java - Android 音乐播放器不播放选定的歌曲

Question

我正在尝试构建一个具有音乐播放功能的应用程序。当应用程序启动时，它会显示歌曲列表，当您单击它时，会显示歌曲名称，但不会播放歌曲。请问我该如何解决这个问题。这是我的 music.java 文件

public class Music extends ListActivity {

private static final int UPDATE_FREQUENCY = 500;
private static final int STEP_VALUE = 4000;

private MediaCursorAdapter mediaAdapter = null;
private TextView selelctedFile = null;
private SeekBar seekbar = null;
private MediaPlayer player = null;
private ImageButton playButton = null;
private ImageButton prevButton = null;
private ImageButton nextButton = null;
private ImageButton floatButton = null;
private ImageButton floatButton2 = null;

private boolean isStarted = true;
private String currentFile = "";
private boolean isMoveingSeekBar = false;

private final Handler handler = new Handler();

private final Runnable updatePositionRunnable = new Runnable() {
    public void run() {
        updatePosition();
    }
};


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


    LinearLayout ms = (LinearLayout) findViewById(R.id.music_search);
    ms.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent Ms = new Intent(Music.this, Google.class);
            startActivity(Ms);
        }
    });

    LinearLayout mr = (LinearLayout) findViewById(R.id.music_read);
    mr.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent Mr = new Intent(Music.this, Pdf.class);
            startActivity(Mr);
        }
    });


    selelctedFile = (TextView) findViewById(R.id.selectedfile);
    seekbar = (SeekBar) findViewById(R.id.seekbar);
    playButton = (ImageButton) findViewById(R.id.play);
    prevButton = (ImageButton) findViewById(R.id.prev);
    nextButton = (ImageButton) findViewById(R.id.next);

    player = new MediaPlayer();

    player.setOnCompletionListener(onCompletion);
    player.setOnErrorListener(onError);
    seekbar.setOnSeekBarChangeListener(seekBarChanged);

    Cursor cursor = getContentResolver().query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, null, null, null, null);

    if (null != cursor) {
        cursor.moveToFirst();

        mediaAdapter = new MediaCursorAdapter(this, R.layout.listitem, cursor);

        setListAdapter(mediaAdapter);

        playButton.setOnClickListener(onButtonClick);
        nextButton.setOnClickListener(onButtonClick);
        prevButton.setOnClickListener(onButtonClick);
    }

}

@Override
protected void onListItemClick(ListView list, View view, int position, long id) {
    super.onListItemClick(list, view, position, id);

    currentFile = (String) view.getTag();

    startPlay(currentFile);
}

@Override
protected void onDestroy() {
    super.onDestroy();

    handler.removeCallbacks(updatePositionRunnable);
    player.stop();
    player.reset();
    player.release();

    player = null;
}

private void startPlay(String file) {
    Log.i("Selected: ", file);

    selelctedFile.setText(file);
    seekbar.setProgress(0);

    player.stop();
    player.reset();

    try {
        player.setDataSource(file);
        player.prepare();
        player.start();
    } catch (IllegalArgumentException e) {
        e.printStackTrace();
    } catch (IllegalStateException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    seekbar.setMax(player.getDuration());
    playButton.setImageResource(android.R.drawable.ic_media_pause);

    updatePosition();

    isStarted = true;
}

private void stopPlay() {
    player.stop();
    player.reset();
    playButton.setImageResource(android.R.drawable.ic_media_play);
    handler.removeCallbacks(updatePositionRunnable);
    seekbar.setProgress(0);

    isStarted = false;
}

private void updatePosition() {
    handler.removeCallbacks(updatePositionRunnable);

    seekbar.setProgress(player.getCurrentPosition());

    handler.postDelayed(updatePositionRunnable, UPDATE_FREQUENCY);
}



private class MediaCursorAdapter extends SimpleCursorAdapter {

    public MediaCursorAdapter(Context context, int layout, Cursor c) {
        super(context, layout, c,
                new String[]{MediaStore.MediaColumns.DISPLAY_NAME, MediaStore.MediaColumns.TITLE, MediaStore.Audio.AudioColumns.DURATION},
                new int[]{R.id.displayname, R.id.title, R.id.duration});
    }

    @Override
    public void bindView(View view, Context context, Cursor cursor) {
        TextView title = (TextView) view.findViewById(R.id.title);
        TextView name = (TextView) view.findViewById(R.id.displayname);
        TextView duration = (TextView) view.findViewById(R.id.duration);

        name.setText(cursor.getString(
                cursor.getColumnIndex(MediaStore.MediaColumns.DISPLAY_NAME)));

        title.setText(cursor.getString(
                cursor.getColumnIndex(MediaStore.MediaColumns.TITLE)));

        long durationInMs = Long.parseLong(cursor.getString(
                cursor.getColumnIndex(MediaStore.Audio.AudioColumns.DURATION)));

        double durationInMin = ((double) durationInMs / 1000.0) / 60.0;

        durationInMin = new BigDecimal(Double.toString(durationInMin)).setScale(2, BigDecimal.ROUND_UP).doubleValue();

        duration.setText("" + durationInMin);

        view.setTag(cursor.getString(cursor.getColumnIndex(MediaStore.MediaColumns.DATA)));
    }

    @Override
    public View newView(Context context, Cursor cursor, ViewGroup parent) {
        LayoutInflater inflater = LayoutInflater.from(context);
        View v = inflater.inflate(R.layout.listitem, parent, false);

        bindView(v, context, cursor);

        return v;
    }
}

private View.OnClickListener onButtonClick = new View.OnClickListener() {

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.play: {
                if (player.isPlaying()) {
                    handler.removeCallbacks(updatePositionRunnable);
                    player.pause();
                    playButton.setImageResource(android.R.drawable.ic_media_play);
                } else {
                    if (isStarted) {
                        player.start();
                        playButton.setImageResource(android.R.drawable.ic_media_pause);

                        updatePosition();
                    } else {
                        startPlay(currentFile);
                    }
                }

                break;
            }
            case R.id.next: {
                int seekto = player.getCurrentPosition() + STEP_VALUE;

                if (seekto > player.getDuration())
                    seekto = player.getDuration();

                player.pause();
                player.seekTo(seekto);
                player.start();

                break;
            }
            case R.id.prev: {
                int seekto = player.getCurrentPosition() - STEP_VALUE;

                if (seekto < 0)
                    seekto = 0;

                player.pause();
                player.seekTo(seekto);
                player.start();

                break;
            }
        }
    }
};

private MediaPlayer.OnCompletionListener onCompletion = new MediaPlayer.OnCompletionListener() {

    @Override
    public void onCompletion(MediaPlayer mp) {
        stopPlay();
    }
};

private MediaPlayer.OnErrorListener onError = new MediaPlayer.OnErrorListener() {

    @Override
    public boolean onError(MediaPlayer mp, int what, int extra) {

        return false;
    }
};

private SeekBar.OnSeekBarChangeListener seekBarChanged = new SeekBar.OnSeekBarChangeListener() {
    @Override
    public void onStopTrackingTouch(SeekBar seekBar) {
        isMoveingSeekBar = false;
    }

    @Override
    public void onStartTrackingTouch(SeekBar seekBar) {
        isMoveingSeekBar = true;
    }

    @Override
    public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
        if (isMoveingSeekBar) {
            player.seekTo(progress);

            Log.i("OnSeekBarChangeListener", "onProgressChanged");
        }
    }
  };
}`

和我的 activity_music 文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.android.beez.study13.Music">



 <LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#ffffff">


    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="#0a0b0e"
        android:orientation="vertical"
        android:paddingBottom="@dimen/activity_vertical_margin"
        android:paddingLeft="@dimen/activity_horizontal_margin"
        android:paddingRight="@dimen/activity_horizontal_margin"
        android:paddingTop="@dimen/activity_vertical_margin"
        tools:context=".Music">

        <ListView
            android:id="@android:id/list"
            android:background="#f0fffdfd"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:textColor="@android:color/black"
            android:layout_weight="1.0" />

        <LinearLayout
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:backgroundTint="#f7262624"
            android:background="@android:drawable/screen_background_light"
            android:orientation="vertical"
            android:padding="10dip">

            <TextView
                android:id="@+id/selectedfile"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:ellipsize="middle"
                android:gravity="center_horizontal"
                android:singleLine="true"
                android:text="No file selected"
                android:textColor="@android:color/black" />

            <SeekBar
                android:id="@+id/seekbar"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:max="100"
                android:paddingBottom="10dip" />

            <LinearLayout
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
              android:background="@android:drawable/screen_background_light"
                android:gravity="center"
                android:backgroundTint="#ca030b03"
                android:orientation="horizontal">

                <ImageButton
                    android:id="@+id/prev"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:background="#000"
                    android:src="@android:drawable/ic_media_previous" />

                <ImageButton
                    android:id="@+id/play"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:src="@android:drawable/ic_media_play" />

                <ImageButton
                    android:id="@+id/next"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:background="#000"
                    android:src="@android:drawable/ic_media_next" />

            </LinearLayout>

         </LinearLayout>

        </LinearLayout>


       </LinearLayout>

     </LinearLayout>`

和我的 listitem.xml 文件

 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:orientation="vertical">

 <TextView
    android:id="@+id/displayname"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:ellipsize="end"
    android:singleLine="true"
    android:textSize="18dip"
    android:textStyle="bold" />

  <LinearLayout
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal">

    <TextView
        android:id="@+id/title"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1.0"
        android:ellipsize="end"
        android:singleLine="true"
        android:textSize="15dip" />

     <TextView
        android:id="@+id/duration"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:ellipsize="end"
        android:gravity="right"
        android:singleLine="true"
        android:textSize="15dip" />
  </LinearLayout>


</LinearLayout>`

Answer 1

假设您的媒体播放器出现故障，请使用 prepareAsync() 而不仅仅是 prepare()。您也可以尝试在您的媒体播放器上设置 onPrepareListener，如下所示:

mediaPlayer.setOnPreparedListener(new OnPreparedListener(){

    @Override
    public void onPrepared(MediaPlayer mp) {
        mediaPlayer.start();
    }
});

要了解为什么需要设置此监听器，请参阅 this link .

Here you can find the difference between prepare() and prepareAsync()

希望这有帮助:)