目錄： （3）Android 官方網站 對 MediaPlayer的介紹 正文： Android 官方網站 對 MediaPlayer的介紹 MediaPlayer public class MediaPlayer extends Object implements VolumeAutomation ...
目錄：
（3）Android 官方網站 對 MediaPlayer的介紹
正文：
MediaPlayer public class MediaPlayer extends Object implements VolumeAutomation, AudioRouting MediaPlayer類被用來控制音/視頻文件和流的播放。可以在VideoView中找到有關如何使用此類中的方法的示例。 這裡涉及的主題是： 1. 狀態圖 2. 有效和無效狀態 3. 許可權 4. 註冊信息和錯誤回調 ★ 開發者指南 有關如何使用MediaPlayer的更多信息，請閱讀Media Playback開發人員指南。 狀態圖 音/視頻文件和流的播放控制是作為一個狀態機來進行管理。下圖顯示了受支持的播放控制操作驅動的MediaPlayer對象的生命周期和狀態。 橢圓表示MediaPlayer對象可能駐留的狀態。弧表示驅動對象狀態轉換的播放控制操作。有兩種類型的弧。 單箭頭的弧表示同步方法調用，而雙箭頭的弧表示非同步方法調用。
從這個狀態圖中，可以看到MediaPlayer對象具有以下狀態：
- 當使用 new 創建MediaPlayer對象或者在調用 reset() 之後，它處於空閑狀態; 並且在調用 release() 之後，它處於 End 狀態。 在這兩個狀態之間是MediaPlayer對象的生命周期。
- 通常，一些播放控制操作可能由於各種原因而失敗，例如不支持的音頻／視頻格式，交錯的音頻／視頻，解析度太高，流超時等。因此，在這些情況下，關註錯誤報告和恢復是非常重要的。有時，由於編程錯誤，也可能在無效狀態下調用播放控制操作。在所有這些錯誤條件下，如果開發者事先通過setOnErrorListener(android.media.MediaPlayer.OnErrorListener)註冊了 OnErrorListener ，則內部播放器引擎會調用開發者提供的 OnErrorListener.onError() 方法。
- 調用 setDataSource(FileDescriptor), 或 setDataSource(String), 或 setDataSource(Context, Uri), 或 setDataSource(FileDescriptor, long, long), 或 setDataSource(MediaDataSource)
- 在開始播放之前，MediaPlayer 對象必須先進入準備狀態。
- 要開始播放，必須調用 start() ，start() 返回成功後，MediaPlayer對象則處於 Started狀態（Started state）。isPlaying()可用來測試 MediaPlayer對象是否處於 Started狀態（Started state）。
- 播放可以暫停和停止，並可以調整當前播放位置。 可以通過pause()暫停播放。 當對pause()的調用返回時，MediaPlayer對象進入Paused狀態（Pausedstate）。 請註意，從“已啟動”狀態（Started state）到“暫停”狀態（Paused state）的轉換（反之亦然）在播放器引擎中非同步發生。 在調用isPlaying()時更新狀態可能需要一些時間，對於流內容，它可能需要幾秒鐘。
- 調用stop()會停止播放並導致處於Started，Paused，Prepared或PlaybackCompleted狀態（state）的MediaPlayer進入Stopped狀態（Stopped state）。
- 可以通過調用seekTo(long, int)調整播放位置
- 當播放到達流的結尾時，播放完成。
| Method Name | Valid Sates | Invalid States | Comments |
| attachAuxEffect | {Initialized, Prepared, Started, Paused, Stopped, PlaybackCompleted} | {Idle, Error} | This method must be called after setDataSource. Calling it does not change the object state. |
| getAudioSessionId | any | {} | This method can be called in any state and calling it does not change the object state. |
| getCurrentPosition | {Idle, Initialized, Prepared, Started, Paused, Stopped, PlaybackCompleted} | {Error} | Successful invoke of this method in a valid state does not change the state. Calling this method in an invalid state transfers the object to the Error state. |
| getDuration | {Prepared, Started, Paused, Stopped, PlaybackCompleted} | {Idle, Initialized, Error} | Successful invoke of this method in a valid state does not change the state. Calling this method in an invalid state transfers the object to the Error state. |
| getVideoHeight | {Idle, Initialized, Prepared, Started, Paused, Stopped, PlaybackCompleted} | {Error} | Successful invoke of this method in a valid state does not change the state. Calling this method in an invalid state transfers the object to the Error state. |
| getVideoWidth | {Idle, Initialized, Prepared, Started, Paused, Stopped, PlaybackCompleted} | {Error} | Successful invoke of this method in a valid state does not change the state. Calling this method in an invalid state transfers the object to the Error state. |
| isPlaying | {Idle, Initialized, Prepared, Started, Paused, Stopped, PlaybackCompleted} | {Error} | Successful invoke of this method in a valid state does not change the state. Calling this method in an invalid state transfers the object to the Error state. |
| pause | {Started, Paused, PlaybackCompleted} | {Idle, Initialized, Prepared, Stopped, Error} | Successful invoke of this method in a valid state transfers the object to the Paused state. Calling this method in an invalid state transfers the object to the Error state. |
| prepare | {Initialized, Stopped} | {Idle, Prepared, Started, Paused, PlaybackCompleted, Error} | Successful invoke of this method in a valid state transfers the object to the Prepared state. Calling this method in an invalid state throws an IllegalStateException. |
| prepareAsync | {Initialized, Stopped} | {Idle, Prepared, Started, Paused, PlaybackCompleted, Error} | Successful invoke of this method in a valid state transfers the object to the Preparing state. Calling this method in an invalid state throws an IllegalStateException. |
| release | any | {} | After release(), the object is no longer available. |
| reset | {Idle, Initialized, Prepared, Started, Paused, Stopped, PlaybackCompleted, Error} | {} | After reset(), the object is like being just created. |
| seekTo | {Prepared, Started, Paused, PlaybackCompleted} | {Idle, Initialized, Stopped, Error} | Successful invoke of this method in a valid state does not change the state. Calling this method in an invalid state transfers the object to the Error state. |
| setAudioAttributes | {Idle, Initialized, Stopped, Prepared, Started, Paused, PlaybackCompleted} | {Error} | Successful invoke of this method does not change the state. In order for the target audio attributes type to become effective, this method must be called before prepare() or prepareAsync(). |
| setAudioSessionId | {Idle} | {Initialized, Prepared, Started, Paused, Stopped, PlaybackCompleted, Error} | This method must be called in idle state as the audio session ID must be known before calling setDataSource. Calling it does not change the object state. |
| setAudioStreamType (deprecated) | {Idle, Initialized, Stopped, Prepared, Started, Paused, PlaybackCompleted} | {Error} | Successful invoke of this method does not change the state. In order for the target audio stream type to become effective, this method must be called before prepare() or prepareAsync(). |
| setAuxEffectSendLevel | any | {} | Calling this method does not change the object state. |
| setDataSource | {Idle} | {Initialized, Prepared, Started, Paused, Stopped, PlaybackCompleted, Error} | Successful invoke of this method in a valid state transfers the object to the Initialized state. Calling this method in an invalid state throws an IllegalStateException. |
| setDisplay | any | {} | This method can be called in any state and calling it does not change the object state. |
| setSurface | any | {} | This method can be called in any state and calling it does not change the object state. |
| setVideoScalingMode | {Initialized, Prepared, Started, Paused, Stopped, PlaybackCompleted} | {Idle, Error} | Successful invoke of this method does not change the state. |
| setLooping | {Idle, Initialized, Stopped, Prepared, Started, Paused, PlaybackCompleted} | {Error} | Successful invoke of this method in a valid state does not change the state. Calling this method in an invalid state transfers the object to the Error state. |
| isLooping | any | {} | This method can be called in any state and calling it does not change the object state. |
| setOnBufferingUpdateListener | any | {} | This method can be called in any state and calling it does not change the object state. |
| setOnCompletionListener | any | {} | This method can be called in any state and calling it does not change the object state. |
| setOnErrorListener | any | {} | This method can be called in any state and calling it does not change the object state. |
| setOnPreparedListener | any | {} | This method can be called in any state and calling it does not change the object state. |
| setOnSeekCompleteListener | any | {} | This method can be called in any state and calling it does not change the object state. |
| setPlaybackParams | {Initialized, Prepared, Started, Paused, PlaybackCompleted, Error} | {Idle, Stopped} | This method will change state in some cases, depending on when it's called. |
| setScreenOnWhilePlaying | any | {} | This method can be called in any state and calling it does not change the object state. |
| setVolume | {Idle, Initialized, Stopped, Prepared, Started, Paused, PlaybackCompleted} | {Error} | Successful invoke of this method does not change the state. |
| setWakeMode | any | {} | This method can be called in any state and calling it does not change the object state. |
| start | {Prepared, Started, Paused, PlaybackCompleted} | {Idle, Initialized, Stopped, Error} | Successful invoke of this method in a valid state transfers the object to the Started state. Calling this method in an invalid state transfers the object to the Error state. |
| stop | {Prepared, Started, Stopped, Paused, PlaybackCompleted} | {Idle, Initialized, Error} | Successful invoke of this method in a valid state transfers the object to the Stopped state. Calling this method in an invalid state transfers the object to the Error state. |
| getTrackInfo | {Prepared, Started, Stopped, Paused, PlaybackCompleted} | {Idle, Initialized, Error} | Successful invoke of this method does not change the state. |
| addTimedTextSource | {Prepared, Started, Stopped, Paused, PlaybackCompleted} | {Idle, Initialized, Error} | Successful invoke of this method does not change the state. |
| selectTrack | {Prepared, Started, Stopped, Paused, PlaybackCompleted} | {Idle, Initialized, Error} | Successful invoke of this method does not change the state. |
| deselectTrack | {Prepared, Started, Stopped, Paused, PlaybackCompleted} | {Idle, Initialized, Error} | Successful invoke of this method does not change the state. |
