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问题:
The following code works great on my Nexus 9 running Android 5.1.1 (Build LMY48M), but won't work on a Nexus 9 running Android 6.0 (Build MPA44l)
List<ScanFilter> filters = new ArrayList<ScanFilter>();
ScanSettings settings = (new ScanSettings.Builder().setScanMode(ScanSettings.SCAN_MODE_LOW_POWER)).build();
ScanFilter.Builder builder = new ScanFilter.Builder();
builder.setManufacturerData((int) 0x0118, new byte[]{(byte) 0xbe, (byte) 0xac}, new byte[]{(byte) 0xff, (byte)0xff});
ScanFilter scanFilter = builder.build();
filters.add(scanFilter);
mBluetoothLeScanner.startScan(filters, settings, new ScanCallback() {
...
});
On Android 5.x, the above code yields a callback when a manufacturer advertisement matching the scan filter is seen. (See example Logcat output below.) On the Nexus 9 with MPA44l, no callbacks are received. If you comment out the scan filter, callbacks are received successfully on the Nexus 9.
09-22 00:07:28.050 1748-1796/org.altbeacon.beaconreference D/BluetoothLeScanner﹕ onScanResult() - ScanResult{mDevice=00:07:80:03:89:8C, mScanRecord=ScanRecord [mAdvertiseFlags=6, mServiceUuids=null, mManufacturerSpecificData={280=[-66, -84, 47, 35, 68, 84, -49, 109, 74, 15, -83, -14, -12, -111, 27, -87, -1, -90, 0, 1, 0, 1, -66, 0]}, mServiceData={}, mTxPowerLevel=-2147483648, mDeviceName=null], mRssi=-64, mTimestampNanos=61272522487278}
Has anybody seen ScanFilters work on Android M?
回答1:
I had a similar problem with an app connecting to bluetooth. Not LE ScanFilter, but it was a permissions issue just like the OP had.
Root cause is that starting with SDK 23, you need to prompt the user for permissions at runtime using Activity's requestPermissions() method.
Here's what worked for me:
Add one of the following two lines to AndroidManifest.xml, inside the root node:
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
In your Activity, before attempting to connect to bluetooth, call Activity's requestPermissions() method, which opens a system dialog to prompt the user for the permission. The permissions dialog opens in a different thread, so be sure to wait for the result before trying to connect to bluetooth.
Override Activity's onRequestPermissionsResult() to handle the result. This method will really only need to do something if the user refused to grant the permission, to tell the user that the app can't do the bluetooth activity.
This blog post has some example code that uses AlertDialogs to tell the user what's going on. It is a good starting point but has some shortcomings:
- It doesn't handle waiting for the
requestPermissions() thread to finish
- The AlertDialog wrapping the call to
requestPermissions() seems extraneous to me. A bare call to requestPermissions() is sufficient.
回答2:
The problem was not the scan filter, but that the scan filter was only being used when the app was in the background. (EDIT: This solution is out of date for Android 10 see below.) Starting with Android M, Bluetooth LE scanning in the background is blocked unless the app has one of the following two permissions:
android.permission.ACCESS_COARSE_LOCATION
android.permission.ACCESS_FINE_LOCATION
The app I was testing did not request either of these permissions, so it did not work in the background (the only time the scan filter was active) on Android M. Adding the first one solved the problem.
I realized this was the problem because I saw the following line in Logcat:
09-22 22:35:20.152 5158 5254 E BluetoothUtils: Permission denial: Need ACCESS_COARSE_LOCATION or ACCESS_FINE_LOCATION permission to get scan results
See here for details: https://code.google.com/p/android-developer-preview/issues/detail?id=2964
EDIT: As of Android 10, coarse location is not enough -- you need fine location and a special background permission to detect BLE advertisements and beacons in the background. See here for details.
Place the following in your AndroidManifest.xml:
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.ACCESS_BLUETOOTH_ADMIN" />
<uses-permission android:name="android.permission.ACCESS_BACKGROUND_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
Then add code like follows to your Activity to dynamically request these permissions from the user:
private static final int PERMISSION_REQUEST_FINE_LOCATION = 1;
private static final int PERMISSION_REQUEST_BACKGROUND_LOCATION = 2;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
...
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (this.checkSelfPermission(Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
if (this.checkSelfPermission(Manifest.permission.ACCESS_BACKGROUND_LOCATION)
!= PackageManager.PERMISSION_GRANTED) {
if (this.shouldShowRequestPermissionRationale(Manifest.permission.ACCESS_BACKGROUND_LOCATION)) {
final AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("This app needs background location access");
builder.setMessage("Please grant location access so this app can detect beacons in the background.");
builder.setPositiveButton(android.R.string.ok, null);
builder.setOnDismissListener(new DialogInterface.OnDismissListener() {
@TargetApi(23)
@Override
public void onDismiss(DialogInterface dialog) {
requestPermissions(new String[]{Manifest.permission.ACCESS_BACKGROUND_LOCATION},
PERMISSION_REQUEST_BACKGROUND_LOCATION);
}
});
builder.show();
}
else {
final AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("Functionality limited");
builder.setMessage("Since background location access has not been granted, this app will not be able to discover beacons in the background. Please go to Settings -> Applications -> Permissions and grant background location access to this app.");
builder.setPositiveButton(android.R.string.ok, null);
builder.setOnDismissListener(new DialogInterface.OnDismissListener() {
@Override
public void onDismiss(DialogInterface dialog) {
}
});
builder.show();
}
}
} else {
if (!this.shouldShowRequestPermissionRationale(Manifest.permission.ACCESS_FINE_LOCATION)) {
requestPermissions(new String[]{Manifest.permission.ACCESS_FINE_LOCATION,
Manifest.permission.ACCESS_BACKGROUND_LOCATION},
PERMISSION_REQUEST_FINE_LOCATION);
}
else {
final AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("Functionality limited");
builder.setMessage("Since location access has not been granted, this app will not be able to discover beacons. Please go to Settings -> Applications -> Permissions and grant location access to this app.");
builder.setPositiveButton(android.R.string.ok, null);
builder.setOnDismissListener(new DialogInterface.OnDismissListener() {
@Override
public void onDismiss(DialogInterface dialog) {
}
});
builder.show();
}
}
}
}
回答3:
Add location permission along with BLE
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
Copy Paste this method to request and grant location permission
@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
switch (requestCode) {
case REQUEST_CODE_ASK_MULTIPLE_PERMISSIONS: {
Map<String, Integer> perms = new HashMap<String, Integer>();
// Initial
perms.put(Manifest.permission.ACCESS_FINE_LOCATION, PackageManager.PERMISSION_GRANTED);
// Fill with results
for (int i = 0; i < permissions.length; i++)
perms.put(permissions[i], grantResults[i]);
// Check for ACCESS_FINE_LOCATION
if (perms.get(Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED
) {
// All Permissions Granted
// Permission Denied
Toast.makeText(ScanningActivity.this, "All Permission GRANTED !! Thank You :)", Toast.LENGTH_SHORT)
.show();
} else {
// Permission Denied
Toast.makeText(ScanningActivity.this, "One or More Permissions are DENIED Exiting App :(", Toast.LENGTH_SHORT)
.show();
finish();
}
}
break;
default:
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
}
}
@TargetApi(Build.VERSION_CODES.M)
private void fuckMarshMallow() {
List<String> permissionsNeeded = new ArrayList<String>();
final List<String> permissionsList = new ArrayList<String>();
if (!addPermission(permissionsList, Manifest.permission.ACCESS_FINE_LOCATION))
permissionsNeeded.add("Show Location");
if (permissionsList.size() > 0) {
if (permissionsNeeded.size() > 0) {
// Need Rationale
String message = "App need access to " + permissionsNeeded.get(0);
for (int i = 1; i < permissionsNeeded.size(); i++)
message = message + ", " + permissionsNeeded.get(i);
showMessageOKCancel(message,
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
requestPermissions(permissionsList.toArray(new String[permissionsList.size()]),
REQUEST_CODE_ASK_MULTIPLE_PERMISSIONS);
}
});
return;
}
requestPermissions(permissionsList.toArray(new String[permissionsList.size()]),
REQUEST_CODE_ASK_MULTIPLE_PERMISSIONS);
return;
}
Toast.makeText(ScanningActivity.this, "No new Permission Required- Launching App .You are Awesome!!", Toast.LENGTH_SHORT)
.show();
}
private void showMessageOKCancel(String message, DialogInterface.OnClickListener okListener) {
new AlertDialog.Builder(ScanningActivity.this)
.setMessage(message)
.setPositiveButton("OK", okListener)
.setNegativeButton("Cancel", null)
.create()
.show();
}
@TargetApi(Build.VERSION_CODES.M)
private boolean addPermission(List<String> permissionsList, String permission) {
if (checkSelfPermission(permission) != PackageManager.PERMISSION_GRANTED) {
permissionsList.add(permission);
// Check for Rationale Option
if (!shouldShowRequestPermissionRationale(permission))
return false;
}
return true;
}
And then in onCreate check for permission
if (Build.VERSION.SDK_INT >= 23) {
// Marshmallow+ Permission APIs
fuckMarshMallow();
}
Hope it save your time.
回答4:
If your app targets Android Q, it's not enough with only coarse location, you need to use fine location, otherwise you will get this error:
E/BluetoothUtils: Permission denial: Need ACCESS_FINE_LOCATION permission to get scan results
See https://developer.android.com/preview/privacy/camera-connectivity#fine-location-telephony-wifi-bt for the official source.
