152 lines
3.3 KiB
Markdown
152 lines
3.3 KiB
Markdown
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# 03_AVRCP歌曲信息与播放状态流程
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## AVRCP 是什么
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```text
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AVRCP = 蓝牙媒体控制协议
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它负责两类事情：
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1. 车机控制手机：播放、暂停、上一曲、下一曲
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2. 手机告诉车机：歌名、歌手、封面、播放状态、进度
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```
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## MediaBrowser 连接流程
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```text
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1. BluetoothAvrcpClient.init(context)
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↓
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2. initMediaBrowserHelper()
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↓
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3. new MediaBrowserClient(context)
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↓
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4. MediaBrowserClient 连接系统服务：
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com.android.bluetooth.avrcpcontroller.BluetoothMediaBrowserService
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↓
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5. 连接成功后创建 MediaControllerCompat
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↓
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6. 注册 MediaControllerCompat.Callback
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↓
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7. 可以接收 metadata 和 playbackState
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```
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## 歌曲信息流程
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```text
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1. 手机音乐 App 播放或切歌
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↓
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2. 手机通过 AVRCP 上报 metadata
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↓
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3. Android 蓝牙服务接收 metadata
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↓
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4. MediaBrowserClient.mediaControlCallback.onMetadataChanged()
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↓
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5. BluetoothAvrcpClient.callback.onMetadataChanged()
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↓
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6. BtMusicManager.onMetadataChanged()
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↓
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7. 解析字段：
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artist
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title
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album
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albumUrl
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duration
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↓
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8. 保存到 MusicInfo
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↓
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9. 通知 BtMusicViewModel.onPlayMusicInfo()
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↓
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10. mLiveDataMusicInfo.postValue(musicInfo)
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↓
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11. BluetoothMusicActivity 更新 UI
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```
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## 播放状态流程
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```text
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1. 手机音乐播放状态变化
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↓
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2. MediaBrowserClient.onPlaybackStateChanged()
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↓
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3. BluetoothAvrcpClient.onPlaybackStateChanged()
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↓
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4. BtMusicManager.onPlaybackStateChanged()
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↓
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5. 判断：
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state == PlaybackStateCompat.STATE_PLAYING
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↓
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6. 更新 MusicInfo.isPlaying
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↓
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7. 更新 MusicInfo.playPosition
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↓
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8. 通知 BtMusicViewModel.onPlayMusicState(isPlaying)
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↓
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9. BluetoothMusicActivity 更新播放按钮图标
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```
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## 同步给 Launcher 的流程
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同样的 AVRCP 数据，还会推给桌面卡片。
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```text
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BluetoothAvrcpClient.onMetadataChanged()
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↓
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BtInfoPushManager.sendMusicInfoToLauncher()
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↓
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转换为 BtMusicInfo
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↓
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DataManager.putObject(BT_MUSIC_INFO, btInfo)
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↓
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发送 ACTION_UPDATE_MUSIC_WIDGET
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↓
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Launcher 卡片刷新
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```
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播放状态也是类似：
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```text
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BluetoothAvrcpClient.onPlaybackStateChanged()
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↓
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BtInfoPushManager.sendMusicStateToLauncher()
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↓
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DataManager.putObject(BT_MUSIC_INFO, btInfo)
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↓
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Launcher 卡片刷新
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```
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## MusicInfo 字段
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| 字段 | 含义 | 来源 |
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|---|---|---|
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| `artist` | 歌手 | `MediaMetadata.METADATA_KEY_ARTIST` |
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| `title` | 歌曲名 | `MediaMetadata.METADATA_KEY_TITLE` |
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| `album` | 专辑 | `MediaMetadata.METADATA_KEY_ALBUM` |
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| `albumUrl` | 封面 | `MediaMetadata.METADATA_KEY_ALBUM_ART_URI` |
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| `songLen` | 总时长 | `MediaMetadata.METADATA_KEY_DURATION` |
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| `playPosition` | 当前进度 | `PlaybackStateCompat.getPosition()` |
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| `isPlaying` | 是否播放 | `PlaybackStateCompat.STATE_PLAYING` |
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## Unknown 处理
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在 `BtMusicManager.onMetadataChanged()` 中：
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```text
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如果 artist/title/album 为空、unknow、Not Provided
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↓
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替换为 strings.xml 中的 unknow 文案
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```
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在 `BluetoothMusicActivity` 中：
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```text
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如果 title 为空或等于 unknow
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↓
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setIsOpenApp(true)
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```
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含义：
|
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```text
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|
A2DP 可能已经连接，但手机音乐 App 没有提供有效歌曲信息。
|
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|
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页面可能提示用户打开手机音乐 App。
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```
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