android - Jetpack Compose 中的可扩展文本

Question

所以我正在使用这样的Text()组合：

Text(
    text = "this is some sample text that is long and so it is 
            ellipsized",
    maxLines = 1,
    overflow = TextOverflow.Ellipsis
)

并且它正确地省略了文本：

问题是我想See More在省略号末尾添加一个标签，提示用户展开可见文本框。我将如何添加它？

Answer 1

要解决这个问题，您需要使用onTextLayoutget TextLayoutResult：它包含有关绘制文本状态的所有信息。

让它适用于多行是一项棘手的任务。为此，您需要计算椭圆文本和“...查看更多”文本的大小，然后，当您拥有这两个值时，您需要计算需要删除多少文本，以便“...查看更多”非常适合在行尾：

@Composable
fun ExpandableText(
    text: String,
    modifier: Modifier = Modifier,
    minimizedMaxLines: Int = 1,
) {
    var cutText by remember(text) { mutableStateOf<String?>(null) }
    var expanded by remember { mutableStateOf(false) }
    val textLayoutResultState = remember { mutableStateOf<TextLayoutResult?>(null) }
    val seeMoreSizeState = remember { mutableStateOf<IntSize?>(null) }
    val seeMoreOffsetState = remember { mutableStateOf<Offset?>(null) }

    // getting raw values for smart cast
    val textLayoutResult = textLayoutResultState.value
    val seeMoreSize = seeMoreSizeState.value
    val seeMoreOffset = seeMoreOffsetState.value

    LaunchedEffect(text, expanded, textLayoutResult, seeMoreSize) {
        val lastLineIndex = minimizedMaxLines - 1
        if (!expanded && textLayoutResult != null && seeMoreSize != null
            && lastLineIndex + 1 == textLayoutResult.lineCount
            && textLayoutResult.isLineEllipsized(lastLineIndex)
        ) {
            var lastCharIndex = textLayoutResult.getLineEnd(lastLineIndex, visibleEnd = true) + 1
            var charRect: Rect
            do {
                lastCharIndex -= 1
                charRect = textLayoutResult.getCursorRect(lastCharIndex)
            } while (
                charRect.left > textLayoutResult.size.width - seeMoreSize.width
            )
            seeMoreOffsetState.value = Offset(charRect.left, charRect.bottom - seeMoreSize.height)
            cutText = text.substring(startIndex = 0, endIndex = lastCharIndex)
        }
    }
    
    Box(modifier) {
        Text(
            text = cutText ?: text,
            maxLines = if (expanded) Int.MAX_VALUE else minimizedMaxLines,
            overflow = TextOverflow.Ellipsis,
            onTextLayout = { textLayoutResultState.value = it },
        )
        if (!expanded) {
            val density = LocalDensity.current
            Text(
                "... See more",
                onTextLayout = { seeMoreSizeState.value = it.size },
                modifier = Modifier
                    .then(
                        if (seeMoreOffset != null)
                            Modifier.offset(
                                x = with(density) { seeMoreOffset.x.toDp() },
                                y = with(density) { seeMoreOffset.y.toDp() },
                            )
                        else
                            Modifier
                    )
                    .clickable {
                        expanded = true
                        cutText = null
                    }
                    .alpha(if (seeMoreOffset != null) 1f else 0f)
            )
        }
    }
}

Answer 2

@Composable
fun ExpandedText(
    text: String,
    expandedText: String,
    expandedTextButton: String,
    shrinkTextButton: String,
    modifier: Modifier = Modifier,
    softWrap: Boolean = true,
    textStyle: TextStyle = LocalTextStyle.current,
    expandedTextStyle: TextStyle = LocalTextStyle.current,
    expandedTextButtonStyle: TextStyle = LocalTextStyle.current,
    shrinkTextButtonStyle: TextStyle = LocalTextStyle.current,
) {
    
    var isExpanded by remember { mutableStateOf(false) }
    
    val textHandler = "${if (isExpanded) expandedText else text} ${if (isExpanded) shrinkTextButton else expandedTextButton}"
    
    val annotatedString = buildAnnotatedString {
        withStyle(
            if (isExpanded) expandedTextStyle.toSpanStyle() else textStyle.toSpanStyle()
        ) {
            append(if (isExpanded) expandedText else text)
        }
        
        append("  ")
        
        withStyle(
            if (isExpanded) shrinkTextButtonStyle.toSpanStyle() else expandedTextButtonStyle.toSpanStyle()
        ) {
            append(if (isExpanded) shrinkTextButton else expandedTextButton)
        }
        
        addStringAnnotation(
            tag = "expand_shrink_text_button",
            annotation = if (isExpanded) shrinkTextButton else expandedTextButton,
            start = textHandler.indexOf(if (isExpanded) shrinkTextButton else expandedTextButton),
            end = textHandler.indexOf(if (isExpanded) shrinkTextButton else expandedTextButton) + if (isExpanded) expandedTextButton.length else shrinkTextButton.length
        )
    }
    
    ClickableText(
        text = annotatedString,
        softWrap = softWrap,
        modifier = modifier,
        onClick = {
            annotatedString
                .getStringAnnotations(
                    "expand_shrink_text_button",
                    it,
                    it
                )
                .firstOrNull()?.let { stringAnnotation ->
                    isExpanded = stringAnnotation.item == expandedTextButton
                }
        }
    )
}

用法

ExpandedText(
            text = food.content,
            expandedText = food.contentFull,
            expandedTextButton = " more",
            shrinkTextButton = " less",
            textStyle = typographySkModernist().body1.copy(
                color = black.copy(alpha = 0.8f)
            ),
            expandedTextStyle = typographySkModernist().body1.copy(
                color = black.copy(alpha = 0.8f)
            ),
            expandedTextButtonStyle = typographySkModernist().body1.copy(
                color = orange,
            ),
            shrinkTextButtonStyle = typographySkModernist().body1.copy(
                color = orange,
            ),
            modifier = Modifier
                .padding(top = 32.dp, start = 24.dp, end = 16.dp)
        )

Answer 3

我发现发布的解决方案有点矫枉过正。这是一个简单的解决方案：

var showMore by remember { mutableStateOf(false) }
val text =
    "Space Exploration Technologies Corp. (doing business as SpaceX) is an American aerospace manufacturer, space transportation services and communications corporation headquartered in Hawthorne, California. SpaceX was founded in 2002 by Elon Musk with the goal of reducing space transportation costs to enable the colonization of Mars. SpaceX manufactures the Falcon 9 and Falcon Heavy launch vehicles, several rocket engines, Cargo Dragon, crew spacecraft and Starlink communications satellites."

Column(modifier = Modifier.padding(20.dp)) {
    Column(modifier = Modifier
        .animateContentSize(animationSpec = tween(100))
        .clickable(
            interactionSource = remember { MutableInteractionSource() },
            indication = null
        ) { showMore = !showMore }) {

        if (showMore) {
            Text(text = text)
        } else {
            Text(text = text, maxLines = 3, overflow = TextOverflow.Ellipsis)
        }
    }
}

Answer 4

一个简单的实现：

@Composable
fun ExpandableText(
    modifier: Modifier = Modifier,
    text: String,
    minimizedMaxLines: Int,
    style: TextStyle
) {
    var expanded by remember { mutableStateOf(false) }
    var hasVisualOverflow by remember { mutableStateOf(false) }
    Box(modifier = modifier) {
        Text(
            text = text,
            maxLines = if (expanded) Int.MAX_VALUE else minimizedMaxLines,
            onTextLayout = { hasVisualOverflow = it.hasVisualOverflow },
            style = style
        )
        if (hasVisualOverflow) {
            Row(
                modifier = Modifier.align(Alignment.BottomEnd),
                verticalAlignment = Alignment.Bottom
            ) {
                val lineHeightDp: Dp = with(LocalDensity.current) { style.lineHeight.toDp() }
                Spacer(
                    modifier = Modifier
                        .width(48.dp)
                        .height(lineHeightDp)
                        .background(
                            brush = Brush.horizontalGradient(
                                colors = listOf(Color.Transparent, Color.White)
                            )
                        )
                )
                Text(
                    modifier = Modifier
                        .background(Color.White)
                        .padding(start = 4.dp)
                        .clickable(
                            indication = null,
                            interactionSource = remember { MutableInteractionSource() },
                            onClick = { expanded = !expanded }
                        ),
                    text = "Show More",
                    color = MaterialTheme.colors.primary,
                    style = style
                )
            }
        }
    }
}