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A Jetpack Compose implementation of the `fadingEdge` effect.
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import androidx.compose.foundation.ScrollState | |
import androidx.compose.material.MaterialTheme | |
import androidx.compose.ui.Modifier | |
import androidx.compose.ui.composed | |
import androidx.compose.ui.draw.drawWithContent | |
import androidx.compose.ui.geometry.Offset | |
import androidx.compose.ui.geometry.Size | |
import androidx.compose.ui.graphics.Brush | |
import androidx.compose.ui.graphics.Color | |
import androidx.compose.ui.platform.debugInspectorInfo | |
import androidx.compose.ui.unit.Dp | |
fun Modifier.horizontalFadingEdge( | |
scrollState: ScrollState, | |
length: Dp, | |
edgeColor: Color? = null, | |
) = composed( | |
debugInspectorInfo { | |
name = "length" | |
value = length | |
} | |
) { | |
val color = edgeColor ?: MaterialTheme.colors.surface | |
Modifier.drawWithContent { | |
val lengthValue = length.toPx() | |
val scrollFromStart = scrollState.value | |
val scrollFromEnd = scrollState.maxValue - scrollState.value | |
val startFadingEdgeStrength = lengthValue * (scrollFromStart / lengthValue).coerceAtMost(1f) | |
val endFadingEdgeStrength = lengthValue * (scrollFromEnd / lengthValue).coerceAtMost(1f) | |
drawContent() | |
drawRect( | |
brush = Brush.horizontalGradient( | |
colors = listOf( | |
color, | |
Color.Transparent, | |
), | |
startX = 0f, | |
endX = startFadingEdgeStrength, | |
), | |
size = Size( | |
startFadingEdgeStrength, | |
this.size.height, | |
), | |
) | |
drawRect( | |
brush = Brush.horizontalGradient( | |
colors = listOf( | |
Color.Transparent, | |
color, | |
), | |
startX = size.width - endFadingEdgeStrength, | |
endX = size.width, | |
), | |
topLeft = Offset(x = size.width - endFadingEdgeStrength, y = 0f), | |
) | |
} | |
} | |
fun Modifier.verticalFadingEdge( | |
scrollState: ScrollState, | |
length: Dp, | |
edgeColor: Color? = null, | |
) = composed( | |
debugInspectorInfo { | |
name = "length" | |
value = length | |
} | |
) { | |
val color = edgeColor ?: MaterialTheme.colors.surface | |
Modifier.drawWithContent { | |
val lengthValue = length.toPx() | |
val scrollFromTop = scrollState.value | |
val scrollFromBottom = scrollState.maxValue - scrollState.value | |
val topFadingEdgeStrength = lengthValue * (scrollFromTop / lengthValue).coerceAtMost(1f) | |
val bottomFadingEdgeStrength = lengthValue * (scrollFromBottom / lengthValue).coerceAtMost(1f) | |
drawContent() | |
drawRect( | |
brush = Brush.verticalGradient( | |
colors = listOf( | |
color, | |
Color.Transparent, | |
), | |
startY = 0f, | |
endY = topFadingEdgeStrength, | |
), | |
size = Size( | |
this.size.width, | |
topFadingEdgeStrength | |
), | |
) | |
drawRect( | |
brush = Brush.verticalGradient( | |
colors = listOf( | |
Color.Transparent, | |
color, | |
), | |
startY = size.height - bottomFadingEdgeStrength, | |
endY = size.height, | |
), | |
topLeft = Offset(x = 0f, y = size.height - bottomFadingEdgeStrength), | |
) | |
} | |
} |
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