使用 Leanback 传输控件

Leanback androidx 库中具有新的播放控件,可改善用户体验。对于视频应用,传输控件支持使用前/后控件进行视频拖动。拖动时,屏幕上会显示缩略图,以帮助用户浏览视频。

该库中包含抽象类和开箱即用的实现,可为开发者提供更精细的控制。使用预构建实现时,您无需编写大量代码即可快速构建功能丰富的应用。 如果需要进行更多自定义设置,您可以扩展该库的任何预构建组件。

控件和播放器

leanback 库将带有传输控件的界面与播放视频的播放器分开。这是通过两个组件来实现的:用于显示传输控件(也可能是视频)的播放支持 fragment 和用于封装媒体播放器的播放器适配器。

播放 Fragment

应用的界面 activity 应使用 PlaybackSupportFragmentVideoSupportFragment。两者都包含 Leanback 传输控件:

您可以自定义 fragment 的 ObjectAdapter 以增强界面。例如,使用 setAdapter() 来添加“相关视频”行。

PlayerAdapter

PlayerAdapter 是一个用于控制底层媒体播放器的抽象类。开发者可以选择预构建的 MediaPlayerAdapter 实现,也可以自行编写此类的实现。

将片段粘合在一起

您必须使用某种“控件粘合剂”将播放 fragment 连接到播放器。leanback 库提供两种粘合剂:

Leanback 传输控件粘合剂

如果您希望应用支持视频拖动,必须使用 PlaybackTransportControlGlue

您还需要指定一个“粘合主机”,用于将粘合剂绑定到播放 fragment,在界面中绘制传输控件并保持其状态,然后将传输控制事件传回给粘合剂。该主机必须与播放 Fragment 类型匹配。将 PlaybackSupportFragmentGlueHostPlaybackFragment 搭配使用,并将 VideoSupportFragmentGlueHostVideoFragment 搭配使用。

下图显示了 leanback 传输控件的各个部分如何组合在一起:

Leanback 传输控件粘合剂

将应用粘合在一起的代码应该位于定义界面的 PlaybackSupportFragmentVideoSupportFragment 内。

在以下示例中,应用构造了一个 PlaybackTransportControlGlue 实例(将其命名为 playerGlue),并将其 VideoSupportFragment 连接到新创建的 MediaPlayerAdapter。由于这是一个 VideoSupportFragment,设置代码会调用 setHost() 以将 VideoSupportFragmentGlueHost 附加到 playerGlue。该代码包含在扩展 VideoSupportFragment 的类中。

Kotlin

class MyVideoFragment : VideoSupportFragment() {

  fun onCreate(savedInstanceState: Bundle) {
      super.onCreate(savedInstanceState)
      val playerGlue = PlaybackTransportControlGlue(getActivity(),
          MediaPlayerAdapter(getActivity()))
      playerGlue.setHost(VideoSupportFragmentGlueHost(this))
      playerGlue.addPlayerCallback(object : PlaybackGlue.PlayerCallback() {
          override fun onPreparedStateChanged(glue: PlaybackGlue) {
              if (glue.isPrepared()) {
                  playerGlue.seekProvider = MySeekProvider()
                  playerGlue.play()
              }
          }
      })
      playerGlue.setSubtitle("Leanback artist")
      playerGlue.setTitle("Leanback team at work")
      val uriPath = "android.resource://com.example.android.leanback/raw/video"
      playerGlue.getPlayerAdapter().setDataSource(Uri.parse(uriPath))
  }
}

Java

public class MyVideoFragment extends VideoSupportFragment {

  @Override
  public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      final PlaybackTransportControlGlue<MediaPlayerAdapter> playerGlue =
              new PlaybackTransportControlGlue(getActivity(),
                      new MediaPlayerAdapter(getActivity()));
      playerGlue.setHost(new VideoSupportFragmentGlueHost(this));
      playerGlue.addPlayerCallback(new PlaybackGlue.PlayerCallback() {
          @Override
          public void onPreparedStateChanged(PlaybackGlue glue) {
              if (glue.isPrepared()) {
                  playerGlue.setSeekProvider(new MySeekProvider());
                  playerGlue.play();
              }
          }
      });
      playerGlue.setSubtitle("Leanback artist");
      playerGlue.setTitle("Leanback team at work");
      String uriPath = "android.resource://com.example.android.leanback/raw/video";
      playerGlue.getPlayerAdapter().setDataSource(Uri.parse(uriPath));
  }
}

请注意,设置代码还定义了 PlayerAdapter.Callback,用于处理来自媒体播放器的事件。

自定义界面粘合剂

您可以自定义 PlaybackBannerControlGluePlaybackTransportControlGlue 来更改 PlaybackControlsRow

自定义标题和描述

如需自定义播放控件顶部的标题和说明,请替换 onCreateRowPresenter()

Kotlin

override fun onCreateRowPresenter(): PlaybackRowPresenter {
    return super.onCreateRowPresenter().apply {
        (this as? PlaybackTransportRowPresenter)
                ?.setDescriptionPresenter(MyCustomDescriptionPresenter())
    }
}

Java

@Override
protected PlaybackRowPresenter onCreateRowPresenter() {
  PlaybackTransportRowPresenter presenter = (PlaybackTransportRowPresenter) super.onCreateRowPresenter();
  presenter.setDescriptionPresenter(new MyCustomDescriptionPresenter());
  return presenter;
}

添加控件

控件粘合剂显示 PlaybackControlsRow 中的操作控件。

PlaybackControlsRow 中的操作分为两组:主要操作和次要操作。主要操作组的控件显示在进度条上方,次要组的控件显示在进度条下方。最初,播放/暂停按钮只有一项主要操作,没有次要操作。

您可以通过替换 onCreatePrimaryActions()onCreateSecondaryActions() 向主要组和次要组添加操作。

Kotlin

private lateinit var repeatAction: PlaybackControlsRow.RepeatAction
private lateinit var pipAction: PlaybackControlsRow.PictureInPictureAction
private lateinit var thumbsUpAction: PlaybackControlsRow.ThumbsUpAction
private lateinit var thumbsDownAction: PlaybackControlsRow.ThumbsDownAction
private lateinit var skipPreviousAction: PlaybackControlsRow.SkipPreviousAction
private lateinit var skipNextAction: PlaybackControlsRow.SkipNextAction
private lateinit var fastForwardAction: PlaybackControlsRow.FastForwardAction
private lateinit var rewindAction: PlaybackControlsRow.RewindAction

override fun onCreatePrimaryActions(primaryActionsAdapter: ArrayObjectAdapter) {
    // Order matters, super.onCreatePrimaryActions() will create the play / pause action.
    // Will display as follows:
    // play/pause, previous, rewind, fast forward, next
    //   > /||      |<        <<        >>         >|
    super.onCreatePrimaryActions(primaryActionsAdapter)
    primaryActionsAdapter.apply {
        add(skipPreviousAction)
        add(rewindAction)
        add(fastForwardAction)
        add(skipNextAction)
    }
}

override fun onCreateSecondaryActions(adapter: ArrayObjectAdapter?) {
    super.onCreateSecondaryActions(adapter)
    adapter?.apply {
        add(thumbsDownAction)
        add(thumbsUpAction)
    }
}

Java

private PlaybackControlsRow.RepeatAction repeatAction;
private PlaybackControlsRow.PictureInPictureAction pipAction;
private PlaybackControlsRow.ThumbsUpAction thumbsUpAction;
private PlaybackControlsRow.ThumbsDownAction thumbsDownAction;
private PlaybackControlsRow.SkipPreviousAction skipPreviousAction;
private PlaybackControlsRow.SkipNextAction skipNextAction;
private PlaybackControlsRow.FastForwardAction fastForwardAction;
private PlaybackControlsRow.RewindAction rewindAction;

@Override
protected void onCreatePrimaryActions(ArrayObjectAdapter primaryActionsAdapter) {
    // Order matters, super.onCreatePrimaryActions() will create the play / pause action.
    // Will display as follows:
    // play/pause, previous, rewind, fast forward, next
    //   > /||      |<        <<        >>         >|
    super.onCreatePrimaryActions(primaryActionsAdapter);
    primaryActionsAdapter.add(skipPreviousAction);
    primaryActionsAdapter.add(rewindAction);
    primaryActionsAdapter.add(fastForwardAction);
    primaryActionsAdapter.add(skipNextAction);
}

@Override
protected void onCreateSecondaryActions(ArrayObjectAdapter adapter) {
    super.onCreateSecondaryActions(adapter);
    adapter.add(thumbsDownAction);
    adapter.add(thumbsUpAction);
}

您必须替换 onActionClicked() 才能处理新操作。

Kotlin

override fun onActionClicked(action: Action) {
    when(action) {
        rewindAction -> {
            // Handle Rewind
        }
        fastForwardAction -> {
            // Handle FastForward
        }
        thumbsDownAction -> {
            // Handle ThumbsDown
        }
        thumbsUpAction -> {
            // Handle ThumbsUp
        }
        else ->
            // The superclass handles play/pause and delegates next/previous actions to abstract methods,
            // so those two methods should be overridden rather than handling the actions here.
            super.onActionClicked(action)
    }
}

override fun next() {
    // Skip to next item in playlist.
}

override fun previous() {
    // Skip to previous item in playlist.
}

Java

@Override
public void onActionClicked(Action action) {
    if (action == rewindAction) {
        // Handle Rewind
    } else if (action == fastForwardAction ) {
        // Handle FastForward
    } else if (action == thumbsDownAction) {
        // Handle ThumbsDown
    } else if (action == thumbsUpAction) {
        // Handle ThumbsUp
    } else {
        // The superclass handles play/pause and delegates next/previous actions to abstract methods,
        // so those two methods should be overridden rather than handling the actions here.
        super.onActionClicked(action);
    }
}

@Override
public void next() {
    // Skip to next item in playlist.
}

@Override
public void previous() {
    // Skip to previous item in playlist.
}

在特殊情况下,您可能需要实现自己的 PlaybackTransportRowPresenter,以呈现自定义控件并使用 PlaybackSeekUi 响应跳转操作。

视频拖动

如果应用使用 VideoSupportFragment,并且您希望支持视频拖动。

拖动

您需要提供 PlaybackSeekDataProvider 的实现。该组件提供滚动时使用的视频缩略图。您必须通过扩展 PlaybackSeekDataProvider 来实现自己的提供程序。请参阅 Android TV GitHub 代码库中的 Android Leanback Showcase 示例应用中的示例。.