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Question

Cette ligne de code me donne des problèmes dans les studios android

if(musicSrv!=null && musicBound && musicSrv.isPng()) 

Le code est venu de ce tutoriel, j'ai trouvé: Music Player

la classe complète code est:

package com.tunein.bryantyoung.tunein; 

import android.app.Activity; 
import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import java.util.ArrayList; 
import java.util.Collections; 
import java.util.Comparator; 
import android.net.Uri; 
import android.content.ContentResolver; 
import android.database.Cursor; 
import android.widget.ListView; 
import android.os.IBinder; 
import android.content.ComponentName; 
import android.content.Context; 
import android.content.Intent; 
import android.content.ServiceConnection; 
import android.view.MenuItem; 
import android.view.View; 
import com.tunein.bryantyoung.tunein.MusicService.MusicBinder; 
import android.widget.MediaController.MediaPlayerControl; 

public class MainActivity extends Activity implements MediaPlayerControl { 
    private ArrayList<Song> songList; 
    private ListView songView; 
    private MusicController controller; 
    private MusicService musicSrv; 
    private Intent playIntent; 
    private boolean musicBound=false; 
    private boolean paused=false, playbackPaused=false; 

    /** 
    * Override methods 
    */ 
    @Override 
    public void start() { 
     musicSrv.go(); 
    } 

    @Override 
    public void pause() { 
     playbackPaused=true; 
     musicSrv.pausePlayer(); 
    } 

    @Override 
    public int getDuration() { 
     if(musicSrv!=null &amp;&amp; musicBound &amp;&amp; musicSrv.isPng()) 
      return musicSrv.getDur(); 
     else return 0; 
    } 

    @Override 
    public int getCurrentPosition() { 
     if(musicSrv!=null &amp;&amp; musicBound &amp;&amp; musicSrv.isPng()) 
     return musicSrv.getPosn(); 
     else return 0; 
    } 

    @Override 
    public void seekTo(int pos) { 
     musicSrv.seek(pos); 
    } 

    @Override 
    public boolean isPlaying() { 
     if(musicSrv!=null &amp;&amp; musicBound) 
      return musicSrv.isPng(); 
     return false; 
    } 

    @Override 
    public int getBufferPercentage() { 
     return 0; 
    } 

    @Override 
    public boolean canPause() { 
     return true; 
    } 

    @Override 
    public boolean canSeekBackward() { 
     return true; 
    } 

    @Override 
    public boolean canSeekForward() { 
     return true; 
    } 

    @Override 
    public int getAudioSessionId() { 
     return 0; 
    } 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     songView = (ListView)findViewById(R.id.song_list);//retrieves the list view using ID 
     songList = new ArrayList<Song>();//instantiates list view 
     getSongList(); 
     Collections.sort(songList, new Comparator<Song>() { 
      public int compare(Song a, Song b) { 
       return a.getTitle().compareTo(b.getTitle()); 
      } 
     }); 
     SongAdapter songAdt = new SongAdapter(this, songList); 
     songView.setAdapter(songAdt); 
     setController(); 
    } 

    @Override 
    protected void onStart() { 
     super.onStart(); 
     if(playIntent==null){ 
      playIntent = new Intent(this, MusicService.class); 
      bindService(playIntent, musicConnection, Context.BIND_AUTO_CREATE); 
      startService(playIntent); 
     } 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     //menu item selected 
     switch (item.getItemId()) { 
      case R.id.action_shuffle: 
       musicSrv.setShuffle(); 
       break; 
      case R.id.action_end: 
       stopService(playIntent); 
       musicSrv=null; 
       System.exit(0); 
       break; 
     } 
     return super.onOptionsItemSelected(item); 
    } 

    @Override 
    protected void onDestroy() { 
     stopService(playIntent); 
     musicSrv=null; 
     super.onDestroy(); 
    } 

    @Override 
    protected void onPause(){ 
     super.onPause(); 
     paused=true; 
    } 

    @Override 
    protected void onResume(){ 
     super.onResume(); 
     if(paused){ 
      setController(); 
      paused=false; 
     } 
    } 

    @Override 
    protected void onStop() { 
     controller.hide(); 
     super.onStop(); 
    } 


    /** 
    * Helpers 
    */ 

    //connect to the service 
    private ServiceConnection musicConnection = new ServiceConnection(){ 

     @Override 
     public void onServiceConnected(ComponentName name, IBinder service) { 
      MusicBinder binder = (MusicBinder)service; 
      //get service 
      musicSrv = binder.getService(); 
      //pass list 
      musicSrv.setList(songList); 
      musicBound = true; 
     } 

     @Override 
     public void onServiceDisconnected(ComponentName name) { 
      musicBound = false; 
     } 
    }; 

    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); 

     //Iterate over the results 
     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); 
       songList.add(new Song(thisId, thisTitle, thisArtist)); 
      } 
      while (musicCursor.moveToNext()); 
     } 
    } 

    public void songPicked(View view){ 
     musicSrv.setSong(Integer.parseInt(view.getTag().toString())); 
     musicSrv.playSong(); 
     if(playbackPaused){ 
      setController(); 
      playbackPaused=false; 
     } 
     controller.show(0); 
    } 

    private void setController(){ 
     //set the controller up 
     controller = new MusicController(this); 

     //Click listeners for next and Prev 
     controller.setPrevNextListeners(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       playNext(); 
      } 
     }, new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       playPrev(); 
      } 
     }); 

     controller.setMediaPlayer(this); 
     controller.setAnchorView(findViewById(R.id.song_list)); 
     controller.setEnabled(true); 
    } 

    //play next 
    private void playNext(){ 
     musicSrv.playNext(); 
     if(playbackPaused){ 
      setController(); 
      playbackPaused=false; 
     } 
     controller.show(0); 
    } 

    //play prev 
    private void playPrev(){ 
     musicSrv.playPrev(); 
     if(playbackPaused){ 
      setController(); 
      playbackPaused=false; 
     } 
     controller.show(0); 
    } 

} 

le code est l'activité principale d'un lecteur de musique app la ligne qui im ​​des problèmes avec est supposé être une déclaration conditionnelle mais je ne suis pas moi-même sûr comment cela fonctionne je n'ai pas fait des déclarations similaires avant.

Answer 1

Le & est un encode web pour le symbole &.

Votre code doit fonctionner si vous changez tous &-&, de sorte que le code sera comme:

musicSrv!=null && musicBound 

Au lieu de:

musicSrv!=null && musicBound 

Hope it helps!