With Android P, Google is paving the way a modern Android. This modernization process entails tackling compatibility issues. We can see the first step with the Developer Preview: Android shows a warning when you try to install an app that is too old.
We tested the warning with the APK of Bootlog Uptime (an app released in 2013 that was designed for Android 1.6 Donut), and the result is a notification prompting you to update the app or contact the developer.
Although the Android documentation said that Android P would advise users before installing applications intended for an SDK inferior to Android 4.2, the truth is that in our tests the notification doesn’t appear when installing the application, but when it is opened. You can read the text in the previous screen shot: it only says that the application may not function.
Other than that, the application keeps working without problems once you click Accept and the notification only appears one time for each installation of an application, so for now you don’t need to worry too much. You can still use old applications.
However, in the future Google plans to close the fence until reaching the point that developers and the operating system come together more. This notification from Android P is the first step that will doubtless end with more serious measures like completely blocking the applications. This year, new applications and updates sent to Google Play will have to be created with the Oreo SDK as the platform.
It’s important to remember the difference between the target SDK and the minimum SDK. An application can be compatible with Lollipop and Marshmallow but be created with Oreo as the target SDK. The change is only on the part of the developer, who has to accommodate the application to the newest practices and changes in the operating system, which is what Google is pursuing.