Test Android apps for cars

Testing your car app ensures that users don't encounter unexpected results or a poor experience. How you test your app depends on whether your app will be running on Android Auto or Android Automotive OS.

See one of the following sections to get started:

• Test your app for Android Auto.
• Test your app for Android Automotive OS.

Test your app for Android Auto

The Desktop Head Unit (DHU) enables your development machine to emulate an Android Auto head unit, so that you can run and test Android Auto apps. The DHU runs on Windows, macOS, and Linux systems.

This section teaches you how to install and run the DHU on your development machine to test your apps. After you've installed the DHU, you can test your Android Auto apps by connecting your mobile device to it via one of the supported connection mechanisms described in Run the DHU.

To report bugs or request features related to the DHU, use this issue tracker.

Install the DHU

Follow these steps to install the DHU on your development machine:

1. Enable developer mode on a mobile device running Android 6.0 (API level 23) or higher, as described in Configure on-device developer options.
2. Compile and install your app on the device.
3. Install Android Auto on the device. If Android Auto is already installed, make sure that you are using the latest version.

4. Open the SDK Manager and navigate to the SDK Tools tab, then download the Android Auto Desktop Head Unit Emulator package.

   

   The DHU is installed in the SDK_LOCATION/extras/google/auto/ directory.

5. On Linux or macOS systems, run the following command in that directory to ensure the DHU binary is executable:

   chmod +x ./desktop-head-unit
   

Additional steps for Linux only

If you are running version 2.0 on a Linux system, you need to install some additional libraries. The DHU binary depends on GLIBC version 2.32 or above. You can check the GLIBC version of your system by running this command:

ldd --version

If the version is lower than 2.32, you must either update GLIBC to 2.32 or above, or upgrade the OS to a version that is compatible with GLIBC 2.32 or above.

You must also install the libc++1 and libc++abi1 libraries. The installation procedure varies depending on your Linux distribution. For example, on Debian-derived Linux distributions, you can install the libraries with this command:

sudo apt-get install libc++1 libc++abi1

Install pre-release versions of the DHU {#:dhu-pre-release}

To get access to pre-release versions of the DHU, you can either use a preview version of Android Studio or change the update channel of your existing Android Studio installation to the beta channel.

Run the DHU

After you install the DHU, you can test your Android Auto apps by connecting your mobile device and workstation over USB. Run the DHU by connecting your mobile device to a development machine using either the Accessory Mode (recommended for DHU 2.0), or ADB Tunneling.

Connecting using Accessory Mode (DHU 2.0 only)

Android Auto supports connecting to the DHU with the Android Open Accessory (AOA) protocol, using the following command:

./desktop-head-unit --usb

By default, the DHU scans through the list of available USB devices and attempts to connect to the first compatible one. To target a specific device, include the device ID as part of the --usb command, as follows:

./desktop-head-unit --usb=[DEVICE_ID]

Connecting using ADB Tunneling

This method requires setting up a connection to the Android Auto head unit server over Android Debug Bridge (ADB). Follow these steps to set up tunneling and run the DHU:

1. Do one of the following to open the Android Auto settings, depending on the version of Android running on the device:

   • Android 10 or higher: On the device tap Settings > Apps & notifications > See all apps > Android Auto > Advanced > Additional settings in the app.
   • Android 9 or lower: In the Android Auto app, tap the Menu, then tap Settings.

2. Scroll to the About section near the bottom and tap Version to display all of the version and permission information.

3. Tap the Version and permission info section 10 times.

   The Allow development settings dialog appears.

4. Tap OK.

   Developer mode is now enabled and you can access developer options in the overflow menu. You only need to enable developer mode the first time you run the Android Auto app.

5. If the head unit server is not already running, tap the three dots in the top right of the screen to open the overflow menu and select Start head unit server (see figure 1).

   On the device, a foreground service appears in the notification area that indicates that the server is running (see figure 2).

   

   Figure 1. Context menu with developer options.

   

   Figure 2. Notification that the head unit server is running.

6. In the Android Auto app, tap Previously connected cars near the top of the Settings, and ensure Add new cars to Android Auto is enabled.

7. Connect the mobile device to the development machine via USB.

8. Make sure the mobile device has its screen unlocked; otherwise it cannot launch the DHU.

9. On the development machine, run the following adb command to forward socket connections from the development machine's port 5277 to the same port number on the Android device. This configuration enables the DHU to connect to the head unit server running on your phone over a TCP socket.

   adb forward tcp:5277 tcp:5277
   

10. Start the DHU by running the command desktop-head-unit.exe (on Windows) or ./desktop-head-unit (on macOS or Linux) from the SDK_LOCATION/extras/google/auto/ directory.

    cd SDK_LOCATION/extras/google/auto
    desktop-head-unit.exe # Windows
    ./desktop-head-unit # macOS or Linux
    

    

11. If this is the first time you are connecting the mobile device to the DHU, check the mobile device's screen to accept the terms of service and adjust permission settings as needed.

After the DHU has started, you can use DHU console commands to run and test your app.

Command line options

By default, the head unit server connects over port 5277. To override the host or port (for example, to forward over SSH), use the --adb=<[localhost:]port> flag, as in the following example:

./desktop-head-unit --adb=5999

By default, the DHU emulates a Android Auto-compatible head unit with a touch screen user interface. You can simulate user touches by clicking the DHU with a mouse. To emulate head units that use a rotary controller for input, you can use the -i controller flag, as in this example:

./desktop-head-unit -i controller

When the DHU is in rotary-controller mode, you can use keyboard shortcuts to simulate controller operations. See the Rotary Controller for more details. In rotary controller mode, the DHU ignores mouse clicks; you must operate Android Auto with the simulated rotary-controller operations.

Option	Description
-c, --config=FILE	Use the specified configuration .ini file. Refer to the Configure the DHU section for more details.
-i, --input=INPUT	Use specified input mode, one of: touch, rotary, or hybrid.
-a, --adb=HOSTPORT	Use ADB transport (optional host:port or port). Defaults to port 5277.
-a, --usb=DEVICE_ID	Use USB (AOA) transport (optional DEVICE_ID).
-v, --version	Show version information.
-l, --licenses	Show open source licenses.
-h, --headless	Run in headless mode (no UI).
-t, --always_show_window_on_top	Show DHU windows on top of other windows (off by default)
-?, --help	Show this help listing.

DHU User Guide

This section describes the features supported by version 2.0 of the DHU and how to use them.

Commands are entered in the terminal window where you started DHU. Multiple commands can be run on the same line by separating them with a ;.

System

Command	Key	Description
help [command]		Shows full command set. If a command name is specified (for example, help day), shows help for that command.
quit exit	Alt+Q	Quits the head unit.
sleep [seconds]		Sleeps for one second. If a delay is specified, sleeps that many seconds. This can be used for scripting the head unit (./desktop-head-unit < script.txt), for example in a CI environment.
screenshot filename.png		Saves a screenshot to filename.png.
licenses		Display licenses of libraries used in DHU
keycode keycode		Send keycode, one of the names listed in the Keycodes section.

Touch and Touchpad

When touch or touchpad is enabled, clicking in either the display window (for touch) or touchpad window (for touchpad) will be registered as touch events.

For touch, you can simulate multi-touch by right clicking on the first finger location, then click-and-hold the right button for the second finger. The centerpoint of the two fingers remains fixed and moving the mouse will allow you to either rotate them around the center or pinch in-and-out (or both).

For touchpad, click-and-hold the left button to scroll between different UI elements on the screen. Clicking the right button will select the element that currently has focus.

Command	Key	Description
tap x y		Simulate a touch event at the specified coordinates

Rotary Controller

The DHU has rotary controller support. When it is enabled, the following actions are supported:

• Up, down, left, and right on the Dpad
• Rotating clockwise and counterclockwise
• Performing a rotation flick (5 steps at once)
• Clicking down on the controller and back on the controller

The commands and key bindings are listed below.

A scroll wheel on a mouse will send dpad rotate commands, and the middle mouse button click (usually the scroll wheel) will send dpad click commands.

Note that most cars have touch screens. Some cars have rotary controller-only, and some have a hybrid touch and controller. Cars can also support a touchpad which can be used for map panning and text entry. Bear these different configurations in mind when simulating different vehicle head units.

Command	Key	Description
dpad {up|down|left|right}	Arrow keys	Movement of the rotary controller.
dpad {ur|dl|ul|dr}		Movement of the rotary controller.
dpad soft {left|right}	Shift + Arrow keys	Side buttons available on some rotary controllers.
dpad click	Return	Pressing the rotary controller.
dpad back	Backspace	Back button available below some rotary controllers.
dpad rotate left	1	Rotary controller left (counter-clockwise) movement.
dpad rotate right	2	Rotary controller right (clockwise) movement.
dpad flick left	Shift+1	Fast counter-clockwise spin of the rotary controller.
dpad flick right	Shift+2	Fast clockwise spin of the rotary controller.
dpad 0-9*#+	Num pad

Microphone

The DHU supports using a microphone for voice input or playing a pre-recorded voice track. For your convenience, we have provided the following sound files for common voice commands. These sound files are installed in the SDK_LOCATION/extras/google/auto/voice/ directory.

File name	Text
navhome.wav	Navigate to home.
navwork.wav	Navigate to work.
navsoh.wav	Navigate to Sydney Opera House.
navgoogle.wav	Navigate to 1600 Amphitheatre Parkway, California, USA.
exitnav.wav	Exit navigation.
howlong.wav	How long until I get there?
showtraffic.wav	Show traffic.
showalternateroute.wav	Show alternate routes.
pause.wav	Pause music
nextturn.wav	When is my next turn?

To run an individual .wav file in the DHU prompt:

mic play /path/to/filename.wav

Command	Key	Description
mic begin	M	Activates the microphone (equivalent to clicking the steering-wheel button) and waits for input from the computer microphone.
mic play filename.wav		Activates the microphone and plays the specified WAV file recording. Note: You will not hear the WAV file being played, but you will hear the response from Android Auto.
mic repeat		Repeats the last recording used with mic play.
mic reject {on|off}		Enables or disables rejection of microphone requests. When on, all microphone requests will be rejected.

Sensors

The DHU supports simulating changes in the vehicle's sensor data with the following commands. To mock sensor data and send them to Android Auto, the corresponding sensors have to be enabled with the configuration .ini file when starting the DHU.

Command	Description
fuel [percentage]	Set the fuel level to the specified percent, or do not pass in a value to disable fuel level.
range [km]	Set the range to the specified kilometers, or do not pass in a value to disable range data.
lowfuel [{on|off}]	Set the low fuel warning sensor, or do not pass in a value to disable the sensor.
accel [x] [y] [z]	Set the accelerometer to the specified x, y, and z values (m/s^2), or do not pass in parameters to unset the accelerometer data. Pass in NAN to skip optional parameters if needed.
compass bearing [pitch] [roll]	Set the compass to the specified bearing, pitch, and roll values (degrees). Pass in NAN to skip optional parameters if needed.
gyro [x] [y] [z]	Set the gyroscope to the specified x, y, and z rotation speed (rad/s), or do not pass in parameters to unset the gyroscope data. Pass in NAN to skip optional parameters if needed.
location lat long [accuracy] [altitude] [speed] [bearing]	Set the location to the specified lat and long values along with the optional accuracy (m), altitude (m), speed (m/s), and bearing (degrees). Pass in NAN to skip optional parameters if needed.
odometer km [current_trip_km]	Set the odometer to the specified kilometers along with an optional current trip km value.
speed [speed]	Set the vehicle speed to the specified value (m/s), or do not pass in a value to disable the sensor.
tollcard {insert|remove}	Indicates whether a toll card was inserted or removed.

Day/Night Mode

The DHU supports simulating changing between day and night mode with the following commands and key bindings.

Command	Key	Description
day	Shift+N	Activate day mode (high-brightness, full color).
night	Ctrl+N	Activate night mode (low-brightness, high-contrast).
daynight nightday	N	Toggle current day or night mode.

Focus Management

The DHU supports simulating whether or not Android Auto has focus on the head unit with the following commands.

Command	Description
focus video {on|off|toggle}	Enables or disables whether Android Auto has video focus on the head unit. Turning off video focus simulates the head unit going into native mode.
focus audio {on|off|toggle}	Enables or disables whether Android Auto has audio focus on the head unit. Turning off audio focus simulates the head unit playing its own audio source.
focus nav {on|off|toggle}	Enables or disables whether Android Auto has navigation focus on the head unit. Turning off navigation focus simulates the head unit running its own navigation system.

Restrictions/Driving Status

The DHU supports simulating certain restrictions when the vehicle is moving, such as disabling the keyboard and disallowing phone configurations.

Command	Key	Description
restrict none	U	Disables all restrictions.
restrict all	Shift+U	Enables all restrictions (for example, to simulate driving).

Instrument Cluster

The DHU supports emulating an instrument cluster (usually located behind the steering wheel) which shows basic info during navigation about the next turn (such as the next road name, distance/time, or a turn arrow) and information about an ongoing phone call.

This can be enabled using the instrumentcluster entry in the [general] section of the configuration file, or by the navcluster or phonecluster entries to control each feature separately.

[general]
...
instrumentcluster = true

Cluster Display

Some vehicles have cluster displays capable of displaying rich visual information such as map tiles. Starting with version 2.1 of the DHU (currently available via the Android Studio Beta update channel ), you can emulate such a display on your development machine.

This can be done using a configuration file with a cluster [display] section. [display] sections support the same video configuration options as the main display configured in the [general] section of the file.

...

# The display name following the colon can be whatever you like.
[display:cluster]
# Setting the displaytype as cluster is what lets the DHU know how to handle it.
displaytype = cluster
resolution = 800x480
dpi = 160
...

This configuration can either be added directly to an existing .ini file or you can reuse it by putting it in a separate file and passing multiple configuration files when launching the DHU. When using multiple configuration files, later definitions of a given value override earlier ones.

# Launch your landscape configuration with your cluster display configuration
./desktop-head-unit -c landscape.ini -c cluster.ini

# Launch the portait configuration with the same cluster display configuration
./desktop-head-unit -c portrait.ini -c cluster.ini

Media Playback Status

The DHU supports an additional information display to show media playback status, for example, what track is playing.

This can be enabled using the playbackstatus entry in the [general] section.

[general]
...
playbackstatus = true

Keycodes

The DHU provides a set of default keycodes that simulates the set of shortcut buttons that are commonly available in different vehicles. For example, the home keycode can be triggered in the DHU prompt as follows:

keycode home

Keycode	Description
home	Go to the home screen.
back	Go back.
call endcall	Make or end a call.
search	Trigger search.
media_play_pause media_play media_pause	Play or pause a media.
media_next media_previous	Go to the next or previous media track.
media	Go to the default media app.
navigation	Go to the default navigation app.
tel	Go to the default telephone app.

Configure the DHU

The DHU supports a configuration .ini file to change the input modes available (touch, controller), the frame rate, resolution and DPI the head unit requests from the phone.

The default location for the configuration file is ~/.android/headunit.ini. If you wish to change the configuration of the head unit on your system, you can modify this file.

You can also specify a configuration file to load using the -c flag.

./desktop-head-unit -c /path/to/config.ini

Sample configuration

[general]
touch = true
touchpad = false
controller = false
instrumentcluster = false
resolution = 800x480
dpi = 160
framerate = 30
fueltypes = unleaded,electric,hydrogen
evconnectors = supercharger

Sample configuration files can be found under the SDK_LOCATION/extras/google/auto/config/ folder to demonstrate different head unit settings you can test against. For more advanced use cases, please refer to the supported settings below.

Input Configuration

Name	Default	Type	Description
inputmode	default	String	Defines the input mode. The options touch, rotary, hybrid enable and disable touchscreen and rotary support and set default keycodes as appropriate, while default defers to the touch and controller options below.
controller	false	Boolean	Enable rotary controller input. Ignored unless inputmode is default.
touch	true	Boolean	Enables touchscreen. Ignored unless inputmode is default.
touchpad	false	Boolean	Enables touchpad.
touchpadnavigation	false	Boolean	Enables touchpad to be used for UI navigation.
touchpadtapasselect	false	Boolean	When true, a tap on the touchpad is a select event.
touchpaduiabsolute	false	Boolean	When touchpadnavigation is true, this sets whether the touches should be treated as absolute or as gestures.

Video Configuration

Android Auto supports three video resolutions:

1. 480p (800x480 -- default)
2. 720p (1280x720)
3. 1080p (1920x1080)

To support different aspect ratios other than the ones above, the head unit is able to specify a margin to letterbox/pillarbox as necessary. For example, if you wanted a 1000x600 screen, you would set the resolution to 720p (1280x720) and a marginwidth of 280 and marginheight of 120. This has the effect of adding a 140px margin on both the left and right edges, and 60px top and bottom.

Example configuration to emulate a typical 6 inch screen (750x450):

[general]
...
resolution = 800x480
marginwidth = 50
marginheight = 30

And a very-wide screen:

[general]
...
resolution = 1280x720
marginwidth = 0
marginheight = 220

Name	Default	Type	Description
resolution	800x480	Strings	One of: 800x480, 1280x720, 1920x1080.
dpi	160	Integer
normalizedpi	false	Boolean	When true, reduces DHU window size to account for larger DPI values. When false, larger DPI values result in larger windows (which does not mimic real displays, but does allow easier inspecting of visual content).
realdpi	160	Integer	Used in video configuration.
framerate	30	Integer	Used in video Configuration.
marginheight	0	Integer	Used in video configuration.
marginwidth	0	Integer	Used in video configuration.
margins	0,0,0,0	String	Used in video configuration, overrides marginwidth and marginheight if present. Format is top, bottom, left, right.
contentinsets	0,0,0,0	String	Used in video configuration. Format is top, bottom, left, right.
stablecontentinsets	0,0,0,0	String	Used in video configuration. Defaults to the value of contentinsets. Format is top, bottom, left, right.
cropmargins	false	Boolean	If margins, marginheight, or marginwidth is specified, a true value for this setting removes those margins from the displayed video. This reflects more closely what the end user sees.
pixelaspectratio	1.0	Float	Used in video configuration.

Sensors Configuration

To mock sensor data and send them to Android Auto, the corresponding sensors have to be enabled using the options below. If a sensor is disabled, any data sent for that sensor using the DHU commands is ignored.

Name	Default	Type	Description
accelerometer	false	Boolean	Enable accelerometer sensor data.
compass	false	Boolean	Enable compass sensor data.
driving_status	false	Boolean	Enable driving status sensor data.
fuel	false	Boolean	Enable fuel sensor data.
gyroscope	false	Boolean	Enable gyroscope sensor data.
location	false	Boolean	Enable vehicle location sensor data.
night_mode	false	Boolean	Enable night mode sensor data.
odometer	false	Boolean	Enable odometer sensor data.
speed	false	Boolean	Enable speed sensor data.
toll_card	false	Boolean	Enable toll card sensor data.

Miscellaneous

Name	Default	Type	Description
instrumentcluster	false	Boolean	Enable instrument cluster. Adds a window to the UI to display navigation and phone status.
navcluster	false	Boolean	Enable instrument cluster. Adds a window to the UI to display navigation status.
phonecluster	false	Boolean	Enable instrument cluster. Adds a window to the UI to display phone status.
playbackstatus	false	Boolean	Enable playback status. Adds a window to the UI to display playback status messages.
driverposition	left	String	One of: left, center, or right.
windowleft		Integer	Set the left position of the main window.
windowtop		Integer	Set the top position of the main window.
fueltypes	unleaded	Strings	One or more of (separated by ,): unleaded leaded diesel-1 diesel-2 biodiesel e85 lpg cng lng hydrogen electric other unknown
evconnectors		Strings	Zero or more of (separated by ,): j1772 mennekes chademo combo-1 combo-2 roadster hpwc gbt supercharger other unknown Should only be set if fueltypes contains electric.

Troubleshooting

DHU showing a blank screen when first connected

This is a known issue we are working on. You can work around this by doing the following:

1. Close the DHU.
2. Follow Step 5 described in Run the DHU to stop and restart the Head Unit Server.
3. Start the DHU again.
4. There may be additional permission granting steps on the phone screen. Complete those steps and the DHU might shut down once more.
5. Restart the DHU.

Test your app for Android Automotive OS

You can use the Android Emulator to test how your apps run on Android Automotive OS. This section describes how to set up an Android Virtual Device (AVD) to test your app.

Edit your run configurations for media apps

Media apps on Automotive OS apps are different than other Android apps. Android Automotive OS interacts with your media app using explicit intents and by sending calls to your media browser service.

In order to test your app, verify that your app has no launch activity in its manifest, and then prevent your automotive module from launching with an activity by following these steps:

1. In Android Studio, select Run > Edit Configurations.

   

2. Select your automotive module from the list of modules in your app.

3. Under Launch Options > Launch, select Nothing.

4. Click Apply, and then click OK.

Add system images

Before you can create AVDs that match specific manufacturer hardware, you need to add system images for these devices through the Android Studio SDK Manager. Then, when you're creating an AVD, you can download these system images to use with the AVD.

Add system images from car manufacturers

Currently, you can add OEM-specific system image for the Polestar 2 & Volvo. Follow these steps to add a system image:

1. In Android Studio, select Tools > SDK Manager.
2. Click the SDK Update Sites tab.
3. Click Add .

4. Enter the following Name and URL, then click OK:

   Name: Polestar 2 System Image

   URL: https://developer.polestar.com/sdk/polestar2-sys-img.xml

   Name: Volvo System Image

   URL: https://developer.volvocars.com/sdk/volvo-sys-img.xml

5. Click Apply, then click OK.

Install generic system images

Android Studio also includes a generic system image for Android Automotive OS that you can also use to test your app. This generic system image includes the Google Assistant so that you can test your app's integration.

Follow these steps to install the generic system image:

1. In Android Studio, select Tools > SDK Manager.
2. Click the SDK Platforms tab.
3. Click Show Package Details.
4. Under Android 9.0 (Pie), select Automotive Intel x86 Atom System Image.

5. Click Apply, then click OK.

   

Create a car AVD and run the emulator

Follow these steps to create an Android Virtual Device (AVD) that represents an Android Automotive OS vehicle and then use that AVD to run the emulator:

1. In Android Studio, select Tools > AVD Manager.
2. Click Create Virtual Device.
3. From the Select Hardware dialog, select Automotive, and then select a device and click Next.
4. Select a system image that targets Automotive, such as Android 9.0 (Automotive), and click Next.
5. Name your AVD and select any other options that you want to customize and then click Finish.
6. From tool window bar, select your Android Automotive OS AVD as your deployment target.
7. Click Run .

Additional testing requirements for media apps

If you are testing a media app, then you should also test for the scenarios that are covered in this section (in addition to testing your app on Android Auto, Android Automotive OS, or both).

Test MediaBrowserService startup scenarios

To help keep drivers and passengers safe, users have additional restrictions on how they can interact with apps while driving. For this reason, Android Auto and Android Automotive OS have some MediaBrowserService startup scenarios that your app must be able to handle so that users can continue to enjoy your content while they're on the road.

Test your app to make sure it can handle each of the following scenarios:

• The MediaBrowserService is run before any Activity is opened.
• The MediaBrowserService is run when no Activity can be shown.
• The MediaBrowserService is run when the user is not signed in.

While testing for these scenarios, be sure to try the following methods:

• Force stop the media app, then launch Android Auto or Android Automotive OS.
• Clear the media app data, then launch Android Auto or Android Automotive OS.

Also make sure to set an appropriate error message when necessary.

Media testing tools

The Media Controller Test app allows you to test the intricacies of media playback on Android and helps verify your media session implementation. To get started with this tool, see Using the media controller test app.