baijum/android-bug-reproduce

Android Bug Reproduction on Emulator

Systematically reproduce and investigate Android bugs using ADB and the emulator.

Prerequisites

• Android SDK installed with emulator and adb on PATH
• At least one AVD configured (check with emulator -list-avds)
• A debug APK (build with ./gradlew assembleDebug if needed)

Workflow

Step 1: Start the emulator

Check for a running emulator first:

adb devices

If none is running, start one:

emulator -list-avds
emulator -avd <avd_name> -no-snapshot-load &

Wait for the device to be ready:

adb wait-for-device
adb shell getprop sys.boot_completed  # should return "1"

Step 2: Install the debug APK

adb install -r app/build/outputs/apk/debug/app-debug.apk

Step 3: Seed test data (if needed)

For features that require existing data (e.g., chord sheets, favorites), seed SharedPreferences directly:

# Stop the app first
adb shell am force-stop com.baijum.ukufretboard

# Write test data to SharedPreferences
adb shell run-as com.baijum.ukufretboard sh -c 'cat > shared_prefs/<pref_file>.xml << '\''XMLEOF'\''
<?xml version="1.0" encoding="utf-8" standalone="yes" ?>
<map>
    <!-- Your test data here -->
</map>
XMLEOF'

Common preference files:

| File | Contents | |------|----------| | chord_sheets.xml | Saved songs/chord sheets (JSON list) | | favorites.xml | Favorited chords | | app_settings.xml | App settings |

Example — seed a chord sheet:

adb shell run-as com.baijum.ukufretboard sh -c 'cat > shared_prefs/chord_sheets.xml << '\''XMLEOF'\''
<?xml version="1.0" encoding="utf-8" standalone="yes" ?>
<map>
    <string name="chord_sheets_json">[{"id":"test-1","title":"Test Song","artist":"Test","content":"[C]Hello [Am]world\nLine 2\nLine 3\nLine 4\nLine 5\nLine 6\nLine 7\nLine 8\nLine 9\nLine 10","strumPatternName":"","labels":[],"createdAt":1700000000000,"updatedAt":1700000000000}]</string>
</map>
XMLEOF'

Step 4: Launch the app and navigate

adb shell am start -n com.baijum.ukufretboard/.MainActivity

Find UI element coordinates with uiautomator

Dump the current UI tree to find element bounds:

adb shell uiautomator dump /sdcard/ui.xml
adb shell cat /sdcard/ui.xml | head -c 5000  # quick preview

Search for a specific element by content-description or text:

adb shell uiautomator dump /sdcard/ui.xml
adb pull /sdcard/ui.xml /tmp/ui.xml
grep -o 'content-desc="[^"]*"[^/]*bounds="[^"]*"' /tmp/ui.xml

Common navigation actions

# Open navigation drawer
adb shell uiautomator dump /sdcard/ui.xml
# Find "Open navigation menu" button bounds, then:
adb shell input tap <x> <y>

# Tap by coordinates (center of element bounds)
# bounds="[left,top][right,bottom]" -> tap at ((left+right)/2, (top+bottom)/2)
adb shell input tap 540 960

# Go back
adb shell input keyevent 4

# Enter text in a focused field
adb shell input text "hello"

# Scroll down
adb shell input swipe 540 1500 540 500 300

Step 5: Add instrumentation logging

When the root cause isn't obvious, add temporary Log.d statements to the relevant code:

import android.util.Log

Log.d("DEBUG_<issue>", "state: autoScrolling=$autoScrolling, scrollValue=${scrollState.value}")

Rebuild and reinstall:

./gradlew assembleDebug && adb install -r app/build/outputs/apk/debug/app-debug.apk

Step 6: Capture and filter logs

# Filter for your debug tag
adb logcat -c  # clear old logs
adb logcat -s "DEBUG_<issue>:D" &

# Or capture to file for analysis
adb logcat -s "DEBUG_<issue>:D" > /tmp/debug_log.txt &

Reproduce the bug, then stop logcat and analyze the output.

Step 7: Take screenshots

adb shell screencap -p /sdcard/screenshot.png
adb pull /sdcard/screenshot.png /tmp/screenshot_before.png

For before/after comparison:

# Before fix
adb shell screencap -p /sdcard/before.png
adb pull /sdcard/before.png /tmp/before.png

# After fix (rebuild, reinstall, reproduce)
adb shell screencap -p /sdcard/after.png
adb pull /sdcard/after.png /tmp/after.png

Step 8: Clean up

Remove debug logging before committing:

# Find all debug log lines added during this session
grep -rn "DEBUG_<issue>" app/src/main/java/

Remove the Log.d lines and the import android.util.Log if no longer needed.

Tips

• Prefer seeding data over UI automation — writing SharedPreferences XML is far more reliable than tapping through UI to create test data.
• Use uiautomator dump before every tap — screen layouts change between devices and orientations; never hardcode coordinates from memory.
• Keep debug tags unique — include the issue number (e.g., DEBUG_issue41) so logs don't mix with other debugging sessions.
• Force-stop before seeding — SharedPreferences are cached in memory; the app must be stopped before writing XML files.