在ExoPlayer中旋转后从相同位置恢复播放

Question

我正在开发Udacity Nanodegree的烘焙应用程序。我有一个ExoPlayer片段的代码。我想从旋转设备时的相同位置恢复播放。我知道不会重新创建活动，因为我在清单中添加了android:configChanges="orientation|keyboardHidden"。现在，我不确定片段将如何应对方向变化。目前，视频从旋转开始就开始播放，即使按后退键也可以继续播放。

我如何： 1.从同一位置播放视频 2.如果我按了返回键，是否停止播放视频？

package com.example.android.bakingapp;

import android.content.Context;
import android.net.Uri;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;

import com.google.android.exoplayer2.ExoPlayerFactory;
import com.google.android.exoplayer2.SimpleExoPlayer;
import com.google.android.exoplayer2.source.ExtractorMediaSource;
import com.google.android.exoplayer2.source.MediaSource;
import com.google.android.exoplayer2.trackselection.AdaptiveTrackSelection;
import com.google.android.exoplayer2.trackselection.DefaultTrackSelector;
import com.google.android.exoplayer2.trackselection.TrackSelection;
import com.google.android.exoplayer2.ui.PlayerView;
import com.google.android.exoplayer2.upstream.DataSource;
import com.google.android.exoplayer2.upstream.DefaultBandwidthMeter;
import com.google.android.exoplayer2.upstream.DefaultDataSourceFactory;
import com.google.android.exoplayer2.util.Util;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;


/**
 * A simple {@link Fragment} subclass.
 * Activities that contain this fragment must implement the
 * {@link ExoPlayerFragment.OnFragmentInteractionListener} interface
 * to handle interaction events.
 * Use the {@link ExoPlayerFragment#newInstance} factory method to
 * create an instance of this fragment.
 */
public class ExoPlayerFragment extends Fragment {
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";
    long currentPosition;
    Bundle bundle;
    SimpleExoPlayer player;
    private String mParam1;
    private String mParam2;

    private PlayerView mPlayerView;
    private OnFragmentInteractionListener mListener;

    public ExoPlayerFragment() {
        // Required empty public constructor
    }

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment ExoPlayerFragment.
     */

    public static ExoPlayerFragment newInstance(String param1, String param2) {
        ExoPlayerFragment fragment = new ExoPlayerFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
        if (savedInstanceState != null) {
            DefaultBandwidthMeter bandwidthMeter = new DefaultBandwidthMeter();
            TrackSelection.Factory videoTrackSelectionFactory =
                    new AdaptiveTrackSelection.Factory(bandwidthMeter);
            DefaultTrackSelector trackSelector =
                    new DefaultTrackSelector(videoTrackSelectionFactory);


            player = ExoPlayerFactory.newSimpleInstance(getContext(), trackSelector);
            player.seekTo(savedInstanceState.getLong("currentPosition"));
        }
    }

    @Override
    public void onSaveInstanceState(@NonNull Bundle outState) {
        super.onSaveInstanceState(outState);
        currentPosition = player.getCurrentPosition();
        outState.putLong("currentPosition", currentPosition);
        Log.d("currentPosition", "onSaveInstanceState: " + currentPosition);
    }

    @Override
    public void onPause() {
        super.onPause();
        player.stop();
        if (Util.SDK_INT <= 23) {
            player.release();
            player = null;
        }
    }

    @Override
    public void onStop() {
        super.onStop();
        if (Util.SDK_INT > 23) {
            player.release();
            player = null;
        }
    }

    @Override
    public void onStart() {
        super.onStart();
        if (Util.SDK_INT > 23) {
            DefaultBandwidthMeter bandwidthMeter = new DefaultBandwidthMeter();
            TrackSelection.Factory videoTrackSelectionFactory =
                    new AdaptiveTrackSelection.Factory(bandwidthMeter);
            DefaultTrackSelector trackSelector =
                    new DefaultTrackSelector(videoTrackSelectionFactory);


            player = ExoPlayerFactory.newSimpleInstance(getContext(), trackSelector);

        }
    }

    @Override
    public void onResume() {
        super.onResume();
        if ((Util.SDK_INT <= 23 || player == null)) {
            DefaultBandwidthMeter bandwidthMeter = new DefaultBandwidthMeter();
            TrackSelection.Factory videoTrackSelectionFactory =
                    new AdaptiveTrackSelection.Factory(bandwidthMeter);
            DefaultTrackSelector trackSelector =
                    new DefaultTrackSelector(videoTrackSelectionFactory);


            player = ExoPlayerFactory.newSimpleInstance(getContext(), trackSelector);

        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_exo_player, container, false);
        mPlayerView = view.findViewById(R.id.video_view);

        DefaultBandwidthMeter bandwidthMeter = new DefaultBandwidthMeter();
        TrackSelection.Factory videoTrackSelectionFactory =
                new AdaptiveTrackSelection.Factory(bandwidthMeter);
        DefaultTrackSelector trackSelector =
                new DefaultTrackSelector(videoTrackSelectionFactory);


        player = ExoPlayerFactory.newSimpleInstance(getContext(), trackSelector);
        mPlayerView.setPlayer(player);
        DataSource.Factory mediaDataSourceFactory = new DefaultDataSourceFactory(getContext(),
                Util.getUserAgent(getContext(),
                        "BakingApp"),
                bandwidthMeter);

        String id = getArguments().getString("id");
        String url = "", videoURL = "";
        String shortDescriptionParameter = getArguments().getString("item");

        try {
            JSONArray jsonArray = new JSONArray(RecipeJson.jsonData);
            JSONObject jsonObject = jsonArray.getJSONObject(Integer.parseInt(id));
            JSONArray jsonArray1 = jsonObject.getJSONArray("steps");
            int index1;
            for (index1 = 0; index1 < jsonArray1.length(); index1++) {
                JSONObject jsonObject1 = jsonArray1.getJSONObject(index1);
                if (jsonObject1.getString("shortDescription").equals(shortDescriptionParameter)) {
                    videoURL = jsonObject1.getString("videoURL");
                    if (videoURL.equals("")) {
                        mPlayerView.setVisibility(View.GONE);
                        Toast.makeText(getContext(), "NO VIDEO", Toast.LENGTH_SHORT).show();
                    } else
                        url = videoURL;
                    break;
                }
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }

        if (!url.equals("")) {
            MediaSource mediaSource = new ExtractorMediaSource.Factory(mediaDataSourceFactory).createMediaSource(Uri.parse(url));
            player.prepare(mediaSource);
            player.setPlayWhenReady(true);

        }
        onButtonPressed(shortDescriptionParameter);

        return view;

    }


    public void onButtonPressed(String shortDescription) {
        if (mListener != null) {
            mListener.onFragmentInteraction(shortDescription);
        }
    }


    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        if (context instanceof OnFragmentInteractionListener) {
            mListener = (OnFragmentInteractionListener) context;
        } else {
            throw new RuntimeException(context.toString()
                    + " must implement OnChangeStepFragmentInteractionListener");
        }
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mListener = null;
    }


    /**
     * This interface must be implemented by activities that contain this
     * fragment to allow an interaction in this fragment to be communicated
     * to the activity and potentially other fragments contained in that
     * activity.
     * <p>
     * See the Android Training lesson <a href=
     * "http://developer.android.com/training/basics/fragments/communicating.html"
     * >Communicating with Other Fragments</a> for more information.
     */
    public interface OnFragmentInteractionListener {
        void onFragmentInteraction(String shortDescription);
    }

}

Answer 1

实际上很容易。

方法1：
在片段的ExoPlayer中创建onCreate的实例，并让该片段保留其实例。这样，您可以在设备方向更改时使播放器保持活动状态。在onCreateView中，将视图附加到播放器上，一切设置完成。

方法2： 在onCreateView上创建您的ExoPlayer。为了使其正常工作，您需要将currentWindowIndex和播放器position保存在片段的onSaveInstanceState中。为了使其正常工作，您必须在使用currentWindowIndex设置player.seekTo(currentWindowIndex, position)并从saveInstanceState Bundle中恢复位置之前，将代码更改为playWhenReady = true。您应该注意，在这种情况下，由于重新创建了播放器，因此播放中会出现间断。 （因此不推荐）