Android 蓝牙 LE 扫描如何检查设备是否超出范围？

Question

我在使用 BluetoothLeScanner 的 startScan 方法时遇到了问题，找到了一个 BLE 设备，但是当我关闭 BLE 设备时，我的手机仍然显示此设备已打开!!

我尝试过使用:

private ScanCallback mScanCallback = new ScanCallback() {
    @Override
    public void onScanResult(int callbackType, ScanResult result) {
        Log.i("ScanCallback", String.format("onScanResult(int callbackType[%d], ScanResult result)", callbackType));
        final BluetoothDevice btDevice = result.getDevice();
        if (btDevice == null){
            Log.e("ScanCallback", "Could not get bluetooth device");
            return;
        }

        final String macAddress = btDevice.getAddress();
        if (callbackType == ScanSettings.CALLBACK_TYPE_MATCH_LOST) {
            // NOTE: I've never got here
            final BluetoothDevice outOfRangeDevice = mBtDevices.get(macAddress);
            ...
        } else {
            ...
        }
    }
    ...
};

伙计，我还没有找到如何检测 BLE 设备在其他资源中丢失的解决方案，例如(Android SDK 引用、论坛、stackoverflow 等)(:

任何帮助将不胜感激!!

Answer 1

在谷歌搜索和浏览 Android 文档的过程中，我找到了检测设备是否超出范围的方法。我想分享我的解决方案:

...
public void scanBLEDevices(final boolean enable) {
    if(mLeScanner == null) {
        Log.d(TAG, "Could not get LEScanner object");
        throw new InternalError("Could not get LEScanner object");
    }

    if (enable) {
        startLeScan();
    } else {
        stopLeScan(false);
    }
}

private void startLeScan() {
    Log.i(TAG, "startLeScan(BluetoothLeScanner mLeScanner)");
    mScanning = true;
    mInRangeBtDevices.clear();
    if (mStartScanCallback != null) {
        mHandler.removeCallbacks(mStartScanCallback);
    }
    if (Build.VERSION.SDK_INT < 21) {
        mBluetoothAdapter.startLeScan(mLeScanCallback);
    } else {
        mLeScanner.startScan(mScanFilters, mScanSettings, mScanCallback);
    }
    mStopScanCallback = new Runnable() {
        @Override
        public void run() {
            stopLeScan(true);
        }
    };
    mHandler.postDelayed(mStopScanCallback, SCAN_PERIOD);
}

private void stopLeScan(final boolean isContinueAfterPause) {
    Log.i(TAG, "stopLeScan(BluetoothLeScanner mLeScanner)");
    mScanning = false;
    if (mStopScanCallback != null) {
        mHandler.removeCallbacks(mStopScanCallback);
    }
    removeOutOfRangeDevices();
    if (Build.VERSION.SDK_INT < 21) {
        mBluetoothAdapter.stopLeScan(mLeScanCallback);
    } else {
        mLeScanner.stopScan(mScanCallback);
    }
    if (isContinueAfterPause) {
        mStartScanCallback = new Runnable() {
            @Override
            public void run() {
                startLeScan();
            }
        };
        mHandler.postDelayed(mStartScanCallback, SCAN_PAUSE);
    }
}

private void removeOutOfRangeDevices() {
    final Set<String> outOfRangeDevices = new HashSet<>();
    for (String btAddress : mBtDevices.keySet()) {
        if (!mInRangeBtDevices.contains(btAddress)) {
            outOfRangeDevices.add(btAddress);
        }
    }
    for (String btAddress : outOfRangeDevices) {
        final BluetoothDevice outOfRangeDevice = mBtDevices.get(btAddress);
        mBtDevicesRSSI.remove(btAddress);
        mBtDevices.remove(btAddress);
    }
}
...

解释:

1. 如您所见，我在每个扫描周期添加了 mInRangeBtDevices 集合，它将保留在当前扫描期间找到的所有设备。
2. 当我停止扫描时，我还会使用一个额外的助手集合 outOfRangeDevices
从以前的列表中删除不再可用的超出范围的设备

我认为这个示例会很有用，您将能够将它集成到您​​自己的代码中