//藍牙發現設備和查找結束廣播
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction(BluetoothDevice.ACTION_FOUND);
intentFilter.addAction(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
registerReceiver(btReceiver, intentFilter);
BroadcastReceiver btReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        if (BluetoothDevice.ACTION_FOUND.equals(intent.getAction())) {
            BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
            if (device != null) {
                //這里收到的是單條設備信息，可以放到List中進行刷新列表
                //設備名稱：device.getName()
                //設備地址：device.getAddress()
                if(device.getBondState() == BluetoothDevice.BOND_BONDED) {
                    //已配對設備
                }
            }
        } else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(intent.getAction())) {
                //查找結束
        }
    }
};

btAdapter.startDiscovery();

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

if(Build.VERSION.SDK_INT>=Build.VERSION_CODES.M
         && checkSelfPermission(Manifest.permission.ACCESS_FINE_LOCATION)!= PackageManager.PERMISSION_GRANTED) {//請求權限
    requestPermissions(new String[]{Manifest.permission.ACCESS_FINE_LOCATION},1);
}

private IBluetooth mService;
public boolean startDiscovery() {
    if (getState() != STATE_ON) {
        return false;
    }
    try {
        mServiceLock.readLock().lock();
        if (mService != null) {
            return mService.startDiscovery(mAttributionSource);
        }
    } catch (RemoteException e) {
        Log.e(TAG, "", e);
    } finally {
        mServiceLock.readLock().unlock();
    }
    return false;
}

public boolean startDiscovery(AttributionSource attributionSource) {
    AdapterService service = getService();
    if (service == null || !callerIsSystemOrActiveUser(TAG, "startDiscovery")) {
        return false;
    }
    if (!Utils.checkScanPermissionForDataDelivery(
        service, attributionSource, "Starting discovery.")) {
        return false;
    }
    return service.startDiscovery(attributionSource);
}
boolean startDiscovery(AttributionSource attributionSource) {
    UserHandle callingUser = UserHandle.of(UserHandle.getCallingUserId());
    debugLog("startDiscovery");
    String callingPackage = attributionSource.getPackageName();
    mAppOps.checkPackage(Binder.getCallingUid(), callingPackage);
    boolean isQApp = Utils.isQApp(this, callingPackage);
    boolean hasDisavowedLocation = Utils.hasDisavowedLocationForScan(this, attributionSource, mTestModeEnabled);
    String permission = null;
    if (Utils.checkCallerHasNetworkSettingsPermission(this)) {
        permission = android.Manifest.permission.NETWORK_SETTINGS;
    } else if (Utils.checkCallerHasNetworkSetupWizardPermission(this)) {
        permission = android.Manifest.permission.NETWORK_SETUP_WIZARD;
    } else if (!hasDisavowedLocation) {
        if (isQApp) {
            if (!Utils.checkCallerHasFineLocation(this, attributionSource, callingUser)) {
                return false;
            }
            permission = android.Manifest.permission.ACCESS_FINE_LOCATION;
        } else {
            if (!Utils.checkCallerHasCoarseLocation(this, attributionSource, callingUser)) {
                return false;
            }
            permission = android.Manifest.permission.ACCESS_COARSE_LOCATION;
        }
    }
    synchronized (mDiscoveringPackages) {
        mDiscoveringPackages.add(new DiscoveringPackage(callingPackage, permission, hasDisavowedLocation));
    }
    return startDiscoveryNative();
}

static jboolean startDiscoveryNative(JNIEnv* env, jobject obj) {
    ALOGV("%s", __func__);
    if (!sBluetoothInterface) return JNI_FALSE;
    int ret = sBluetoothInterface->start_discovery();
    return (ret == BT_STATUS_SUCCESS) ? JNI_TRUE : JNI_FALSE;
}

static int start_discovery(void) {
    if (!interface_ready()) return BT_STATUS_NOT_READY;
  
    do_in_main_thread(FROM_HERE, base::BindOnce(btif_dm_start_discovery));
    return BT_STATUS_SUCCESS;
}

void btif_dm_start_discovery(void) {
    ...... 
    /* Will be enabled to true once inquiry busy level has been received */
    btif_dm_inquiry_in_progress = false;
    /* find nearby devices */
    BTA_DmSearch(btif_dm_search_devices_evt, is_bonding_or_sdp());
}

void BTA_DmSearch(tBTA_DM_SEARCH_CBACK* p_cback, bool is_bonding_or_sdp) {
    tBTA_DM_API_SEARCH* p_msg = (tBTA_DM_API_SEARCH*)osi_calloc(sizeof(tBTA_DM_API_SEARCH));
    /* Queue request if a device is bonding or performing service discovery */
    if (is_bonding_or_sdp) {
        p_msg->hdr.event = BTA_DM_API_QUEUE_SEARCH_EVT;
    } else {
        p_msg->hdr.event = BTA_DM_API_SEARCH_EVT;
    }
    p_msg->p_cback = p_cback;
    bta_sys_sendmsg(p_msg);
}

void bta_sys_sendmsg(void* p_msg) {
    if (do_in_main_thread(
            FROM_HERE,
            base::Bind(&bta_sys_event, static_cast<BT_HDR_RIGID*>(p_msg))) !=
        BT_STATUS_SUCCESS) {
      LOG(ERROR) << __func__ << ": do_in_main_thread failed";
    }
}

bt_status_t do_in_main_thread(const base::Location& from_here, base::OnceClosure task) {
    if (!main_thread.DoInThread(from_here, std::move(task))) {
      LOG(ERROR) << __func__ << ": failed from " << from_here.ToString();
      return BT_STATUS_FAIL;
    }
    return BT_STATUS_SUCCESS;
}