如何在 Jetpack Compose 中使用 Coil 制作首字母图标

Question

So I am using the Coil library for our image processing and I noticed in the place holder it only takes an int. I want however to display initials if a user does not have an avatar or incase of any error show initials, like this image see below. Problem is, I am new in jetpack compose and not sure how I can achieve this. See my code below.

I have this card that has icon, and some details my Profile Card

ProfileCard( 
    personName = String.format("%s %s", e.firstName, e.lastName),
    personC = entity.program ?: "", 
    painter = rememberAsyncImagePainter(model = getProfileAvatar(entity.id)),
    onCardClick = {})

My getProfileAvatar()

private fun getProfileAvatar(id: String) : ImageRequest {
    val url = ServiceAPI.photoUrl(id) 
    return ImageRequest.Builder(requireContext()) 
        .data(url) 
        .addHeader() ) 
        .build() }

Will appreciate feedback, I did see a couple of post, but don't address the Jetpack part.

Answer 1

You can use coil's SubcomposeAsyncImage for that. It allows you to use any composable function as a placeholder/error state:

SubcomposeAsyncImage(
    model = getProfileAvatar()
) {
    val state = painter.state
    if (state is AsyncImagePainter.State.Loading || state is AsyncImagePainter.State.Error) {
        Text(text = "NG")
    } else {
        SubcomposeAsyncImageContent()
    }
}

Answer 2

Example:

val personName by remember{ mutableStateOf(String.format("%s %s", entity.firstName, entity.lastName)) }
val painter = rememberAsyncImagePainter(
    model = ImageRequest.Builder(LocalContext.current)
        .allowHardware(false)
        .data("https://xxxx.xxxx.user_avatar.jpg")
        .size(Size.ORIGINAL)
        .build()
)
val isErrorState = painter.state is AsyncImagePainter.State.Error
val textMeasure = rememberTextMeasurer()
val textLayoutResult = textMeasure.measure(text = buildAnnotatedString { append(personName) }, style = TextStyle(color = Color.White, fontSize = 16.sp))

ProfileCard(
    modifier = Modifier.drawBehind {
        if(isErrorState) {
            drawText(textLayoutResult = textLayoutResult)
        }
    },
    personName = personName,
    personC = entity.program ?: "",
    painter = rememberAsyncImagePainter(model = getProfileAvatar(entity.id)),
    onCardClick = {}
)

Answer 3

Coil has no built-in support for composable placeholders.
However you have different options.

You can use the SubcomposeAsyncImage using the painter.state to define different Composables:

SubcomposeAsyncImage(
    model = url,
    contentDescription = "contentDescription",
    contentScale = ContentScale.Crop,
    modifier = Modifier.clip(CircleShape)
) {
    val state = painter.state
    if (state is AsyncImagePainter.State.Loading || state is AsyncImagePainter.State.Error) {

        //text with a background circle
        Text(
            modifier = Modifier
                .padding(16.dp)
                .drawBehind {
                    drawCircle(
                        color = Teal200,
                        radius = this.size.maxDimension
                    )
                },
            text = "NG",
            style = TextStyle(color = Color.White, fontSize = 20.sp)
        )
    } else {
        SubcomposeAsyncImageContent()
    }

Also the placeholder parameter in the AsyncImage accepts a Painter . You can define your custom TextPainter

AsyncImage(
    model = ImageRequest.Builder(LocalContext.current)
        .data(url)
        .build(),
    placeholder = TextPainter(
        circleColor= Teal200,
        textMeasurer = rememberTextMeasurer(),
        text="NG",
        circleSize = Size(200f, 200f)
    ),
    contentDescription = null,
    contentScale = ContentScale.Crop,
    modifier = Modifier.padding(16.dp)
)

where:

class TextPainter(val circleColor: Color,
                  val circleSize : Size,
                  val textMeasurer: TextMeasurer,
                  val text : String,
) : Painter() {

    val textLayoutResult: TextLayoutResult =
        textMeasurer.measure(
            text = AnnotatedString(text),
            style = TextStyle(color = Color.White, fontSize = 20.sp)
        )

    override val intrinsicSize: Size get() = circleSize

    override fun DrawScope.onDraw() {
        //the circle background
        drawCircle(
            color = circleColor,
            radius = size.maxDimension/2
        )
        
        val textSize = textLayoutResult.size
        //The text
        drawText(
            textLayoutResult = textLayoutResult,
            topLeft = Offset(
                (this.size.width - textSize.width) / 2f,
                (this.size.height - textSize.height) / 2f
            )
        )
    }
}