Create a flow using flow builder in kotlin

Preface

In this article , We will discuss different types of flow builders and how to use them to create flows .

Let's get started .

We will introduce the following ：

• Type of flow generator
• Use Flow Builder Create stream

Type of flow generator

Yes 4 There are three types of traffic generators ：

1. flowOf()： It is used to create flows from a given set of projects .
2. asFlow()： It's an extension function , It helps to convert types to streams .
3. flow{}： This is where we are Flow Of Hello World The... Used in the example .
4. channelFlow{}： This builder uses the send provided by the builder itself to create a stream with elements .
   Example ：

lowOf()

flowOf(4, 2, 5, 1, 7)
.collect {
    Log.d(TAG, it.toString())
}

asFlow()

(1..5).asFlow()
.collect {
    Log.d(TAG, it.toString())
}

flow{}

flow {
    (0..10).forEach {
        emit(it)
    }
}
.collect {
    Log.d(TAG, it.toString())
}

channelFlow{}

channelFlow {
    (0..10).forEach {
        send(it)
    }
}
.collect {
    Log.d(TAG, it.toString())
}

Now? , We will learn how to use Flow Builder creation Flow. We can use Flow Builder Create for any task Flow.

Use Flow Builder Create stream

Let's learn it by example .

Move files from one location to another

ad locum , We will use Flow Builder establish Flow, In order to move files from one location to another in the background thread , And send the completion status on the main thread .

val moveFileflow = flow {
        // move file on background thread
        FileUtils.move(source, destination)
        emit("Done")

}
.flowOn(Dispatcher.Default)

CoroutineScope(Dispatchers.Main).launch {
    moveFileflow.collect {
        // when it is done
    }
}

Download Image

ad locum , We will use Flow Builder Create our Flow To download the image , This will download the image in the background thread and continue to send the progress to the collector on the main thread .

val downloadImageflow = flow {
        // our image downloading code
        // start downloading
        // send progress
        emit(10)
        // downloading...
        // ......
        // ......
        // send progress
        emit(75)
        // downloading...
        // ......
        // ......
        // send progress
        emit(100)

}
.flowOn(Dispatcher.Default)

CoroutineScope(Dispatchers.Main).launch {
    downloadImageflow.collect {
        // we will get the progress here
    }
}

This is the creation of Flow The way .