Over the last few years, I have worked on building Android SDKs — mainly for payment flows, app security checks, and internal enterprise tools. These SDKs have been integrated into real client applications, which gave me practical experience with handling integration challenges, debugging issues in diverse environments, and designing APIs that other developers can use easily.Working on SDKs is very different from building apps. You don’t control the environment, you don’t control how integrators write code, and you definitely don’t control how they initialize things.
Because of this, SDK design must be clean, safe, defensive, and easy to integrate.
In this blog, I’m sharing some of the most important lessons I learned while building Android SDKs. These are practical, real-world insights that can save you from painful production issues, client complaints, and hours of debugging.
- Create a Clear Facade Layer — Don’t Expose Internals
One of the first architectural decisions for any SDK is how you expose your APIs. The biggest mistake beginners make is exposing too many classes or forcing clients to interact with internal modules directly.
A clean SDK must have a facade layer — a single, easy-to-understand entry point that exposes only the essential APIs.
Why a Facade Layer?
- Makes integration simple (“just call SdkManager.initialize()”).
- Prevents accidental misuse of internal classes.
- Gives you flexibility to change internal implementation without breaking clients.
- Reduces the learning curve for integrators.
Example
object MySdk {
fun initialize(context: Context, config: SdkConfig) { … }
fun startPayment(request: PaymentRequest): Result { … }
fun logout() { … }
}
Even if your internal architecture has multiple layers — data, network, security, local cache — the integrator should only see clean, intuitive APIs.
2. Never Force Integrators to Extend Application Class
A surprisingly common mistake in SDK development is asking the client to extend your SDK’s Application class or copy your Application implementation.
This is a design smell.
Every app has only one Application class. If your SDK forces the client to override it, then:
- The client’s existing Application logic breaks.
- They must merge your logic with theirs manually.
- It becomes extremely error-prone and difficult to maintain.
Better Approach
offer a manual initialization:
MySdk.initialize(applicationContext)
Never enforce Application extension. Give integrators flexibility.
3. Always Perform Basic Validations Inside the SDK
SDK methods must validate inputs before making network calls. If validation is deferred to the backend:
- You waste network time.
- You add latency for users.
- You increase load on the server.
- You make debugging harder for integrators.
Example: JWT Token Input
Suppose an API requires a JWT token.
Basic client-side validation that SDK should do:
- JWT is not null/empty.
- JWT does not contain spaces.
- JWT follows basic header.payload.signature format.
- JWT length is within acceptable limits.
private fun validateJwt(jwt: String?) {
require(!jwt.isNullOrBlank()) { "JWT cannot be empty" }
require(!jwt.contains(" ")) { "JWT cannot contain spaces" }
require(jwt.split(".").size == 3) { "Invalid JWT format" }
}
Imagine sending malformed JWT to server every time and waiting for 2 seconds for each avoidable error. A single validation check in SDK removes that delay and improves UX.
4. Make Error Messages Informative + Assign Unique Error Codes
When an SDK is large, it may throw similar errors from different parts of the code. If the error message is the same, it becomes impossible to know where the failure originated.
Solution:
- Use meaningful error messages.
- Assign unique error codes per module or per failure type.
Example design:
enum class SdkError(val code: Int, val message: String) {
NETWORK_TIMEOUT(1001, "Network call timed out"),
INVALID_JWT_FORMAT(2001, "JWT format invalid"),
JWT_EMPTY(2002, "JWT is empty"),
PAYMENT_PARSE_ERROR(3004, "Failed to parse server response")
}
When a client reports an issue like:
Error Code: 2001
You instantly know:
- It’s a JWT issue.
- It happened in input validation.
- It failed at format check.
This improves debugging speed drastically.
5. Implement Logging & Log File Upload Mechanism
When an SDK misbehaves, the integrator will say:
“Your SDK is crashing. Please fix.”
But without logs, you’re blind.
A good SDK should:
- Maintain its own structured logs.
- Store logs in a file inside app-specific directory.
- Upload logs automatically when a crash occurs.
- Provide a mechanism for the integrator to trigger log upload manually.
Recommended Flow
Option A — Auto-upload on crash or specific exception
- Catch exceptions in SDK layer.
- Write logs.
- Send log file to server.
Option B — Deferred upload using WorkManager
If you don’t want to push logs instantly (maybe for privacy or optimization):
- Queue log files.
- WorkManager uploads them once per day.
Option C — Controlled by Server
Your server response can include a flag:
{
"enableLogUpload": true
}
When this value becomes true (on any API call), SDK immediately uploads the latest log file.
This approach keeps the SDK lightweight, intelligent, and responsive without overwhelming the server.
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Final Thoughts
Building an Android SDK is not just writing code — it’s creating a reliable product that other developers will trust. If your SDK crashes their app or is hard to integrate, they will blame you, not their code.
Over the years, these principles have helped me build stable and developer-friendly SDKs:
- Provide a clean facade layer.
- Never force integrators to modify Application class.
- Validate everything before making network calls.
- Use error codes for fast debugging.
- Implement robust logging and smart log uploads.
If you’re starting your SDK journey or improving an existing one, following these principles will save you from unnecessary headaches and help you deliver a polished, production-ready SDK.
This article was previously published on proandroiddev.com
