Created
May 28, 2024 10:27
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Animated focus indicator
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| class MainActivity : ComponentActivity() { | |
| override fun onCreate(savedInstanceState: Bundle?) { | |
| super.onCreate(savedInstanceState) | |
| enableEdgeToEdge() | |
| setContent { | |
| BorderPathTheme { | |
| Scaffold(modifier = Modifier.fillMaxSize()) { innerPadding -> | |
| Box( | |
| modifier = Modifier | |
| .fillMaxSize() | |
| .padding(innerPadding), | |
| contentAlignment = Alignment.Center | |
| ) { | |
| BorderThing() | |
| } | |
| } | |
| } | |
| } | |
| } | |
| } | |
| @Composable | |
| fun BorderThing() { | |
| val anim = rememberInfiniteTransition() | |
| val progress = anim.animateFloat( | |
| initialValue = 0f, | |
| targetValue = 1f, | |
| animationSpec = infiniteRepeatable( | |
| animation = tween(1000, easing = LinearEasing), | |
| repeatMode = RepeatMode.Reverse | |
| ) | |
| ) | |
| Box( | |
| modifier = Modifier.padding(16.dp) | |
| ) { | |
| Box( | |
| modifier = Modifier | |
| .width(200.dp) | |
| .height(50.dp) | |
| .animatedBorder({ progress.value }, Color.Blue, MaterialTheme.colorScheme.outline) | |
| ) | |
| } | |
| } | |
| fun Modifier.animatedBorder(provideProgress: () -> Float, colorFocused: Color, colorUnfocused: Color) = this.drawWithCache { | |
| val width = size.width | |
| val height = size.height | |
| val shape = CircleShape | |
| // Only works with RoundedCornerShape... | |
| val outline = shape.createOutline(size, layoutDirection, this) as Outline.Rounded | |
| // ... correction: Only works with same corner sizes everywhere | |
| val radius = outline.roundRect.topLeftCornerRadius.x | |
| val diameter = 2 * radius | |
| // Clockwise path | |
| val pathCw = Path() | |
| // Start top center | |
| pathCw.moveTo(width / 2, 0f) | |
| // Line to right | |
| pathCw.lineTo(width - radius, 0f) | |
| // Top right corner | |
| pathCw.arcTo(Rect(width - diameter, 0f, width, diameter), -90f, 90f, false) | |
| // Right edge | |
| pathCw.lineTo(width, height - radius) | |
| // Bottom right corner | |
| pathCw.arcTo(Rect(width - diameter, height - diameter, width, height), 0f, 90f, false) | |
| // Line to bottom center | |
| pathCw.lineTo(width / 2, height) | |
| // As above, but mirrored horizontally | |
| val pathCcw = Path() | |
| pathCcw.moveTo(width / 2, 0f) | |
| pathCcw.lineTo(radius, 0f) | |
| pathCcw.arcTo(Rect(0f, 0f, diameter, diameter), -90f, -90f, false) | |
| pathCcw.lineTo(0f, height - radius) | |
| pathCcw.arcTo(Rect(0f, height - diameter, diameter, height), 180f, -90f, false) | |
| pathCcw.lineTo(width / 2, height) | |
| val pmCw = PathMeasure().apply { | |
| setPath(pathCw, false) | |
| } | |
| val pmCcw = PathMeasure().apply { | |
| setPath(pathCcw, false) | |
| } | |
| fun DrawScope.drawIndicator(progress: Float, pathMeasure: PathMeasure) { | |
| val subPath = Path() | |
| pathMeasure.getSegment(0f, pathMeasure.length * EaseOut.transform(progress), subPath) | |
| drawPath(subPath, colorFocused, style = Stroke(3.dp.toPx(), cap = StrokeCap.Round)) | |
| } | |
| onDrawBehind { | |
| // Draw the shape | |
| drawOutline(outline, colorUnfocused, style = Stroke(2.dp.toPx())) | |
| // Draw the indicators | |
| drawIndicator(provideProgress(), pmCw) | |
| drawIndicator(provideProgress(), pmCcw) | |
| } | |
| } |
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example of using it please