Working with Emulators

Complete guide to using Android emulators with JetStart - from creation to automated deployment and optimization for blazing-fast development.

Why Use Emulators?

Physical device advantages:

✓ Real hardware performance
✓ Actual sensors (GPS, camera, etc.)
✓ True user experience

Emulator advantages:

✓ No device needed - develop anywhere
✓ Instant deployment - jetstart dev --emulator
✓ Multiple configurations - test different screen sizes/Android versions
✓ Snapshot/restore - save app state
✓ Network simulation - test offline scenarios
✓ Faster iteration - no USB cables/adb wireless setup

Best of both worlds: Use emulator for rapid development, physical device for final testing.

Prerequisites

System Requirements

Minimum:

RAM: 8 GB (16 GB recommended)
CPU: Intel VT-x / AMD-V support (hardware virtualization)
Disk: 10 GB free space per emulator
OS: Windows 10+, macOS 10.14+, Ubuntu 18.04+

Check virtualization:

# Windows (PowerShell)
Get-ComputerInfo | Select-Object -ExpandProperty HyperVRequirementVirtualizationFirmwareEnabled

# macOS
sysctl kern.hv_support

# Linux
egrep -c '(vmx|svm)' /proc/cpuinfo
# Output > 0 means supported

JetStart Emulator Manager

JetStart includes built-in emulator management - no Android Studio required!

Launch Manager

jetstart android-emulator

Interactive menu:

JetStart Android Emulator Manager

What would you like to do?
❯ List existing emulators
  Start emulator
  Stop emulator
  ─────────────────────────
  Create JetStart-optimized emulator
  Create custom emulator
  Delete emulator
  ─────────────────────────
  Exit

Create JetStart-Optimized Emulator

One-time setup (recommended for beginners):

Run jetstart android-emulator
Select "Create JetStart-optimized emulator"
Wait 2-5 minutes for download and creation

Configuration:

Name: JetStart_Pixel_7_API_34
Device: Pixel 7
API Level: 34 (Android 14)
ABI: x86_64
RAM: 2048 MB
Storage: 2048 MB
GPU: auto

Optimized for:

Fast boot time (~10 seconds)
Hot reload performance
Balanced resource usage
JetStart development workflow

Create Custom Emulator

For advanced users:

Run jetstart android-emulator
Select "Create custom emulator"
Choose configuration interactively:
- Device (Pixel 7, Pixel 5, Tablet, etc.)
- API level (24-34)
- RAM (1024-8192 MB)
- Storage (2048-8192 MB)

Example:

Device: Pixel 5
API Level: 30 (Android 11)
ABI: x86_64
RAM: 4096 MB
Storage: 4096 MB
Name: My_Custom_Pixel5

Automated Deployment Workflow

Quick Start

1. Create emulator (one-time):

jetstart android-emulator
# Select "Create JetStart-optimized emulator"

2. Start emulator:

jetstart android-emulator
# Select "Start emulator" → Choose your emulator

3. Deploy app automatically:

cd my-app
jetstart dev --emulator

What happens:

Detects running emulator automatically
Reads package name from app/build.gradle
Waits for client connection
Triggers initial APK build
Installs APK via ADB
Launches app
Future changes use hot reload (no reinstall!)

Specify Emulator by Name

Multiple emulators running?

jetstart dev --emulator --avd JetStart_Pixel_7_API_34

Workflow:

# Terminal 1: Start specific emulator
jetstart android-emulator
# → Start emulator → JetStart_Pixel_7_API_34

# Terminal 2: Deploy to that emulator
cd my-app
jetstart dev --emulator --avd JetStart_Pixel_7_API_34

Performance Optimization

Emulator Settings

Fast boot (recommended):

AVD Manager → Edit → Show Advanced Settings
Boot option: Quick Boot

Saves emulator state on exit → 2-3 second boot vs 20-30 seconds

Graphics acceleration:

Graphics: Automatic (ANGLE/SwiftShader based on hardware)

Host GPU provides 10-50x better graphics performance

Resource Allocation

Recommended settings:

Use Case	RAM	CPU Cores	Storage
Basic testing	2048 MB	2	2048 MB
JetStart dev (recommended)	2048 MB	4	2048 MB
Heavy apps/games	4096 MB	4	4096 MB
Multiple emulators	1024 MB each	2 each	2048 MB each

Don't over-allocate:

Emulator RAM < 50% of host RAM
CPU cores < 75% of host cores
Leave resources for IDE, dev server, browser

Startup Time Optimization

Cold boot benchmark:

Standard emulator: 60-90 seconds
JetStart-optimized: 10-15 seconds
Quick Boot enabled: 2-3 seconds

Optimization checklist:

Use x86_64 ABI (not ARM)
Enable hardware acceleration (HAXM/WHPX/KVM)
Enable Quick Boot
Allocate 2-4 GB RAM (not more)
Use SSD for Android SDK location
Close other VMs/emulators

Common Workflows

Workflow 1: Single Emulator Development

Setup:

# One-time: Create emulator
jetstart android-emulator
# → Create JetStart-optimized emulator

# One-time: Start emulator
jetstart android-emulator
# → Start emulator → JetStart_Pixel_7_API_34

Daily development:

cd my-app
jetstart dev --emulator

# Leave emulator running
# Edit code → Instant hot reload
# No manual deployment needed

Workflow 2: Multiple Device Testing

Setup:

# Create multiple emulators
jetstart android-emulator
# → Create custom: Pixel_5_API_30
# → Create custom: Tablet_API_34

Testing:

# Terminal 1: Start first emulator
emulator @Pixel_5_API_30 &

# Terminal 2: Start second emulator
emulator @Tablet_API_34 &

# Terminal 3: Deploy to both
cd my-app
jetstart dev --emulator
# Prompts to select which emulator or deploys to first detected

Workflow 3: Physical + Emulator Hybrid

Best for: Final testing on real hardware

# Development: Emulator (fast iteration)
jetstart dev --emulator

# Testing: Physical device (real performance)
jetstart dev
# Scan QR code with phone

Troubleshooting

Issue: "No emulators running"

Symptoms:

jetstart dev --emulator
✗ Error: No emulators detected

Solutions:

1. Start emulator first:

jetstart android-emulator
# → Start emulator → Choose your emulator

2. Check emulator is actually running:

adb devices
# Should show:
# emulator-5554  device

3. Restart ADB:

adb kill-server
adb start-server
adb devices

Issue: "Emulator extremely slow"

Symptoms:

Boot takes 5+ minutes
UI lags/stutters
Hot reload takes 10+ seconds

Solutions:

1. Enable hardware acceleration:

Windows (Intel):

# Download and install Intel HAXM
# https://github.com/intel/haxm/releases

Windows (AMD):

# Enable WHPX
Enable-WindowsOptionalFeature -Online -FeatureName HypervisorPlatform

Linux:

# Enable KVM
sudo modprobe kvm-intel  # or kvm-amd
lsmod | grep kvm  # Verify loaded

2. Use x86_64 emulator (not ARM):

# Check ABI
emulator -list-avds

# Re-create with x86_64 if needed
jetstart android-emulator
# → Delete old ARM emulator
# → Create new x86_64 emulator

3. Reduce RAM allocation:

4096 MB → 2048 MB
# Less is often faster (reduces swapping)

Issue: "APK installation failed"

Symptoms:

✗ Installation failed: INSTALL_FAILED_INSUFFICIENT_STORAGE

Solutions:

1. Increase emulator storage:

# Edit emulator config
~/.android/avd/[emulator-name]/config.ini

# Change:
disk.dataPartition.size=2048M
# To:
disk.dataPartition.size=4096M

2. Wipe emulator data:

emulator @My_Emulator -wipe-data

3. Delete and recreate emulator:

jetstart android-emulator
# → Delete emulator → [name]
# → Create new emulator

Issue: "Emulator won't start"

Symptoms:

Black screen
Crashes on startup
Error: "Cannot launch AVD"

Solutions:

1. Check virtualization enabled:

# Windows (PowerShell as Admin)
Get-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V

# Must show: State = Enabled

2. Conflicting software:

Disable: VMware, VirtualBox, Docker Desktop (using Hyper-V)
Or: Use Android Emulator hypervisor driver (alternative)

3. Corrupted emulator:

# Delete and recreate
jetstart android-emulator
# → Delete → [name]
# → Create new

Issue: "`jetstart dev --emulator` doesn't auto-deploy"

Symptoms:

Emulator starts
No APK installation
No app launch

Causes & Solutions:

1. Package name not found:

# Check build.gradle has applicationId
# app/build.gradle:
android {
    defaultConfig {
        applicationId "com.jetstart.myapp"  // ← Required
    }
}

2. build.gradle syntax error:

# Test Gradle manually
./gradlew assembleDebug
# Fix any errors

3. First connection required:

Emulator deployment triggers on first client connection
Wait for JetStart app to connect via WebSocket
Then APK builds and installs automatically

Advanced Topics

Snapshots

Save emulator state:

# While emulator running
adb emu avd snapshot save my_snapshot

# Restore later
adb emu avd snapshot load my_snapshot

Use cases:

Save app in specific state for testing
Quick return to clean slate
Reproduce bugs consistently

Network Simulation

Test offline scenarios:

# Disable network
adb shell svc wifi disable
adb shell svc data disable

# Enable network
adb shell svc wifi enable
adb shell svc data enable

Throttle bandwidth:

Emulator UI → Extended Controls → Cellular → Network type
Select: EDGE (slow), 3G, LTE

Screen Recording

Record emulator screen:

adb shell screenrecord /sdcard/demo.mp4

# Stop recording (Ctrl+C)

# Pull video
adb pull /sdcard/demo.mp4

Best Practices

✓ DO:

Emulator management:

Keep 1-2 emulators for daily use
Use Quick Boot for instant startup
Close emulator when done (saves resources)
Update system images periodically

Development:

Use jetstart dev --emulator for automated deployment
Keep emulator running during development
Test on emulator first, physical device for final QA
Use snapshots for consistent test scenarios

Performance:

Allocate 2-4 GB RAM (not more)
Enable hardware acceleration
Use x86_64 ABI
Close other resource-intensive apps

✗ DON'T:

Avoid:

Creating 10+ emulators (use 2-3 max)
Running multiple emulators simultaneously (unless testing)
Allocating too much RAM (causes swapping)
Using ARM emulators (extremely slow without ARM hardware)
Keeping emulator running 24/7

Don't rely on:

Emulator for GPS accuracy (use physical device)
Emulator for camera testing (use physical device)
Emulator for performance benchmarks (use physical device)

Comparison: Emulator vs Physical Device

Feature	Emulator	Physical Device
Setup time	5 min (one-time)	Instant (if you have one)
Deployment	Automatic	QR code scan
Boot time	2-10 seconds	N/A (always on)
Hot reload speed	Same (<100ms)	Same (<100ms)
Hardware sensors	Simulated	Real
Performance	70-90% native	100% native
Screen sizes	Any	Fixed
Android versions	Any (API 24-34)	Fixed
Network control	Full simulation	Limited
Cost	Free	$200-$1000

Next Steps

Learn more:

Creating First App - Setup project with emulator
Android Emulator Command - CLI reference
Debugging Tips - Debug emulator apps
Performance Optimization - Optimize workflow

Troubleshooting:

Common Issues - General problems
Android SDK Issues - SDK/emulator problems

Why Use Emulators?​

Prerequisites​

System Requirements​

JetStart Emulator Manager​

Launch Manager​

Create JetStart-Optimized Emulator​

Create Custom Emulator​

Automated Deployment Workflow​

Quick Start​

Specify Emulator by Name​

Performance Optimization​

Emulator Settings​

Resource Allocation​

Startup Time Optimization​

Common Workflows​

Workflow 1: Single Emulator Development​

Workflow 2: Multiple Device Testing​

Workflow 3: Physical + Emulator Hybrid​

Troubleshooting​

Issue: "No emulators running"​

Issue: "Emulator extremely slow"​

Issue: "APK installation failed"​

Issue: "Emulator won't start"​

Issue: "jetstart dev --emulator doesn't auto-deploy"​

Advanced Topics​

Snapshots​

Network Simulation​

Screen Recording​

Best Practices​

✓ DO:​

✗ DON'T:​

Comparison: Emulator vs Physical Device​

Next Steps​

Why Use Emulators?

Prerequisites

System Requirements

JetStart Emulator Manager

Launch Manager

Create JetStart-Optimized Emulator

Create Custom Emulator

Automated Deployment Workflow

Quick Start

Specify Emulator by Name

Performance Optimization

Emulator Settings

Resource Allocation

Startup Time Optimization

Common Workflows

Workflow 1: Single Emulator Development

Workflow 2: Multiple Device Testing

Workflow 3: Physical + Emulator Hybrid

Troubleshooting

Issue: "No emulators running"

Issue: "Emulator extremely slow"

Issue: "APK installation failed"

Issue: "Emulator won't start"

Issue: "`jetstart dev --emulator` doesn't auto-deploy"

Advanced Topics

Snapshots

Network Simulation

Screen Recording

Best Practices

✓ DO:

✗ DON'T:

Comparison: Emulator vs Physical Device

Next Steps