Android BLE扫描部分设备名称返回null问题求助

我是一名Android应用开发初学者，正在开发一款与ESP32微控制器通信的BLE应用。已成功配置应用（开启BLE和位置权限），并能扫描附近BLE设备，但发现调用BA.startDiscovery()时，部分设备的名称被检测为null。

调试日志 #

E/SCAN BUTTON: Clicked 
E/CHECK: CHECKING LOCATION PERMISSION 
E/INFO: LOCATION PERMISSION ALREADY GRANTED: 
E/INFO: LOCATION PERMISSION IS OK, START BLE DISCOVERY 
I/BluetoothAdapter: startDiscovery
E/CALLBACK: onReceive
E/BroadcastReceiver: SCANNING IN PROGRESS
E/CALLBACK: onReceive
I/System.out: DEVICE NAME FOUND = DESKTOP-KPO80BS
I/System.out: DEVICE MAC FOUND = 64:6E:69:78:B9:54
E/CALLBACK: onReceive
I/System.out: DEVICE NAME FOUND = null
I/System.out: DEVICE MAC FOUND = 5E:52:CD:CD:EB:EA
E/CALLBACK: onReceive
I/System.out: DEVICE NAME FOUND = [LG] webOS TV UP75003LF
I/System.out: DEVICE MAC FOUND = 4C:BC:E9:4E:62:17
E/CALLBACK: onReceive
I/System.out: DEVICE NAME FOUND = null
I/System.out: DEVICE MAC FOUND = 7F:CA:0B:28:8E:86
E/CALLBACK: onReceive
I/System.out: DEVICE NAME FOUND = CGATES-DV8947
I/System.out: DEVICE MAC FOUND = 10:76:36:B5:7C:A4
E/CALLBACK: onReceive
I/System.out: DEVICE NAME FOUND = [LG] webOS TV UP75003LF
I/System.out: DEVICE MAC FOUND = 7C:5E:DC:65:EB:E9
E/CALLBACK: onReceive
I/System.out: DEVICE NAME FOUND = JBL Bar 5.1_5883
I/System.out: DEVICE MAC FOUND = 7E:96:FC:6A:9F:A9
E/CALLBACK: onReceive
I/System.out: DEVICE NAME FOUND = null
I/System.out: DEVICE MAC FOUND = 4E:AE:EC:2B:D9:52
E/CALLBACK: onReceive
E/BroadcastReceiver: DISCOVERY FINISHED 

设备显示效果 #

build.gradle配置 #

plugins {
    id 'com.android.application'
}

android {
    namespace 'com.example.location_test_v2'
    compileSdk 33

    defaultConfig {
        applicationId "com.example.location_test_v2"
        minSdk 25
        targetSdk 33
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}

dependencies {

    implementation "androidx.fragment:fragment:1.5.6"
    implementation "androidx.activity:activity:1.7.0"
    implementation 'androidx.appcompat:appcompat:1.6.1'
    implementation 'com.google.android.material:material:1.8.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
    testImplementation 'junit:junit:4.13.2'
    androidTestImplementation 'androidx.test.ext:junit:1.1.5'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.1'
}

configurations.implementation {
    exclude group: 'org.jetbrains.kotlin', module: 'kotlin-stdlib-jdk8'
}

扫描回调代码 #

private final BroadcastReceiver devicesFoundReceiver = new BroadcastReceiver() {
    public void onReceive(Context context, Intent intent) {
        Log.e("CALLBACK", "onReceive");
        String action = intent.getAction();
        if (BluetoothDevice.ACTION_FOUND.equals(action)) {

            BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
            String deviceName = device.getName();
            String deviceHardwareAddress = device.getAddress(); // MAC address

            System.out.print("DEVICE NAME FOUND = ");
            System.out.println(deviceName);
            System.out.print("DEVICE MAC FOUND = ");
            System.out.println(deviceHardwareAddress);
            list.add(deviceName);
            
        }
        else if(BA.ACTION_DISCOVERY_FINISHED.equals(action)){
            Log.e("BroadcastReceiver", "DISCOVERY FINISHED ");
            ArrayAdapter adapter = new ArrayAdapter(MainActivity.this, android.R.layout.simple_list_item_1,list);
            listview.setAdapter(adapter);
        }
        else if(BA.ACTION_DISCOVERY_STARTED.equals(action)){
            listview.setAdapter(null);
            Log.e("BroadcastReceiver", "SCANNING IN PROGRESS");
        }
    }
};

问题解决建议 #

核心原因 #

BluetoothAdapter.startDiscovery()是经典蓝牙扫描API，并非专为BLE设备设计。对于BLE设备，它可能无法正确解析广播包中的设备名称；部分BLE设备本身未设置广播名称；或者Android系统的扫描缓存/过滤逻辑导致名称无法被获取。

方案1：改用BLE专用扫描API #

替换经典扫描为BLE原生扫描API，能直接获取BLE广播数据，从中解析设备名称：

// 初始化BLE扫描器
BluetoothLeScanner bleScanner = BluetoothAdapter.getDefaultAdapter().getBluetoothLeScanner();

// 配置扫描参数
ScanSettings scanSettings = new ScanSettings.Builder()
        .setScanMode(ScanSettings.SCAN_MODE_LOW_LATENCY) // 低延迟模式，适合主动扫描
        .build();

// 开始扫描（可添加过滤条件，这里为空）
bleScanner.startScan(new ArrayList<>(), scanSettings, new ScanCallback() {
    @Override
    public void onScanResult(int callbackType, ScanResult result) {
        super.onScanResult(callbackType, result);
        BluetoothDevice device = result.getDevice();
        String deviceName = device.getName();
        
        // 如果getName()为null，从广播包中解析名称
        if (deviceName == null) {
            ScanRecord scanRecord = result.getScanRecord();
            if (scanRecord != null) {
                deviceName = scanRecord.getDeviceName();
                // 若仍为空，自定义默认名称
                if (deviceName == null) deviceName = "Unknown BLE Device";
            }
        }
        
        String macAddress = device.getAddress();
        // 将设备信息添加到列表
        list.add(deviceName + " (" + macAddress + ")");
    }

    @Override
    public void onScanFailed(int errorCode) {
        super.onScanFailed(errorCode);
        Log.e("BLE_SCAN", "扫描失败，错误码：" + errorCode);
    }
});

方案2：优化现有代码的null值处理 #

如果暂时不想切换扫描API，可在现有回调中处理null名称，避免列表显示异常：

// 修改回调中的设备名称处理逻辑
String deviceName = device.getName();
// 当名称为null时替换为自定义文本
if (deviceName == null) {
    deviceName = "未知设备";
}
list.add(deviceName);

方案3：检查ESP32的BLE配置 #

确保ESP32的BLE广播中正确设置了设备名称，以Arduino代码为例：

#include <BLEDevice.h>

void setup() {
  // 初始化BLE设备并设置广播名称
  BLEDevice::init("ESP32_MyDevice"); 
  // ... 其他BLE配置代码
}

如果ESP32未设置广播名称，扫描到的设备名称自然为null。

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