歌曲在媒体播放器中同时播放。安卓工作室

Question

我在 android studio 中创建了一个音乐应用程序。我遇到的问题是，当我想在第一首歌曲的中间播放第二首歌曲时，它会在第一首歌曲的顶部播放。第一首歌没有停止播放。它会继续播放第二首选定的歌曲。

在应用程序中，我有两个活动 MainActivity.java 有歌曲列表，NowPlaying.java 播放歌曲。

两个java类的代码如下：

MainActivity.java

public class MainActivity extends AppCompatActivity {

String[] songList;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    populateList();
}


private void populateList() {
    songList = new String[]{"Jalma", "Demons", "Parelima", "Mero Balyakal Ko Sathi", "Audai Jadai",
            "Case 420", "Euta Sathi", "Cheerleader"};

    ListAdapter arrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1,
            songList);

    ListView theList = (ListView) findViewById(R.id.theList);
    theList.setAdapter(arrayAdapter);
    theList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            ListView theList = (ListView) findViewById(R.id.theList);

            String selectedSong = (String) (theList.getItemAtPosition(position));
            Intent toSecondActivity = new Intent(MainActivity.this, NowPlaying.class);
            toSecondActivity.putExtra("playSong", selectedSong);
            startActivity(toSecondActivity);
        }
    });


}

}

NowPlaying.java

public class NowPlaying extends AppCompatActivity {

MediaPlayer song;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_now_playing2);

    song = MediaPlayer.create(this, R.raw.demons);
    song.start();
    song.pause();

    selectSong();
    pauseButton();
    getSongList();
    getNextButton();
    getPreviousButton();

}

/**
 * Method for selecting the song
 * Moves to startSong method
 */
public void selectSong(){

    checkIfSongIsPlaying();
        String nextPlay = getIntent().getStringExtra("playSong");
    TextView lyricsBox = (TextView) findViewById(R.id.lyricsBox);
    lyricsBox.setMovementMethod(new ScrollingMovementMethod());

        if (nextPlay.equals("Demons")) {
            song = MediaPlayer.create(this, R.raw.demons);
            lyricsBox.setText(R.string.demonsLyrics);
        }
        else if(nextPlay.equals("Jalma")){
            song = MediaPlayer.create(this, R.raw.jalma);
            lyricsBox.setText(R.string.jalmaLyrics);
        }
        else if(nextPlay.equals("Parelima")){
            song = MediaPlayer.create(this, R.raw.parelima);
            lyricsBox.setText(R.string.parelimaLyrics);
        }

        else if (nextPlay.equals("Case 420")) {
            song = MediaPlayer.create(this, R.raw.case420);
            lyricsBox.setText(R.string.case420Lyrics);
        } else if (nextPlay.equals("Mero Balyakal Ko Sathi")) {
            song = MediaPlayer.create(this, R.raw.balyakalsathi);
            lyricsBox.setText(R.string.balyakalSathi);
        } else if (nextPlay.equals("Euta Sathi")) {
            song = MediaPlayer.create(this, R.raw.eutasathi);
            lyricsBox.setText(R.string.eutaSathi);

        } else if (nextPlay.equals("Audai Jadai")) {
            song = MediaPlayer.create(this, R.raw.audaijadai);
            lyricsBox.setText(R.string.audaijadaiLyrics);

        } else if (nextPlay.equals("Cheerleader")) {
            song = MediaPlayer.create(this, R.raw.cheerleader);
            lyricsBox.setText(R.string.cheerleaderLyrics);
        }
        playSong();

}

public void checkIfSongIsPlaying(){

    if(song !=null){
        song.pause();

    }
}

/**
 * Method to start song (play the song)
 *
 */
public void playSong(){
    song.start();
    getSongtitle();
    getSeekbar();
    onSongCompletion();

}

/**
 * Method for pause Button
 * to pause song once clicked and change button background to play image
 * Again play the song if the button is pressed again. and change background back to pause image
 */

public void pauseButton(){
    final Button playButton = (Button) findViewById(R.id.playButton);
    playButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (song.isPlaying()) {
                playButton.setBackgroundResource(R.drawable.playbutton);
                song.pause();
            } else {
                playButton.setBackgroundResource(R.drawable.pausebutton);
                song.start();
            }
        }
    });
}

/**
 * Method to get the song title from first java file and display in the title
 */
public void getSongtitle(){

    String nextPlay = getIntent().getStringExtra("playSong");
    TextView songTitle = (TextView) findViewById(R.id.songTitle);
    songTitle.setText(nextPlay);


}//end of getSongtitle method


/**
 * Method for song list button
 * Goes back to the first java file once the button is cliked,
 * displays the song list
 */
public void getSongList(){
    Button lyricsButton = (Button) findViewById(R.id.lyricsButton);
    lyricsButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            startActivity(new Intent(NowPlaying.this, MainActivity.class));
        }
    });
}



Runnable run = new Runnable() {
    @Override
    public void run() {
        getSeekbar();
    }
};


/**
 * Method to update the seekbar.
 * implement touch in seekbar to change song position
 */
        public void getSeekbar(){
            SeekBar seekBar = (SeekBar) findViewById(R.id.seekBar);
           seekBar.setMax(song.getDuration());
            seekBar.setProgress(song.getCurrentPosition());
            seekBar.postDelayed(run, 1000);
            TextView endTimer = (TextView) findViewById(R.id.endTimer);
            TextView startTimer = (TextView) findViewById(R.id.startTimer);

            double  finalTime = song.getDuration();
            double startTime = song.getCurrentPosition();
            double timeRemaining = finalTime - song.getCurrentPosition();
            startTimer.setText(String.format("%d:%d", TimeUnit.MILLISECONDS.toMinutes((long)startTime ), TimeUnit.MILLISECONDS.toSeconds((long) startTime) - TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes((long) startTime))));
            endTimer.setText(String.format("%d:%d", TimeUnit.MILLISECONDS.toMinutes((long) timeRemaining), TimeUnit.MILLISECONDS.toSeconds((long) timeRemaining) - TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes((long) timeRemaining))));

            seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {

                int seek_to;

                @Override
                public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
                    seek_to = progress;
                }

                @Override
                public void onStartTrackingTouch(SeekBar seekBar) {

                }

                @Override
                public void onStopTrackingTouch(SeekBar seekBar) {
                    song.seekTo(seek_to);
                }
            });
        }


/**
 * Lists the song list after song is completeted
 */
public void onSongCompletion(){

    song.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
        @Override
        public void onCompletion(MediaPlayer song) {
            song.reset();
            startActivity(new Intent(NowPlaying.this, MainActivity.class));

        }
    });
}



/**
 * Method for next button
 * the song skips every 10 seconds once clicked
 */

public void getNextButton(){

    Button nextButton = (Button) findViewById(R.id.nextButton);
    nextButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            int startTime = song.getCurrentPosition();
            int forwardTime = 10000;
            startTime += forwardTime;
            if (startTime <= song.getDuration()) {
                song.seekTo(startTime);
            } else {
                song.stop();

            }
        }
    });

} // end of getNextButton


/**
 * Method for previous button
 * the song skips back 10 seconds once clicked
 */
public void getPreviousButton(){
    Button previousButton = (Button) findViewById(R.id.previousButton);
    previousButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            int startTime = song.getCurrentPosition();
            int previousTime = 10000;
            startTime -= previousTime;

            if (startTime >= 0) {
                song.seekTo(startTime);
            } else {
                song.seekTo(0);
                song.start();

            }
        }
    });
} //end of getPreviousButton method

}

我想要的是，如果用户想要播放第二首歌曲，而正在播放第一首歌曲。要停止的第一首歌曲和要播放的第二首歌曲。然而，在应用程序中，歌词、搜索栏、时间会更新，但歌曲会同时播放（彼此叠加）。

Answer 1

你为什么不写 song.stop();而不是 song.pause();在 checkIfSongIsPlaying 上。你也可以写 song.reset();在更改歌曲之前进行确认。

让我知道这是否可行

Answer 2

• 发生这种情况是因为每次单击 listview 中的项目时都会创建 NowPlaying 的新对象（这会创建新的 MediaPlayer 对象）。为了克服这个问题，您可以将NowPlaying 设为单例类。

• 另外，看看你在onCreate 方法中调用的方法。在start 之后立即调用pause 方法没有意义。

示例：

MainActivity.java

....
....
 String selectedSong = (String) (theList.getItemAtPosition(position));
 // instead of intents use the advantage of singleton class.
 NowPlaying.getInstance(selectedSong);
....
....

NowPlaying.java

最好为此创建一个新的 java 文件，你可以使用 get 和 set 方法设置活动的值。

public class public class NowPlaying extends AppCompatActivity {
    NowPlaying nowplaying; 
    String selectedSong;
    MediaPlayer song;
    public static NowPlaying getInstance(String selectedSong){
        if(nowplaying == null){
             nowplaying = new NowPlaying();
        }
        this.selectedSong = selectedSong;
        return nowplaying;
    }

将这些函数分开。

        // these two methods are calling one after the other which won't allow the song to play completely.
        song.start();
        song.pause(); // keep this method in different method such as pause btn click listener.
        .....
        ... rest of code ...
        .....

   }

希望，这有帮助..！