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Native contract — printer & NFC

Source of truth: the current android-pos-wrapper (WebView shell). In the native Flutter app these WebView-injected JS bridges are replaced by Flutter platform channels to the same underlying Android APIs / SDK. Vendored into this repo:

  • android/app/libs/SmartPos_1.9.4_R250117.jar — the ZCS SmartPos SDK (com.zcs.sdk.*).
  • android/app/libs/zxing-core-3.3.0.jar — QR support used by the SDK.
  • assets/images/lacrypta_logo.png — receipt header logo.

⚠️ Correction vs. the initial exploration: the printer SDK is ZCS SmartPos (com.zcs.sdk.DriverManager / Printer), not a "Ciontek CTK PosApiHelper". Confirmed by reading android-pos-wrapper/app/src/main/java/test/apidemo/service/PrintThread.java.

1. Printer (ZCS SmartPos SDK)

Wrapper exposed window.Android.print(jsonString) → PrintThread.print(JSONObject).

SDK init

DriverManager mDriverManager = DriverManager.getInstance();
Printer mPrinter = mDriverManager.getPrinter();

Status / paper-out

int printStatus = mPrinter.getPrinterStatus();
if (printStatus == SdkResult.SDK_PRN_STATUS_PAPEROUT) { // retry every 2s }

Receipt layout (top → bottom) — from PrintThread.print:

  1. Header bitmap: imageUrl (downloaded) if present, else assets/images/lacrypta_logo.png via mPrinter.setPrintAppendBitmap(bmp, ALIGN_CENTER).
  2. mPrinter.setPrintLine(10) separator.
  3. Right-aligned BTC/USD {btcPrice} + normal Bloque: #{blockNumber}.
  4. Current date yyyy-MM-dd HH:mm:ss, then --------------------------------.
  5. Items loop (textSize 18): "{name} ({price}) x {qty}", one per line.
  6. TOTAL block (textSize 40): ***** TOTAL *****, {currencyB} {totalB}, center {currency} {total}, right {totalSats} sats.
  7. Message (textSize 25, centered), default "Welcome to efectivo digital".
  8. Optional QR: mPrinter.setPrintAppendQRCode(qrcode, 500, 500, ALIGN_CENTER).
  9. mPrinter.setPrintStart().

Formatting via PrnStrFormat (setTextSize, setAli, setFont(PrnTextFont.MONOSPACE)).

Print JSON schema (input)

{
  "items": [{ "name": "string", "qty": 1, "price": 100.0 }],
  "totalSats": 1500000,
  "total": 5432.25,
  "currency": "ARS",
  "currencyB": "USD",
  "totalB": "3.72",
  "message": "Welcome to efectivo digital",
  "blockNumber": "872992",
  "btcPrice": "0.08 M",
  "qrcode": "optional string",
  "imageUrl": "optional header image URL"
}

Flutter binding

MethodChannel("pos/printer") → Kotlin holds a single Printer instance and reimplements the layout above. Method print(Map order) returns the ZCS status int. Bundle the vendored .jars in android/app/build.gradle (implementation files('libs/SmartPos_1.9.4_R250117.jar'), zxing). Port getCurrentDate() and the paper-out retry.

2. NFC (Android NfcAdapter)

Wrapper used standard NfcAdapter foreground dispatch; on a discovered tag it decoded the first NDEF record and called window.injectedNFC.handleRead(text) (errors → handleError(reason)).

Read logic (NfcService.onNewIntent)

  • Trigger NfcAdapter.ACTION_NDEF_DISCOVERED.
  • Ndef.get(tag).getCachedNdefMessage().getRecords()[0].
  • Require TNF_WELL_KNOWN + RTD_TEXT.
  • Encoding: (payload[0] & 0x80)==0 ? "UTF-8" : "UTF-16"; skip language code len = payload[0] & 0x3F; text = new String(payload, len+1, payload.length-len-1, enc).
  • Payload is a LaWallet card URL, typically lnurlw://….

window.Android.isNFCAvailable() returned hardcoded true; native version should query real NfcAdapter capability.

Flutter binding

MethodChannel("pos/nfc") + EventChannel("pos/nfc/reads"):

  • isAvailable() -> bool
  • startRead() — enable reader mode / foreground dispatch.
  • stopRead() — disable + cancel pending read.
  • read events stream the decoded NDEF text to Dart.

Evaluate the nfc_manager plugin first (uses reader mode); fall back to a custom channel if the CS30Pro needs reader-mode tuning. Manifest: NFC, CAMERA, INTERNET, WAKE_LOCK; portrait lock; keep-screen-on.

3. Parity notes / decisions to make during M0

  • The vendored logo is lacrypta_logo.png; the wrapper's latest PrintThread actually referenced R.mipmap.bitcoinpizzaday (an event-specific header). Decide the default header for v1.
  • Confirm exact SdkResult status constants for overheat/voltage on the target firmware.
  • Confirm reader-mode vs. foreground-dispatch behaviour on the physical CS30Pro (needs device).