使用 ViewPager2 建立含有分頁的滑動檢視畫面

滑動檢視畫面可讓您透過橫向移動的手勢 (也就是左右「滑動」)，在同層級畫面 (如分頁) 之間導覽。這種導覽模式又稱為「橫向分頁」。本主題將說明如何建立方便切換分頁且包含滑動檢視畫面的版面，也將說明如何顯示不歸為分頁的標題列。

實作滑動檢視畫面

您可以使用 AndroidX 的 ViewPager2 小工具建立滑動檢視畫面。如要使用 ViewPager2 和分頁，需要在專案中的 ViewPager2 和 Material Design 元件新增依附元件。

如要透過 ViewPager2 設定版面配置，請將 <ViewPager2> 元素新增到您的 XML 版面配置中。例如，如果滑動檢視畫面中的每個頁面都要耗用整個版面配置，則版面配置應如下所示：

<androidx.viewpager2.widget.ViewPager2
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/pager"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

如要插入代表各個頁面的子檢視畫面，請將這個版面配置掛接到 FragmentStateAdapter。以下說明如何使用它來滑動 Fragment 物件集合：

Kotlin

class CollectionDemoFragment : Fragment() {
    // When requested, this adapter returns a DemoObjectFragment,
    // representing an object in the collection.
    private lateinit var demoCollectionAdapter: DemoCollectionAdapter
    private lateinit var viewPager: ViewPager2

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        return inflater.inflate(R.layout.collection_demo, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        demoCollectionAdapter = DemoCollectionAdapter(this)
        viewPager = view.findViewById(R.id.pager)
        viewPager.adapter = demoCollectionAdapter
    }
}

class DemoCollectionAdapter(fragment: Fragment) : FragmentStateAdapter(fragment) {

    override fun getItemCount(): Int = 100

    override fun createFragment(position: Int): Fragment {
        // Return a NEW fragment instance in createFragment(int)
        val fragment = DemoObjectFragment()
        fragment.arguments = Bundle().apply {
            // Our object is just an integer :-P
            putInt(ARG_OBJECT, position + 1)
        }
        return fragment
    }
}

private const val ARG_OBJECT = "object"

// Instances of this class are fragments representing a single
// object in our collection.
class DemoObjectFragment : Fragment() {

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View {
        return inflater.inflate(R.layout.fragment_collection_object, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        arguments?.takeIf { it.containsKey(ARG_OBJECT) }?.apply {
            val textView: TextView = view.findViewById(android.R.id.text1)
            textView.text = getInt(ARG_OBJECT).toString()
        }
    }
}

Java

public class CollectionDemoFragment extends Fragment {
    // When requested, this adapter returns a DemoObjectFragment,
    // representing an object in the collection.
    DemoCollectionAdapter demoCollectionAdapter;
    ViewPager2 viewPager;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container,
            @Nullable Bundle savedInstanceState) {
        return inflater.inflate(R.layout.collection_demo, container, false);
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        demoCollectionAdapter = new DemoCollectionAdapter(this);
        viewPager = view.findViewById(R.id.pager);
        viewPager.setAdapter(demoCollectionAdapter);
    }
}

public class DemoCollectionAdapter extends FragmentStateAdapter {
    public DemoCollectionAdapter(Fragment fragment) {
        super(fragment);
    }

    @NonNull
    @Override
    public Fragment createFragment(int position) {
        // Return a NEW fragment instance in createFragment(int)
        Fragment fragment = new DemoObjectFragment();
        Bundle args = new Bundle();
        // Our object is just an integer :-P
        args.putInt(DemoObjectFragment.ARG_OBJECT, position + 1);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public int getItemCount() {
        return 100;
    }
}

// Instances of this class are fragments representing a single
// object in our collection.
public class DemoObjectFragment extends Fragment {
    public static final String ARG_OBJECT = "object";

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container,
            @Nullable Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_collection_object, container, false);
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        Bundle args = getArguments();
        ((TextView) view.findViewById(android.R.id.text1))
                .setText(Integer.toString(args.getInt(ARG_OBJECT)));
    }
}

下列各節說明如何新增分頁，以便瀏覽頁面。

使用 TabLayout 新增分頁

TabLayout 可讓您以橫向排列的方式顯示分頁。與 ViewPager2 搭配使用時，TabLayout 可提供熟悉的介面，以便在滑動檢視畫面中瀏覽頁面。

圖 1：含有四個分頁的 TabLayout。

如要在 ViewPager2 中加入 TabLayout，請在 <ViewPager2> 元素上方加入 <TabLayout> 元素，如下所示：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <com.google.android.material.tabs.TabLayout
        android:id="@+id/tab_layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <androidx.viewpager2.widget.ViewPager2
        android:id="@+id/pager"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />

</LinearLayout>

接下來，請建立 TabLayoutMediator，將 TabLayout 連結至 ViewPager2，並依下列方式附加：

Kotlin

class CollectionDemoFragment : Fragment() {
    ...
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        val tabLayout = view.findViewById(R.id.tab_layout)
        TabLayoutMediator(tabLayout, viewPager) { tab, position ->
            tab.text = "OBJECT ${(position + 1)}"
        }.attach()
    }
    ...
}

Java

public class CollectionDemoFragment extends Fragment {
    ...
    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        TabLayout tabLayout = view.findViewById(R.id.tab_layout);
        new TabLayoutMediator(tabLayout, viewPager,
                (tab, position) -> tab.setText("OBJECT " + (position + 1))
        ).attach();
    }
    ...
}

如需分頁版面配置的其他設計指南，請參閱「分頁質感設計說明文件」。

其他資源

如要進一步瞭解 ViewPager2，請參閱下列其他資源：

範例

影片