选择要使用 MediaPlayer 播放的音乐文件
Posted
技术标签:
【中文标题】选择要使用 MediaPlayer 播放的音乐文件【英文标题】：Select a music file to play with MediaPlayer 【发布时间】：2013-06-07 04:42:59 【问题描述】：我是 android 编程新手，现在我的应用程序出现问题。我打算编写具有以下功能的 MediaPlayer 应用程序：使用意图从存储中选择一个文件，然后开始播放该文件。我使用“MediaPlayer.create(context, uri)”方法，但目前出现错误
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//openFile();
Button openFile = (Button) this.findViewById(R.id.ButtonOpen);
openFile.setOnClickListener(new OnClickListener()
@Override
public void onClick(View v)
Intent chooseFile;
Intent intent;
chooseFile = new Intent(Intent.ACTION_GET_CONTENT);
chooseFile.setType("file/*");
intent = Intent.createChooser(chooseFile, "Choose a file");
startActivityForResult(intent, ACTIVITY_CHOOSE_FILE);
Uri uri = intent.getData();
initViews(uri);
);
private void initViews(Uri uri)
mButtonPlayStop = (Button) findViewById(R.id.ButtonPlayStop);
mButtonPlayStop.setOnClickListener(new OnClickListener()
@Override
public void onClick(View v)
buttonClick();
);
mMediaPlayer = MediaPlayer.create(this, uri);
private void starPlayProgressUpdater()
mSeekBar.setProgress(mMediaPlayer.getCurrentPosition());
if (mMediaPlayer.isPlaying())
Runnable notification = new Runnable()
@Override
public void run()
starPlayProgressUpdater();
;
mHandler.postDelayed(notification, 1000);
else
mMediaPlayer.pause();
mButtonPlayStop.setText(getString(R.string.play_str));
mSeekBar.setProgress(0);
private void buttonClick()
if (mButtonPlayStop.getText() == getString(R.string.play_str))
mButtonPlayStop.setText(getString(R.string.pause_str));
try
mMediaPlayer.start();
starPlayProgressUpdater();
catch (IllegalStateException e)
mMediaPlayer.pause();
else
mButtonPlayStop.setText(getString(R.string.play_str));
mMediaPlayer.pause();
它会在“mMediaPlayer = MediaPlayer.create(this, uri);”中抛出 NullPointerException。 uri有问题。谁能给我指路？
感谢 Ilango j，我修改了代码，现在我可以选择并播放音乐文件。但我的期望是选择文件然后仅在单击播放/暂停按钮（带进度条）后播放，但我的 buttonClick 得到了新的 NullPointerException
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mContext = (Context) getApplicationContext();
Button openFile = (Button) this.findViewById(R.id.ButtonOpen);
openFile.setOnClickListener(new OnClickListener()
@Override
public void onClick(View v)
initView();
);
private void initView()
mButtonPlayStop = (Button) findViewById(R.id.ButtonPlayStop);
mButtonPlayStop.setOnClickListener(new OnClickListener()
@Override
public void onClick(View v)
buttonClick();
);
Intent intent = new Intent(Intent.ACTION_PICK, android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI);
startActivityForResult(intent, 10);
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)
if (requestCode == RESULT_OK && requestCode == 10)
Uri uri = data.getData();
mMediaPlayer = MediaPlayer.create(mContext, uri);
mSeekBar = (SeekBar) findViewById(R.id.SeekBar01);
mSeekBar.setMax(mMediaPlayer.getDuration());
mSeekBar.setOnTouchListener(new OnTouchListener()
@Override
public boolean onTouch(View v, MotionEvent event)
seekChange(v);
return false;
);
private void starPlayProgressUpdater()
mSeekBar.setProgress(mMediaPlayer.getCurrentPosition());
if (mMediaPlayer.isPlaying())
Runnable notification = new Runnable()
@Override
public void run()
starPlayProgressUpdater();
;
mHandler.postDelayed(notification, 1000);
else
mMediaPlayer.pause();
mButtonPlayStop.setText(getString(R.string.play_str));
mSeekBar.setProgress(0);
private void seekChange(View v)
if (mMediaPlayer.isPlaying())
SeekBar sb = (SeekBar) v;
mMediaPlayer.seekTo(sb.getProgress());
private void buttonClick()
if (mButtonPlayStop.getText().equals(getString(R.string.play_str)))
mButtonPlayStop.setText(getString(R.string.pause_str));
try
mMediaPlayer.start();
starPlayProgressUpdater();
catch (IllegalStateException e)
mMediaPlayer.pause();
else
mButtonPlayStop.setText(getString(R.string.play_str));
mMediaPlayer.pause();
你能给个建议吗？
【问题讨论】：
【参考方案1】：首先开始活动以从 sd 卡中获取 pic 媒体文件。替换以下代码
Button openFile = (Button) this.findViewById(R.id.ButtonOpen);
openFile.setOnClickListener(new OnClickListener()
@Override
public void onClick(View v)
Intent intent = new Intent(Intent.ACTION_PICK, android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI);
startActivityForResult(intent, 10);
);
然后在onActivityResult
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)
if(resultCode == RESULT_OK && requestCode == 10)
Uri uriSound=data.getData();
play(this, uriSound);
并调用以下方法创建媒体播放器并播放选定的音频文件。
private void play(Context context, Uri uri)
try
MediaPlayer mp = new MediaPlayer();
mp.setDataSource(context, uri);
mp.start();
catch (IllegalArgumentException e)
// TODO Auto-generated catch block
e.printStackTrace();
catch (SecurityException e)
// TODO Auto-generated catch block
e.printStackTrace();
catch (IllegalStateException e)
// TODO Auto-generated catch block
e.printStackTrace();
catch (IOException e)
// TODO Auto-generated catch block
e.printStackTrace();
【讨论】：
感谢您的指导，我根据您的评论修改了我的代码。但我的期望是“从存储中选择音乐文件，然后使用播放按钮开始/暂停解码”。现在我的 buttonClick 面临新错误 这里的错字...应该是... if(resultCode == RESULT_OK 如果我想选择多个文件怎么办，他们的多选对话框有什么方式吗？【参考方案2】：如果有人像我一样在这个问题上遇到困难，我对上面的答案做了一些修复，这个 sn-p 应该可以工作：
private final int SELECT_MUSIC = 1;
public void pickMusic()
Intent i = new Intent(Intent.ACTION_PICK, android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI);
startActivityForResult(i,SELECT_MUSIC);
public void onActivityResult(int requestCode, int resultCode, Intent data)
if (resultCode == RESULT_OK)
if (requestCode == SELECT_MUSIC)
Uri selectedMusicUri = data.getData();
if (selectedMusicUri != null)
String pathFromUri = getRealPathFromURI(this, selectedMusicUri);
MediaPlayer mp = new MediaPlayer();
try
mp.setDataSource(this, Uri.parse(pathFromUri));
mp.prepare();
mp.start();
catch (IOException e)
e.printStackTrace();
private String getRealPathFromURI(Context context, Uri contentUri)
String[] projection = MediaStore.Audio.Media.DATA ;
CursorLoader loader = new CursorLoader(context, contentUri, projection, null, null, null);
Cursor cursor = loader.loadInBackground();
int column_index = cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DATA);
cursor.moveToFirst();
return cursor.getString(column_index);
【讨论】：
【参考方案3】：看MediaPlayer的创建源码，是这样的：
public static MediaPlayer create(Context context, Uri uri, SurfaceHolder holder)
try
MediaPlayer mp = new MediaPlayer();
mp.setDataSource(context, uri);
if (holder != null)
mp.setDisplay(holder);
mp.prepare();
return mp;
catch (IOException ex)
Log.d(TAG, "create failed:", ex);
// fall through
catch (IllegalArgumentException ex)
Log.d(TAG, "create failed:", ex);
// fall through
catch (SecurityException ex)
Log.d(TAG, "create failed:", ex);
// fall through
return null;
因此，在您的情况下，错误可能是您传入参数的 URI 错误或格式错误，因此 create 方法返回 null。在创建 mediaPlayer 对象时检查 URI 是否正确。
我也看到了这一行：
if (mButtonPlayStop.getText() == getString(R.string.play_str))
不要使用== 来比较字符串的内容。请改用.equals()：
if (mButtonPlayStop.getText().equals(getString(R.string.play_str)))
【讨论】：
感谢您的评论，我知道了以上是关于选择要使用 MediaPlayer 播放的音乐文件的主要内容，如果未能解决你的问题，请参考以下文章
android 使用MediaPlayer播放音乐要添加的权限是啥？
MediaPlayer音乐播放器上一首下一首播放停止自动下一首进度条