如何首先扫描到所有的蓝牙设备

要扫描周围的蓝牙设备，您可以使用 Android 平台提供的 BluetoothAdapter 类。以下是一些可能有用的代码示例：

1. 获取 BluetoothAdapter 对象：

BluetoothAdapter bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

2. 检查蓝牙是否已启用：

if (bluetoothAdapter == null || !bluetoothAdapter.isEnabled()) {
    // 蓝牙未启用，需要提示用户进行启用
    Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
    startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
}

3. 开始扫描：

bluetoothAdapter.startDiscovery();

4. 注册 BroadcastReceiver 监听扫描结果：

private BroadcastReceiver discoveryReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        if (BluetoothDevice.ACTION_FOUND.equals(action)) {
            BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
            // 处理扫描到的设备
        } else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {
            // 扫描完成
        }
    }
};

5. 注册 BroadcastReceiver 和取消扫描：

// 注册 BroadcastReceiver
IntentFilter filter = new IntentFilter();
filter.addAction(BluetoothDevice.ACTION_FOUND);
filter.addAction(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
registerReceiver(discoveryReceiver, filter);

// 取消扫描
bluetoothAdapter.cancelDiscovery();

// 取消 BroadcastReceiver 注册
unregisterReceiver(discoveryReceiver);