Running App on Emulator

Introduction

When developing a Flutter application, testing it on a virtual device (emulator/simulator) is one of the most important steps. Flutter allows you to run apps on both Android Emulators and iOS Simulators without needing a physical device. This saves time, simplifies testing across multiple screen sizes, and allows you to debug issues effectively.

In this article, we’ll explore:

What emulators/simulators are and why they’re useful.
How to set up an Android Emulator.
How to set up an iOS Simulator.
Running Flutter apps on virtual devices.
Common issues and fixes.
Best practices for emulator use in Flutter development.

By the end, you’ll be able to confidently run your Flutter app on Android and iOS virtual devices.

What Are Emulators and Simulators?

Emulator (Android): A virtual version of an Android device that mimics hardware and software behavior.
Simulator (iOS): A virtual representation of an iPhone or iPad. Unlike Android emulators, iOS simulators do not replicate hardware, only software.

Why Use Them?

No need for multiple physical devices.
Easy to test different screen sizes and OS versions.
Faster workflow when debugging.
Integrated with Android Studio, VS Code, and Xcode.

Setting Up an Android Emulator

Step 1: Install Android Studio

Download Android Studio from developer.android.com/studio.
Install with Android Virtual Device (AVD) Manager included.

Step 2: Install Required SDKs

Open Android Studio → SDK Manager.
Install the latest Android SDK Platform and Google APIs.
Install Android Emulator under SDK Tools.

Step 3: Create a Virtual Device

Open Android Studio → Tools → AVD Manager.
Click Create Virtual Device.
Choose a device model (e.g., Pixel 5).
Select a system image (e.g., Android 13).
Configure device settings and click Finish.

Step 4: Launch Emulator

From AVD Manager, click the green Play button.
The emulator boots up like a real phone.

Setting Up an iOS Simulator (macOS Only)

Step 1: Install Xcode

Download Xcode from the Mac App Store.
Install Command Line Tools: xcode-select --install

Step 2: Open Simulator

Launch Xcode → Xcode menu → Open Developer Tool → Simulator.
Or run: open -a Simulator

Step 3: Select Device

From Simulator menu → Device → choose iPhone 14, iPhone SE, iPad, etc.

Running Flutter App on Emulator/Simulator

Method 1: From Command Line

List available devices: flutter devices
Run app on specific device: flutter run -d emulator-5554 (Replace emulator-5554 with your emulator ID).

Method 2: From VS Code

Open your Flutter project in VS Code.
At the bottom right, click the device selector.
Choose Android Emulator or iOS Simulator.
Press F5 or click Run → Start Debugging.

Method 3: From Android Studio

Open project in Android Studio.
Select target device from toolbar dropdown.
Click the green Run button.

Common Issues and Fixes

1. Emulator Not Showing in Flutter

Run: flutter doctor --android-licenses flutter doctor
Ensure Android SDK path is correctly set.

2. iOS Simulator Not Detected

Make sure Xcode is installed.
Run: sudo xcode-select --switch /Applications/Xcode.app/Contents/Developer

3. App Takes Too Long to Load

Allocate more RAM to emulator.
Use x86_64 system images with HAXM/Hypervisor acceleration.

4. Hot Reload Not Working

Check you’re running in debug mode, not release mode.

Best Practices for Emulator Use

Use multiple emulators for different screen sizes (phone, tablet, foldable).
Snapshot states to avoid long boot times.
Keep SDKs updated for Android/iOS.
Use real devices for performance testing, emulators only for functionality.
Enable Hot Reload for faster development cycles.