经典蓝牙-A2DP音频传输模块

📋 模块概述

A2DP(Advanced Audio Distribution Profile)音频传输模块提供高质量音频流传输功能,用于连接蓝牙音频设备(耳机、音箱等)并传输音频数据。

核心类: android.znhaas.bluetooth.BluetoothA2dpManager

连接管理: android.znhaas.bluetooth.BluetoothA2dpConnection

协议处理: android.znhaas.bluetooth.BluetoothA2dpHandler

🎯 主要功能

• ✅ A2DP设备连接/断开
• ✅ 高质量音频流传输
• ✅ 音频播放控制
• ✅ 连接状态监听
• ✅ Handler线程安全处理
• ✅ 支持多设备管理

🏗️ 架构设计

继承统一架构

@RequiresApi(Build.VERSION_CODES.M)
class BluetoothA2dpManager(context: Context) : BaseBluetoothManager<BluetoothStatusListener>(
    context, Protocol.A2DP
) {
    private val a2dpHandler = BluetoothA2dpHandler()
    private val a2dpConnection = BluetoothA2dpConnection(context)
    
    companion object {
        // A2DP特定消息类型
        private const val MSG_AUDIO_DATA = 10
        private const val MSG_START_STREAMING = 11
        private const val MSG_STOP_STREAMING = 12
    }
}

Handler消息处理

override fun handleProtocolMessage(msg: Message): Boolean {
    return when (msg.what) {
        MSG_AUDIO_DATA -> {
            val audioMsg = msg.obj as AudioDataMessage
            handleAudioDataInHandler(audioMsg.deviceAddress, audioMsg.audioData)
            true
        }
        MSG_START_STREAMING -> {
            val address = msg.obj as String
            handleStartStreamingInHandler(address)
            true
        }
        MSG_STOP_STREAMING -> {
            val address = msg.obj as String
            handleStopStreamingInHandler(address)
            true
        }
        else -> false
    }
}

📚 核心API

1. 初始化

val a2dpManager = BluetoothA2dpManager(context)
a2dpManager.initialize()

2. 连接A2DP设备

connectA2dpDevice(device: BluetoothDeviceInfo): Boolean

val audioDevice = BluetoothDeviceInfo(
    address = "AA:BB:CC:DD:EE:FF",
    name = "Bluetooth Headset",
    deviceType = DeviceType.AUDIO_HEADSET
)

val success = a2dpManager.connectA2dpDevice(audioDevice)
if (success) {
    Log.d(TAG, "A2DP设备连接成功")
}

3. 断开连接

disconnectA2dpDevice(address: String): Boolean

a2dpManager.disconnectA2dpDevice("AA:BB:CC:DD:EE:FF")

4. 音频流控制

开始音频流

a2dpManager.startAudioStreaming("AA:BB:CC:DD:EE:FF")

停止音频流

a2dpManager.stopAudioStreaming("AA:BB:CC:DD:EE:FF")

5. 连接状态监听

a2dpManager.setConnectionListener { address, state ->
    when (state) {
        BluetoothProfile.STATE_CONNECTED -> {
            Log.d(TAG, "A2DP已连接: $address")
        }
        BluetoothProfile.STATE_DISCONNECTED -> {
            Log.d(TAG, "A2DP已断开: $address")
        }
        BluetoothProfile.STATE_CONNECTING -> {
            Log.d(TAG, "A2DP连接中: $address")
        }
        BluetoothProfile.STATE_DISCONNECTING -> {
            Log.d(TAG, "A2DP断开中: $address")
        }
    }
}

🔧 完整使用示例

class BluetoothAudioActivity : AppCompatActivity() {
    
    private lateinit var a2dpManager: BluetoothA2dpManager
    private var currentDevice: String? = null
    
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_bluetooth_audio)
        
        // 初始化
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            a2dpManager = BluetoothA2dpManager(this)
            a2dpManager.initialize()
            setupListeners()
        }
        
        // 连接按钮
        connectButton.setOnClickListener {
            connectAudioDevice()
        }
        
        // 播放按钮
        playButton.setOnClickListener {
            currentDevice?.let { addr ->
                a2dpManager.startAudioStreaming(addr)
            }
        }
        
        // 停止按钮
        stopButton.setOnClickListener {
            currentDevice?.let { addr ->
                a2dpManager.stopAudioStreaming(addr)
            }
        }
    }
    
    private fun setupListeners() {
        a2dpManager.setConnectionListener { address, state ->
            runOnUiThread {
                when (state) {
                    BluetoothProfile.STATE_CONNECTED -> {
                        currentDevice = address
                        statusText.text = "已连接音频设备"
                        playButton.isEnabled = true
                        stopButton.isEnabled = true
                    }
                    BluetoothProfile.STATE_DISCONNECTED -> {
                        currentDevice = null
                        statusText.text = "音频设备已断开"
                        playButton.isEnabled = false
                        stopButton.isEnabled = false
                    }
                }
            }
        }
    }
    
    private fun connectAudioDevice() {
        val device = BluetoothDeviceInfo(
            address = "AA:BB:CC:DD:EE:FF",
            name = "Bluetooth Headset",
            deviceType = DeviceType.AUDIO_HEADSET
        )
        
        lifecycleScope.launch(Dispatchers.IO) {
            val success = a2dpManager.connectA2dpDevice(device)
            withContext(Dispatchers.Main) {
                if (success) {
                    Toast.makeText(this@BluetoothAudioActivity, 
                        "音频设备连接成功", Toast.LENGTH_SHORT).show()
                }
            }
        }
    }
    
    override fun onDestroy() {
        super.onDestroy()
        a2dpManager.cleanup()
    }
}

⚠️ 注意事项

1. 系统要求

@RequiresApi(Build.VERSION_CODES.M) // 需要Android 6.0+

2. 权限要求

<uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />
<uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />

3. Profile连接

A2DP使用Android系统的BluetoothProfile API:

// 自动获取BluetoothA2dp实例
bluetoothAdapter.getProfileProxy(context, serviceListener, BluetoothProfile.A2DP)

4. 音频路由

配合BluetoothAudioRoutingManager实现音频路由切换:

// 切换到蓝牙音频
audioRoutingManager.routeAudioToBluetooth()

// 切换到扬声器
audioRoutingManager.routeAudioToSpeaker()

🔗 相关资源

• 源码: app/src/main/java/android/znhaas/bluetooth/BluetoothA2dpManager.kt
• 音频路由: android.znhaas.bluetooth.BluetoothAudioRoutingManager
• HFP模块: 配合HFP实现完整蓝牙通话功能

📚 扩展阅读

• A2DP协议标准
• Android BluetoothA2dp API