Building a Multi-Display Emulator Using AOSP: Step-by-Step Guide

Today, I’ll walk you through operating the Android emulator with multiple displays, an increasingly relevant task given the rise of in-car screens in modern vehicles.

Understanding the Need for Multi-Display in AAOS

With the advent of new energy vehicles, cars are now equipped with multiple screens, such as instrument clusters, central control screens, co-driver screens, rear-seat screens, and even armrest screens. As the demand for multi-screen functionality grows, AAOS is continually improving its support for these features. This tutorial focuses on building and running a multi-display emulator using AOSP, a capability that has been evolving with recent updates in AAOS14.

Step 1: Setting Up Your Environment

Before you start building the emulator, ensure your environment is set up correctly:

cd aosp
source build/envsetup.sh
lunch sdk_car_md_x86_64-ap2a-userdebug

This configuration (sdk_car_md_x86_64-userdebug) is designed specifically for multi-display support on the emulator.

Step 2: Building the Emulator

Once the environment is configured, initiate the build process:

make

This step compiles the source code, setting up the emulator with multi-display capabilities. The compilation might take some time, depending on your system's resources.

Step 3: Running the Emulator

After the build completes, you can start the emulator with the following command:

emulator -no-snapshot

This command launches the emulator without using any saved states, ensuring a fresh start each time.

For additional help and options, use:

emulator -help

This will provide you with more command-line options to fine-tune the emulator's behavior.

Step 4: Debugging Multi-Display

To interact with and debug multiple displays, several commands are at your disposal:

• Check Current Activity Focus:

  dumpsys activity activities | grep mFoc

• Launch an App on a Specific Display:

  am start -n com.android.car.settings/.Settings_Launcher_Homepage --display 2

• Dump Display Information:

  dumpsys display

• Display ID Information:

  dumpsys SurfaceFlinger --display-id

• Capture Screenshots of All Displays:

  screencap -d [display-id] -p ./screenshot.png

These commands allow you to monitor and manipulate the multi-display setup directly from the terminal.

Step 5: Customizing Display Configurations

In many cases, the default display configurations may not suit your needs. You can modify screen resolution, density, and other settings in the Makefile and configuration files:

• Adjusting Screen Resolution and Density:

  Modify the following section in car_md.mk:

  EMULATOR_MULTIDISPLAY_HW_CONFIG := 1,1320,1080,220,0,2,1920,1080,220,0,3,1920,1080,220,0

• Updating Configuration for Display Layouts:

  Modify display_settings.xml to reflect the changes:

  <display name="port:1" forcedDensity="220" dontMoveToTop="true"/>

These changes help align the emulator's display configurations with real-world vehicle screen setups.

Step 6: Reviewing the UI and Multi-Display Operation

After making the necessary adjustments, you can observe how the multi-display emulator handles different in-car screens:

• Instrument Screen
• Central Control Screen
• Co-pilot Screens

Conclusion

By following these steps, you can build and run a multi-display emulator using AOSP, paving the way for developing and testing applications designed for the next generation of in-car experiences. This guide should serve as a solid foundation for anyone looking to explore the capabilities of AAOS in a multi-screen environment.

For more insights and future updates, stay tuned to my blog!

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Author: Harsh Pal