Android ADB Bridge (base skill)#

Generic Android bridge for any app. Reads screens via OCR, executes taps/scrolling/typing.

📦 This is the base skill#

Other skills depend on this one. It ships the shared parts:

FileRoleocr_bridge.pyThe OCR loop — screenshot → RapidOCR → click/swipe → re-verify. This is what dependents use.requirements-adb.txtPinned deps for the OCR-loop venv. Dependents install it as $BASE/requirements-adb.txt.bridge_daemon.pyAppium backend (fallback only; see the failure mode below)start_bridge.shLaunches the Appium daemon (fallback only)

Dependents: 12306-android-adb, pdd-android-adb, hospital-android-adb. Each documents $PY $BASE/ocr_bridge.py <cmd> where BASE is this skill's directory, so it works from any working directory.

ClawHub has no dependency resolver — installing a dependent skill does not install this one. Install it explicitly:

bash

clawhub install appium-android-adb

ocr_bridge.py imports no Appium (only uiautomator2 + rapidocr-onnxruntime), so dependents pay nothing for the Appium backend they never use. Note the name under-sells the skill: the OCR loop is the reason it exists and the reason others depend on it.

Two backends:

BackendStatusBest forLimitationsuiautomator2 + RapidOCR ( ocr_bridge.py)✅ Primary (proven end-to-end on 12306 booking 2026-08-30)UC WebView apps, scrolling, booking buttons, Chinese inputNeeds rapidocr_onnxruntime in a venvAppium ( bridge_daemon.py)⚠️ FallbackNative apps, structured dumps, find/ waitDead on many consumer devices: Realme etc. block WRITE_SECURE_SETTINGS, so io.appium.settings and IME switching fail → session never starts

⚠️ Appium Failure Mode (hit this in production)#

On a Realme RMX3350 the Appium path was unusable:

• shell lacks WRITE_SECURE_SETTINGS → io.appium.settings commands fail
• d.set_input_ime() blocked → fastinput IME can't be activated → send_keys fails
• Result: Appium session creation error ("settings command problem"), bridge daemon useless

Rule: try the OCR loop FIRST. Only fall back to Appium if the app is fully native and OCR is insufficient.

Quick Start (primary — OCR loop)#

bash

# One-time venv (Python 3.10+), shared with the three dependent skills.
# The pins live in requirements-adb.txt, in this skill's directory; adjust BASE
# if you installed the skill somewhere other than the default.
# Pinned deliberately — an unpinned `pip install` resolves "latest" at install
# time, so the code that actually runs is whatever PyPI happened to serve that
# day and can change under you (ClawHub review [T08]).
BASE=~/.openclaw/workspace/skills/appium-android-adb   # this skill
python3 -m venv ~/.openclaw/workspace/.venv-adb
~/.openclaw/workspace/.venv-adb/bin/pip install -r $BASE/requirements-adb.txt

# Every interaction is one command:
PY=~/.openclaw/workspace/.venv-adb/bin/python
$PY ocr_bridge.py dump                     # OCR whole screen: (text, l, t, r, b)
$PY ocr_bridge.py markers                  # page-state markers
$PY ocr_bridge.py tap-text 预订 --idx 0     # click OCR match, then re-OCR verify
$PY ocr_bridge.py tap 540 1987             # click exact coordinates
$PY ocr_bridge.py swipe up --scale 0.35    # normal list scroll
$PY ocr_bridge.py jump --n 3               # 3 rapid swipes (unstuck virtual list)
$PY ocr_bridge.py wait-text 提交订单        # poll until text appears

uiautomator2 auto-installs its atx-agent on the phone at first connect() — no Appium needed.

The bare $PY ocr_bridge.py … form above works here because you're in this skill's directory. Dependent skills invoke it as $PY $BASE/ocr_bridge.py … instead — $BASE being this skill's path — so their commands run from any working directory. Use $BASE in anything you write that has to work outside this directory.

The Proven Loop#

1. shot(): adb exec-out screencap -p (streamed over USB — nothing is written to /sdcard) → RapidOCR → [(text, l, t, r, b)]. The screencap + pull pair survives only as a fallback for old platform-tools, and deletes its device-side file.

   Historical note: this step used to leave s.png in /sdcard forever, outside the private 0700 screenshot dir the Safety section promises. Fixed in 1.3.5 — see ClawHub review finding [T09].

2. Decide: page-state via markers(), position via deps() (HH:MM at x<250)

3. Act: d.click(cx, cy) / d.swipe_ext('up', scale=0.35) / d.swipe(x1,y1,x2,y2,duration=0.4)

4. Always re-OCR after every action and verify the screen actually changed — this is what makes the loop robust against the virtual list's lies.

Chinese Input (no IME needed)#

IME switching is blocked on locked-down devices. The proven route:

python

d.set_clipboard('苏州')          # uiautomator2 clipboard (works where fastinput fails)
d.long_click(400, 330, duration=1.2)   # long-press the input field
# → OCR: the 粘贴 (paste) menu item appears → tap it

ocr_bridge.py type 苏州 --x 400 --y 330 sets clipboard and long-presses the field.

Clear the field first — pasting over existing text concatenates instead of replacing (hit on the PDD search box). ocr_bridge.py type clears any focused EditText by default ( --no-clear to skip).

FLAG_SECURE Pages (payment screens) — a11y Tree as the Eye#

Payment pages (e.g. PDD 多多钱包, PayConfirmActivity) set FLAG_SECURE: screencap returns black/0-byte files. The accessibility tree still works — read and tap via it:

bash

$PY ocr_bridge.py a11y                 # all text nodes + bounds + [SELECTED] flag
$PY ocr_bridge.py a11y-selected        # nodes with selected="true" (spec chips)
$PY ocr_bridge.py a11y-tap 直接免拼    # click text found in the a11y tree

Also the authoritative state check for selection chips when OCR is ambiguous: selected="true" in the tree beats pixel guessing.

Scrolling a UC WebView Virtual List#

• Normal advance: d.swipe_ext('up', scale=0.35) (≈2 train cards per scroll on 12306)
• List "skips" a section (target train keeps getting jumped over): do jump — 3 rapid large swipes ( scale=0.5, 1.2s apart), then micro-swipes back ( scale=0.15–0.25, or d.swipe(540, 1900, 540, 800, duration=0.4))
• Track position with departure-time markers: deps() = HH:MM texts at x<250 — you always know which time window is on screen, independent of the DOM

Option B: bridge_daemon.py (Appium, fallback only)#

bash

# One-shot commands run with a short-lived session by default (safer):
python3 bridge_daemon.py dump
python3 bridge_daemon.py tap '{"text": "查询车票"}'
python3 bridge_daemon.py scroll '{"direction": "down"}'

# Persistent mode is opt-in — only if you need low-latency batches:
bash ~/.openclaw/workspace/skills/appium-android-adb/start_bridge.sh
# ...which runs: python3 bridge_daemon.py --daemon

A background daemon is NOT auto-started by single commands; one-shot mode creates a session, executes, and quits. Screenshots and IPC files live in the private 0700 dir ~/.cache/appium-bridge. Cannot run simultaneously with uiautomator2 (same AccessibilityService).

Appium binds to loopback only. Both launch paths pass --address 127.0.0.1, because Appium exposes full control of the attached device — without it the server binds broadly and anything else on the LAN could drive the phone. If you start Appium yourself, do the same:

bash

appium --address 127.0.0.1

Commands (bridge_daemon.py)#

All from ~/.openclaw/workspace/skills/appium-android-adb/. All return JSON.

dump — read the screen#

bash

python3 bridge_daemon.py dump

Returns:

json

{
  "ok": true,
  "package": "com.MobileTicket",
  "activity": "com.alipay.mobile.nebulacore.ui.H5Activity",
  "title": "上海 <> 苏州",
  "alerts": [{"text": "温馨提示"}],
  "buttons": [
    {"text": "查询车票", "id": "", "bounds": "[99,970][981,1102]", "x": 540, "y": 1036},
    {"text": "预订", "id": "", "bounds": "[870,1988][1008,2075]", "x": 939, "y": 2031}
  ],
  "trains": [
    {"text": "G 7 0 0 4次列车...", "bounds": "[66,1793][291,1919]", "clickable": true, "x": 178, "y": 1856}
  ],
  "webview_contexts": ["NATIVE_APP"]
}

tap — click element by text#

bash

python3 bridge_daemon.py tap '{"text": "查询车票"}'
python3 bridge_daemon.py tap '{"text": "预订", "index": 0}'
python3 bridge_daemon.py tap '{"id": "btn_submit"}'

tap_bounds — click using bounds from dump#

bash

python3 bridge_daemon.py tap_bounds '{"bounds": "[870,1988][1008,2075]"}'

⚠️ Only works reliably if the element has proper bounds (h > 20px). Collapsed virtual list items (h=6px) will NOT respond.

tap_coords — click at exact coordinates#

bash

python3 bridge_daemon.py tap_coords '{"x": 540, "y": 1200}'

find — inspect element matches#

bash

python3 bridge_daemon.py find '{"text": "7004"}'

scroll — swipe the screen#

bash

python3 bridge_daemon.py scroll '{"direction": "down"}'
python3 bridge_daemon.py scroll '{"direction": "down", "distance": "micro"}'

⚠️ May not work on UC WebView (used by 12306, Alipay apps). The WebView filters touch events. For UC WebView scrolling, use the OCR loop / d.swipe_ext() instead.

screenshot — take phone screenshot#

bash

python3 bridge_daemon.py screenshot
# Returns {"ok": true, "path": "/tmp/screen.png"}

type — input text#

bash

python3 bridge_daemon.py type '{"text": "上海"}'

wait — poll until element appears#

bash

python3 bridge_daemon.py wait '{"text": "提交订单", "timeout": 30}'

When to Use Which#

SituationRecommended ToolUC WebView apps (12306, Alipay, many Chinese apps) — everythingOCR loop ( ocr_bridge.py)Screen state / text readingocr_bridge.py dump / markers / depsClicking anything visibleocr_bridge.py tap-text / tap (u2 click)Scrolling UC WebView listsocr_bridge.py swipe / jump / microChinese text inputd.set_clipboard + long-press pasteNative apps with structured dumps / find / waitbridge_daemon.py (Appium) — if the device allows it

⚠️ UC WebView Virtual List — Critical Knowledge#

Apps using UC WebView (12306, many Chinese apps) use virtual lists that collapse most items' accessibility bounds:

• Visible items: Have real bounds (h=60-130px), clickable via accessibility service
• Off-screen items: COLLAPSED to y≈407 (top) or y≈2255 (bottom), h=6px — DOM lies
• The DOM is unreliable: sometimes renders (usable), mostly collapsed. OCR is the dependable eye.

What Works on UC WebView#

1. d.click(x, y) from uiautomator2 — reliably delivers touches (unlike raw ADB)
2. Scrolling via d.swipe_ext() / d.swipe()
3. OCR + coordinate click (RapidOCR reads Chinese out of the box — no tesseract language packs)
4. d.set_clipboard() + long-press paste for Chinese input
5. d.dump_hierarchy() sometimes gives accurate data — use when it renders, never depend on it

What Does NOT Work on UC WebView#

1. Raw adb shell input tap — filtered by UC WebView (observed 2026-08-30)
2. Clicking collapsed text elements (train names, times, seat info) — h=6px bounds
3. mobile: scrollGesture via Appium — returns False
4. W3C Actions swipe — touch events filtered
5. JS injection ( execute_script) — no WEBVIEW contexts exposed
6. d.set_input_ime() / fastinput on Realme — WRITE_SECURE_SETTINGS blocked

🛡️ Safety & Consent#

• Trigger boundary: use this skill only when the user explicitly asks to control their phone (a specific booking/purchase/app task). Never touch the device speculatively or from background tasks.
• Confirm before irreversible actions: before submitting an order, a checkout step, or any tap that changes live app state, tell the user what will happen and wait for confirmation. Payment credentials (PIN, fingerprint) are ALWAYS entered by the user — scripts never request or store them.
• Screen data: screenshots/OCR captures can contain personal data. They are stored in a private 0700 dir ( ~/.cache/ocr-bridge, override OCR_BRIDGE_DIR) and shots older than 1 hour are purged automatically on every screenshot; ocr_bridge.py clean purges immediately. Note that clean only ages out that host-side dir — it cannot reach the device, so nothing is written to /sdcard in the first place: captures stream over USB via adb exec-out, and the older screencap + pull fallback deletes its own device file.
• Appium exposure: the server is bound to 127.0.0.1 on every launch path. It offers unrestricted control of the connected device, so never start it on 0.0.0.0, and stop it when you're done.
• No secret echoes: typed/pasted content is never echoed in output or logs (only its length). One-shot bridge commands stop any Appium server they started themselves — no services left running.
• Bridge IPC: bridge_daemon.py keeps its command/response files in a private 0700 dir ( ~/.cache/appium-bridge) and rejects files not owned by the current user. Appium runs WITHOUT --allow-insecure/ --relaxed-security.

Troubleshooting#

Appium session creation error / "settings command problem": Device blocks WRITE_SECURE_SETTINGS (Realme etc.). Stop fighting it — use the OCR loop. uiautomator2 conflict: "AccessibilityService already registered" means Appium is running. Kill Appium first ( pkill -f appium). OCR finds nothing / misreads: RapidOCR is noisy on small text — narrow search to a region (x/y bounds) and re-shoot; the screen may still be animating (sleep 2-3s after actions). Train number not found: DOM text has spaces ( G 7 0 0 4), but OCR text does not ( G7004). Match with regex on OCR: ^[GDCK]\d+. tesseract missing: Don't install it — RapidOCR (rapidocr-onnxruntime) needs no language data and read Chinese reliably in production.