Android 12+：请求BLUETOOTH_CONNECT权限前如何检测蓝牙耳机是否连接

针对Android 12+下需BLUETOOTH_CONNECT权限才能检测蓝牙耳机，但不想向无耳机用户发起权限请求的矛盾，可通过以下方式解决：

1. 用AudioManager检测蓝牙音频设备（无需权限） #

Android 12+中，AudioManager的getDevices()方法可获取当前连接的音频设备，且无需蓝牙权限。用此方法先判断是否存在蓝牙音频设备：

private boolean hasBluetoothAudioDeviceConnected() {
    AudioManager audioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
    AudioDeviceInfo[] devices = audioManager.getDevices(AudioManager.GET_DEVICES_OUTPUTS);
    for (AudioDeviceInfo device : devices) {
        if (device.getType() == AudioDeviceInfo.TYPE_BLUETOOTH_A2DP 
            || device.getType() == AudioDeviceInfo.TYPE_BLUETOOTH_SCO) {
            return true;
        }
    }
    return false;
}

2. 监听蓝牙连接广播，动态触发权限申请 #

注册广播接收器监听蓝牙设备连接/断开事件，仅当检测到蓝牙音频设备连接时，才发起权限申请：

private static final int REQUEST_BLUETOOTH_CONNECT = 1001;
private BroadcastReceiver bluetoothConnectionReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        if (BluetoothDevice.ACTION_ACL_CONNECTED.equals(action)) {
            BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
            if (device != null && device.getBluetoothClass().hasService(BluetoothClass.Service.AUDIO)) {
                requestPermissions(new String[]{Manifest.permission.BLUETOOTH_CONNECT}, REQUEST_BLUETOOTH_CONNECT);
            }
        }
    }
};

// 在onCreate中注册广播
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    IntentFilter filter = new IntentFilter();
    filter.addAction(BluetoothDevice.ACTION_ACL_CONNECTED);
    filter.addAction(BluetoothDevice.ACTION_ACL_DISCONNECTED);
    registerReceiver(bluetoothConnectionReceiver, filter);
}

// 在onDestroy中注销广播
@Override
protected void onDestroy() {
    super.onDestroy();
    unregisterReceiver(bluetoothConnectionReceiver);
}

3. 权限申请后的逻辑处理 #

用户授权后，调用你原有的检测方法确认状态，再处理WebRTC音频切换：

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    if (requestCode == REQUEST_BLUETOOTH_CONNECT) {
        if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            if (isBluetoothHeadsetConnected()) {
                // 执行WebRTC音频切换至蓝牙耳机的逻辑
            }
        }
    }
}

4. 处理应用启动时已连接耳机的场景 #

应用启动时若已有蓝牙音频设备连接，广播不会触发，可在启动时直接检测并申请权限：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // ...其他初始化逻辑
    if (hasBluetoothAudioDeviceConnected()) {
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.BLUETOOTH_CONNECT)
                != PackageManager.PERMISSION_GRANTED) {
            requestPermissions(new String[]{Manifest.permission.BLUETOOTH_CONNECT}, REQUEST_BLUETOOTH_CONNECT);
        } else {
            if (isBluetoothHeadsetConnected()) {
                // 执行音频切换逻辑
            }
        }
    }
}

内容的提问来源于stack exchange，提问作者Mike Keskinov