mobiai-android-device

Android Device Interaction

Expert-level knowledge for interacting with Android devices and emulators via ADB.

When to Use

• Reproducing a bug on an Android emulator or device
• Taking screenshots or capturing logs
• Automating UI interactions for testing
• Managing emulators

Device Setup

Detect Connected Devices

adb devices -l

This shows all connected devices and emulators. Use -s <serial> to target a specific device, or -e for the only running emulator.

Start an Emulator

Use the helper script or run manually:

# List available AVDs
emulator -list-avds

# Start with recommended flags for automation
emulator -avd <avd-name> \
  -no-window \
  -no-audio \
  -no-boot-anim \
  -gpu swiftshader_indirect \
  -no-snapshot-load

Wait for boot to complete:

adb -e wait-for-device
adb -e shell getprop sys.boot_completed  # Returns "1" when ready

Screen Size

adb shell wm size
# Output: Physical size: 1080x2340

UI Inspection — CRITICAL

Always dump the UI before every interaction. This is the most important rule.

Dump UI Hierarchy

adb shell uiautomator dump /sdcard/ui.xml && adb pull /sdcard/ui.xml ./ui-dump.xml

Never cat the full XML — it can be thousands of lines and will blow up your context. Instead, search for the element you need:

# List all visible text elements with their bounds
grep -o 'text="[^"]*"[^/]*bounds="[^"]*"' ./ui-dump.xml

# Search for a specific element by text
grep -o '[^<]*text="Submit"[^/]*' ./ui-dump.xml

# Search by resource-id
grep -o '[^<]*resource-id="[^"]*btn_submit[^"]*"[^/]*' ./ui-dump.xml

# Search by content-desc
grep -o '[^<]*content-desc="[^"]*Close[^"]*"[^/]*' ./ui-dump.xml

Only cat ./ui-dump.xml as a last resort if grep doesn't find what you need.

The XML contains every visible element with:

• text — visible text on the element
• resource-id — programmatic ID (e.g., com.example.app:id/btn_submit)
• content-desc — accessibility label
• bounds="[x1,y1][x2,y2]" — pixel coordinates