如何在Android应用中实现类似BUMBLE的蓝牙状态实时监听功能

一、监听蓝牙状态变化 #

Android系统会在蓝牙状态改变时发送ACTION_STATE_CHANGED广播，通过广播接收器可实时感知状态变化：

• 动态注册广播接收器（推荐在Activity/Fragment生命周期内注册，避免内存泄漏）：

private val bluetoothStateReceiver = object : BroadcastReceiver() {
    override fun onReceive(context: Context?, intent: Intent?) {
        val state = intent?.getIntExtra(BluetoothAdapter.EXTRA_STATE, BluetoothAdapter.ERROR)
        when (state) {
            BluetoothAdapter.STATE_OFF -> {
                // 蓝牙已关闭，执行功能降级逻辑
                handleBluetoothOff()
            }
            BluetoothAdapter.STATE_ON -> {
                // 蓝牙已开启，恢复完整功能
                handleBluetoothOn()
            }
            BluetoothAdapter.STATE_TURNING_OFF -> {
                // 蓝牙正在关闭，提前清理资源
                prepareForBluetoothShutdown()
            }
            BluetoothAdapter.STATE_TURNING_ON -> {
                // 蓝牙正在开启，准备恢复操作
                prepareForBluetoothStartup()
            }
        }
    }
}

// 在onResume注册，onPause注销
override fun onResume() {
    super.onResume()
    val filter = IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED)
    registerReceiver(bluetoothStateReceiver, filter)
}

override fun onPause() {
    super.onPause()
    unregisterReceiver(bluetoothStateReceiver)
}

二、避免蓝牙状态突变导致崩溃 #

在所有BLE操作前必须检查蓝牙状态，同时用异常捕获处理不可预见的情况：

• 封装蓝牙状态检查工具方法：

private fun isBluetoothEnabled(): Boolean {
    val bluetoothAdapter = BluetoothAdapter.getDefaultAdapter()
    return bluetoothAdapter != null && bluetoothAdapter.isEnabled
}

• 在BLE操作前校验状态：

fun startBleScan() {
    if (!isBluetoothEnabled()) {
        showBluetoothDisabledHint()
        return
    }
    try {
        bluetoothLeScanner?.startScan(scanCallback)
    } catch (e: IllegalStateException) {
        // 捕获蓝牙未开启或资源释放后的异常
        Log.e(TAG, "Failed to start BLE scan: ${e.message}")
        showBluetoothDisabledHint()
    }
}

• 蓝牙关闭时主动清理资源：

private fun handleBluetoothOff() {
    // 停止扫描
    bluetoothLeScanner?.stopScan(scanCallback)
    // 断开所有BLE连接并释放资源
    connectedGattDevices.forEach { gatt ->
        gatt.disconnect()
        gatt.close()
    }
    connectedGattDevices.clear()
    // 更新UI提示用户开启蓝牙
    updateUiForBluetoothDisabled()
    // 保存当前应用状态
    saveAppState()
}

三、保存与恢复应用状态 #

当蓝牙关闭时，保存应用关键状态，蓝牙恢复后自动还原操作：

• 用ViewModel临时保存状态（适合内存级临时存储）：

class BleViewModel : ViewModel() {
    val scannedDevices = mutableStateListOf<BleDevice>()
    var targetDeviceUuid: String? = null
    var isScanning: Boolean = false
}

• 用SharedPreferences持久化保存（适合应用重启后恢复）：

private fun saveAppState() {
    val prefs = getSharedPreferences("BleAppState", Context.MODE_PRIVATE)
    prefs.edit()
        .putString("targetDeviceUuid", targetDeviceUuid)
        .putBoolean("isScanning", isScanning)
        .apply()
}

private fun restoreAppState() {
    val prefs = getSharedPreferences("BleAppState", Context.MODE_PRIVATE)
    targetDeviceUuid = prefs.getString("targetDeviceUuid", null)
    isScanning = prefs.getBoolean("isScanning", false)
}

• 蓝牙开启后恢复功能：

private fun handleBluetoothOn() {
    restoreAppState()
    // 恢复之前的操作
    if (isScanning) {
        startBleScan()
    }
    targetDeviceUuid?.let { uuid ->
        connectToBleDevice(uuid)
    }
    // 更新UI到正常状态
    updateUiForBluetoothEnabled()
}

四、优化用户体验 #

• 引导用户开启蓝牙：检测到蓝牙关闭时，弹出系统对话框请求开启：

private fun requestEnableBluetooth() {
    val enableBtIntent = Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE)
    startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT)
}

// 处理开启结果
override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    super.onActivityResult(requestCode, resultCode, data)
    if (requestCode == REQUEST_ENABLE_BT) {
        if (resultCode == RESULT_OK) {
            handleBluetoothOn()
        } else {
            // 用户拒绝开启，保持降级状态
            updateUiForBluetoothDisabled()
        }
    }
}

• 通知栏提示：可发送持续性通知，告知用户蓝牙对应用的重要性，方便快速跳转开启。

内容的提问来源于stack exchange，提问作者Shuvam Mandal