如果从 BOOT_COMPLETED 初始化，前台服务中的 BLE 扫描器不会返回扫描结果

Question

所以情况如下。我有一个 Android 应用程序在运行 Android 10 的 AndroidTV 设备上运行。

该应用程序包含一个前台服务，它不断扫描特定设备（通过 MAC 地址）。像这样：

import no.nordicsemi.android.support.v18.scanner.BluetoothLeScannerCompat
import no.nordicsemi.android.support.v18.scanner.ScanCallback
import no.nordicsemi.android.support.v18.scanner.ScanFilter
import no.nordicsemi.android.support.v18.scanner.ScanResult
import no.nordicsemi.android.support.v18.scanner.ScanSettings

fun scan() {
    BluetoothLeScannerCompat.getScanner()
        .startScan(
            /* MAC address filters */ filters, 
            ScanSettings.Builder()
                .setLegacy(false)
                .setScanMode(ScanSettings.SCAN_MODE_LOW_LATENCY)
                .setUseHardwareBatchingIfSupported(false)
                .setReportDelay(5000)
                .build(), 
            /* Standard callback */ callback
        )
}

当应用程序从启动器（MainActivity）启动时，效果很好：

override fun onCreate(savedInstanceState: Bundle?) {
    // ... UI stuff ...

    startForegroundService(Intent(this, BleService::class.java))
}

但是，当电视盒重新启动时，服务会像这样初始化（BOOT_COMPLETED）接收器：

class BootCompletedReceiver: BroadcastReceiver() {
    override fun onReceive(context: Context?, intent: Intent?) {
        if (intent?.action == Intent.ACTION_BOOT_COMPLETED) {
            context?.startForegroundService(Intent(context, BleService::class.java))
        }
    }
}

现在奇怪的是，当这样启动服务时，没有任何scanResults！即使蓝牙设备在范围内。然而，因此从启动器打开应用程序并重新启动扫描仪确实会产生结果。

BluetoothAdapter        D  isLeEnabled(): ON
BluetoothLeScanner      D  onScannerRegistered() - status=0 scannerId=5 mScannerId=0
BluetoothScanJob        I  Start Scan
BluetoothS...b$callback I  [onBatchScanResults]: Results=[]

需要考虑的一些事项：

服务正确初始化并启动 BLE 扫描仪，无论哪种方式都没有错误

• 我总是在 LogCat 中得到
onScannerRegistered()
• 确认因此这不可能是
BOOT_COMPLETED
• 广播 的问题 我尝试在服务启动和扫描仪初始化之间添加 20 秒的延迟。
• 有或没有报告延迟使用都没有区别
• 我已经添加了所有清单和运行时权限。请参阅下面我的清单以供参考：

<manifest <!-- Removed for brevity -->>

    <!-- Removed for brevity -->

    <!-- Bluetooth access up to SDK 30 -->
    <uses-permission android:name="android.permission.BLUETOOTH" android:maxSdkVersion="30" />
    <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" android:maxSdkVersion="30" />
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" android:maxSdkVersion="30" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" android:maxSdkVersion="30" />

    <!-- Bluetooth access from SDK 30 onwards -->
    <uses-permission android:name="android.permission.BLUETOOTH_CONNECT"/>
    <uses-permission android:name="android.permission.FOREGROUND_SERVICE"/>
    <uses-permission android:name="android.permission.BLUETOOTH_SCAN"
        android:usesPermissionFlags="neverForLocation"
        tools:targetApi="31" />

    <!-- Foreground service -->
    <uses-permission android:name="android.permission.FOREGROUND_SERVICE_CONNECTED_DEVICE"/>

    <!-- Autostart service -->
    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />

    <!-- Require BLE hardware capability -->
    <uses-feature
        android:name="android.hardware.bluetooth_le"
        android:required="true"/>

    <application <!-- Removed for brevity -->>

        <receiver
            android:name=".service.BootCompletedReceiver"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED" />
            </intent-filter>
        </receiver>

        <service
            android:name=".service.BleService"
            android:label="@string/service_name"
            android:description="@string/service_description"
            android:exported="false"
            android:foregroundServiceType="connectedDevice"/>

        <activity
            android:name=".ui.main.MainActivity"
            android:exported="true">

            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <provider
            android:name="androidx.startup.InitializationProvider"
            android:authorities="${applicationId}.androidx-startup"
            tools:node="remove">
        </provider>

    </application>

</manifest>

Answer 1

ACCESS_BACKGROUND_LOCATION

请注意<= 11.

如果您同时请求前台位置权限和后台位置权限，系统会忽略该请求，并且不会授予您的应用任何权限。

https://developer.android.com/develop/sensors-and-location/location/permissions#request-background-location