Hey there! I get it—abstract explanations about SDK vs non-SDK interfaces can feel vague, so let's dive into concrete details tailored to Android development, especially since you're exploring Android P's restrictions.

SDK (Software Development Kit) interfaces are the officially supported, documented, and stable tools/classes/methods provided by Google for building Android apps. These are part of the public Android SDK (including Jetpack libraries like AndroidX) and are designed for developers to use safely across different Android versions.

They’re the "official" way to interact with the Android system—Google guarantees backward compatibility (or provides clear deprecation paths if they’re phased out) and maintains full documentation for them.

Non-SDK interfaces are internal, undocumented parts of the Android system that Google doesn’t expose to third-party developers. These include:

• Methods/classes marked with the @hide annotation in the Android framework source code
• Private system libraries or components meant only for the OS itself or pre-installed system apps
• Internal APIs that aren’t listed in the official SDK docs

Android P and later versions impose strict restrictions on accessing these interfaces because they’re not designed for public use.

Let’s break down the critical gaps:

• Documentation & Support: SDK interfaces have full official docs, code completion in Android Studio, and Google’s support for troubleshooting. Non-SDK interfaces have zero official docs, and Google won’t help if they break your app.
• Compatibility: SDK interfaces are tested across Android versions—if a method is deprecated, Google gives advance notice (usually 2-3 versions) before removing it. Non-SDK interfaces can be modified, renamed, or removed in any system update with no warning.
• Accessibility: SDK interfaces are directly accessible in your code (e.g., you can import android.app.Activity and use it immediately). Non-SDK interfaces require workarounds like reflection, and Android P+ blocks many of these access paths by default.
• App Stability: Using SDK interfaces ensures your app behaves consistently across devices and OS versions. Non-SDK interfaces can cause crashes, ANRs, or unexpected behavior when the system updates—your app might work on Android 10 but fail completely on Android 11.

While Google strongly discourages using non-SDK interfaces, some developers turn to them for specific use cases:

• Unavailable Features: Sometimes a system capability isn’t exposed via the SDK—for example, early Android versions didn’t have a public API to customize the status bar’s icon colors, so developers used non-SDK interfaces to work around this.
• Performance Tweaks: A small number of internal methods might offer better performance than their SDK counterparts (e.g., low-level memory management methods), but this is rare and risky.
• Temporary Workarounds: When the SDK lacks a solution for a specific edge case, developers might use a non-SDK interface as a stopgap until Google releases an official SDK alternative.

SDK Interface Examples #

These are the ones you’ll use every day:

• UI Components: android.widget.TextView, androidx.recyclerview.widget.RecyclerView (from AndroidX)
• Data Handling: android.content.SharedPreferences, androidx.room.RoomDatabase (Jetpack Room)
• System Interaction: android.content.Intent, android.Manifest.permission.ACCESS_FINE_LOCATION
• Networking: okhttp3.OkHttpClient (official Jetpack-recommended library)

Non-SDK Interface Examples #

These are the ones you should avoid unless absolutely necessary:

• Hidden Framework Methods: android.app.ActivityManager.getService() (marked @hide—requires reflection to call)
• Internal System Classes: com.android.internal.os.RuntimeInit (used for system initialization, not for third-party apps)
• Private Property Methods: android.os.SystemProperties.get() (a system-level property accessor that’s restricted in modern Android)
• Internal Activity Methods: android.app.ActivityThread.currentActivityThread() (gives access to the system’s main thread handler, but can break across versions)

内容的提问来源于stack exchange，提问作者aya salama