为FragmentStateAdapter#createFragment
-以前的方法名称在过去被证明是错误的来源。OFFSCREEN_PAGE_LIMIT_DEFAULT
值从0更改为-1。如果OFFSCREEN_PAGE_LIMIT_DEFAULTconstant
使用,则无需更改客户端代码。样本代码
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;
}
}
PagerTitleStrip
或 PagerTabStrip
与ViewPager2一起使用,或者还有替代方法?
实际上,现在有一个ViewPager2的官方样本仓库(在下面链接)
回购包含以下示例(引自以下回购自述文件)
样品
- 带视图的ViewPager2-显示如何将带视图的ViewPager2设置为页面
- 带片段的ViewPager2-显示如何将带片段的ViewPager2设置为页面
- 具有可变集合的ViewPager2(视图)-演示将ViewPager2和视图作为页面和页面适配器中的突变的用法
- 具有可变集合(片段)的ViewPager2-演示带有片段的ViewPager2作为页面的用法,以及页面适配器中的突变
- 具有TabLayout(视图)的ViewPager2-显示如何将具有Views的ViewPager2设置为页面,并将其链接到TabLayout
在Kotlin中带有片段的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
与ThirdFragment.kt
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:
在Android中使用ViewPager2
API变更
FragmentStateAdapter替换FragmentStatePagerAdapter
RecyclerView.Adapter替代PagerAdapter
registerOnPageChangeCallback替换addPageChangeListener
用简单的话来说,它们使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。它完全取决于RecyclerView.Adapter的膨胀布局。
这是示例gitHub回购链接
例:-
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:
这是我使用带有3个完整片段的TabLayout实现ViewPager2的操作:
布局包含ViewPager2
有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;
}
使用的依赖项:
implementation "androidx.viewpager2:viewpager2:1.0.0"
implementation 'com.google.android.material:material:1.1.0-alpha10'
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);
}
}
这里的布局:
<?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);
}
}
结果,现在我使用androidx.viewpager2.widget.ViewPager2
了自定义片段。
它的工作!!!
真好
PS另一种工具:
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);
createFragment
回调FragmentStateAdapter
(如方法所述)create
a Fragment
。而不是提供一个已经创建并且正在闲逛的游戏。通过使用您的方法,您会搞砸FragmentManager's
操作。
如何使用它解释得很清楚。让我给出有关ViewPager2的小但非常关键的技巧和细节,尤其是当它位于有关如何防止内存泄漏的片段中时
不要使用带有片段的构造函数,尤其是在使用时TabLayout
。
public FragmentStateAdapter(@NonNull Fragment fragment) {
this(fragment.getChildFragmentManager(), fragment.getLifecycle());
}
因为它有内存泄漏的风险,描述在这里
取而代之的是使用FragmentManager和LifeCycle。并且不要发送lifeCycle
fragment作为参数,请使用viewLifeCycleOwner
的生命周期,因为viewLifeCycleOwner表示fragment的生命周期view
。
class NavigableFragmentStateAdapter(
fragmentManager: FragmentManager,
lifecycle: Lifecycle
) : FragmentStateAdapter(fragmentManager, lifecycle) {
}
并在中设置适配器 onCreateView
viewPager.adapter =
NavigableFragmentStateAdapter(childFragmentManager, viewLifecycleOwner.lifecycle)
TabLayout
ViewPager2片段时,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
/programming/61779776/leak-canary-detects-memory-leaks-for-tablayout-with-viewpager2
片段中的ViewPager2在被导航组件Navigation替换它所在的片段后泄漏
TabLayoutMediator(tabLayout, viewPager2, tabConfigurationStrategy).detach()
viewPager2.adapter = null
onDestroyView
片段的内部方法
如果您希望将ViewPager的页面navHostFragment
与导航组件一起使用,以导航回子片段,则将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)
}
另外,如果您希望看到一些示例,如何将ViewPager2与导航组件,动态功能模块结合使用,并与BottomNavigationView结合使用,则可以查看此github存储库中的教程。
我首先创建了一个视图寻呼机,然后使用以下https://developer.android.com/training/animation/vp2-migration中给出的说明迁移到了视图寻呼机2。