Scaffold { innerPadding ->
    Box(modifier = Modifier.padding(innerPadding)) {
        ...          
    }
}

Row(modifier = Modifier.fillMaxWidth().padding(8.dp, 0.dp, 8.dp, 0.dp),
    verticalAlignment = Alignment.CenterVertically,
    horizontalArrangement = Arrangement.SpaceBetween
) {
    Text("左")
    Text("中央")
    Text("右")
}

Spacer(modifier = Modifier.height(10.dp))

/**
 * シンプルな横線描画
 *
 * @param color 線の色
 * @param border 線の太さ
 * @param margin 線の描画開始/終了のマージン
 */
@Composable fun Line(
    modifier: Modifier = Modifier,
    color: Color = if (isSystemInDarkTheme()) Color.White else Color.Black,
    border: Dp = 1.dp,
    margin: Dp = 0.dp
) {
    Canvas(modifier.fillMaxWidth().height(border)) {
        drawLine(
            color = color,
            start = Offset(margin.toPx(), border.toPx() / 2),
            end = Offset(size.width - margin.toPx() * 2, border.toPx() / 2),
            strokeWidth = border.toPx(),
            //pathEffect = PathEffect.dashPathEffect(listOf(24f, 24f).toFloatArray(), 0f),
        )
    }
}

/**
 * 画面背景(イメージ)
 *
 * @param fileName Assetsに配置した画像ファイル名
 */
@Composable fun ImageBackground(
    fileName: String,
    modifier: Modifier = Modifier,
    content: @Composable () -> Unit
) {
    val context = LocalContext.current
    val bitmap: Bitmap? by rememberSaveable { mutableStateOf(context.assetsToBitmap(fileName)) }

    BoxWithConstraints(modifier = modifier.fillMaxSize()) {
        bitmap?.let {
            Image(
                bitmap = it.asImageBitmap(),
                contentDescription = null,
                modifier = Modifier.fillMaxSize(),
                contentScale = ContentScale.Crop
            )
        }
        content()
    }
}

/**
 * Assetsにあるイメージファイルを読込みBitmapを返す
 */
fun Context.assetsToBitmap(fileName: String): Bitmap? {
    return try {
        with(assets.open(fileName)) {
            BitmapFactory.decodeStream(this)
        }
    } catch (e: IOException) { null }
}

/**
 * 画面背景(グラデーション)
 *
 * 参考: Now in Android / Android Open Source Project
 * https://github.com/android/nowinandroid
 *
 * @param topColor 上から下に向かうグラデーション色
 * @param bottomColor 下から上に向かうグラデーション色
 */
@Composable fun GradientBackground(
    modifier: Modifier = Modifier,
    topColor: Color = Color.Unspecified,
    bottomColor: Color = Color.Unspecified,
    content: @Composable () -> Unit
) {
    val currentTopColor by rememberUpdatedState(topColor)
    val currentBottomColor by rememberUpdatedState(bottomColor)

    BoxWithConstraints(modifier = modifier.fillMaxSize().drawWithCache {
        // Compute the start and end coordinates such that the gradients are angled 11.06
        // degrees off the vertical axis
        val offset = size.height * tan(Math.toRadians(11.06).toFloat())

        val start = Offset(size.width / 2 + offset / 2, 0f)
        val end = Offset(size.width / 2 - offset / 2, size.height)

        // Create the top gradient that fades out after the halfway point vertically
        val topGradient = Brush.linearGradient(
            0f to if (currentTopColor == Color.Unspecified) {
                Color.Transparent
            }
            else {
                currentTopColor
            },
            0.724f to Color.Transparent,
            start = start,
            end = end,
        )
        // Create the bottom gradient that fades in before the halfway point vertically
        val bottomGradient = Brush.linearGradient(
            0.2552f to Color.Transparent,
            1f to if (currentBottomColor == Color.Unspecified) {
                Color.Transparent
            }
            else {
                currentBottomColor
            },
            start = start,
            end = end,
        )

        onDrawBehind {
            // There is overlap here, so order is important
            drawRect(topGradient)
            drawRect(bottomGradient)
        }
    }) {
        content()
    }
}

// フォーカスリセットまたはkeyboardControllerで隠す
val focusRequester = remember { FocusRequester() }
val interactionSource = remember { MutableInteractionSource() }
val keyboardController = LocalSoftwareKeyboardController.current

Surface (modifier = Modifier
    .clickable(
        interactionSource = interactionSource,
        enabled = true,
        indication = null,
        onClick = {
            focusRequester.requestFocus()
        }
    )
    .focusRequester(focusRequester)
    .focusTarget()
    .onFocusChanged {              
        if (it.isFocused) {
            //keyboardController?.hide()
        }
    },
) {}