尋找 BLE 裝置

如要尋找 BLE 裝置，請使用 startScan()敬上 方法。這個方法需要 ScanCallback 做為參數。 您必須實作這個回呼，因為這就是掃描結果傳回的方式。 由於掃描會耗用大量電力，因此請留意下列事項 規範：

• 找到需要的裝置後，請立即停止掃描。
• 絕不掃描迴圈，並且一律設定掃描時間限制。符合以下條件的裝置 可能已超出範圍，會繼續掃描 會消耗電量

在以下範例中，BLE 應用程式提供一項活動 (DeviceScanActivity) 掃描可用的藍牙 LE 裝置和螢幕 要提供給使用者的清單下列程式碼片段說明如何開始及停止 掃描：

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)
    }
}

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);
    }
}

如果只要掃描特定類型的周邊裝置，可以改為呼叫： startScan(List<ScanFilter>, ScanSettings, ScanCallback)、 提供 ScanFilter 清單 限制掃描範圍的裝置 ScanSettings 物件，該物件 指定掃描作業的相關參數。

以下程式碼範例是 ScanCallback、 也就是提供 BLE 掃描結果的介面找到結果後 這些程式碼會新增到 DeviceScanActivity 的清單轉接器，以供 內容。

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()
    }
}

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();
            }
        };