MediaPlayer的状态变化监听器

Question

在这个图表中有很多states：

但是使用标准监听器，我只能监听一些基本状态。那么有可能监听MediaPlayer的所有状态变化吗？

- neworld

Answer 1

不幸的是，我发现除了将MediaPlayer与自定义状态机容器包围外，没有其他方法能够实现这一点。

补充 ...

您可以创建一个容器，它是单例的并且定义了自己的状态。所有与MediaPlayer的交互都通过此容器完成。所有其他类都需要访问容器的API。

下面是一个简单的概述：

public class MyContainer implements OnBufferingUpdateListener, 
                                            OnCompletionListener, 
                                            OnErrorListener,  
                                            OnInfoListener, 
                                            OnPreparedListener 
{
    static enum MP_STATES
    {
        MPS_IDLE,
        MPS_INITIALIZED,
        MPS_PREPARING,
        MPS_PREPARED,
        MPS_STARTED,
        MPS_STOPPED,
        MPS_PAUSED,
        MPS_PLAYBACK_COMPLETED,
        MPS_ERROR,
        MPS_END,
    }

    private static MyContainer s_mpm = null;
    private MP_STATES m_eState;
    private MediaPlayer m_mp;

    public static MyContainer get()
    {
        if (null == s_mpm)
        {
            s_mpm = new MyContainer();          
        }
        return s_mpm;
    }

    private MyContainer()
    {       
        m_mp = new MediaPlayer();
        m_mp.setOnBufferingUpdateListener(this);
        m_mp.setOnCompletionListener(this);
        m_mp.setOnErrorListener(this);
        m_mp.setOnInfoListener(this);
        m_mp.setOnPreparedListener(this);

        m_eState = MP_STATES.MPS_IDLE;
    }

    public MP_STATES getState()
    {
        return m_eState;
    }

    public void setUrl(String szUrl)
    {
        bringToIdleState();

        try {
            m_mp.setDataSource(szUrl);
            m_eState = MP_STATES.MPS_INITIALIZED;
        } catch (IllegalArgumentException e) {
            e.printStackTrace();
        } catch (SecurityException e) {
            e.printStackTrace();
        } catch (IllegalStateException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        m_mp.prepareAsync();
        m_eState = MP_STATES.MPS_PREPARING;
    }

    public void play()
    {
        switch (m_eState)
        {
            case MPS_PREPARED:
            case MPS_PAUSED:
                m_mp.start();
                m_eState = MP_STATES.MPS_STARTED;
                break;
            default:
                // !! throw exception
        }       
    }

    public void pause()
    {
        switch (m_eState)
        {
            case MPS_STARTED:
                m_mp.pause();
                m_eState = MP_STATES.MPS_PAUSED;
                break;
            default:
                // !! throw exception
        }       
    }

    public void release() 
    {
        m_mp.release();
        m_mp = null;
    }

    private void bringToIdleState()
    {
        // reset() should bring MP to IDLE
        m_mp.reset();
        m_eState = MP_STATES.MPS_IDLE;      
    }   

    // ** Callbacks

    @Override
    public void onPrepared(MediaPlayer mp) 
    {
        m_eState = MP_STATES.MPS_PREPARED;    
        m_mp.start();
        m_eState = MP_STATES.MPS_STARTED;           
    }

    @Override
    public boolean onInfo(MediaPlayer mp, int what, int extra) 
    {
        return false;
    }

    @Override
    public boolean onError(MediaPlayer mp, int what, int extra) 
    {
        m_eState = MP_STATES.MPS_IDLE;
        return false;
    }

    @Override
    public void onCompletion(MediaPlayer mp) 
    {
          // play the next song
    }

    @Override
    public void onBufferingUpdate(MediaPlayer mp, int percent) 
    {
    }

}

}

- paiego

---

我在帖子中添加了一个示例。顺便说一下，即使MP状态是公共的，我仍然会将MP与这样的容器包围起来，以抽象和限制对MP的访问。 - paiego

干得好。工作顺畅。 - C-lio Garcia