Android vehicle development job interview exercises ~

Recently, I saw a lot of articles on car development on the Internet, but there are few corresponding interview questions. For some people who want to interview for Android car positions in car companies, they are quite confused. Knowing where to start, can you pass the interview questions from previous years with Android?

Of course not. Although some basics of Android need to be mastered, the main content of the interview is still linked to the realization of some projects in the car. So this article will take out the interview questions that will be asked by Android car development positions in car companies, and let everyone analyze them (currently there are 22 questions here, and some are still being sorted out).

1. What is Android Auto? What is its purpose?

Android Auto is a technology developed by Google for the vehicle environment, which aims to make certain applications of Android phones safer and more convenient when running in vehicles.

The purpose of Android Auto is to connect mobile applications (such as music, maps, contacts, messages, navigation, etc.) with the driver's in-vehicle infotainment system and control it through the in-vehicle screen and voice recognition function. In this way, the driver can concentrate more on the road and traffic without the distraction of operating a mobile phone.

Through the connection with the vehicle infotainment system, Android Auto can receive information from outside the vehicle, such as road conditions, weather, missed calls, text messages, etc., and display them on the vehicle screen. In addition, it can also convert the driver's voice commands into text or operations through a Bluetooth connection and respond.

2. Why use Android Auto instead of just the normal Android app?

The main reasons for using Android Auto are safety and convenience.

First of all, when drivers use ordinary Android applications, it is easy to cause distracted driving and increase the risk of accidents. Using Android Auto can control mobile phone applications through voice commands or the control panel in the car, which greatly reduces driver distraction. .

Second, the interface design of Android Auto is more suitable for drivers, easier to read and operate. For example, it has bigger buttons and fonts, a simpler menu structure, etc. This allows the driver to use the in-vehicle system more conveniently and focus more on driving.

In addition, Android Auto also provides some special functions, such as Google map navigation in driving mode, voice calls, message broadcast and other functions. These functions are specially designed for driving, which are safer and easier to use. distracts the driver's attention.

To sum up, the use of Android Auto can better improve the safety and comfort of driving, and it is a special application designed to meet the needs of drivers.

3. What types of apps are supported by Android Auto?

The types of apps supported by Android Auto include, but are not limited to, the following:

Navigation applications: Map applications such as Google Maps, Waze, Sygic, Here Maps, etc.
Communication applications: communication applications such as phone calls, text messages, and voicemails.
Media Apps: Such as apps that play music, podcasts, and radio, such as Spotify, Pandora, TuneIn Radio, iHeartRadio, etc.
News and Information Apps: Apps such as News, Weather, Stocks, and more, such as CNN, Fox News, The Weather Channel, The Economist, and more.
Travel and travel applications: applications such as travel guides, car rentals, and airline ticket reservations.
Social Media and Messaging Apps: Social media and messaging apps like Facebook, WhatsApp, Line, WeChat, Telegram, etc.

While Android Auto supports many apps, not all Android apps will run on Android Auto. Only adapted apps will run on Android Auto.

4. How to add apps to Android Auto?

To add apps to Android Auto, you can refer to the following steps:

Make sure the app is Android Auto Compatible. You can use the Auto App Testing tool and Auto Compatibility Tests Library for testing.
Add declarations to your application's AndroidManifest.xml file to indicate the type of interaction your application will have with the in-vehicle system and the supported operations.

<uses-feature
    android:name="android.hardware.type.automotive"
    android:required="true" />
<uses-library
    android:name="com.google.android.gms.car"
    android:required="true" />
<meta-data
    android:name="com.google.android.gms.car.application"
    android:resource="@xml/automotive_app_desc" />

Create the automotive_app_desc.xml file under the res/xml/ directory and add an application descriptor element to determine the application's name, icon, and supported operations.

<?xml version="1.0" encoding="utf-8"?>
<automotiveApp xmlns:android="http://schemas.android.com/apk/res/android" >
    <uses name="应用程序名称" />
    <uses icon="应用程序图标" />
    <uses action="android.intent.action.MAIN" />
    <uses action="android.media.action.MEDIA_PLAY_FROM_SEARCH" />
    <uses action="android.media.action.MEDIA_PLAY" />
    <uses action="android.media.action.MEDIA_PAUSE" />
</automotiveApp>

Write interfaces suitable for in-vehicle systems, such as scalable text, bright colors, and easy-to-operate buttons.
Use the Android Auto preview library to make sure your app will work properly on the car's system.
Publish the application and publish it on Google Play after passing the review.

It should be noted that Android Auto is not available for all in-vehicle systems, only in-vehicle entertainment systems with the Android Auto app installed or standalone devices supported by Android Auto can use Android Auto. Therefore, it is necessary to confirm the compatibility of the operating system version and Android Auto when selecting a vehicle or a stand-alone device.

5. How to make app UI for Android Auto?

To make app UI for Android Auto, you can follow these steps:

Determine the target user and functionality of the application, and design it with the constraints of the in-vehicle environment and user needs in mind.
Refer to Design Guidelines and Styles for Android Auto https://developer.android.com/design/autofor specifications and requirements for Android Auto application UIs.
Determine the main content and functionality of the application, including layout, colors, fonts, and icons. Follow Android Auto's design guidelines when designing, and use colors and icons that are appropriate for the environment in the car.
Identify the primary method of navigation and operation of the application, such as using swipe gestures or button controls. Design to follow Android Auto's navigation and operation guidelines, and provide users with an easy-to-operate interface.
Use Android Auto's API and class library to ensure that the application's data and operations are compatible with the in-vehicle environment and work with other Android Auto applications.
During the design and testing phase, use the Android Auto emulator or connect an actual Android Auto device for testing. Make sure that the application complies with the specifications and requirements of Android Auto, and provide users with the best experience.

Making application UI suitable for Android Auto needs to follow the design guidelines and requirements of Android Auto, and use related APIs and class libraries for development and testing. Only applications that meet the specifications and requirements can run on the Android Auto platform and provide users with the best experience.

6. What communication protocols does Android Auto support?

The communication protocols supported by Android Auto include the following:

Android Automotive Message Broker (AMB): AMB is one of the important components of the Android Auto Middleware Platform (Automotive Middleware Platform), and it is a protocol for solving communication between various vehicle devices.
Media Transfer Protocol (MTP): MTP is a communication protocol primarily used to transfer audio, image, and video files between computers and devices.
Bluetooth: Android Auto supports the use of Bluetooth connection to connect with the vehicle system, which allows the vehicle system and the mobile phone to exchange data, such as media, phone calls, navigation, etc.
USB: Android Auto supports connecting to the vehicle system via USB, which allows the mobile phone to use the power and data transmission capabilities of the vehicle system to obtain a better experience.
Wi-Fi: Android Auto also supports the use of Wi-Fi connections, which require the use of a hotspot to connect the car's system to the phone.

Android Auto achieves information interaction with the vehicle system through the above communication protocols to improve driving experience and safety. Which protocol to choose depends on the specific needs of the car manufacturer, in-vehicle system, and car owner.

7. What are the audio and video playback APIs for Android Auto?

The audio and video playback APIs of Android Auto mainly include the following types:

MediaSessionCompat: This class is one of the general solutions for encapsulating media data in the Android system. Various operations of audio and video playback can be managed and controlled through MediaSessionCompat, including play, pause, next song, previous song, etc.
MediaBrowserServiceCompat: This class is a service in the Android system, which is used to provide a media browser for remote client connections. MediaBrowserServiceCompat implements audio and video playback services by encapsulating media data, resources and instructions in a media browser.
MediaPlayerCompat: This class encapsulates various playback control methods of MediaPlayer in the Android system. It provides basic playback operations including open, close, pause, play, stop, reset, etc.
MediaControllerCompat: This class is a media controller provided by the Android system, which can control media playback, pause, resume, stop, playback mode and other operations.

The above APIs are mainly used to control media playback on Android devices. In Android Auto, the audio and video playback interaction with the vehicle system can be realized by integrating the above APIs with the vehicle system.

8. How to push Android Auto notification?

To display notifications on Android Auto, push notifications can be done through the following steps:

create a notification

Create a notification using NotificationCompat.Builder:

NotificationCompat.Builder builder = new NotificationCompat.Builder(context, CHANNEL_ID)
        .setSmallIcon(R.mipmap.ic_launcher)
        .setContentTitle(title)
        .setContentText(message)
        .setPriority(NotificationCompat.PRIORITY_DEFAULT)
        .setAutoCancel(true);

Use CarExtender to add Android Auto display attributes

Use NotificationCompat.CarExtenderthe and NotificationCompat.CarExtender.UnreadConversationclasses to set extended properties.

NotificationCompat.CarExtender extender = new NotificationCompat.CarExtender();
extender.setUnreadConversation(conversationBuilder.build());

builder.extend(extender);

push notification

Use to NotificationManagerCompatsend notifications:

NotificationManagerCompat notificationManager = NotificationManagerCompat.from(context);
notificationManager.notify(notificationId, builder.build());

This will display notifications on Android Auto. Note that the relevant Android Auto app must be installed and connected to the vehicle system for notifications to appear.

9. How to prevent the Android Auto app from being hacked?

Here are a few things you can consider to prevent your Android Auto app from being hacked:

Handling of private APIs: Android Auto applications can only use official public APIs, and the use of private or unofficial APIs may be rejected by Google or cause the application to crash on Android Auto. So make sure to only use officially exposed APIs.
Data Encryption: Use encryption algorithms and the HTTPS protocol when transferring sensitive data to Android Auto. This protects data from being stolen and tampered with by hackers.
App Permissions: Grant apps only the permissions they need. When your application uses certain sensitive permissions (such as location information, contacts, etc.), the user should be prompted accordingly. If your app doesn't need some permissions, don't ask for authorization.
Clean up the code base: Do not include unused code or libraries in your application, as they may contain known vulnerabilities or present security risks.
Security Testing: Conduct different types of security testing on your application. You can use simulated attacks or other security testing tools to test, and fix any security vulnerabilities in time when detected.
Continuous updates: Keep the app updated to ensure that all known vulnerabilities and vulnerable code are fixed, and follow security best practices and updates to Android Auto-related security requirements.

By taking the steps above, you can reduce the risk of your Android Auto app being hacked. Before developing an Android Auto application, make sure you have read and understood the Android Auto-related security requirements.

10. How to push the application on the mobile phone to Android Auto?

To push an app from your phone to Android Auto, you need to make sure the app complies with Android Auto's requirements. Here are some points you might want to consider:

Apps must be an approved developer for Android Auto.
Apps must support Android Auto's adaptive interface.
Apps must have permissions compatible with Android Auto.
Apps must be registered for use with Android Auto.

Once an app is compliant, it can be pushed to Android Auto by following these steps:

Open the app's code in Android Studio.
Add a new intent to your application's manifest file:

<intent-filter>
  <action android:name="android.intent.action.MAIN" />
  <category android:name="android.intent.category.DEFAULT" />
  <category android:name="android.intent.category.LAUNCHER" />
  <category android:name="android.intent.category.CAR_MODE" />
</intent-filter>

Package the application into an APK file and install it on the Android phone.
Connect your phone to your Android Auto-enabled car media center.
On the main Android Auto screen, find and open your app.
If the application meets the requirements, it should work fine.

11. How to display map and navigation with Android Auto?

To implement Android Auto to display maps and navigation through programs, you can refer to the following steps:

Create a new project in Android Studio and select the "Car Application for Auto" template.
Add the following permission statement to the AndroidManifest.xml file:

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.INTERNET" />

Add the following dependencies to your build.gradle file:

implementation 'com.google.android.gms:play-services-location:17.0.0'
implementation 'com.google.android.gms:play-services-maps:17.0.0'

Create a layout file containing a MapFragment called "map".

implementation 'com.google.android.gms:play-services-location:17.0.0'
implementation 'com.google.android.gms:play-services-maps:17.0.0'

Write the Java code to display the map and set the navigation route in the MapFragment. For example, the following code can be used:

private GoogleMap mMap;

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    mMap = ((MapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();
    mMap.setMyLocationEnabled(true);
    mMap.setOnMapClickListener(new GoogleMap.OnMapClickListener() {
        @Override
        public void onMapClick(LatLng point) {
            getDirections(point);
        }
    });
}

public void getDirections(LatLng point) {
    Location myLocation = mMap.getMyLocation();
    LatLng myLatLng = new LatLng(myLocation.getLatitude(),
            myLocation.getLongitude());
    Intent intent = new Intent(Intent.ACTION_VIEW, 
            Uri.parse("http://maps.google.com/maps?saddr="
            + myLatLng.latitude + "," + myLatLng.longitude
            + "&daddr=" + point.latitude + "," + point.longitude));
    intent.setClassName("com.google.android.apps.maps", "com.google.android.maps.MapsActivity");
    startActivity(intent);
}

Run the app in Android Auto and test the map and navigation functionality.

It should be noted that the above code is just a simple example, and the actual application needs to be modified and debugged according to specific requirements.

12. How to use Android Auto to display charging station information on the vehicle?

To display charging station information on Android Auto, you can follow these steps:

Add Google Play Services library and Android Auto library to Android project.
Create an enum class that contains constants for filtering charging station results.

public enum FilterTypeEnum {
    TYPE_ALL("all"),
    TYPE_FAST_CHARGING("fast"),
    TYPE_LEVEL_2("level2");

    private final String filterType;

    FilterTypeEnum(String filterType) {
        this.filterType = filterType;
    }

    public String getFilterType() {
        return filterType;
    }
}

Use Google Map SDK and Places API to get nearby charging stations.

Places.initialize(getApplicationContext(), API_KEY);
PlacesClient placesClient = Places.createClient(this);

List<Place.Field> placeFields = Arrays.asList(Place.Field.ID, Place.Field.NAME,
                     Place.Field.ADDRESS, Place.Field.LAT_LNG,
                     Place.Field.TYPES);

RectangularBounds bounds = RectangularBounds.newInstance(
                     new LatLng(LAT, LNG),
                     RADIUS_IN_METERS);

FindCurrentPlaceRequest request = FindCurrentPlaceRequest.newInstance(placeFields);
placesClient.findCurrentPlace(request).addOnSuccessListener((response) -> {
    List<PlaceLikelihood> placesList = response.getPlaceLikelihoods();

    for (PlaceLikelihood placeLikelihood : placesList) {
        Place currentPlace = placeLikelihood.getPlace();              
        List<Integer> placeTypes = currentPlace.getTypes();              
        LatLng latLng = currentPlace.getLatLng();                
        String placeName = currentPlace.getName();   
        String address = currentPlace.getAddress();
        // 判断充电站类型并过滤
        if (placeTypes.contains(Place.Type.ELECTRIC_VEHICLE_CHARGING_STATION)) {
            if (filterType.equals(FilterTypeEnum.TYPE_ALL.getFilterType())) {
                // 添加充电站标记到地图上
                mMap.addMarker(new MarkerOptions().position(latLng).title(placeName).snippet(address));
            } else if (filterType.equals(FilterTypeEnum.TYPE_FAST_CHARGING.getFilterType())) {
                // 如果选中了只显示快充站，判断该充电站是否是快充站
                if (placeTypes.contains(Place.Type.ELECTRIC_VEHICLE_CHARGING_STATION)) {
                    mMap.addMarker(new MarkerOptions().position(latLng).title(placeName).snippet(address));
                }
            } else if (filterType.equals(FilterTypeEnum.TYPE_LEVEL_2.getFilterType())) {
                // 如果选中了只显示 Level 2 站，判断该充电站是否是 Level 2 站
                if (placeTypes.contains(Place.Type.ELECTRIC_VEHICLE_CHARGING_STATION)) {
                    mMap.addMarker(new MarkerOptions().position(latLng).title(placeName).snippet(address));
                }
            }
        }
    }
});

Create a list of charging stations in the Android Auto app, display nearby charging stations in a map, and filter the results if desired.

// 定义过滤器类型数组
private final String[] FILTER_TYPE_OPTIONS = new String[]{
    FilterTypeEnum.TYPE_ALL.getFilterType(),
    FilterTypeEnum.TYPE_FAST_CHARGING.getFilterType(),
    FilterTypeEnum.TYPE_LEVEL_2.getFilterType()
};

// 创建过滤器类型下拉列表框
ArrayAdapter<String> adapter = new ArrayAdapter<>(getApplicationContext(), R.layout.filter_type_item, FILTER_TYPE_OPTIONS);
Spinner filterTypeSpinner = findViewById(R.id.filter_type_spinner);
filterTypeSpinner.setAdapter(adapter);

// 监听过滤器类型下拉列表框的选择事件，根据所选类型过滤地图中的充电站
filterTypeSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
    @Override
    public void onItemSelected(AdapterView<?> adapterView, View view, int position, long l) {
        String filterType = FILTER_TYPE_OPTIONS[position];
        mMap.clear();
        // 过滤地图上的充电站
        getNearbyChargingStations(filterType);
    }

    @Override
    public void onNothingSelected(AdapterView<?> adapterView) {

    }
});

These steps will allow you to get nearby charging stations via the Android Auto app, filtering if desired.

13. How do I use voice commands in the Android Auto app?

To use voice commands in the Android Auto app, follow these steps:

Add the following permission statement to the AndroidManifest.xml file:

<uses-permission android:name="android.permission.RECORD_AUDIO" />

Add the following dependencies to your build.gradle file:

implementation 'com.google.android.support:wearable:2.5.0-alpha1'
implementation 'com.google.android.gms:play-services-places:17.0.0'

Add the following speech recognition logic to the code:

private static final int SPEECH_REQUEST_CODE = 0;

private void displaySpeechRecognizer() {
    Intent intent = new Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH);
    intent.putExtra(RecognizerIntent.EXTRA_LANGUAGE_MODEL,
            RecognizerIntent.LANGUAGE_MODEL_FREE_FORM);
    startActivityForResult(intent, SPEECH_REQUEST_CODE);
}

@Override
protected void onActivityResult(int requestCode, int resultCode,
        Intent data) {
    if (requestCode == SPEECH_REQUEST_CODE && resultCode == RESULT_OK) {
        List<String> results = data.getStringArrayListExtra(
                RecognizerIntent.EXTRA_RESULTS);
        String spokenText = results.get(0);
        // 这里可以使用意图处理语音命令，例如打开地图或搜索
    }
    super.onActivityResult(requestCode, resultCode, data);
}

The displaySpeechRecognizer() method is called when the user taps the speech button.

@Override
public boolean onVoiceCommand(String command, Bundle extras) {
    if (command.equals("voice_search")) {
        displaySpeechRecognizer();
        return true;
    }
    return false;
}

In the above code, we first define a SPEECH_REQUEST_CODE constant used to recognize the voice callback, and add a displaySpeechRecognizer() method, which will open a voice recognition interface, the user can issue voice commands to it, and then use the recognition result as a character String passed back to MainActivity. Then, we get the recognition result in the onActivityResult() callback function and use intents to handle voice commands, such as opening a map or searching. Finally, in the onVoiceCommand() callback function, we check whether the user clicked the voice search button, and if so, call the displaySpeechRecognized() method.

It should be noted that in the Android Auto project, it is necessary to test whether the voice function meets the safety standards in the Auto safety test tool.

14. How to perform vehicle diagnosis in Android Auto?

Performing vehicle diagnostics in Android Auto requires the following:

The vehicle diagnostic interface supports OBD-II protocol.
Connect the router with the Android device.

Generally, you can use OBD-II scanner or on-board computer to read vehicle parameters and diagnose, then connect scanner or on-board computer to router via Wi-Fi or Bluetooth, and then connect router to Android device via Wi-Fi connect.

In Android applications, the following libraries and tools can be used to read OBD-II diagnostic data and display diagnostic results in Android Auto:

Android Accessory Framework (Android Accessory Framework), can use OBD-II scanner or car computer as peripheral of Android device, and read OBD-II diagnostic data through the interface.
OBD-II Toolbox (OBD-II Toolbox) is an OBD-II software toolkit that can read and parse OBD-II diagnostic data and provide an interface for Android applications.
Android Auto App Template, a template application based on Android Studio, provides sample code and layout files for displaying diagnostic results on Android Auto.

In the app, vehicle diagnostics can be performed in Android Auto using the following steps:

Use the Peripheral Framework or OBD-II Toolkit to read OBD-II diagnostic data and format the data into the desired data structure.
Add a control, such as a TextView or ListView, that displays the diagnostic results to the application's layout file.
In the application's activity, use the Adapter to bind the diagnosis result to the display control, and display the diagnosis result on Android Auto. You can use RecyclerView or ListView, and customize the Adapter according to your needs.

15. How to perform vehicle control in Android Auto?

Android Auto does not support the use of applications that require manual operation while driving, including vehicle control applications. Therefore, it is not recommended to implement vehicle control functions in Android Auto.

In some specific scenarios, it may be necessary to implement some vehicle control functions that do not require manual intervention, such as automatic driving vehicle control. For this scenario, consider the following suggestions:

Make sure the vehicle supports remote control features such as Internet-based remote start, remote lock, etc.
Design an Internet-based remote control application that allows users to remotely control the vehicle while the vehicle is parked. This application does not require manual operation, but only needs to receive instructions sent by the user to realize remote control.
In this application, security mechanisms are used to ensure user rights, such as user login, verification code verification, etc. to achieve identity verification and security control.
Use two different channels for the transmission of control commands, such as HTTP protocol and Websocket protocol, to increase the security and reliability of command transmission.
According to different models and control interfaces of the vehicle, different control commands are adapted, such as engine start and stop, horn beeping, window lifting, vehicle locking and unlocking, etc.

When realizing the function of vehicle control, it is necessary to fully consider safety factors to avoid vehicle failure or personal injury caused by malicious attacks or misoperations. Especially in autonomous driving or advanced assisted driving scenarios, it is necessary to fully consider safety and compliance with laws and regulations to ensure the safety and legality of vehicle control.

16. How to use the car camera in Android Auto?

Using the car camera in Android Auto requires the following steps:

Determines the camera types and resolutions supported by Android Auto. Android Auto supports USB-connected rear cameras and supports the following resolutions: 1280 x 720, 720 x 480, and 640 x 480. In addition, Android Auto also supports OEM cameras provided by automakers.
Provide the camera with the required permissions as required by Android Auto. Add the following permissions to the AndroidManifest file:

<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera" android:required="true" />

Add a camera layout interface to the application. You can use CameraView or SurfaceView in XML layout file for camera preview and capture camera image.
Get camera reference and preview in Activity or Fragment. For example:

// 获取后置摄像头
CameraManager cameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
String[] cameraIdList = cameraManager.getCameraIdList(); // 获取摄像头列表
String cameraId = cameraIdList[0]; // 获取后置摄像头
CameraCharacteristics characteristics = cameraManager.getCameraCharacteristics(cameraId);

// 显示摄像头预览
TextureView textureView = (TextureView) findViewById(R.id.textureView); // 布局文件中定义的预览布局
SurfaceTexture surfaceTexture = textureView.getSurfaceTexture();
surfaceTexture.setDefaultBufferSize(previewSize.getWidth(), previewSize.getHeight());
Surface surface = new Surface(surfaceTexture);
CaptureRequest.Builder builder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
builder.addTarget(surface);
cameraDevice.createCaptureSession(Arrays.asList(surface),new CameraCaptureSession.StateCallback() {...}, null);

During the implementation process, security and user privacy need to be considered to ensure that the use of the camera complies with user intentions and laws and regulations. In addition, it is necessary to provide a friendly UI interface and operating experience, so that users can use the car camera without affecting driving safety.

17. How to use car sensors in Android Auto?

Using on-board sensors in Android Auto requires the following steps:

Determines the sensor types and parameters supported by Android Auto. The sensors supported by Android Auto include accelerometers, gyroscopes, magnetometers, and GPS positioning. You can use sensor libraries or APIs to obtain sensor data and process it.
Provide the required permissions to the sensor as required by Android Auto. Add the following permissions to the AndroidManifest file:

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-feature android:name="android.hardware.sensor.accelerometer" android:required="true" />
<uses-feature android:name="android.hardware.sensor.gyroscope" android:required="true" />
<uses-feature android:name="android.hardware.sensor.compass" android:required="true" />

Add sensor actions and listeners to your application. For example, a code sample to get accelerometer data:

SensorManager sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
Sensor accelerometer = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);

SensorEventListener sensorEventListener = new SensorEventListener() {
    @Override
    public void onSensorChanged(SensorEvent event) {
        float x = event.values[0];
        float y = event.values[1];
        float z = event.values[2];
        // 处理加速度计数据
    }

    @Override
    public void onAccuracyChanged(Sensor sensor, int accuracy) {
        // 传感器精度变化
    }
};

sensorManager.registerListener(sensorEventListener, accelerometer, SensorManager.SENSOR_DELAY_NORMAL);

Process and display sensor data according to business needs or user needs. For GPS positioning data, Google Maps API can be used to analyze and display, and realize functions such as vehicle position and destination navigation.

In the implementation process, the stability and security of data transmission need to be considered to ensure the accuracy and timeliness of sensor reading and processing. In addition, special attention needs to be paid to the impact of sensor use on vehicle safety to ensure that sensor operation does not interfere with driver concentration and control.

18. How to use vehicle information in Android Auto?

Android Auto allows applications to access vehicle information (vehicle speed, fuel level, etc.) and vehicle status (door status, etc.). To use vehicle information in Android Auto, you need to follow the steps below:

Determine the vehicle information types and parameters supported by Android Auto, as well as the vehicle state types and parameters. The vehicle information supported by Android Auto includes vehicle speed, fuel level, mileage, etc., and the vehicle status includes door status, engine status, etc. Vehicle information and vehicle status data can be obtained using an API or a vehicle information library.
Provide the required permissions for vehicle information as required by Android Auto. Add the following permissions to the AndroidManifest file:

<uses-permission android:name="android.car.permission.CAR_INFORMATION" />
<uses-permission android:name="android.car.permission.CAR_STATE" />

Add operations and listeners to vehicle information in the application. For example, a code sample to get the speed of a car:

CarInfoManager carInfoManager = CarInfoManager.getInstance(car);
CarPropertyManager carPropertyManager = CarPropertyManager.getInstance(car);

CarProperty<CarFloatArray> speedProperty = carPropertyManager.getProperty(CarSensorManager.SENSOR_TYPE_CAR_SPEED, CarProperty.PERMISSION_READ);

CarPropertyEventListener<CarFloatArray> carPropertyEventListener = new CarPropertyEventListener<CarFloatArray>() {
    @Override
    public void onChangeEvent(CarPropertyValue<CarFloatArray> value) {
        float speed = value.getValue()[0];
        // 处理车速数据
    }
};

carPropertyManager.registerListener(carPropertyEventListener, speedProperty);

Process and display vehicle information according to business needs or user needs. For example, adjust navigation routes and prompts based on vehicle speed and fuel level information.

During the implementation process, the security and privacy protection of vehicle information need to be considered to ensure that the reading and processing of vehicle information complies with relevant laws and regulations. In addition, it is necessary to pay special attention to the impact of vehicle information operation on vehicle driving to ensure that vehicle information operation will not interfere with the driver's attention and control ability.

19. How to use car navigation in Android Auto?

Using vehicle navigation in Android Auto requires the following steps:

Check navigation permissions

Before using vehicle navigation, you need to check whether the application has navigation permission. This can be checked with the following code:

// 检查是否具有导航权限
if (!NavigationManager.getInstance().hasNavigationPermission()) {
    // 请求导航权限
    NavigationManager.getInstance().requestNavigationPermission();
}

If the application does not have navigation permission, it needs to request navigation permission.

get current location

With navigation permissions, the current location can be obtained using the LocationManager class. The current location can be obtained using the following code:

LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
Location lastKnownLocation = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (lastKnownLocation != null) {
    double latitude = lastKnownLocation.getLatitude();
    double longitude = lastKnownLocation.getLongitude();
    // 处理获取到的位置信息
}

If you need to dynamically obtain location information, you need to register a location listener and implement the corresponding callback method.

set destination

After getting the current location, you can use the NavigationManager class to set the destination. The destination can be set with the following code:

NavigationManager.getInstance().setDestination(new LatLng(destLatitude, destLongitude), "目的地名称");

where destLatitude and destLongitude are the latitude and longitude of the destination.

start navigating

After the destination is set, navigation can be started using the NavigationManager class. Navigation can be started with the following code:

NavigationManager.getInstance().startNavigation();

During navigation, various methods provided by the NavigationManager class can be used to process navigation data, update navigation information, and so on.

When using vehicle navigation, it is necessary to fully consider factors such as user experience and vehicle safety, and reasonably control the navigation function to ensure the reliability and security of the application.

In general, using vehicle navigation in Android Auto requires steps such as checking the navigation permission, obtaining the current location, setting the destination, and starting navigation. During the implementation process, it is necessary to pay attention to factors such as user experience and vehicle safety to ensure the reliability and safety of functions.

20. How to use bluetooth devices in Android Auto?

Using a Bluetooth device with Android Auto requires the following steps:

Check bluetooth permissions

Before using a Bluetooth device, you need to check whether the application has Bluetooth permission. This can be checked with the following code:

BluetoothAdapter bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
if (bluetoothAdapter != null && bluetoothAdapter.isEnabled()) {
    // 拥有蓝牙权限，可以使用蓝牙设备
} else {
    // 没有蓝牙权限，需要请求蓝牙权限
}

If the application does not have Bluetooth permission, it needs to request Bluetooth permission.

Connect a Bluetooth device

In the case of normal bluetooth permissions, you can use the BluetoothAdapter class to search for and connect to bluetooth devices. You can search for bluetooth devices using the following code:

bluetoothAdapter.startDiscovery();

When a Bluetooth device is found, the ACTION_FOUND broadcast is triggered. You can register a broadcast receiver to listen for broadcasts with the following code:

BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        if (BluetoothDevice.ACTION_FOUND.equals(action)) {
            // 处理发现蓝牙设备的操作
        }
    }
};
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
registerReceiver(broadcastReceiver, filter);

After discovering a bluetooth device, you can use the following code to connect to a bluetooth device:

bluetoothAdapter.getRemoteDevice(address).connect();

where address is the MAC address of the Bluetooth device.

use bluetooth device

After connecting a Bluetooth device, you can use the BluetoothSocket class for Bluetooth communication. A BluetoothSocket object can be obtained using the following code:

BluetoothSocket socket = device.createRfcommSocketToServiceRecord(uuid);
socket.connect();

Among them, device is the connected Bluetooth device object, and uuid is the UUID of the communication protocol.

After obtaining the BluetoothSocket object, you can use the InputStream and OutputStream objects for data transmission. For example, the data can be read using the following code:

InputStream inputStream = socket.getInputStream();
byte[] buffer = new byte[1024];
int length = inputStream.read(buffer);
String data = new String(buffer, 0, length);

When using Bluetooth devices, factors such as user experience and vehicle safety need to be fully considered, and the functions of Bluetooth devices should be used reasonably to ensure the reliability and security of the application.

In general, using Bluetooth devices in Android Auto requires steps such as checking Bluetooth permissions, connecting Bluetooth devices, and using Bluetooth devices. During the implementation process, it is necessary to pay attention to factors such as user experience and vehicle safety to ensure the reliability and safety of functions.

21. How to implement Wi-Fi hotspot in Android Auto?

To implement Wi-Fi hotspot in Android Auto, you need to use the API provided by the Android operating system. Specific steps are as follows:

Add permissions

Add the following permissions to the AndroidManifest.xml file:

<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

Get Wi-Fi Manager

Get the Wi-Fi manager using the getSystemService() method:

WifiManager wifiManager = (WifiManager) getSystemService(Context.WIFI_SERVICE);

Configure Wi-Fi Hotspot

Create a Wi-Fi configuration object and set parameters such as SSID, password, and encryption method:

WifiConfiguration wifiConfiguration = new WifiConfiguration();
wifiConfiguration.SSID = "hotspot_name";  // 设置热点 SSID
wifiConfiguration.preSharedKey = "password";  // 设置热点密码
wifiConfiguration.allowedAuthAlgorithms.set(WifiConfiguration.AuthAlgorithm.OPEN);  // 设置热点加密方式
wifiConfiguration.allowedKeyManagement.set(WifiConfiguration.KeyMgmt.WPA_PSK);  // 设置热点加密方式

In general, to implement Wi-Fi hotspot in Android Auto, you need to add permissions, get Wi-Fi manager, configure Wi-Fi hotspot, enable hotspot and obtain hotspot information, and stop hotspot.

22. How to play music and video with Android Auto?

To play music and video in Android Auto, you need to use the MediaSessionCompat and MediaBrowserServiceCompat classes provided by the Android operating system. Specific steps are as follows:

Add permissions

Add the following permissions to the AndroidManifest.xml file:

<uses-permission android:name="android.permission.MEDIA_CONTENT_CONTROL" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

createMediaBrowserServiceCompat

Create a service class that inherits from MediaBrowserServiceCompat. Override the onCreate() method and create a MediaSessionCompat object in it:

public class MediaBrowserService extends MediaBrowserServiceCompat {

    private MediaSessionCompat mediaSession;

    @Override
    public void onCreate() {
        super.onCreate();

        // 创建媒体会话
        mediaSession = new MediaSessionCompat(this, "MediaBrowserService");
        
        // 设置回调
        mediaSession.setCallback(new MediaSessionCallback());
        
        // 开启媒体会话
        setSessionToken(mediaSession.getSessionToken());
    }

    // ...
}

Create MediaSessionCompat.Callback

Create a callback class that inherits from MediaSessionCompat.Callback. Rewrite onPlay(), onPause(), onStop(), onSeekTo() and other methods:

public class MediaSessionCallback extends MediaSessionCompat.Callback {

    // 播放音乐
    @Override
    public void onPlay() {
        super.onPlay();
        
        // 构造媒体播放器
        mediaPlayer = new MediaPlayer();
        mediaPlayer.setDataSource(getContext(), mediaUri);
        mediaPlayer.setOnPreparedListener(MediaPlayer::start);
        mediaPlayer.prepareAsync();
        
        // 更新媒体会话状态
        mediaSession.setPlaybackState(new PlaybackStateCompat.Builder()
                .setState(PlaybackStateCompat.STATE_PLAYING, 0, 1)
                .build());
    }

    // 暂停音乐
    @Override
    public void onPause() {
        super.onPause();
        
        // 暂停媒体播放器
        mediaPlayer.pause();
        
        // 更新媒体会话状态
        mediaSession.setPlaybackState(new PlaybackStateCompat.Builder()
                .setState(PlaybackStateCompat.STATE_PAUSED, 0, 1)
                .build());
    }

    // 停止音乐
    @Override
    public void onStop() {
        super.onStop();
        
        // 停止媒体播放器
        mediaPlayer.stop();
        mediaPlayer.release();
        mediaPlayer = null;
        
        // 更新媒体会话状态
        mediaSession.setPlaybackState(new PlaybackStateCompat.Builder()
                .setState(PlaybackStateCompat.STATE_STOPPED, 0, 1)
                .build());
    }

    // 跳转到指定位置
    @Override
    public void onSeekTo(long pos) {
        super.onSeekTo(pos);
        
        // 跳转媒体播放器到指定位置
        mediaPlayer.seekTo((int) pos);
    }

    // ...
}

connect client

Use the MediaBrowserCompat class on the client side (for example, in an Android Auto player) to connect to the server. After the connection is successful, use the MediaBrowserCompat.SubscriptionCallback class to subscribe to the information of the media library:

MediaBrowserCompat mediaBrowser = new MediaBrowserCompat(context, new ComponentName(context, MediaBrowserService.class), new MediaBrowserCompat.ConnectionCallback() {

    @Override
    public void onConnected() {
        super.onConnected();
        
        // 订阅媒体库数据
        mediaBrowser.subscribe(mediaBrowser.getRoot(), new MediaBrowserCompat.SubscriptionCallback() {
            @Override
            public void onChildrenLoaded(@NonNull String parentId, @NonNull List<MediaBrowserCompat.MediaItem> children) {
                super.onChildrenLoaded(parentId, children);
                
                // 更新 UI
                updateMediaList(children);
            }
        });
    }
    
    // ...
}, null);
mediaBrowser.connect();

play media

When there is music or video to play, use the MediaSessionCompat class to control the media player:

// 设置媒体信息
MediaMetadataCompat.Builder metadataBuilder = new MediaMetadataCompat.Builder();
metadataBuilder.putString(MediaMetadata.METADATA_KEY_TITLE, "Song title");
metadataBuilder.putString(MediaMetadata.METADATA_KEY_ARTIST, "Artist name");
metadataBuilder.putString(MediaMetadata.METADATA_KEY_ALBUM_ART_URI, "album_art_uri");
MediaMetadataCompat metadata = metadataBuilder.build();
mediaSession.setMetadata(metadata);

// 播放音乐
mediaSession.getController().getTransportControls().play();

In general, to play music and video in Android Auto, you need to create MediaBrowserServiceCompat service, MediaSessionCompat media session, MediaSessionCompat.Callback callback, MediaBrowserCompat client connection and subscription, MediaSessionCompat control media player several steps.

at last

In fact, in the interview, no one can be sure that the interviewer will ask you those questions, and what we can do is to conduct a comprehensive review to make up for our technical shortcomings. Because of the length of the article and the progress of the organization, there is only so much to show. If you want to know more about the knowledge points related to Android car development: You canhttps://qr18.cn/F05ZCM refer to the knowledge points related to the Android interview .https://qr18.cn/CKV8OZ

Android Car Learning Manual:`https://qr18.cn/F05ZCM`

Chapter 1 - Android Auto Overview
Chapter 2 - Developing Automotive Media Applications
Chapter 3 - Building an Android Auto Instant Messenger Application
Chapter 4 - Building Point-Focused Applications for Car Navigation and Maps
Chapter 5 - Building Android Automotive OS Video Applications