蓝牙LE扫描在后台无法在Android M上运行

Question

以下代码适用于运行Android 5.1.1(Build LMY48M)的Nexus 9,但不适用于运行Android 6.0的Nexus 9(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() {
  ...
});

在Android 5.x上,当看到与扫描过滤器匹配的制造商广告时,上述代码产生回调.(参见下面的示例Logcat输出.)在带有MPA44l的Nexus 9上,没有收到回调.如果您注释掉扫描过滤器,则会在Nexus 9上成功接收回调.

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}

有没有人看过ScanFilters在Android M上工作？

Answer 1

我的应用程序连接到蓝牙也有类似的问题.不是LE ScanFilter,但它是一个权限问题,就像OP一样.

根本原因在于,首先是SDK 23,你需要提示用户在系统运行时的权限Activity的requestPermissions()方法.

这对我有用:

1. AndroidManifest.xml在根节点内添加以下两行之一:

   <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
   <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
   

2. 在你的活动,试图连接到蓝牙之前,调用Activity的requestPermissions()方法,这将打开一个系统对话框,以提示输入权限的用户.权限对话框在另一个线程中打开,因此在尝试连接到蓝牙之前一定要等待结果.

3. 覆盖Activity的onRequestPermissionsResult()处理结果.如果用户拒绝授予权限,该方法实际上只需要做一些事情,告诉用户应用程序不能进行蓝牙活动.

这篇博文有一些示例代码,它使用AlertDialogs告诉用户发生了什么.这是一个很好的起点,但有一些缺点:

• 它不处理等待requestPermissions()线程完成
• 包含调用的AlertDialog requestPermissions()对我来说似乎无关紧要.裸露的电话requestPermissions()就足够了.

Answer 2

问题不在于扫描过滤器,而是在应用程序在后台时才使用扫描过滤器.从Android M开始,除非应用具有以下两种权限之一,否则后台蓝牙LE扫描将被阻止:

android.permission.ACCESS_COARSE_LOCATION
android.permission.ACCESS_FINE_LOCATION

我正在测试的应用程序没有请求这些权限中的任何一个,因此它在Android M后台(在扫描过滤器处于活动状态的唯一时间)不起作用.添加第一个解决了问题.

我意识到这是问题,因为我在Logcat中看到以下行:

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

有关详细信息,请参阅此处:https: //code.google.com/p/android-developer-preview/issues/detail？id = 2964

Answer 3

添加位置权限以及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" />

复制粘贴此方法以请求和授予位置权限

  @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;
    }

然后在onCreate上检查是否允许

 if (Build.VERSION.SDK_INT >= 23) {
            // Marshmallow+ Permission APIs
            fuckMarshMallow();
        }

希望它能节省您的时间.