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@darnmason
Last active February 19, 2024 17:10
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A custom Android ViewGroup that contains a single child and allows you to swipe it to the left, with a callback once the swipe is complete. For example to dismiss a view. Works well in a LinearLayout with animateLayoutChanges=true when setting the SwipeView visibility to GONE on swipe.
import android.content.Context
import android.support.v4.view.ViewCompat
import android.support.v4.widget.ViewDragHelper
import android.util.AttributeSet
import android.view.MotionEvent
import android.view.View
import android.widget.FrameLayout
class SwipeView @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0) : FrameLayout(context, attrs, defStyleAttr) {
fun setOnSwipeListener(listener: () -> Unit) {
swipeCallback = listener
}
fun destroy() {
dragHelper.abort()
swipeCallback = null
}
companion object {
private const val AUTO_SWIPE_VELOCITY = 800.0
}
private var previousState = ViewDragHelper.STATE_IDLE
private var draggingLeft = false
private var draggedThreshold = false
private var swipeComplete = false
private var swipeCallback: (() -> Unit)? = null
private val dragHelperCallback = object : ViewDragHelper.Callback() {
override fun tryCaptureView(child: View, pointerId: Int) = child === getSlidingView()
override fun getViewHorizontalDragRange(child: View) = width
override fun clampViewPositionHorizontal(child: View, left: Int, dx: Int) = Math.min(left, 0)
override fun onViewPositionChanged(changedView: View, left: Int, top: Int, dx: Int, dy: Int) {
draggingLeft = Math.abs(left) > width / 20 && dx <= 0
draggedThreshold = Math.abs(left) > width / 2
}
override fun onViewReleased(releasedChild: View, xvel: Float, yvel: Float) {
if (Math.abs(xvel) > AUTO_SWIPE_VELOCITY) {
swipeComplete = true
dragHelper.flingCapturedView(-width, 0, -width, 0)
ViewCompat.postInvalidateOnAnimation(this@SwipeView)
} else {
var finalLeft = 0
if (draggedThreshold) {
finalLeft = -width
swipeComplete = true
}
if (dragHelper.settleCapturedViewAt(finalLeft, 0)) {
ViewCompat.postInvalidateOnAnimation(this@SwipeView)
}
}
}
override fun onViewDragStateChanged(state: Int) {
if (state != previousState && state == ViewDragHelper.STATE_IDLE && swipeComplete) {
getSlidingView()?.post(swipeCallback)
}
previousState = state
}
}
private val dragHelper: ViewDragHelper = ViewDragHelper.create(this, 1f, dragHelperCallback)
private fun getSlidingView(): View? {
return getChildAt(0)
}
override fun onTouchEvent(event: MotionEvent?): Boolean {
event?.let { ev ->
dragHelper.processTouchEvent(ev)
parent?.let {
when (ev.actionMasked) {
MotionEvent.ACTION_MOVE -> {
parent.requestDisallowInterceptTouchEvent(draggingLeft)
}
MotionEvent.ACTION_CANCEL, MotionEvent.ACTION_UP -> {
draggingLeft = false
parent.requestDisallowInterceptTouchEvent(false)
}
}
}
return true
}
return super.onTouchEvent(event)
}
override fun onInterceptTouchEvent(event: MotionEvent?): Boolean {
return event?.takeIf { dragHelper.shouldInterceptTouchEvent(event) } != null || super.onInterceptTouchEvent(event)
}
override fun computeScroll() {
if (dragHelper.continueSettling(true)) {
ViewCompat.postInvalidateOnAnimation(this)
}
}
}
@vkotovv
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vkotovv commented Jul 29, 2019

It would be great if there will an option to select direction (left, right). Also, it looks like this code will activate swipeCallback even if swiped to the right, if X is large enough.

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