为同一设备获取不同的 ID。 为什么？

Question

I am getting different Android IDs for same device for 2 apps in spite of they are being signed with same keystore. This problem is occurring only in Android Oreo OS. Can anyone help me why there are 2 different Android IDS generated?

The method i am using for Android Id -

int deviceId = Settings.Secure.getString(pContext.getContentResolver(), Settings.Secure.ANDROID_ID)

Answer 1

Its behaving as intended. in Android 8.0, the value of ANDROID_ID is now scoped per app means ANDROID_ID is now unique for every app

Please Read about Android 8.0 Behavior Changes

• For apps that were installed prior to an OTA to a version of Android 8.0 (API level 26) (API level 26), the value of ANDROID_ID remains the same unless uninstalled and then reinstalled after the OTA. To preserve values across uninstalls after OTA, developers can associate the old and new values by using Key/Value Backup.

• For apps installed on a device running Android 8.0, the value of ANDROID_ID is now scoped per app signing key, as well as per user. The value of ANDROID_ID is unique for each combination of app-signing key, user, and device. As a result, apps with different signing keys running on the same device no longer see the same Android ID (even for the same user).

Answer 2

That is the expected behaviour on Oreo and above devices. Device Id is now unique for every app for each user.

Android official documentation:

For apps installed on a device running Android 8.0, the value of ANDROID_ID is now scoped per app signing key, as well as per user. The value of ANDROID_ID is unique for each combination of app-signing key, user, and device. As a result, apps with different signing keys running on the same device no longer see the same Android ID (even for the same user).

Link: https://developer.android.com/about/versions/oreo/android-8.0-changes

Answer 3

Since Android 8, android_id is "unique to each combination of app-signing key, user, and device" so as to deny "developers the ability to track users across multiple applications". These unique IDs are stored in

/data/system/users//settings_ssaid.xml.

When android_id value init, the first time set the value? Which case does the android_id value change? As evident, android_id "is randomly generated when the user first sets up the device and should remain constant for the lifetime of the user's device" unless a factory reset is performed which clears all settings.

On Android 8+ the app specific android_id "value may change if a factory reset is performed on the device or if an APK signing key changes".

Keeping all in view it doesn't seem a good idea to build a device_id with android_id.