Exoplayer 2.17.1 无法解析符号 ExoPlayerFacory、ExtractorMediaSource、ExoPlayerView

Question

我是Android开发人员的新手，我正在尝试制作一个应用程序。我想显示一个视频列表，玩家应该能够播放他们想要的任何视频。我在教程中发现，埃法赛者是这样做的唯一方法。

我在Gradle中添加了以下依赖项：

import android.net.Uri;
import android.os.Bundle;
import android.util.Log;
import androidx.appcompat.app.AppCompatActivity;
import com.google.android.exoplayer2.ExoPlayerFactory;
import com.google.android.exoplayer2.SimpleExoPlayer;
import com.google.android.exoplayer2.extractor.DefaultExtractorsFactory;
import com.google.android.exoplayer2.extractor.ExtractorsFactory;
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.TrackSelector;
import com.google.android.exoplayer2.ui.SimpleExoPlayerView;
import com.google.android.exoplayer2.upstream.BandwidthMeter;
import com.google.android.exoplayer2.upstream.DefaultBandwidthMeter;
import com.google.android.exoplayer2.upstream.DefaultHttpDataSourceFactory;

public class MainVideo extends AppCompatActivity {

    SimpleExoPlayerView exoPlayerView;
    SimpleExoPlayer exoPlayer;
    String videoURL = "https://media.geeksforgeeks.org/wp-content/uploads/20201217163353/Screenrecorder-2020-12-17-16-32-03-350.mp4";
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        exoPlayerView = findViewById(R.id.idExoPlayerVIew);
        try {
    
            BandwidthMeter bandwidthMeter = new DefaultBandwidthMeter();
    
            TrackSelector trackSelector = new DefaultTrackSelector(new AdaptiveTrackSelection.Factory(bandwidthMeter));
            exoPlayer = ExoPlayerFactory.newSimpleInstance(this, trackSelector);
            Uri videouri = Uri.parse(videoURL);
            DefaultHttpDataSourceFactory dataSourceFactory = new DefaultHttpDataSourceFactory("exoplayer_video");
            ExtractorsFactory extractorsFactory = new DefaultExtractorsFactory();
            MediaSource mediaSource = new ExtractorMediaSource(videouri, dataSourceFactory, extractorsFactory, null, null);
            exoPlayerView.setPlayer(exoPlayer);
            exoPlayer.prepare(mediaSource);
            exoPlayer.setPlayWhenReady(true);
    
        } catch (Exception e) {
            Log.e("TAG", "Error : " + e.toString());
        }
    }

}

I am getting cannot resolve symbol with simple exoplayerview, defaulthttpdataourcefactory< /code>，exoplayerFactory，extractormediasource，simple exoplayerview等...