android - Jetpack Compose 中的选取框文本效果

Question

过去，文本中可以包含一种动画，如果文本超出限制，它会自动水平滚动。这是通过包含以下内容完成的:android:ellipsize="marquee" ，结果类似于此处显示的结果:

问题是在 Jetpack Compose 中我看不到在可组合文本中包含该选项的方法，有 TextOverflow其中包括 剪辑、省略或可见 选项，但我不知道是否有办法在 Jetpack Compose 中包含或使用“Marquee”选项。有什么办法吗？

Answer 1

Compose 尚不支持此功能，但实现起来并不难。您将需要 TargetBasedAnimation ，这将更新文本偏移量，和 SubcomposeLayout ，它位于大多数集合之下。在里面你可以定义文本的大小，也可以放置第二个类似的Text ，它将从右边缘出现。

@Composable
fun MarqueeText(
    text: String,
    modifier: Modifier = Modifier,
    textModifier: Modifier = Modifier,
    gradientEdgeColor: Color = Color.White,
    color: Color = Color.Unspecified,
    fontSize: TextUnit = TextUnit.Unspecified,
    fontStyle: FontStyle? = null,
    fontWeight: FontWeight? = null,
    fontFamily: FontFamily? = null,
    letterSpacing: TextUnit = TextUnit.Unspecified,
    textDecoration: TextDecoration? = null,
    textAlign: TextAlign? = null,
    lineHeight: TextUnit = TextUnit.Unspecified,
    overflow: TextOverflow = TextOverflow.Clip,
    softWrap: Boolean = true,
    onTextLayout: (TextLayoutResult) -> Unit = {},
    style: TextStyle = LocalTextStyle.current,
) {
    val createText = @Composable { localModifier: Modifier ->
        Text(
            text,
            textAlign = textAlign,
            modifier = localModifier,
            color = color,
            fontSize = fontSize,
            fontStyle = fontStyle,
            fontWeight = fontWeight,
            fontFamily = fontFamily,
            letterSpacing = letterSpacing,
            textDecoration = textDecoration,
            lineHeight = lineHeight,
            overflow = overflow,
            softWrap = softWrap,
            maxLines = 1,
            onTextLayout = onTextLayout,
            style = style,
        )
    }
    var offset by remember { mutableStateOf(0) }
    val textLayoutInfoState = remember { mutableStateOf<TextLayoutInfo?>(null) }
    LaunchedEffect(textLayoutInfoState.value) {
        val textLayoutInfo = textLayoutInfoState.value ?: return@LaunchedEffect
        if (textLayoutInfo.textWidth <= textLayoutInfo.containerWidth) return@LaunchedEffect
        val duration = 7500 * textLayoutInfo.textWidth / textLayoutInfo.containerWidth
        val delay = 1000L

        do {
            val animation = TargetBasedAnimation(
                animationSpec = infiniteRepeatable(
                    animation = tween(
                        durationMillis = duration,
                        delayMillis = 1000,
                        easing = LinearEasing,
                    ),
                    repeatMode = RepeatMode.Restart
                ),
                typeConverter = Int.VectorConverter,
                initialValue = 0,
                targetValue = -textLayoutInfo.textWidth
            )
            val startTime = withFrameNanos { it }
            do {
                val playTime = withFrameNanos { it } - startTime
                offset = (animation.getValueFromNanos(playTime))
            } while (!animation.isFinishedFromNanos(playTime))
            delay(delay)
        } while (true)
    }

    SubcomposeLayout(
        modifier = modifier.clipToBounds()
    ) { constraints ->
        val infiniteWidthConstraints = constraints.copy(maxWidth = Int.MAX_VALUE)
        var mainText = subcompose(MarqueeLayers.MainText) {
            createText(textModifier)
        }.first().measure(infiniteWidthConstraints)

        var gradient: Placeable? = null

        var secondPlaceableWithOffset: Pair<Placeable, Int>? = null
        if (mainText.width <= constraints.maxWidth) {
            mainText = subcompose(MarqueeLayers.SecondaryText) {
                createText(textModifier.fillMaxWidth())
            }.first().measure(constraints)
            textLayoutInfoState.value = null
        } else {
            val spacing = constraints.maxWidth * 2 / 3
            textLayoutInfoState.value = TextLayoutInfo(
                textWidth = mainText.width + spacing,
                containerWidth = constraints.maxWidth
            )
            val secondTextOffset = mainText.width + offset + spacing
            val secondTextSpace = constraints.maxWidth - secondTextOffset
            if (secondTextSpace > 0) {
                secondPlaceableWithOffset = subcompose(MarqueeLayers.SecondaryText) {
                    createText(textModifier)
                }.first().measure(infiniteWidthConstraints) to secondTextOffset
            }
            gradient = subcompose(MarqueeLayers.EdgesGradient) {
                Row {
                    GradientEdge(gradientEdgeColor, Color.Transparent)
                    Spacer(Modifier.weight(1f))
                    GradientEdge(Color.Transparent, gradientEdgeColor)
                }
            }.first().measure(constraints.copy(maxHeight = mainText.height))
        }

        layout(
            width = constraints.maxWidth,
            height = mainText.height
        ) {
            mainText.place(offset, 0)
            secondPlaceableWithOffset?.let {
                it.first.place(it.second, 0)
            }
            gradient?.place(0, 0)
        }
    }
}

@Composable
private fun GradientEdge(
    startColor: Color, endColor: Color,
) {
    Box(
        modifier = Modifier
            .width(10.dp)
            .fillMaxHeight()
            .background(
                brush = Brush.horizontalGradient(
                    0f to startColor, 1f to endColor,
                )
            )
    )
}

private enum class MarqueeLayers { MainText, SecondaryText, EdgesGradient }
private data class TextLayoutInfo(val textWidth: Int, val containerWidth: Int)

用法:

MarqueeText("Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt")

结果: