android – 如何重启BluetoothLeScanner？

2023年2月10日 312次阅读

我在
Android端使用BluetoothLeScanner将Android设备连接到iOS.这一切都是第一次完美运作.

问题是,在连接到其中一个已发现的iOS设备后,我停止扫描(stopScan(scanCallback))以保存能量.

如果以后连接设备由于某种原因断开连接我再次开始扫描…但似乎在’重新启动’扫描后不再工作 – 它没有发现任何更多的设备…不知道为什么但我被迫重新启动应用程序.

任何想法如何解决这一问题？

我也使用ScanFilter按UUID过滤设备,并使用ScanSettings.SCAN_MODE_BALANCED进行扫描模式.

这是代码：

private void startScanner() {
    BluetoothManager bluetoothManager = (BluetoothManager) activity.getSystemService(activity.BLUETOOTH_SERVICE);
    BluetoothAdapter adapter = bluetoothManager.getAdapter();
    scanner = adapter.getBluetoothLeScanner();
    ScanSettings settings = new ScanSettings.Builder().setScanMode(ScanSettings.SCAN_MODE_BALANCED).build();
    scanner.startScan(scanFilters(), settings, scanCallback);
    System.out.println("Scanner started");
}

private List<ScanFilter> scanFilters() {
    ScanFilter filter = new ScanFilter.Builder().setServiceUuid(THE_BT_UUID).build();
    List<ScanFilter> list = new ArrayList<ScanFilter>(1);
    list.add(filter);
    return list;
}



private final ScanCallback scanCallback = new ScanCallback() {
    @Override
    public void onScanResult(int callbackType, ScanResult result) {
        BluetoothDevice device = result.getDevice();
        if (device != null) {
            callback.foundRemoteDevice(BluetoothCentral.this, device);
        }
    }
}


public void connectToDevice(BluetoothDevice device) {
    if (gatt == null) {
        gatt = device.connectGatt(activity, false, gattCallback);
        scanner.stopScan(scanCallback);
    }
}


private final BluetoothGattCallback gattCallback = new BluetoothGattCallback() {
    @Override
    public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
        System.out.println("onConnectionStateChange; status: " + status + ", state: " + newState);

        switch (newState) {
            case BluetoothProfile.STATE_CONNECTED:
                System.out.println("STATE_CONNECTED");
                if (!startedServiceDiscovery) {
                    gatt.discoverServices();
                    startedServiceDiscovery = true;
                }
                break;
            case BluetoothProfile.STATE_DISCONNECTED:
                callback.didDisconnectFromDevice(BluetoothCentral.this, gatt.getDevice());
                gatt = null;
                startScanner();
                break;
            default:
                System.out.println("STATE_OTHER");
        }

    }
}

请注意,我在connectGatt调用之后立即停止扫描,并在获得BluetoothProfile.STATE_DISCONNECTED回调时再次启动它.

最佳答案 正如我的评论,帮助您解决问题,我在这里添加我的评论作为答案.

Code seems ok to me, did you try adding logs in onScanResult method.
to check if device is getting detected but something else is failing.
One more thing, I see if I restart scanning it takes time to get the
device detected in comparison of first scanning.

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