RxAndroidBle库scanBleDevices方法调用报错问题求助

Hey there! Let's break down the issues you're facing with RxAndroidBle 1.10.0 in Kotlin and fix them step by step.

First Issue: Error in Java-style scanBleDevices call #

The core problem here is Kotlin doesn't use Java's new keyword for object instantiation. Your original code uses new ScanSettings.Builder() which is invalid in Kotlin. Here's the corrected version:

// Initialize RxBleClient correctly
val rxBleClient = RxBleClient.create(this)

// Build scan settings without the 'new' keyword
val scanSettings = ScanSettings.Builder()
    // Uncomment these if needed
    // .setScanMode(ScanSettings.SCAN_MODE_LOW_LATENCY)
    // .setCallbackType(ScanSettings.CALLBACK_TYPE_ALL_MATCHES)
    .build()

// Start scan - no filters added here, but you can add them later
val scanSubscription = rxBleClient.scanBleDevices(scanSettings)
    .subscribe(
        { scanResult ->
            // Process your scan result here
            println("Discovered device: ${scanResult.bleDevice.macAddress}")
        },
        { error ->
            // Handle scan errors here
            error.printStackTrace()
        }
    )

// Don't forget to dispose when you're done scanning
// scanSubscription.dispose()

Second Issue: Observable type error & scanBleDevices parameter mismatch #

You're hitting two separate problems here:

1. Observable type error: Make sure you're importing the correct RxJava 2 Observable (RxAndroidBle 1.x relies on RxJava 2). Double-check your imports include:

   import io.reactivex.Observable
   import com.polidea.rxandroidble2.scan.ScanResult
   

   Using the wrong Observable class (like RxJava 3 or Java's built-in Observable) will cause the "No type arguments expected" error.

2. Parameter mismatch for scanBleDevices: The method expects ScanSettings plus a vararg ScanFilter (variable number of filters). In Kotlin, to pass a single filter to a vararg parameter, you need to use the spread operator (*). Here's the fixed function:

private fun scanBleDevices(): Observable<ScanResult> {
    val scanSettings = ScanSettings.Builder()
        .setScanMode(ScanSettings.SCAN_MODE_LOW_LATENCY)
        .setCallbackType(ScanSettings.CALLBACK_TYPE_ALL_MATCHES)
        .build()

    val scanFilter = ScanFilter.Builder()
        // .setDeviceAddress("B4:99:4C:34:DC:8B") // Uncomment if filtering by address
        .build()

    // Use spread operator to pass the single filter to vararg parameter
    return rxBleClient.scanBleDevices(scanSettings, *arrayOf(scanFilter))
    
    // If you don't need any filters, you can simplify to:
    // return rxBleClient.scanBleDevices(scanSettings)
}

Quick Additional Check #

Don't forget to ensure your app has the necessary BLE permissions in AndroidManifest.xml (and request runtime location permission for Android 6.0+):

<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-feature android:name="android.hardware.bluetooth_le" android:required="true" />

内容的提问来源于stack exchange，提问作者Alejandro Gorgues