caspar b7cf7256ac Restore real InputConnection to fix barcode scanner input

Returning null from onCreateInputConnection() prevented the Chromium
renderer from relaying hardware key events into HTML inputs, breaking
scanner input on the Urovo CT58C. Return the real InputConnection from
super and rely on the multi-layer keyboard suppression (JS inputmode,
InputMethodManager, EditorInfo flags, manifest flags) which is already
proven to work on this device.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

2026-10-08 00:37:43 -04:00

3.4 KiB

Raw Blame History

JoykooScanner — Android Barcode Scanner Kiosk App

What This Is

Native Android app (Kotlin) that wraps https://smart.joykoo.mx/ in a fullscreen WebView for dedicated Chinese industrial handheld barcode scanners. The scanner operates in HID/keyboard-wedge mode — it sends Android key events like a physical keyboard.

Critical Design Decision

The Android soft keyboard must NEVER appear. Keyboard suppression uses multiple layers — do not remove any of them:

NoSoftKeyboardWebView.onCheckIsTextEditor() → false
EditorInfo flags IME_FLAG_NO_EXTRACT_UI | IME_FLAG_NO_FULLSCREEN in onCreateInputConnection()
InputMethodManager.hideSoftInputFromWindow() posted after each InputConnection request and on page load / window focus
JavaScript injection setting inputmode="none" on all <input>, <textarea>, and contenteditable elements via MutationObserver
Manifest windowSoftInputMode="stateAlwaysHidden|adjustNothing"

The real InputConnection from super.onCreateInputConnection() must be returned — returning null breaks hardware key input from the barcode scanner on devices like the Urovo CT58C.

Project Structure

app/src/main/java/mx/joykoo/scanner/
  AppConfig.kt              — URL, allowed hosts, gesture thresholds (single config point)
  MainActivity.kt           — Fullscreen kiosk activity, WebView setup, navigation, lifecycle
  NoSoftKeyboardWebView.kt  — IME suppression via null InputConnection
  ScannerIntegration.kt     — Interface stub for future vendor scanner SDK

Build

Language: Kotlin, targeting JVM 1.8 bytecode
SDK: compileSdk 34, minSdk 24, targetSdk 34
Dependencies: androidx core-ktx, appcompat, webkit, swiperefreshlayout
Gradle: 8.7 with Kotlin DSL, AGP 8.5.2, Kotlin 1.9.24
Package: mx.joykoo.scanner

Build prerequisites (not yet installed on this server)

sudo dnf install java-17-openjdk-devel — only the JRE is installed, need javac
Android SDK cmdline-tools — download to ~/Android/Sdk/, then install:
- platform-tools
- platforms;android-34
- build-tools;34.0.0

Set env vars:

JAVA_HOME=/usr/lib/jvm/java-17-openjdk-17.0.20.1.1-1.2.el9.x86_64
ANDROID_HOME=~/Android/Sdk

./gradlew assembleDebug

Server environment (RHEL 9.8)

JRE 17 installed at /usr/lib/jvm/java-17-openjdk-17.0.20.1.1-1.2.el9.x86_64
323 GB free on /home, 5.5 GB free on /
curl, wget, unzip, zip available
No Android SDK present anywhere

Configuration

All configurable values are in AppConfig.kt:

HOME_URL — the webpage to load
ALLOWED_HOSTS — domains that stay inside the WebView
BACK_PRESS_EXIT_COUNT / BACK_PRESS_WINDOW_MS — back-button exit guard
ADMIN_TAP_COUNT / ADMIN_TAP_WINDOW_MS — hidden admin exit gesture (7 taps top-left corner)

URLs on joykoo.mx or smart.joykoo.mx (and subdomains) load inside the WebView
All other URLs are silently blocked
Back button goes back in WebView history; 3 rapid presses exits when no history
Admin exit: 7 rapid taps in top-left 60dp corner → confirmation dialog (PIN-ready stub)

Security

HTTPS only, no cleartext, no SSL error bypass
No JavaScript interfaces exposed
No file:// or content:// access
Network security config enforces system trust anchors only
Domain allowlist in WebViewClient

UI Strings

Spanish (es) — this is for a Mexico-based company.

3.4 KiB Raw Blame History