EventChannel support

[lzunsec]

I want to pass data from Rust to Flutter in a stream way. That is, I don't want Flutter do call Rust to get an answer, but Rust could call and send stuff to Flutter at any time.

There's a solution for that in Java, called EventChannel, like here: https://github.com/seamusv/event_channel_sample/blob/master/android/app/src/main/java/com/yourcompany/event_channel_sample/MainActivity.java#L28

Would be nice to have them directly on Rust!

[welcome[bot]]

Hi! Thanks for opening your first issue here! :smile:

[fzyzcjy]

There are a few approaches:

1. To reuse current codebase, maybe let Flutter call Rust and open a "stream", and later rust can put things into this stream and flutter will receive it. This is what I have done for my own app for "let rust send logging data to flutter".
2. You may modify flutter_rust_bridge, use the fact that Rust can send data to Dart via IntoDart (and the underlying dart_native_api)

Feel free to make a PR!

[fzyzcjy]

Well I looked at EventChannel example. It is just like approach 1, the stream.

[lzunsec]

Is it possible to open a never ending stream from flutter into rust such that rust can always send things back? This would be nice because the EventChannel thing I listed requires rust to call java to call flutter, so it's platform specific and bad.

[fzyzcjy]

Is it possible to open a never ending stream from flutter into rust such that rust can always send things back?

Yes. For my personal usage (the logging), I do not end the stream

[lzunsec]

On the docs it says

pub struct LogEntry {
    pub time_millis: i64,
    pub level: i32,
    pub tag: String,
    pub msg: String,
}

// Simplified just for demonstration.
// To compile, you need a OnceCell, or Mutex, or RwLock
// Also see https://github.com/fzyzcjy/flutter_rust_bridge/issues/398
lazy_static! { static ref log_stream_sink: StreamSink<LogEntry>; }

pub fn create_log_stream(s: StreamSink<LogEntry>) {
    stream_sink = s;
}

I think it should be

pub fn create_log_stream(s: StreamSink<LogEntry>) {
    log_stream_sink = s;
}

right?

Anyways, I'm getting

the trait bound DartCObject: From<LogEntry> is not satisfied

even after codegen.

Also I think it would be nice to mention

use flutter_rust_bridge::{StreamSink};

cau I thouoght it was a Rust thing, not a type from this lib

[fzyzcjy]

right?

Sure

[fzyzcjy]

even after codegen.

Please file a separate issue about this

Also I think it would be nice to mention

Sure, feel free to PR

[lzunsec]

Hmmm I'm using https://github.com/fzyzcjy/flutter_rust_bridge/pull/293 I think this might be the reason of the errors, cause it's old. Now I don't know what to do, cause I need it working but also need StreamSink

[lzunsec]

https://github.com/fzyzcjy/flutter_rust_bridge/pull/537

[lzunsec]

Sorry my type was not pub so it wasn't being translated. Anyways, do you think I should have many streams per instance or just one stream and filter the messages? I don't know how expensive this stream is.

Thank you for your help!

[fzyzcjy]

Sorry my type was not pub so it wasn't being translated

Feel free to PR and warn (or log) such cases

Anyways, do you think I should have many streams per instance or just one stream and filter the messages? I don't know how expensive this stream is.

IMHO it is not expensive, so it should not be problem if only dozens of streams. But if you have a million stream maybe too much

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[github-actions[bot]]

This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new issue.