停止扫描信标：stopRangingBeaconsInRegion() 不工作
Stop scanning of beacons: stopRangingBeaconsInRegion() not working
我正在使用 Android 信标库扫描 Android 应用程序的 Eddystone 信标。我在连接信标服务后开始监控，然后在找到信标时开始测距。
我需要根据用户的选择停止扫描信标（停止监视和测距）。我正在使用
beaconManager.stopMonitoringBeaconsInRegion(region);
beaconManager.stopRangingBeaconsInRegion(region);
在我的 stopScan() 中停止扫描。但是测距并没有停止，尽管监控停止了。我做错了什么吗？
完整代码如下：
public class BlankFragment extends Fragment implements BeaconConsumer {
public BlankFragment() {
// Required empty public constructor
}
private static final int PERMISSION_REQUEST_FINE_LOCATION = 1;
private Region region;
private Map<String /* uid */, Beacon> deviceToBeaconMap = new HashMap<>();
String LOG_TAG = BlankFragment.class.getSimpleName();
SharedPreferences sp;
View rootView;
private BeaconManager beaconManager;
boolean isScanning = false;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
sp = PreferenceManager.getDefaultSharedPreferences(getActivity());
sp.registerOnSharedPreferenceChangeListener(listener);
beaconManager = BeaconManager.getInstanceForApplication(getContext());
beaconManager.getBeaconParsers().add(new BeaconParser().
setBeaconLayout("s:0-1=feaa,m:2-2=00,p:3-3:-41,i:4-13,i:14-19"));
beaconManager.bind(this);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
rootView = inflater.inflate(R.layout.fragment_near_me, container, false);
return rootView;
}
@Override
public void onStop() {
super.onStop();
if (isScanning)
stopScan();
}
@Override
public void onDestroy() {
super.onDestroy();
deviceToBeaconMap.clear();
beaconManager.unbind(this);
}
@Override
public void onBeaconServiceConnect() {
region = new Region("nearMeScanning", null, null, null);
Log.i(LOG_TAG, "OnBeaconServiceConnect called");
beaconManager.addMonitorNotifier(new MonitorNotifier() {
@Override
public void didEnterRegion(Region region) {
try {
beaconManager.startRangingBeaconsInRegion(region);
Log.i(LOG_TAG, "In beacon region");
} catch (RemoteException e) {
Log.e(LOG_TAG, "Remote Exception while starting Ranging", e);
}
}
@Override
public void didExitRegion(Region region) {
try {
beaconManager.stopRangingBeaconsInRegion(region);
Log.i(LOG_TAG, "Exited beacon region");
} catch (RemoteException e) {
Log.e(LOG_TAG, "Remote Exception while stoping Ranging", e);
}
}
@Override
public void didDetermineStateForRegion(int i, Region region) {
Log.i(LOG_TAG, "State of region changed " + i);
}
});
beaconManager.addRangeNotifier(new RangeNotifier() {
@Override
public void didRangeBeaconsInRegion(Collection<org.altbeacon.beacon.Beacon> beacons, Region region) {
if (beacons.size() > 0) {
for (org.altbeacon.beacon.Beacon scannedBeacon : beacons) {
setOnLostRunnable();
String deviceUUID = scannedBeacon.getId1().toString().substring(2) + scannedBeacon.getId2().toString().substring(2);
String deviceAddress = scannedBeacon.getBluetoothAddress();
int rssi = scannedBeacon.getRssi();
Beacon beacon;
if (!deviceToBeaconMap.containsKey(deviceUUID)) {
beacon = new Beacon(deviceAddress, rssi, deviceUUID);
deviceToBeaconMap.put(deviceUUID, beacon);
if (BuildConfig.DEBUG)
Log.d(LOG_TAG, "New Beacon added " + deviceUUID + " DeviceAddress " + deviceAddress);
} else {
deviceToBeaconMap.get(deviceUUID).lastSeenTimestamp = System.currentTimeMillis();
deviceToBeaconMap.get(deviceUUID).rssi = rssi;
}
}
}
}
});
if (sp.getBoolean(Constants.SharedPreferences.IS_VISIBILITY_ON, false)) {
refreshScan();
} else {
visbilityOffTasks();
}
}
@Override
public Context getApplicationContext() {
return getActivity().getApplicationContext();
}
@Override
public void unbindService(ServiceConnection serviceConnection) {
getActivity().unbindService(serviceConnection);
}
@Override
public boolean bindService(Intent intent, ServiceConnection serviceConnection, int i) {
return getActivity().bindService(intent, serviceConnection, i);
}
private void refreshScan() {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (getActivity().checkSelfPermission(Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
if (BuildConfig.DEBUG)
Log.d(LOG_TAG, "Will check for permissions");
requestPermissions(new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
PERMISSION_REQUEST_FINE_LOCATION);
} else {
if (sp.getBoolean(Constants.SharedPreferences.IS_VISIBILITY_ON, false))
startScan();
}
} else {
if (sp.getBoolean(Constants.SharedPreferences.IS_VISIBILITY_ON, false))
startScan();
}
}
private void startScan() {
if (sp.getBoolean(Constants.SharedPreferences.IS_VISIBILITY_ON, false)) {
Log.i(LOG_TAG, "Starting scanning");
try {
beaconManager.startMonitoringBeaconsInRegion(region);
isScanning = true;
} catch (RemoteException e) {
Log.e(LOG_TAG, "Remote Exception while starting Ranging", e);
}
}
}
private void stopScan() {
try {
beaconManager.stopMonitoringBeaconsInRegion(region);
beaconManager.stopRangingBeaconsInRegion(region);
isScanning = false;
} catch (RemoteException e) {
Log.e(LOG_TAG, "Remote Exception while stoping Ranging", e);
}
Log.i(LOG_TAG, "Stopping scanning");
}
SharedPreferences.OnSharedPreferenceChangeListener listener = new SharedPreferences.OnSharedPreferenceChangeListener() {
public void onSharedPreferenceChanged(SharedPreferences sp, String key) {
if (key.equalsIgnoreCase(Constants.SharedPreferences.IS_VISIBILITY_ON) && getActivity() != null) {
if (sp.getBoolean(Constants.SharedPreferences.IS_VISIBILITY_ON, false)) {
Log.i(LOG_TAG, "Visibility turned ON");
refreshScan();
} else {
Log.i(LOG_TAG, "Visibility turned off");
visbilityOffTasks();
}
}
}
};
private void visbilityOffTasks() {
stopScan();
deviceToBeaconMap.clear();
}
int onLostTimeoutMillis = 15000;
private void setOnLostRunnable() {
removeHandler.postDelayed(removeLostDevices, onLostTimeoutMillis);
}
private static final Handler removeHandler = new Handler(Looper.getMainLooper());
Runnable removeLostDevices = new Runnable() {
@Override
public void run() {
long time = System.currentTimeMillis();
Iterator<Map.Entry<String, Beacon>> itr = deviceToBeaconMap.entrySet().iterator();
while (itr.hasNext()) {
Beacon beacon = itr.next().getValue();
if (beacon != null && !beacon.deviceAddress.equalsIgnoreCase("default"))
if ((time - beacon.lastSeenTimestamp) > onLostTimeoutMillis) {
itr.remove();
if (BuildConfig.DEBUG)
Log.d(LOG_TAG, "Removing beacon " + beacon.deviceAddress + " Time is " + (time - beacon.lastSeenTimestamp));
}
}
removeHandler.postDelayed(this, onLostTimeoutMillis);
}
};
}
这是我观察到的扫描日志。即使停止扫描信标后，它们仍会继续出现。
12-25 22:27:59.103 30207-30207/com.robocats.main I/BlankFragment: Visibility turned ON
12-25 22:27:59.104 30207-30207/com.robocats.main I/BlankFragment: Starting scanning
12-25 22:27:59.105 30207-30207/com.robocats.main I/BlankFragment: State of region changed 0
12-25 22:27:59.105 30207-30207/com.robocats.main I/BlankFragment: State of region changed 0
12-25 22:27:59.105 30207-30207/com.robocats.main I/BlankFragment: State of region changed 0
12-25 22:27:59.105 30207-30207/com.robocats.main I/BlankFragment: State of region changed 0
12-25 22:27:59.105 30207-30207/com.robocats.main I/BlankFragment: State of region changed 0
12-25 22:27:59.105 30207-30207/com.robocats.main I/BlankFragment: State of region changed 0
12-25 22:27:59.105 30207-30207/com.robocats.main I/BlankFragment: State of region changed 0
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: State of region changed 1
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: In beacon region
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: State of region changed 1
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: In beacon region
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: State of region changed 1
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: In beacon region
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: State of region changed 1
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: In beacon region
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: State of region changed 1
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: In beacon region
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: State of region changed 1
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: In beacon region
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: State of region changed 1
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: In beacon region
12-25 22:28:09.515 30207-30207/com.robocats.main D/BlankFragment: Removing beacon 0C:F3:EE:09:3A:77 Time is 15036
12-25 22:28:09.642 30207-30207/com.robocats.main D/BlankFragment: Removing beacon 0C:F3:EE:09:3A:77 Time is 15161
12-25 22:28:13.497 30207-3224/com.robocats.main D/BlankFragment: New Beacon added 6bd54ac521c218b8f418000000000073 DeviceAddress 0C:F3:EE:09:3A:77
12-25 22:28:13.510 30207-3224/com.robocats.main D/BlankFragment: New Beacon added 6bd54ac521c218b8f418000000000073 DeviceAddress 0C:F3:EE:09:3A:77
12-25 22:28:19.086 30207-3381/com.robocats.main D/BlankFragment: New Beacon added 2f234454f4911ba9ffa100000d5181da DeviceAddress 0C:F3:EE:09:3C:63
12-25 22:28:19.096 30207-3381/com.robocats.main D/BlankFragment: New Beacon added 2f234454f4911ba9ffa100000d5181da DeviceAddress 0C:F3:EE:09:3C:63
12-25 22:28:22.886 30207-30207/com.robocats.main I/BlankFragment: Visibility turned off
12-25 22:28:22.887 30207-30207/com.robocats.main I/BlankFragment: Stopping scanning
12-25 22:28:23.586 30207-3468/com.robocats.main D/BlankFragment: New Beacon added 2f234454f4911ba9ffa100000d5181da DeviceAddress 0C:F3:EE:09:3C:63
12-25 22:28:23.589 30207-3468/com.robocats.main D/BlankFragment: New Beacon added 4b3833f4b99a463283e84bfcc601a926 DeviceAddress 48:59:02:49:FA:3F
12-25 22:28:24.706 30207-3483/com.robocats.main D/BlankFragment: New Beacon added 6bd54ac521c218b8f418000000000073 DeviceAddress 0C:F3:EE:09:3A:77
出于某种原因，我看到 onBeaconServiceConnect() 中的代码是 运行 两次。这可能是原因。让我知道为什么会发生这种情况。
我认为问题是由 Android 生命周期创建多个 BlankFragment 副本引起的。每次创建 BlankFragment 时，都会调用 onCreate 方法，并且代码会绑定到扫描服务并开始测距。因为在没有调用 onDestroy 的情况下创建了多个片段，所以您最终会同时遇到多个实例。调用 stopScan 时，它只会停止对最近创建的 Fragment 实例的测距。
一种解决方案是停止测距和监控，然后在片段离开视野时解除绑定。
我正在使用 Android 信标库扫描 Android 应用程序的 Eddystone 信标。我在连接信标服务后开始监控，然后在找到信标时开始测距。
我需要根据用户的选择停止扫描信标（停止监视和测距）。我正在使用
beaconManager.stopMonitoringBeaconsInRegion(region);
beaconManager.stopRangingBeaconsInRegion(region);
在我的 stopScan() 中停止扫描。但是测距并没有停止，尽管监控停止了。我做错了什么吗？
完整代码如下：
public class BlankFragment extends Fragment implements BeaconConsumer {
public BlankFragment() {
// Required empty public constructor
}
private static final int PERMISSION_REQUEST_FINE_LOCATION = 1;
private Region region;
private Map<String /* uid */, Beacon> deviceToBeaconMap = new HashMap<>();
String LOG_TAG = BlankFragment.class.getSimpleName();
SharedPreferences sp;
View rootView;
private BeaconManager beaconManager;
boolean isScanning = false;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
sp = PreferenceManager.getDefaultSharedPreferences(getActivity());
sp.registerOnSharedPreferenceChangeListener(listener);
beaconManager = BeaconManager.getInstanceForApplication(getContext());
beaconManager.getBeaconParsers().add(new BeaconParser().
setBeaconLayout("s:0-1=feaa,m:2-2=00,p:3-3:-41,i:4-13,i:14-19"));
beaconManager.bind(this);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
rootView = inflater.inflate(R.layout.fragment_near_me, container, false);
return rootView;
}
@Override
public void onStop() {
super.onStop();
if (isScanning)
stopScan();
}
@Override
public void onDestroy() {
super.onDestroy();
deviceToBeaconMap.clear();
beaconManager.unbind(this);
}
@Override
public void onBeaconServiceConnect() {
region = new Region("nearMeScanning", null, null, null);
Log.i(LOG_TAG, "OnBeaconServiceConnect called");
beaconManager.addMonitorNotifier(new MonitorNotifier() {
@Override
public void didEnterRegion(Region region) {
try {
beaconManager.startRangingBeaconsInRegion(region);
Log.i(LOG_TAG, "In beacon region");
} catch (RemoteException e) {
Log.e(LOG_TAG, "Remote Exception while starting Ranging", e);
}
}
@Override
public void didExitRegion(Region region) {
try {
beaconManager.stopRangingBeaconsInRegion(region);
Log.i(LOG_TAG, "Exited beacon region");
} catch (RemoteException e) {
Log.e(LOG_TAG, "Remote Exception while stoping Ranging", e);
}
}
@Override
public void didDetermineStateForRegion(int i, Region region) {
Log.i(LOG_TAG, "State of region changed " + i);
}
});
beaconManager.addRangeNotifier(new RangeNotifier() {
@Override
public void didRangeBeaconsInRegion(Collection<org.altbeacon.beacon.Beacon> beacons, Region region) {
if (beacons.size() > 0) {
for (org.altbeacon.beacon.Beacon scannedBeacon : beacons) {
setOnLostRunnable();
String deviceUUID = scannedBeacon.getId1().toString().substring(2) + scannedBeacon.getId2().toString().substring(2);
String deviceAddress = scannedBeacon.getBluetoothAddress();
int rssi = scannedBeacon.getRssi();
Beacon beacon;
if (!deviceToBeaconMap.containsKey(deviceUUID)) {
beacon = new Beacon(deviceAddress, rssi, deviceUUID);
deviceToBeaconMap.put(deviceUUID, beacon);
if (BuildConfig.DEBUG)
Log.d(LOG_TAG, "New Beacon added " + deviceUUID + " DeviceAddress " + deviceAddress);
} else {
deviceToBeaconMap.get(deviceUUID).lastSeenTimestamp = System.currentTimeMillis();
deviceToBeaconMap.get(deviceUUID).rssi = rssi;
}
}
}
}
});
if (sp.getBoolean(Constants.SharedPreferences.IS_VISIBILITY_ON, false)) {
refreshScan();
} else {
visbilityOffTasks();
}
}
@Override
public Context getApplicationContext() {
return getActivity().getApplicationContext();
}
@Override
public void unbindService(ServiceConnection serviceConnection) {
getActivity().unbindService(serviceConnection);
}
@Override
public boolean bindService(Intent intent, ServiceConnection serviceConnection, int i) {
return getActivity().bindService(intent, serviceConnection, i);
}
private void refreshScan() {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (getActivity().checkSelfPermission(Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
if (BuildConfig.DEBUG)
Log.d(LOG_TAG, "Will check for permissions");
requestPermissions(new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
PERMISSION_REQUEST_FINE_LOCATION);
} else {
if (sp.getBoolean(Constants.SharedPreferences.IS_VISIBILITY_ON, false))
startScan();
}
} else {
if (sp.getBoolean(Constants.SharedPreferences.IS_VISIBILITY_ON, false))
startScan();
}
}
private void startScan() {
if (sp.getBoolean(Constants.SharedPreferences.IS_VISIBILITY_ON, false)) {
Log.i(LOG_TAG, "Starting scanning");
try {
beaconManager.startMonitoringBeaconsInRegion(region);
isScanning = true;
} catch (RemoteException e) {
Log.e(LOG_TAG, "Remote Exception while starting Ranging", e);
}
}
}
private void stopScan() {
try {
beaconManager.stopMonitoringBeaconsInRegion(region);
beaconManager.stopRangingBeaconsInRegion(region);
isScanning = false;
} catch (RemoteException e) {
Log.e(LOG_TAG, "Remote Exception while stoping Ranging", e);
}
Log.i(LOG_TAG, "Stopping scanning");
}
SharedPreferences.OnSharedPreferenceChangeListener listener = new SharedPreferences.OnSharedPreferenceChangeListener() {
public void onSharedPreferenceChanged(SharedPreferences sp, String key) {
if (key.equalsIgnoreCase(Constants.SharedPreferences.IS_VISIBILITY_ON) && getActivity() != null) {
if (sp.getBoolean(Constants.SharedPreferences.IS_VISIBILITY_ON, false)) {
Log.i(LOG_TAG, "Visibility turned ON");
refreshScan();
} else {
Log.i(LOG_TAG, "Visibility turned off");
visbilityOffTasks();
}
}
}
};
private void visbilityOffTasks() {
stopScan();
deviceToBeaconMap.clear();
}
int onLostTimeoutMillis = 15000;
private void setOnLostRunnable() {
removeHandler.postDelayed(removeLostDevices, onLostTimeoutMillis);
}
private static final Handler removeHandler = new Handler(Looper.getMainLooper());
Runnable removeLostDevices = new Runnable() {
@Override
public void run() {
long time = System.currentTimeMillis();
Iterator<Map.Entry<String, Beacon>> itr = deviceToBeaconMap.entrySet().iterator();
while (itr.hasNext()) {
Beacon beacon = itr.next().getValue();
if (beacon != null && !beacon.deviceAddress.equalsIgnoreCase("default"))
if ((time - beacon.lastSeenTimestamp) > onLostTimeoutMillis) {
itr.remove();
if (BuildConfig.DEBUG)
Log.d(LOG_TAG, "Removing beacon " + beacon.deviceAddress + " Time is " + (time - beacon.lastSeenTimestamp));
}
}
removeHandler.postDelayed(this, onLostTimeoutMillis);
}
};
}
这是我观察到的扫描日志。即使停止扫描信标后，它们仍会继续出现。
12-25 22:27:59.103 30207-30207/com.robocats.main I/BlankFragment: Visibility turned ON
12-25 22:27:59.104 30207-30207/com.robocats.main I/BlankFragment: Starting scanning
12-25 22:27:59.105 30207-30207/com.robocats.main I/BlankFragment: State of region changed 0
12-25 22:27:59.105 30207-30207/com.robocats.main I/BlankFragment: State of region changed 0
12-25 22:27:59.105 30207-30207/com.robocats.main I/BlankFragment: State of region changed 0
12-25 22:27:59.105 30207-30207/com.robocats.main I/BlankFragment: State of region changed 0
12-25 22:27:59.105 30207-30207/com.robocats.main I/BlankFragment: State of region changed 0
12-25 22:27:59.105 30207-30207/com.robocats.main I/BlankFragment: State of region changed 0
12-25 22:27:59.105 30207-30207/com.robocats.main I/BlankFragment: State of region changed 0
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: State of region changed 1
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: In beacon region
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: State of region changed 1
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: In beacon region
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: State of region changed 1
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: In beacon region
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: State of region changed 1
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: In beacon region
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: State of region changed 1
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: In beacon region
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: State of region changed 1
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: In beacon region
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: State of region changed 1
12-25 22:28:00.061 30207-2969/com.robocats.main I/BlankFragment: In beacon region
12-25 22:28:09.515 30207-30207/com.robocats.main D/BlankFragment: Removing beacon 0C:F3:EE:09:3A:77 Time is 15036
12-25 22:28:09.642 30207-30207/com.robocats.main D/BlankFragment: Removing beacon 0C:F3:EE:09:3A:77 Time is 15161
12-25 22:28:13.497 30207-3224/com.robocats.main D/BlankFragment: New Beacon added 6bd54ac521c218b8f418000000000073 DeviceAddress 0C:F3:EE:09:3A:77
12-25 22:28:13.510 30207-3224/com.robocats.main D/BlankFragment: New Beacon added 6bd54ac521c218b8f418000000000073 DeviceAddress 0C:F3:EE:09:3A:77
12-25 22:28:19.086 30207-3381/com.robocats.main D/BlankFragment: New Beacon added 2f234454f4911ba9ffa100000d5181da DeviceAddress 0C:F3:EE:09:3C:63
12-25 22:28:19.096 30207-3381/com.robocats.main D/BlankFragment: New Beacon added 2f234454f4911ba9ffa100000d5181da DeviceAddress 0C:F3:EE:09:3C:63
12-25 22:28:22.886 30207-30207/com.robocats.main I/BlankFragment: Visibility turned off
12-25 22:28:22.887 30207-30207/com.robocats.main I/BlankFragment: Stopping scanning
12-25 22:28:23.586 30207-3468/com.robocats.main D/BlankFragment: New Beacon added 2f234454f4911ba9ffa100000d5181da DeviceAddress 0C:F3:EE:09:3C:63
12-25 22:28:23.589 30207-3468/com.robocats.main D/BlankFragment: New Beacon added 4b3833f4b99a463283e84bfcc601a926 DeviceAddress 48:59:02:49:FA:3F
12-25 22:28:24.706 30207-3483/com.robocats.main D/BlankFragment: New Beacon added 6bd54ac521c218b8f418000000000073 DeviceAddress 0C:F3:EE:09:3A:77
出于某种原因，我看到 onBeaconServiceConnect() 中的代码是 运行 两次。这可能是原因。让我知道为什么会发生这种情况。
我认为问题是由 Android 生命周期创建多个 BlankFragment 副本引起的。每次创建 BlankFragment 时，都会调用 onCreate 方法，并且代码会绑定到扫描服务并开始测距。因为在没有调用 onDestroy 的情况下创建了多个片段，所以您最终会同时遇到多个实例。调用 stopScan 时，它只会停止对最近创建的 Fragment 实例的测距。
一种解决方案是停止测距和监控，然后在片段离开视野时解除绑定。