构建详细信息视图

androidx.leanback 库提供的媒体浏览界面类包括用于显示有关媒体项的其他信息的类，例如说明或评论。它们还包括用于对该项采取措施的类，例如购买或播放其内容。

本指南讨论如何为媒体项详细信息创建演示者类，以及如何在用户选择媒体项时扩展DetailsSupportFragment 类以实现媒体项的详细信息视图。

注意：此处显示的实现示例使用其他活动来包含DetailsSupportFragment。但是，可以通过使用片段事务将BrowseSupportFragment 替换为同一活动中的DetailsSupportFragment 来避免创建第二个活动。有关使用片段事务的更多信息，请参阅创建片段。

构建详细信息演示者

在 Leanback UI 工具包提供的媒体浏览框架中，您使用演示者对象来控制屏幕上数据的显示，包括媒体项详细信息。为此，框架提供了AbstractDetailsDescriptionPresenter 类，它是媒体项详细信息演示者的几乎完整实现。您只需实现onBindDescription() 方法即可将视图字段绑定到您的数据对象，如下面的代码示例所示

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.");
    }
}

扩展详细信息片段

当使用DetailsSupportFragment 类显示媒体项详细信息时，扩展该类以提供其他内容，例如预览图像和媒体项的操作。您还可以提供其他内容，例如相关媒体项列表。

以下示例代码演示了如何使用上一节中显示的演示者类来添加正在查看的媒体项的预览图像和操作。此示例还显示了相关媒体项行的添加，该行出现在详细信息列表下方。

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);
    }
}

创建详细信息活动

像DetailsSupportFragment 这样的片段必须包含在活动中才能用于显示。为您的详细信息视图创建活动（与浏览活动分开）允许您使用Intent 调用您的详细信息视图。本节说明如何构建一个活动来包含您对媒体项详细信息视图的实现。

通过构建引用DetailsSupportFragment 实现的布局来创建详细信息活动

<!-- 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，创建一个活动类，该类使用上一代码示例中显示的布局

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，将此新活动添加到清单中。请记住，应用 Leanback 主题以确保用户界面与媒体浏览活动一致。

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

</application>

为点击的项目定义侦听器

在您实现DetailsSupportFragment后，修改您的主要媒体浏览视图，以便在用户点击媒体项目时跳转到详细信息视图。要启用此行为，请在BrowseSupportFragment中添加一个OnItemViewClickedListener对象，该对象会触发一个意图来启动项目详细信息活动。

以下示例演示了如何实现一个监听器，以便在用户在主要媒体浏览活动中点击媒体项目时启动详细信息视图。

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