Android蓝牙LE扫描如何检查设备是否超出范围？

Question

我使用BluetoothLeScanner 的startScan 方法遇到了问题，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！！

我试过用：

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

任何帮助将不胜感激！

Answer 1

在谷歌搜索和探索 Android 文档期间，我想出了如何检测设备是否超出范围。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，我在每个扫描周期都添加了mInRangeBtDevices 集合，该集合将保留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帮助程序集合outOfRangeDevices 从以前的列表中删除不再可用的超出范围的设备

我认为这个例子会很有用，你可以将它集成到你自己的代码中

Answer 2

这个one 看起来不错（JAVA）：

据我了解，您需要实现 startLeScan()。

查找 BLE 设备

要查找 BLE 设备，请使用 startLeScan() 方法。此方法将 BluetoothAdapter.LeScanCallback 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。由于扫描会消耗大量电量，因此您应遵守以下准则：

找到所需设备后，立即停止扫描。 切勿循环扫描，并为扫描设置时间限制。以前可用的设备可能已超出范围，继续扫描会耗尽电池电量。 以下 sn -p 显示了如何开始和停止扫描：

public class DeviceScanActivity extends ListActivity {

    private BluetoothAdapter mBluetoothAdapter;
    private boolean mScanning;
    private Handler mHandler;

    // Stops scanning after 10 seconds.
    private static final long SCAN_PERIOD = 10000;
    ...
    private void scanLeDevice(final boolean enable) {
        if (enable) {
            // Stops scanning after a pre-defined scan period.
            mHandler.postDelayed(new Runnable() {
                @Override
                public void run() {
                    mScanning = false;
                    mBluetoothAdapter.stopLeScan(mLeScanCallback);
                }
            }, SCAN_PERIOD);

            mScanning = true;
            mBluetoothAdapter.startLeScan(mLeScanCallback);
        } else {
            mScanning = false;
            mBluetoothAdapter.stopLeScan(mLeScanCallback);
        }
        ...
    }
...}

考虑检查this 教程。 还有this一个。