Created
October 19, 2020 05:59
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A recyclerview to apply the scaling effect on scrolling
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import android.animation.ArgbEvaluator | |
import android.content.Context | |
import android.graphics.ColorMatrix | |
import android.graphics.ColorMatrixColorFilter | |
import android.util.AttributeSet | |
import android.util.Log | |
import android.view.View | |
import android.widget.ImageView | |
import android.widget.TextView | |
import androidx.core.content.ContextCompat | |
import androidx.recyclerview.widget.LinearLayoutManager | |
import androidx.recyclerview.widget.RecyclerView | |
import com.omvana.mixer.R | |
import kotlin.math.pow | |
class HorizontalCarouselRecyclerView(context: Context, attrs: AttributeSet) : RecyclerView(context, attrs) { | |
fun <T : ViewHolder> initialize(newAdapter: Adapter<T>) { | |
layoutManager = ArcLayoutManager(context, HORIZONTAL) | |
newAdapter.registerAdapterDataObserver(object : RecyclerView.AdapterDataObserver() { | |
override fun onChanged() { | |
post { | |
addOnScrollListener(object : OnScrollListener() { | |
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) { | |
super.onScrolled(recyclerView, dx, dy) | |
onScrollChanged() | |
} | |
}) | |
} | |
} | |
}) | |
adapter = newAdapter | |
} | |
private fun onScrollChanged() { | |
post { | |
(0 until childCount).forEach { position -> | |
val child = getChildAt(position) | |
val childCenterX = (child.left + child.right) / 2 | |
val scaleValue = getGaussianScale(childCenterX, 0.8f, 0.2f, 150.toDouble()) | |
child.scaleX = scaleValue | |
child.scaleY = scaleValue | |
} | |
} | |
} | |
private fun getGaussianScale( | |
childCenterX: Int, | |
minScaleOffest: Float, | |
scaleFactor: Float, | |
spreadFactor: Double | |
): Float { | |
val recyclerCenterX = (left + right) / 2 | |
return (Math.E.pow(-(childCenterX - recyclerCenterX.toDouble()).pow(2.toDouble()) / (2 * spreadFactor.pow(2.toDouble()))) * scaleFactor + minScaleOffest).toFloat() | |
} | |
} |
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