我正在创建一个音乐播放器应用程序。我要从设备中获取歌曲列表，但是当我点击歌曲时，新活动正在打开，但歌曲并未播放，只是打开了活动而已
我多次检查已检查的代码，但未找到任何解决方案 如果我使用不同的方法来获取设备歌曲，则它可以工作，但该方法不能找到所有歌曲，而只能找到几首歌曲。
播放列表活动
public class PlayListActivity extends AppCompatActivity {
private static final int MY_PERMISSIONS_REQUEST_READ = 7;
private static final int REQUEST_PERMISSION = 5;
private static final int MY_PERMISSIONS_REQUEST_READ_MEDIA = 99;
public static ArrayList<TrackObjects> songsList;
private ListView songView;
ArrayList<HashMap<String, String>> songsListData = new ArrayList<HashMap<String, String>>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.playlist);
songView = (ListView) findViewById(R.id.songlist);
songsList = new ArrayList<TrackObjects>();
songView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int
position, long l) {
Intent i1 = new Intent(PlayListActivity.this, MainActivity.class);
i1.putExtra("pos", position);
i1.putExtra("songs", songsList);
startActivity(i1);
}
});
int permissionCheck = ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE);
Collections.sort(songsList, new Comparator<TrackObjects>() {
public int compare(TrackObjects a, TrackObjects b) {
return a.getTitle().compareTo(b.getTitle());
}
});
TracksAdapter songAdt = new TracksAdapter(PlayListActivity.this, songsList);
songView.setAdapter(songAdt);
if (permissionCheck != PackageManager.PERMISSION_GRANTED) {
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, MY_PERMISSIONS_REQUEST_READ_MEDIA);
} else {
getSongList();
}
}
public void getSongList() {
//retrieve song info
ContentResolver musicResolver = getContentResolver();
Uri musicUri = android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
Cursor musicCursor = musicResolver.query(musicUri, null, null, null, null);
if (musicCursor != null && musicCursor.moveToFirst()) {
//get columns
int titleColumn = musicCursor.getColumnIndex
(android.provider.MediaStore.Audio.Media.TITLE);
int idColumn = musicCursor.getColumnIndex
(android.provider.MediaStore.Audio.Media._ID);
int artistColumn = musicCursor.getColumnIndex
(android.provider.MediaStore.Audio.Media.ARTIST);
//add songs to list
do {
long thisId = musicCursor.getLong(idColumn);
String thisTitle = musicCursor.getString(titleColumn);
String thisArtist = musicCursor.getString(artistColumn);
songsList.add(new TrackObjects(thisId, thisTitle, thisArtist));
}
while (musicCursor.moveToNext());
}
}
@Override
public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
switch (requestCode) {
case MY_PERMISSIONS_REQUEST_READ_MEDIA:
if ((grantResults.length > 0) && (grantResults[0] == PackageManager.PERMISSION_GRANTED)) {
getSongList();
}
break;
default:
break;
}
}
}
MainActivity（歌曲演奏活动）：
public class MainActivity extends AppCompatActivity {
static MediaPlayer mp;
int position;
SeekBar sb;
ArrayList mySongs;
Thread updateSeekBar;
ImageButton pause, forward, reverse, next, previous;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
pause = (ImageButton) findViewById(R.id.pause);
forward = (ImageButton) findViewById(R.id.forward);
previous = (ImageButton) findViewById(R.id.previous);
next = (ImageButton) findViewById(R.id.next);
reverse = (ImageButton) findViewById(R.id.reverse);
sb = (SeekBar) findViewById(R.id.seekBar);
updateSeekBar = new Thread() {
@Override
public void run() {
int totalDuration = mp.getDuration();
int currentPosition = 0;
while (currentPosition < totalDuration) {
try {
sleep(500);
currentPosition = mp.getCurrentPosition();
sb.setProgress(currentPosition);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
};
if (mp != null) {
mp.stop();
mp.release();
}
Intent i = getIntent();
Bundle b = i.getExtras();
assert b != null;
mySongs = (ArrayList) b.getParcelableArrayList("songs");
position = b.getInt("pos",0);
Uri u = Uri.parse(mySongs.get(position).toString());
if (mp!=null) {
mp= (MediaPlayer) MediaPlayer.create(MainActivity.this, u);
mp.start();
sb.setMax(mp.getDuration());
updateSeekBar.start();
sb.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int i,
boolean b) {
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
mp.seekTo(seekBar.getProgress());
}
});
pause.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
sb.setMax(mp.getDuration());
if (mp.isPlaying()) {
pause.setBackgroundResource(R.mipmap.play_button);
mp.pause();
} else {
pause.setBackgroundResource(R.mipmap.pause);
mp.start();
}
}
});
forward.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
sb.setMax(mp.getDuration());
mp.seekTo(mp.getCurrentPosition() + 5000);
}
});
reverse.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
sb.setMax(mp.getDuration());
mp.seekTo(mp.getCurrentPosition() - 5000);
}
});
next.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mp.stop();
mp.release();
position = ((position + 1) % mySongs.size());
Uri u = Uri.parse(mySongs.get(position).toString());
mp = MediaPlayer.create(getApplicationContext(), u);
mp.start();
}
});
previous.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mp.stop();
mp.release();
position = ((position - 1) < 0) ? (mySongs.size() - 1) : (position - 1);
Uri u = Uri.parse(mySongs.get(
position).toString());//%mysongs so that it do not go to invalid position
mp = MediaPlayer.create(getApplicationContext(), u);
mp.start();
}
});
}
}
}
TracksAdapter（歌曲列表适配器）：
public class TracksAdapter extends BaseAdapter {
private ArrayList<TrackObjects> tracks;
private LayoutInflater trackInf;
public TracksAdapter(Context c, ArrayList<TrackObjects> theTracks) {
tracks = theTracks;
trackInf = LayoutInflater.from(c);
}
@Override
public int getCount() {
return tracks.size();
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
//map to song layout
@SuppressLint("ViewHolder") LinearLayout songLay = (LinearLayout) trackInf.inflate
(R.layout.songtracks, parent, false);
//get title and artist views
TextView trackView = (TextView) songLay.findViewById(R.id.track_title);
TextView artistView = (TextView) songLay.findViewById(R.id.track_artist);
//get song using position
TrackObjects currSong = tracks.get(position);
//get title and artist strings
trackView.setText(currSong.getTitle());
artistView.setText(currSong.getArtist());
//set position as tag
songLay.setTag(position);
return songLay;
}
@Override
public Object getItem(int position) {
return null;
}
@Override
public long getItemId(int position) {
return 0;
}
}
TrackObjects（对象类）：
public class TrackObjects implements Serializable {
private long id;
private String title;
private String artist;
public TrackObjects(long id, String title, String artist) {
this.id = id;
this.title = title;
this.artist = artist;
}
protected TrackObjects(Parcel in) {
id = in.readLong();
title = in.readString();
artist = in.readString();
}
public long getId() {
return id;
}
public String getTitle() {
return title;
}
public String getArtist() {
return artist;
}
{
}}
答案 0 :(得分：0)
问题是您没有将URL传递给MainActivity中的媒体播放器。您的代码如下：
mySongs = (ArrayList) b.getParcelableArrayList("songs");
position = b.getInt("pos",0);
Uri u = Uri.parse(mySongs.get(position).toString());
在这里
mySongs.get(position).toString();
它将从列表中返回TrackObjects，使用toString()将返回对象参考数据。因此，最终您不会将任何URL传递给媒体播放器。
解决方案：
在TrackObjects类中添加一个新的字符串变量，例如private String songUrl;，并在下一行而不是上一行
Uri u = Uri.parse(mySongs.get(position).getSongUrl());
希望它能解决您的问题。