Android - Horizontally (right-to-left) circular background color transition

Question

I want to know how can I implement this animation?

Small image frame and text movement is independent from the animation. It's just like simple pager action with some scale and alpha transformation. Only problem is the color change of background like this.

I'm open to both XML and Jetpack Compose way solutions. Please..

Answer 1

My Solution

import android.graphics.Path
import android.view.MotionEvent
import androidx.annotation.FloatRange
import androidx.compose.animation.core.*
import androidx.compose.foundation.layout.Box
import androidx.compose.runtime.*
import androidx.compose.ui.ExperimentalComposeUiApi
import androidx.compose.ui.Modifier
import androidx.compose.ui.draw.clip
import androidx.compose.ui.geometry.Offset
import androidx.compose.ui.geometry.Size
import androidx.compose.ui.graphics.Outline
import androidx.compose.ui.graphics.Shape
import androidx.compose.ui.graphics.asComposePath
import androidx.compose.ui.input.pointer.pointerInteropFilter
import androidx.compose.ui.unit.Density
import androidx.compose.ui.unit.LayoutDirection
import kotlin.math.hypot

@Composable
fun <T> CircularReveal(
    targetState: T,
    modifier: Modifier = Modifier,
    animationSpec: FiniteAnimationSpec<Float> = tween(),
    content: @Composable (T) -> Unit,
) {
    val transition = updateTransition(targetState, label = "Circular reveal")
    transition.CircularReveal(modifier, animationSpec, content = content)
}

@Composable
fun <T> Transition<T>.CircularReveal(
    modifier: Modifier = Modifier,
    animationSpec: FiniteAnimationSpec<Float> = tween(),
    content: @Composable (targetState: T) -> Unit,
) {
    var offset: Offset? by remember { mutableStateOf(null) }
    val currentlyVisible = remember { mutableStateListOf<T>().apply { add(currentState) } }
    val contentMap = remember {
        mutableMapOf<T, @Composable () -> Unit>()
    }
    if (currentState == targetState) {
        // If not animating, just display the current state
        if (currentlyVisible.size != 1 || currentlyVisible[0] != targetState) {
            // Remove all the intermediate items from the list once the animation is finished.
            currentlyVisible.removeAll { it != targetState }
            contentMap.clear()
        }
    }
    if (!contentMap.contains(targetState)) {
        // Replace target with the same key if any
        val replacementId = currentlyVisible.indexOfFirst {
            it == targetState
        }
        if (replacementId == -1) {
            currentlyVisible.add(targetState)
        } else {
            currentlyVisible[replacementId] = targetState
        }
        contentMap.clear()
        currentlyVisible.forEach { stateForContent ->
            contentMap[stateForContent] = {
                val progress by animateFloat(
                    label = "Progress",
                    transitionSpec = { animationSpec }
                ) {
                    val targetedContent = stateForContent != currentlyVisible.last() || it == stateForContent
                    if (targetedContent) 1f else 0f
                }
                Box(Modifier.circularReveal(progress = progress, offset = offset)) {
                    content(stateForContent)
                }
            }
        }
    }
    Box(
        modifier = modifier.pointerInteropFilter {
            if (it.action == MotionEvent.ACTION_DOWN) {
                if (!started) offset = Offset(it.x, it.y)
            }
            started
        }
    ) {
        currentlyVisible.forEach {
            key(it) {
                contentMap[it]?.invoke()
            }
        }
    }
}

private val <T> Transition<T>.started get() =
    currentState != targetState || isRunning

fun Modifier.circularReveal(
    @FloatRange(from = 0.0, to = 1.0) progress: Float,
    offset: Offset? = null,
) = clip(CircularRevealShape(progress, offset))

class CircularRevealShape(
    @FloatRange(from = 0.0, to = 1.0) private val progress: Float,
    private val offset: Offset? = null,
) : Shape {
    override fun createOutline(
        size: Size,
        layoutDirection: LayoutDirection,
        density: Density,
    ): Outline {
        return Outline.Generic(Path().apply {
            addCircle(
                offset?.x ?: (size.width / 2f),
                offset?.y ?: (size.height / 2f),
                longestDistanceToACorner(size, offset) * progress,
                Path.Direction.CW
            )
        }.asComposePath())
    }

    private fun longestDistanceToACorner(size: Size, offset: Offset?): Float {
        if (offset == null) {
            return hypot(size.width / 2f, size.height / 2f)
        }

        val topLeft = hypot(offset.x, offset.y)
        val topRight = hypot(size.width - offset.x, offset.y)
        val bottomLeft = hypot(offset.x, size.height - offset.y)
        val bottomRight = hypot(size.width - offset.x, size.height - offset.y)

        return topLeft.coerceAtLeast(topRight).coerceAtLeast(bottomLeft).coerceAtLeast(bottomRight)
    }
}

@Preview
@Composable
fun CircularRevealAnimationPreview() {
    val isSystemDark = isSystemInDarkTheme()
    var darkTheme by remember { mutableStateOf(isSystemDark) }
    val onThemeToggle = { darkTheme = !darkTheme }

    CircularReveal(
        targetState = darkTheme,
        animationSpec = tween(1500)
    ) { isDark ->
        MyAppTheme(darkTheme = isDark) {
            Surface(
                modifier = Modifier.fillMaxSize(),
                color = MaterialTheme.colors.background,
                onClick = onThemeToggle
            ) {
                Box(
                    contentAlignment = Alignment.Center
                ) {
                    Icon(
                        modifier = Modifier.size(120.dp),
                        imageVector = if (isDark) Icons.Default.DarkMode else Icons.Default.LightMode,
                        contentDescription = "Toggle",
                    )
                }
            }
        }
    }
}

Answer 2

The solution

After lots of hours searching, I've found the perfect one;

https://github.com/2307vivek/BubblePager