Android 6.0及以上版本无法扫描BLE设备的技术求助

Hey there, let's tackle this BLE scanning issue on Android 6.0! The root cause here is almost always tied to runtime permissions—a key change introduced in Android 6.0 (API 23) that didn't affect your Android 5.1.1 device. Let's break down the fix step by step.

1. Understand the Core Problem #

Android 6.0 shifted from install-time permission grants to runtime requests for "dangerous" permissions. BLE scanning relies on location permissions (ACCESS_COARSE_LOCATION or ACCESS_FINE_LOCATION) because BLE beacons can be used to infer a user's physical location. Your Samsung J3 (5.1.1) works because it uses the old permission model where permissions are granted upfront during installation.

2. Verify Gradle & Manifest Setup #

First, confirm your configuration includes the necessary declarations and SDK targets:

Module-level build.gradle Snippet #

Ensure your target SDK version is aligned with modern practices (runtime permissions are enforced if targetSdkVersion >= 23):

android {
    compileSdkVersion 33
    defaultConfig {
        applicationId "com.your.ble.app"
        minSdkVersion 21
        targetSdkVersion 33
        versionCode 1
        versionName "1.0"
    }
}

Required AndroidManifest.xml Permissions #

Even with runtime permissions, you must declare these in your manifest:

<!-- BLE core permissions -->
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<!-- Location permissions for BLE scanning -->
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

<!-- Declare app requires BLE hardware -->
<uses-feature android:name="android.hardware.bluetooth_le" android:required="true" />

3. Fix Your Scanning Activity #

You need to add runtime permission checks before initiating any BLE scan. Here's how to modify your activity:

Step 1: Define Constants & Variables #

Add these to your activity class:

private static final int REQUEST_LOCATION_PERMISSION = 100;
private BluetoothLeScanner bleScanner;
private BluetoothAdapter bluetoothAdapter;

Step 2: Check Permissions Before Scanning #

Add logic to request permissions if they're not already granted before starting the scan:

private void startBleScan() {
    // First, ensure Bluetooth is enabled
    if (bluetoothAdapter == null || !bluetoothAdapter.isEnabled()) {
        Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
        startActivityForResult(enableBtIntent, 1);
        return;
    }

    // Check if location permission is granted
    if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION)
            != PackageManager.PERMISSION_GRANTED) {
        // Request permission from the user
        ActivityCompat.requestPermissions(this,
                new String[]{Manifest.permission.ACCESS_COARSE_LOCATION},
                REQUEST_LOCATION_PERMISSION);
        return;
    }

    // Permission granted—start scanning
    bleScanner = bluetoothAdapter.getBluetoothLeScanner();
    bleScanner.startScan(scanCallback);
}

Step 3: Handle Permission Request Results #

Override the callback to resume scanning once permission is granted:

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    if (requestCode == REQUEST_LOCATION_PERMISSION) {
        if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            // Permission approved—start scanning
            startBleScan();
        } else {
            // Permission denied—notify the user
            Toast.makeText(this, "Location permission is required to scan BLE devices", Toast.LENGTH_SHORT).show();
        }
    }
}

Step 4: (Optional) Check Location Services #

Some Android 6.0 devices require Location Services to be enabled for BLE scanning. Add this check if you encounter further issues:

private boolean isLocationEnabled() {
    LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    return locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER) ||
            locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
}

Call this in startBleScan() and prompt the user to enable location services if it's disabled.

4. Quick Best Practices #

• Always stop BLE scans when they're no longer needed (e.g., in onPause() or onDestroy()) to save battery.
• If your targetSdkVersion is below 23, Android 6.0 will auto-grant permissions at install time, but adding runtime handling ensures future compatibility.

内容的提问来源于stack exchange，提问作者bircastri