我想实施流式视频列表应用。我使用RecyclerView来显示我的列表项。项目类型包括4种类型：文章，状态，照片和视频。我们应该只关注视频类型。这是我的RecyclerView适配器代码：
public class FollowedPostAdapter extends RecyclerView.Adapter implements OnFollowTagCallback, OnLikeCallback {
private Context context;
private List<PostItem> newsFeedList;
public RecyclerView recyclerView;
public LinearLayoutManager linearLayoutManager;
private HashMap<Integer, DemoPlayer> playerList;
private int visibleThreshold = 5;
// private int previousTotal = 0;
private int visibleItemCount, firstVisibleItem, totalItemCount;
private boolean loading;
private OnRecyclerViewLoadMoreListener loadMoreListener;
private final String text_comment;
private final String mReadMoreHtml;
private long userId;
public FollowedPostAdapter(Context context, RecyclerView recyclerView, List<PostItem> newsFeedList) {
this.context = context;
playerList = new HashMap<>();
this.newsFeedList = newsFeedList;
this.recyclerView = recyclerView;
this.linearLayoutManager = (LinearLayoutManager) recyclerView.getLayoutManager();
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
RecyclerView.ViewHolder viewHolder;
if (viewType == Constants.VIEWTYPE_ARTICLE) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.post_followed_article_item, parent, false);
viewHolder = new ArticleViewHolder(view);
} else if (viewType == Constants.VIEWTYPE_STATUS) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.post_followed_status_item, parent, false);
viewHolder = new StatusViewHolder(view);
} else if (viewType == Constants.VIEWTYPE_PHOTO) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.post_followed_photo_item, parent, false);
viewHolder = new PhotoViewHolder(view);
} else if (viewType == Constants.VIEWTYPE_VIDEO) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.post_followed_video_item, parent, false);
viewHolder = new VideoViewHolder(view);
} else {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.progressbar_item, parent, false);
viewHolder = new ProgressBarViewHolder(view);
}
return viewHolder;
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
if (holder instanceof ArticleViewHolder) {
// code
} else if (holder instanceof StatusViewHolder) {
// code
} else if (holder instanceof PhotoViewHolder) {
// code
} else if (holder instanceof VideoViewHolder) {
PostItem item = newsFeedList.get(position);
VideoViewHolder mHolder = (VideoViewHolder) holder;
LinearLayout.LayoutParams lp = (LinearLayout.LayoutParams) mHolder.videoView.getLayoutParams();
lp.height = (int) (ScreenHelper.getScreenWidth((Activity) context) * Constants.POST_IMAGE_RATIO);
mHolder.videoView.setLayoutParams(lp);
mHolder.setup(item);
Picasso.with(context).load(item.imageCover).error(R.drawable.ic_user_avatar).placeholder(R.drawable.ic_user_avatar).into(mHolder.iv_avatar);
if (item.tags != null && item.tags.size() > 0) {
// get first tag as main tag
generateTagViews(mHolder.tag_flow_layout, item.tags.subList(0, 1), position);
mHolder.tag_flow_layout.setVisibility(View.VISIBLE);
mHolder.tag_flow_layout.setVisibility(View.VISIBLE);
// mHolder.indicator.setVisibility(View.VISIBLE);
} else {
mHolder.tag_flow_layout.setVisibility(View.GONE);
// mHolder.indicator.setVisibility(View.GONE);
}
if (item.time_created != null) {
mHolder.tv_time.setText(item.time_created);
//mHolder.indicator.setVisibility(View.VISIBLE);
mHolder.tv_time.setVisibility(View.VISIBLE);
} else {
//mHolder.indicator.setVisibility(View.GONE);
mHolder.tv_time.setVisibility(View.GONE);
}
if (item.description_short.isEmpty())
mHolder.tv_description.setVisibility(View.GONE);
else {
mHolder.tv_description.setText(item.description_short);
mHolder.tv_description.setVisibility(View.VISIBLE);
}
mHolder.btn_comment.setText(String.valueOf(item.count_comment));
mHolder.btn_like.setText(String.valueOf(item.count_like));
mHolder.btn_unlike.setText(String.valueOf(item.count_unlike));
mHolder.btn_share.setText(String.valueOf(item.count_share));
if (item.tags.size() != 0) {
int tagId = item.tags.get(0).tag_id;
setFollowButtonActive(mHolder.btn_follow, TagHelper.isTagFollowed(tagId));
} else
setFollowButtonActive(mHolder.btn_follow, false);
}
}
@Override
public void onViewRecycled(RecyclerView.ViewHolder holder) {
super.onViewRecycled(holder);
if (holder instanceof VideoViewHolder) {
DemoPlayer player = playerList.get(holder.getAdapterPosition());
if (player != null) {
player.release();
playerList.remove(holder.getAdapterPosition());
}
}
}
public void pauseAllPlayers() {
for (int i = 0; i <= newsFeedList.size(); i++) {
DemoPlayer player = playerList.get(i);
if (player != null) {
if (player.getPlayerControl().isPlaying())
player.getPlayerControl().pause();
RecyclerView.ViewHolder holder = recyclerView.findViewHolderForLayoutPosition(i);
if (holder != null && holder instanceof VideoViewHolder) {
((VideoViewHolder) holder).btn_play.setVisibility(View.VISIBLE);
}
}
}
}
public void refreshData() {
notifyDataSetChanged();
}
public class ArticleViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
//
}
public class StatusViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
// code
}
public class PhotoViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
// code
}
public class VideoViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener, SurfaceHolder.Callback, AudioCapabilitiesReceiver.Listener, DemoPlayer.Listener, DemoPlayer.CaptionListener, DemoPlayer.Id3MetadataListener {
@Bind(R.id.iv_avatar)
ImageView iv_avatar;
@Bind(R.id.tag_flow_layout)
FlowLayout tag_flow_layout;
@Bind(R.id.tv_time)
TextView tv_time;
@Bind(R.id.btn_follow)
FancyButton btn_follow;
@Bind(R.id.btn_comment)
FancyButton btn_comment;
@Bind(R.id.btn_like)
FancyButton btn_like;
@Bind(R.id.btn_unlike)
FancyButton btn_unlike;
@Bind(R.id.btn_share)
FancyButton btn_share;
@Bind(R.id.root)
FrameLayout videoView;
@Bind(R.id.btn_play)
ImageView btn_play;
@Bind(R.id.tv_description)
TextView tv_description;
// player's variable
private EventLogger eventLogger;
// private VideoControllerView mediaController;
private View shutterView;
private AspectRatioFrameLayout videoFrame;
private SurfaceView surfaceView;
private SubtitleLayout subtitleLayout;
private DemoPlayer player;
private boolean playerNeedsPrepare;
private long playerPosition = 0;
private Uri contentUri;
private int contentType;
private String contentId;
public static final int TYPE_DASH = 0;
public static final int TYPE_SS = 1;
public static final int TYPE_HLS = 2;
public static final int TYPE_OTHER = 3;
private static final String EXT_DASH = ".mpd";
private static final String EXT_SS = ".ism";
private static final String EXT_HLS = ".m3u8";
private AudioCapabilitiesReceiver audioCapabilitiesReceiver;
public VideoViewHolder(View view) {
super(view);
ButterKnife.bind(this, view);
iv_avatar.setOnClickListener(this);
btn_follow.setOnClickListener(this);
btn_comment.setOnClickListener(this);
btn_like.setOnClickListener(this);
btn_unlike.setOnClickListener(this);
btn_share.setOnClickListener(this);
// player's setup
View root = view.findViewById(R.id.root);
root.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
doPlayResume();
}
});
// root.setOnTouchListener(new View.OnTouchListener() {
// @Override
// public boolean onTouch(View view, MotionEvent motionEvent) {
// if (motionEvent.getAction() == MotionEvent.ACTION_DOWN) {
// toggleControlsVisibility();
// } else if (motionEvent.getAction() == MotionEvent.ACTION_UP) {
// view.performClick();
// }
// return true;
// }
// });
// root.setOnKeyListener(new View.OnKeyListener() {
// @Override
// public boolean onKey(View v, int keyCode, KeyEvent event) {
// if (keyCode == KeyEvent.KEYCODE_BACK || keyCode == KeyEvent.KEYCODE_ESCAPE
// || keyCode == KeyEvent.KEYCODE_MENU) {
// return false;
// }
// return mediaController.dispatchKeyEvent(event);
// }
// });
shutterView = view.findViewById(R.id.shutter);
videoFrame = (AspectRatioFrameLayout) view.findViewById(R.id.video_frame);
surfaceView = (SurfaceView) view.findViewById(R.id.surface_view);
surfaceView.getHolder().addCallback(this);
subtitleLayout = (SubtitleLayout) view.findViewById(R.id.subtitles);
// mediaController = new VideoControllerView(context);
// mediaController.setAnchorView((ViewGroup) root);
audioCapabilitiesReceiver = new AudioCapabilitiesReceiver(context, this);
audioCapabilitiesReceiver.register();
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.iv_avatar:
viewTagDetail(getAdapterPosition());
break;
case R.id.btn_follow:
followTag((FancyButton) v, getAdapterPosition());
break;
case R.id.btn_comment:
commentPost(getAdapterPosition());
break;
case R.id.btn_like:
likePost(getAdapterPosition(), btn_like, btn_unlike);
break;
case R.id.btn_unlike:
unlikePost(getAdapterPosition(), btn_like, btn_unlike);
break;
case R.id.btn_share:
sharePost(getAdapterPosition());
break;
case R.id.btn_play:
doPlayResume();
break;
}
}
public void setup(PostItem item) {
releasePlayer();
player = playerList.get(getAdapterPosition());
contentUri = Uri.parse(item.link);
contentType = TYPE_OTHER;
contentId = String.valueOf(item.post_id);
configureSubtitleView();
if (player == null) {
preparePlayer(false);
} else {
player.setBackgrounded(false);
}
}
// public void saveCurrentPosition() {
// if (player != null)
// videoItemList.get(getAdapterPosition()).position = player.getCurrentPosition();
// }
public void doPlayResume() {
if (player == null) {
return;
}
if (player.getPlayerControl().isPlaying()) {
player.getPlayerControl().pause();
} else {
player.getPlayerControl().start();
}
showControls();
}
@Override
public void onAudioCapabilitiesChanged(AudioCapabilities audioCapabilities) {
if (player == null) {
return;
}
boolean backgrounded = player.getBackgrounded();
boolean playWhenReady = player.getPlayWhenReady();
releasePlayer();
preparePlayer(playWhenReady);
player.setBackgrounded(backgrounded);
}
private DemoPlayer.RendererBuilder getRendererBuilder() {
String userAgent = Util.getUserAgent(context, "ExoPlayerDemo");
switch (contentType) {
case TYPE_SS:
return new SmoothStreamingRendererBuilder(context, userAgent, contentUri.toString(),
new SmoothStreamingTestMediaDrmCallback());
case TYPE_DASH:
return new DashRendererBuilder(context, userAgent, contentUri.toString(),
new WidevineTestMediaDrmCallback(contentId));
case TYPE_HLS:
return new HlsRendererBuilder(context, userAgent, contentUri.toString());
case TYPE_OTHER:
return new ExtractorRendererBuilder(context, userAgent, contentUri);
default:
throw new IllegalStateException("Unsupported type: " + contentType);
}
}
private void preparePlayer(boolean playWhenReady) {
if (player == null) {
player = new DemoPlayer(getRendererBuilder());
playerList.put(getAdapterPosition(), player);
player.addListener(this);
player.setCaptionListener(this);
player.setMetadataListener(this);
player.seekTo(playerPosition);
playerNeedsPrepare = true;
// mediaController.setMediaPlayer(player.getPlayerControl());
// mediaController.setEnabled(true);
eventLogger = new EventLogger();
eventLogger.startSession();
player.addListener(eventLogger);
player.setInfoListener(eventLogger);
player.setInternalErrorListener(eventLogger);
}
if (playerNeedsPrepare) {
player.prepare();
playerNeedsPrepare = false;
}
player.setSurface(surfaceView.getHolder().getSurface());
player.setPlayWhenReady(playWhenReady);
}
private void releasePlayer() {
if (player != null) {
player.release();
player = null;
eventLogger.endSession();
eventLogger = null;
btn_play.setVisibility(View.VISIBLE);
}
}
@Override
public void onStateChanged(boolean playWhenReady, int playbackState) {
if (playbackState == ExoPlayer.STATE_ENDED) {
showControls();
}
}
@Override
public void onError(Exception e) {
if (e instanceof UnsupportedDrmException) {
// Special case DRM failures.
UnsupportedDrmException unsupportedDrmException = (UnsupportedDrmException) e;
int stringId = Util.SDK_INT < 18 ? R.string.drm_error_not_supported
: unsupportedDrmException.reason == UnsupportedDrmException.REASON_UNSUPPORTED_SCHEME
? R.string.drm_error_unsupported_scheme : R.string.drm_error_unknown;
Toast.makeText(context, stringId, Toast.LENGTH_LONG).show();
}
playerNeedsPrepare = true;
showControls();
}
@Override
public void onVideoSizeChanged(int width, int height, int unappliedRotationDegrees, float pixelWidthHeightRatio) {
shutterView.setVisibility(View.GONE);
videoFrame.setAspectRatio(
height == 0 ? 1 : (width * pixelWidthHeightRatio) / height);
}
private boolean haveTracks(int type) {
return player != null && player.getTrackCount(type) > 0;
}
// private void toggleControlsVisibility() {
// if (mediaController.isShowing()) {
// mediaController.hide();
// } else {
// showControls();
// }
// }
private void showControls() {
// mediaController.show(5000);
if (player.getPlayerControl().isPlaying())
btn_play.setVisibility(View.GONE);
else
btn_play.setVisibility(View.VISIBLE);
}
@Override
public void onCues(List<Cue> cues) {
subtitleLayout.setCues(cues);
}
@Override
public void onId3Metadata(Map<String, Object> metadata) {
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
if (player != null) {
player.setSurface(holder.getSurface());
}
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
if (player != null) {
holder.lockCanvas();
player.blockingClearSurface();
}
}
private void configureSubtitleView() {
CaptionStyleCompat style;
float fontScale;
if (Util.SDK_INT >= 19) {
style = getUserCaptionStyleV19();
fontScale = getUserCaptionFontScaleV19();
} else {
style = CaptionStyleCompat.DEFAULT;
fontScale = 1.0f;
}
subtitleLayout.setStyle(style);
subtitleLayout.setFractionalTextSize(SubtitleLayout.DEFAULT_TEXT_SIZE_FRACTION * fontScale);
}
@TargetApi(19)
private float getUserCaptionFontScaleV19() {
CaptioningManager captioningManager =
(CaptioningManager) context.getSystemService(Context.CAPTIONING_SERVICE);
return captioningManager.getFontScale();
}
@TargetApi(19)
private CaptionStyleCompat getUserCaptionStyleV19() {
CaptioningManager captioningManager =
(CaptioningManager) context.getSystemService(Context.CAPTIONING_SERVICE);
return CaptionStyleCompat.createFromCaptionStyle(captioningManager.getUserStyle());
}
private int inferContentType(Uri uri, String fileExtension) {
String lastPathSegment = !TextUtils.isEmpty(fileExtension) ? "." + fileExtension
: uri.getLastPathSegment();
if (lastPathSegment == null) {
return TYPE_OTHER;
} else if (lastPathSegment.endsWith(EXT_DASH)) {
return TYPE_DASH;
} else if (lastPathSegment.endsWith(EXT_SS)) {
return TYPE_SS;
} else if (lastPathSegment.endsWith(EXT_HLS)) {
return TYPE_HLS;
} else {
return TYPE_OTHER;
}
}
}
public class ProgressBarViewHolder extends RecyclerView.ViewHolder {
public ProgressBarViewHolder(View view) {
super(view);
}
}
public void unregisterEventBus() {
EventBus.getDefault().unregister(this);
}
}
当项目类型为视频时，我会创建一个ExoPlayer实例来播放此视频，并将此实例添加到HashMap以供日后使用（键值为项目＆＃39; s位置）。如果视频项目正在回收，我会释放播放器并将其从HashMap中删除。
一切看起来都不错但是有问题。我想视频项目位于0位置（现在我们可以看到此项目中的视频预览）。我向下滚动RecyclerView就足以隐藏项目0.此时，项目0的VideoViewHolder尚未回收。然后，我向上滚动以显示项目0.视图现在是空白的，不显示视频预览。我点击第0项播放视频，播放器只播放音频（声音），不播放视频。播放几秒钟后，视频现在可见。
我进行了调试，发现在向下滚动隐藏视频项后，SurfaceView被销毁。向上滚动以显示视频项目时，会创建SurfaceView。我认为这就是VideoViewHolder显示空白视图而不是视频预览的原因。
以下是我的问题：滚动回视频项后如何显示视频预览？
答案 0 :(得分：1)
以下是ExoPlayer documentation
的说明在Android N之前，SurfaceView渲染未与视图动画正确同步。在早期版本中，当SurfaceView放入滚动容器或受到动画影响时，这可能会导致不必要的效果。这些效果包括SurfaceView的内容似乎略微落后于应该显示的位置，并且视图在受到动画时变为黑色。
要在Android N之前实现流畅的动画或视频滚动，因此必须使用TextureView 而不是SurfaceView。如果不需要平滑动画或滚动，则首选SurfaceView
要启用TextureView surface_type，您必须在xml文件中设置它，如下所示
<com.google.android.exoplayer2.ui.SimpleExoPlayerView
android:id="@+id/playerView"
android:layout_width="match_parent"
android:layout_height="200dp"
app:surface_type="texture_view"/>