Question 1

How does a platform channel work?

Accepted Answer

The Dart side sends a message over a named channel, and the native side (Kotlin/Swift) receives it in a handler registered under the same name and returns a result. The call is asynchronous and data is serialised automatically — only simple types cross (numbers, strings, lists, maps), so a complex object has to be converted to a map first. Distinguish the three kinds: MethodChannel (one call, one reply), EventChannel (a stream from native), BasicMessageChannel (free-form). Add the practical detail: the channel name must match character for character on both sides, and a mismatch produces MissingPluginException — the most common mistake here.

Question 2

When do you drop down to native code?

Accepted Answer

I follow an order. I check pub.dev first: camera, location, notifications, file picking, biometrics — all have well-maintained plugins, and writing your own channel costs both time and ongoing maintenance. I go native in three cases only: (1) an in-house SDK has to be integrated, which is common in banking and insurance; (2) no plugin exists or the one that does is abandoned — if the last commit is two years old, depending on it is a risk; (3) a platform-specific performance API is genuinely needed. When choosing a plugin I have criteria too: last release date, open issue count, and whether it supports both platforms.

Question 3

How do you test a platform channel?

Accepted Answer

I split it in two. The Dart side — I mock the channel: the Flutter test binding lets you replace the handler, so I can verify the success path, PlatformException and MissingPluginException without a device. That covers most of the testing. The native side — with Kotlin/Swift unit tests using each platform's own tooling. End to end — only through an integration test on a real device, and few of those. One point worth making: because the error paths are easy to test on the Dart side, there is no excuse for skipping them.

Platform channels and native integration

📚 Sources and documentation