1

我正在 JetPack Compose 中开发一个问答测验应用程序。我有如下卡

Card(modifier = Modifier
        .wrapContentHeight(Alignment.CenterVertically)
        .wrapContentWidth(Alignment.CenterHorizontally)
        .padding(10.dp)
        .width(300.dp)
        .height(600.dp)
        .clip(RoundedCornerShape(8.dp)),
        elevation = 10.dp,
        backgroundColor = Color.White

    )
    {

        Column(
            modifier = Modifier
                .wrapContentHeight(Alignment.CenterVertically)
                .wrapContentWidth(Alignment.CenterHorizontally)
                .padding(8.dp),
            horizontalAlignment = Alignment.Start,
            verticalArrangement = Arrangement.Top

            ){

            Text(
                text = "Question : " + query.question_id,
                style = Typography.h1
            )
            Spacer(modifier = Modifier.height(2.dp))
            Text(
                text = query.question,
                style = Typography.subtitle1

            )
            Spacer(modifier = Modifier.height(5.dp))
            Text(
                text = "Options",
                style = Typography.h1
            )
            Spacer(modifier = Modifier.height(2.dp))
            OptionsDetailsList(lstOptions = lstOptions)
            
            Spacer(modifier = Modifier.height(10.dp))
            
            Button(onClick = {
            }
            ) {
                Text(text = "View Answer")
            }
            Spacer(modifier = Modifier.height(10.dp))
        }
    }
}

答案列表是一个 LazyColumn，如下所示

@Composable
fun OptionsDetailsList(lstOptions: List<CertAnswers>){
    Log.d("ListOptions Count" , lstOptions.size.toString())
    LazyColumn(){
        item {
            Spacer(modifier = Modifier.requiredHeight(1.dp))
        }
        items(lstOptions){
                item ->
            Text(text = item.answer,
                modifier=Modifier.padding(3.dp),
                style = Typography.subtitle1,
            )
            Spacer(modifier = Modifier.requiredHeight(1.dp))
        }
    }
}

我的答案数据模型如下

data class CertAnswers(
    @PrimaryKey (autoGenerate = true)
    val id : Int,
    var question_id : Int,
    val ans_title: String,
    val answer : String,
    var isSolution: Boolean
)

我isSolution可以得到一个选项是否是正确的答案。但我只想显示按钮单击并更新LazyColumn以显示不同颜色的相关选项。我尝试OptionsDetailsList在单击按钮时再次调用该方法，但它不起作用。我如何更新LazyColumnon Button Click inside CardView。

4

1 回答 1

0

您需要在CardView指示按钮是否被点击时存储一个状态值。rememberSaveable将确保在重新组合和滚动期间保存它。query.question_id我以: 的形式传递key，以防万一它发生变化，该值很可能应该重新初始化。在文档中查看有关撰写状态的更多信息

var answerRevealed by rememberSaveable(query.question_id) { mutableStateOf(false) }

您可以根据此状态更改惰性列元素的背景。ps 我建议你使用Modifier作为最后一个参数，所以最后不需要逗号，你可以很容易地添加/删除/重新排序修饰符：

@Composable
fun OptionsDetailsList(answerRevealed: Boolean, lstOptions: List<CertAnswers>) {
    Log.d("ListOptions Count", lstOptions.size.toString())
    LazyColumn() {
        item {
            Spacer(modifier = Modifier.requiredHeight(1.dp))
        }
        items(lstOptions) { item ->
            Text(
                text = item.answer,
                style = Typography().subtitle1,
                modifier = Modifier
                    .padding(3.dp)
                    .background(
                        if (answerRevealed) {
                            if (item.isSolution) {
                                Color.Green
                            } else {
                                Color.Red
                            }
                        } else {
                            Color.Transparent
                        }
                    )
            )
            Spacer(modifier = Modifier.requiredHeight(1.dp))
        }
    }
}

在您的按钮中，只需将此状态设置为true. 您还可以在点击按钮后隐藏按钮，或更改文本。

// hide after onClick
if (!answerRevealed) {
    Button(onClick = {
        answerRevealed = true
    }
    ) {
        Text(text = "View Answer")
    }
}
// or change text
Button(onClick = {
    answerRevealed = true
}
) {
    Text(text = if (answerRevealed) "Hide Answer" else "View Answer")
}
于 2021-09-16T20:57:21.217 回答