ConstrainLayout that has ability to infinitely scroll background image vertically or horizontally

InfiniteBackgroundLayout.kt

import android.animation.ValueAnimator
import android.content.Context
import android.util.AttributeSet
import android.view.animation.LinearInterpolator
import android.widget.ImageView
import androidx.constraintlayout.widget.ConstraintLayout
import androidx.constraintlayout.widget.ConstraintSet
import androidx.core.content.res.ResourcesCompat

/**
 * 支持横竖方向无限滚动背景图的 ConstraintLayout
 * @author Dante
 * 2020/12/22
 */
class InfiniteBackgroundLayout @JvmOverloads constructor(
        context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0
) : ConstraintLayout(context, attrs, defStyleAttr) {

    private var backgroundRes: Int = 0

    // 单位s
    private var scrollDuration: Int = 0

    private var orientation: Int = 0

    private lateinit var imageStart: ImageView
    private lateinit var imageEnd: ImageView

    private var animator: ValueAnimator? = null
    private val isScrollVertical get() = orientation == 0

    init {
        context.obtainStyledAttributes(attrs, R.styleable.InfiniteBackgroundLayout, defStyleAttr, 0).apply {
            backgroundRes =
                    getResourceId(R.styleable.InfiniteBackgroundLayout_backgroundResource, 0)
            scrollDuration =
                    getInteger(R.styleable.InfiniteBackgroundLayout_scrollDuration, 0)
            orientation = getInteger(R.styleable.InfiniteBackgroundLayout_scrollOrientation, 0)
        }.recycle()

        if (scrollDuration == 0) {
            scrollDuration = if (isScrollVertical) {
                UIUtils.getScreenHeight() / 74
            } else {
                UIUtils.getScreenWidth() / 74
            }
        }

        val drawable = ResourcesCompat.getDrawable(resources, backgroundRes, null)
        if (drawable != null) {
            imageStart = ImageView(context, attrs, defStyleAttr).apply {
                id = generateViewId()
                scaleType = ImageView.ScaleType.CENTER_CROP
                setImageDrawable(drawable)
            }
            imageEnd = ImageView(context, attrs, defStyleAttr).apply {
                id = generateViewId()
                scaleType = ImageView.ScaleType.CENTER_CROP
                setImageDrawable(drawable)
            }

            initView(drawable.intrinsicWidth, drawable.intrinsicHeight)
        }
    }


    private fun initView(width: Int, height: Int) {
        addView(imageStart, LayoutParams(width, height))
        addView(imageEnd, LayoutParams(width, height))
        ConstraintSet().also {
            it.clone(this)
            if (isScrollVertical) {
                it.connect(
                        imageStart.id,
                        ConstraintSet.TOP,
                        ConstraintSet.PARENT_ID,
                        ConstraintSet.TOP
                )
                it.constrainWidth(imageStart.id, LayoutParams.MATCH_PARENT)
//                it.constrainHeight(imageStart.id, LayoutParams.WRAP_CONTENT)

                it.connect(imageEnd.id, ConstraintSet.TOP, imageStart.id, ConstraintSet.BOTTOM)
                it.constrainWidth(imageEnd.id, LayoutParams.MATCH_PARENT)
//                it.constrainHeight(imageEnd.id, LayoutParams.WRAP_CONTENT)
            } else {
                it.connect(
                        imageStart.id,
                        ConstraintSet.START,
                        ConstraintSet.PARENT_ID,
                        ConstraintSet.START
                )
//                it.constrainWidth(imageStart.id, LayoutParams.WRAP_CONTENT)
                it.constrainHeight(imageStart.id, LayoutParams.MATCH_PARENT)

                it.connect(imageEnd.id, ConstraintSet.START, imageStart.id, ConstraintSet.END)
//                it.constrainWidth(imageEnd.id, LayoutParams.WRAP_CONTENT)
                it.constrainHeight(imageEnd.id, LayoutParams.MATCH_PARENT)
            }
            it.applyTo(this)
        }
    }
    override fun onWindowFocusChanged(hasWindowFocus: Boolean) {
        super.onWindowFocusChanged(hasWindowFocus)

        if (!this::imageStart.isInitialized) return
        animateBackground(hasWindowFocus)
    }

    private fun animateBackground(start: Boolean) {
        if (start) {
            if (animator == null) {
                imageStart.post {
                    val translation =
                            if (isScrollVertical) imageStart.measuredHeight.toFloat() else imageStart.measuredWidth.toFloat()
                    animator = ValueAnimator.ofFloat(0f, -translation)
                            .setDuration(scrollDuration * 1000L)
                    animator!!.interpolator = LinearInterpolator()
                    animator!!.repeatMode = ValueAnimator.RESTART
                    animator!!.repeatCount = ValueAnimator.INFINITE
                    animator!!.addUpdateListener {
                        if (isScrollVertical) {
                            imageStart.translationY = it.animatedValue as Float
                            imageEnd.translationY = it.animatedValue as Float
                        } else {
                            imageStart.translationX = it.animatedValue as Float
                            imageEnd.translationX = it.animatedValue as Float
                        }
                    }
                    animator!!.start()
                }
            } else {
                animator!!.resume()
            }
        } else {
            animator?.pause()
        }
    }


    fun getScreenWidth(): Int {
        return resources.displayMetrics.widthPixels
    }

    fun getScreenHeight(): Int {
        return resources.displayMetrics.heightPixels
    }

}

Add following to attrs.xml before use:

    <declare-styleable name="InfiniteBackgroundLayout">
        <attr name="backgroundResource" format="reference" />
        <attr name="scrollDuration" format="integer" />
        <attr name="scrollOrientation" format="enum">
            <enum name="vertical" value="0"/>
            <enum name="horizontal" value="1"/>
        </attr>
    </declare-styleable>