I’m trying to create a flow from an EditText change in Android, I’m using

flow {…}

builder, So I’m creating a watcher inside it here is the code, my question is how I clear inner listeners when flow canceled ?

fun EditText.textChangesFlow(): Flow<TextViewTextChangeEvent> {
    flow<TextViewTextChangeEvent> {
        val watcher = object : TextWatcher {
            override fun afterTextChanged(s: Editable?) {
                emit(TextViewTextChangeEvent(s.toString()))
            }

            override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {
            }

            override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {
            }
        }
        addTextChangedListener(watcher)
         //how to call this when flow is canceled or finished
        //removeTextChangedListener(watcher)

    }
}

Add an

awaitClose { … clear inner listeners here … }

at the end of your

flow { … }

lambda:

flow<TextViewTextChangedEvent> {
    ...
    ...
    awaitClose { removeTextChangedListener(watcher) }
  }

You must use

channelFlow

not

flow

. Within the scope of channelFlow you can use awaitClose. You must also change

emit

to

send

channelFlow<TextViewTextChangedEvent> {
    ...
    ...
    awaitClose { removeTextChangedListener(watcher) }
  }

Do I need to make

textChangesFlow

suspend function, I have a compile error with

send()

and

emit()

The scope inside channel flow should be suspend. So I wouldn't think so

But the callback

afterTextChanged

is not suspend. So yes, either use

offer(…)

or wrap it inside a launch:

launch { send(…) }

.

I used

launch{...}

but is it safe to call?

Not sure what you mean by ‘safe’?

I'd suggest using

callbackFlow

instead of

channelFlow

. While both provide exactly the same behavior,

callbackFlow

makes the intent clearer in this case. Also, since 1.3.4 there is a lint warning with

callbackFlow

that notifies you if you forget about

awaitClose

.

@hellman wrote a blog post about it: https://www.hellsoft.se/instant-search-with-kotlin-coroutines/