要查找 BLE 设备，您可以使用 startScan() 方法。此方法采用 ScanCallback 作为参数。 您必须实现此回调，因为这是返回扫描结果的方式。 由于扫描非常耗电，因此您应该注意以下事项： 指南：
- 找到所需设备后，立即停止扫描。
- 永不循环扫描，并始终设置扫描时间限制。具有如下特征的设备： 可能已经超出有效范围， 很耗电。
在以下示例中，BLE 应用提供了一个 activity (DeviceScanActivity)，用于扫描可用的蓝牙 LE 设备和显示屏 向用户列出它们以下代码段展示了如何启动和停止 扫描：
Kotlin
private val bluetoothLeScanner = bluetoothAdapter.bluetoothLeScanner private var scanning = false private val handler = Handler() // Stops scanning after 10 seconds. private val SCAN_PERIOD: Long = 10000 private fun scanLeDevice() { if (!scanning) { // Stops scanning after a pre-defined scan period. handler.postDelayed({ scanning = false bluetoothLeScanner.stopScan(leScanCallback) }, SCAN_PERIOD) scanning = true bluetoothLeScanner.startScan(leScanCallback) } else { scanning = false bluetoothLeScanner.stopScan(leScanCallback) } }
Java
private BluetoothLeScanner bluetoothLeScanner = bluetoothAdapter.getBluetoothLeScanner(); private boolean scanning; private Handler handler = new Handler(); // Stops scanning after 10 seconds. private static final long SCAN_PERIOD = 10000; private void scanLeDevice() { if (!scanning) { // Stops scanning after a predefined scan period. handler.postDelayed(new Runnable() { @Override public void run() { scanning = false; bluetoothLeScanner.stopScan(leScanCallback); } }, SCAN_PERIOD); scanning = true; bluetoothLeScanner.startScan(leScanCallback); } else { scanning = false; bluetoothLeScanner.stopScan(leScanCallback); } }
要仅扫描特定类型的外围设备，您可以改为调用 startScan(List<ScanFilter>, ScanSettings, ScanCallback)、 提供一系列 ScanFilter 对象，这些对象限制了扫描要查找的设备， ScanSettings 对象， 指定有关扫描的参数。
以下代码示例是 ScanCallback、 该接口是用于提供 BLE 扫描结果的接口。找到结果后， 它们会添加到 DeviceScanActivity 中的列表适配器中，以显示给 用户。
Kotlin
private val leDeviceListAdapter = LeDeviceListAdapter() // Device scan callback. private val leScanCallback: ScanCallback = object : ScanCallback() { override fun onScanResult(callbackType: Int, result: ScanResult) { super.onScanResult(callbackType, result) leDeviceListAdapter.addDevice(result.device) leDeviceListAdapter.notifyDataSetChanged() } }
Java
private LeDeviceListAdapter leDeviceListAdapter = new LeDeviceListAdapter(); // Device scan callback. private ScanCallback leScanCallback = new ScanCallback() { @Override public void onScanResult(int callbackType, ScanResult result) { super.onScanResult(callbackType, result); leDeviceListAdapter.addDevice(result.getDevice()); leDeviceListAdapter.notifyDataSetChanged(); } };