此页面由 Cloud Translation API 翻译。

构建详情视图

androidx.leanback 库提供的媒体浏览界面类包含用于显示媒体项相关附加信息（例如说明）的类或评价。其中也包含用于对相应商品执行操作的类，例如购买该商品或播放其内容。

本指南介绍如何为媒体项目详情创建 Presenter 类，以及如何扩展 DetailsSupportFragment 类，用于实现详情视图。

注意：此处显示的实现示例使用一个额外的 activity 包含 DetailsSupportFragment。不过，您可以使用BrowseSupportFragmentDetailsSupportFragment fragment 事务。如需详细了解如何使用 fragment 事务，请参阅创建 fragment。

构建详情 Presenter

在 Leanback UI 工具包提供的媒体浏览框架中，您可以使用 Presenter 对象来控制数据（包括媒体项目详情）在屏幕上的显示。为此，框架提供 AbstractDetailsDescriptionPresenter 类，该类几乎是对媒体项的 Presenter 的完整实现。。您只需实现 onBindDescription() 方法将视图字段绑定到数据对象，如以下代码示例：

Kotlin

class DetailsDescriptionPresenter : AbstractDetailsDescriptionPresenter() {

    override fun onBindDescription(viewHolder: AbstractDetailsDescriptionPresenter.ViewHolder, itemData: Any) {
        val details = itemData as MyMediaItemDetails
        // In a production app, the itemData object contains the information
        // needed to display details for the media item:
        // viewHolder.title.text = details.shortTitle

        // Here we provide static data for testing purposes:
        viewHolder.apply {
            title.text = itemData.toString()
            subtitle.text = "2014   Drama   TV-14"
            body.text = ("Lorem ipsum dolor sit amet, consectetur "
                    + "adipisicing elit, sed do eiusmod tempor incididunt ut labore "
                    + " et dolore magna aliqua. Ut enim ad minim veniam, quis "
                    + "nostrud exercitation ullamco laboris nisi ut aliquip ex ea "
                    + "commodo consequat.")
        }
    }
}

Java

public class DetailsDescriptionPresenter
        extends AbstractDetailsDescriptionPresenter {

    @Override
    protected void onBindDescription(ViewHolder viewHolder, Object itemData) {
        MyMediaItemDetails details = (MyMediaItemDetails) itemData;
        // In a production app, the itemData object contains the information
        // needed to display details for the media item:
        // viewHolder.getTitle().setText(details.getShortTitle());

        // Here we provide static data for testing purposes:
        viewHolder.getTitle().setText(itemData.toString());
        viewHolder.getSubtitle().setText("2014   Drama   TV-14");
        viewHolder.getBody().setText("Lorem ipsum dolor sit amet, consectetur "
                + "adipisicing elit, sed do eiusmod tempor incididunt ut labore "
                + " et dolore magna aliqua. Ut enim ad minim veniam, quis "
                + "nostrud exercitation ullamco laboris nisi ut aliquip ex ea "
                + "commodo consequat.");
    }
}

扩展详情 Fragment

使用 DetailsSupportFragment 类用于显示媒体项目详情，请扩展该类以提供其他内容，例如预览媒体项的图片和操作您还可以提供其他内容，例如相关媒体项。

以下示例代码演示了如何使用为正在查看的媒体项添加预览图片和操作。本示例还会显示添加了相关媒体项行，该行显示在详情列表下方。

Kotlin

private const val TAG = "MediaItemDetailsFragment"

class MediaItemDetailsFragment : DetailsSupportFragment() {
    private lateinit var rowsAdapter: ArrayObjectAdapter

    override fun onCreate(savedInstanceState: Bundle?) {
        Log.i(TAG, "onCreate")
        super.onCreate(savedInstanceState)

        buildDetails()
    }

    private fun buildDetails() {
        val selector = ClassPresenterSelector().apply {
            // Attach your media item details presenter to the row presenter:
            FullWidthDetailsOverviewRowPresenter(DetailsDescriptionPresenter()).also {
                addClassPresenter(DetailsOverviewRow::class.java, it)
            }
            addClassPresenter(ListRow::class.java, ListRowPresenter())
        }
        rowsAdapter = ArrayObjectAdapter(selector)

        val res = activity.resources
        val detailsOverview = DetailsOverviewRow("Media Item Details").apply {

            // Add images and action buttons to the details view
            imageDrawable = res.getDrawable(R.drawable.jelly_beans)
            addAction(Action(1, "Buy $9.99"))
            addAction(Action(2, "Rent $2.99"))
        }
        rowsAdapter.add(detailsOverview)

        // Add a related items row
        val listRowAdapter = ArrayObjectAdapter(StringPresenter()).apply {
            add("Media Item 1")
            add("Media Item 2")
            add("Media Item 3")
        }
        val header = HeaderItem(0, "Related Items")
        rowsAdapter.add(ListRow(header, listRowAdapter))

        adapter = rowsAdapter
    }
}

Java

public class MediaItemDetailsFragment extends DetailsSupportFragment {
    private static final String TAG = "MediaItemDetailsFragment";
    private ArrayObjectAdapter rowsAdapter;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        Log.i(TAG, "onCreate");
        super.onCreate(savedInstanceState);

        buildDetails();
    }

    private void buildDetails() {
        ClassPresenterSelector selector = new ClassPresenterSelector();
        // Attach your media item details presenter to the row presenter:
        FullWidthDetailsOverviewRowPresenter rowPresenter =
            new FullWidthDetailsOverviewRowPresenter(
                new DetailsDescriptionPresenter());

        selector.addClassPresenter(DetailsOverviewRow.class, rowPresenter);
        selector.addClassPresenter(ListRow.class,
                new ListRowPresenter());
        rowsAdapter = new ArrayObjectAdapter(selector);

        Resources res = getActivity().getResources();
        DetailsOverviewRow detailsOverview = new DetailsOverviewRow(
                "Media Item Details");

        // Add images and action buttons to the details view
        detailsOverview.setImageDrawable(res.getDrawable(R.drawable.jelly_beans));
        detailsOverview.addAction(new Action(1, "Buy $9.99"));
        detailsOverview.addAction(new Action(2, "Rent $2.99"));
        rowsAdapter.add(detailsOverview);

        // Add a related items row
        ArrayObjectAdapter listRowAdapter = new ArrayObjectAdapter(
                new StringPresenter());
        listRowAdapter.add("Media Item 1");
        listRowAdapter.add("Media Item 2");
        listRowAdapter.add("Media Item 3");
        HeaderItem header = new HeaderItem(0, "Related Items", null);
        rowsAdapter.add(new ListRow(header, listRowAdapter));

        setAdapter(rowsAdapter);
    }
}

创建详情 Activity

必须包含 DetailsSupportFragment 等 fragment 以便在一个 activity 中用于显示。为您的详细信息创建 activity 视图（独立于浏览 activity）可让您使用 Intent。本次部分介绍了如何构建一个 Activity 来容纳您实现的详情视图，您的媒体项。

通过构建一个引用您的 DetailsSupportFragment：

<!-- file: res/layout/details.xml -->

<fragment xmlns:android="http://schemas.android.com/apk/res/android"
    android:name="com.example.android.mediabrowser.MediaItemDetailsFragment"
    android:id="@+id/details_fragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
/>

接下来，创建一个使用上一代码示例中所示布局的 activity 类：

Kotlin

class DetailsActivity : FragmentActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.details)
    }
}

Java

public class DetailsActivity extends FragmentActivity
{
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.details);
    }
}

最后，将这个新 activity 添加到清单中。请务必应用 Leanback 主题，以确保界面与媒体浏览 activity 一致。

<application>
  ...
  <activity android:name=".DetailsActivity"
    android:exported="true"
    android:theme="@style/Theme.Leanback"/>

</application>

为点击的项目定义监听器

实现 DetailsSupportFragment 后，修改您的主媒体浏览视图，以在用户点击媒体时切换到详情视图内容。要启用此行为，请将 OnItemViewClickedListener 对象添加到触发 intent 以启动项的 BrowseSupportFragment 活动详情

以下示例展示了如何实现一个监听器，以便在用户玩游戏时启动详情视图。点击主媒体浏览 activity 中的媒体项：

Kotlin

class BrowseMediaActivity : FragmentActivity() {
    ...
    override fun onCreate(savedInstanceState: Bundle?) {
        ...
        // Create the media item rows
        buildRowsAdapter()

        // Add a listener for selected items
        browseFragment.onItemViewClickedListener = OnItemViewClickedListener { _, item, _, _ ->
            println("Media Item clicked: ${item}")
            val intent = Intent(this@BrowseMediaActivity, DetailsActivity::class.java).apply {
                // Pass the item information
                extras.putLong("id", item.getId())
            }
            startActivity(intent)
        }
    }
}

Java

public class BrowseMediaActivity extends FragmentActivity {
    ...
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        ...
        // Create the media item rows
        buildRowsAdapter();

        // Add a listener for selected items
        browseFragment.OnItemViewClickedListener(
            new OnItemViewClickedListener() {
                @Override
                public void onItemClicked(Object item, Row row) {
                    System.out.println("Media Item clicked: " + item.toString());
                    Intent intent = new Intent(BrowseMediaActivity.this,
                            DetailsActivity.class);
                    // Pass the item information
                    intent.getExtras().putLong("id", item.getId());
                    startActivity(intent);
                }
            });
    }
}

提供卡片视图

使用传输控件