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March 12, 2020 20:02
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import android.content.Context | |
import android.util.AttributeSet | |
import android.util.Log | |
import android.view.MotionEvent | |
import android.view.View | |
import android.webkit.WebView | |
import androidx.customview.widget.ViewDragHelper | |
class NestedScrollingWebView @JvmOverloads constructor(context: Context, | |
attrs: AttributeSet? = null) : WebView(context, attrs) { | |
companion object { | |
private val TAG = "NestedScrollingWebView" | |
} | |
private var isBeingDragged = false | |
private var activePointerId = ViewDragHelper.INVALID_POINTER | |
private var lastMotionX = 0f | |
private var lastMotionY = 0f | |
private var nestedXOffset = 0f | |
private var nestedYOffset = 0f | |
// object-local variables for receiving output, hurray for JVM | |
private val scrollConsumed = IntArray(2) | |
init { | |
// ...because why else would you be using this widget? | |
isNestedScrollingEnabled = true | |
} | |
override fun overScrollBy(deltaX: Int, deltaY: Int, scrollX: Int, scrollY: Int, | |
scrollRangeX: Int, scrollRangeY: Int, maxOverScrollX: Int, maxOverScrollY: Int, | |
isTouchEvent: Boolean): Boolean { | |
// Log.d("TRACKME", "$deltaX, $deltaY, $scrollX, $scrollY, $scrollRangeX, $scrollRangeY, $maxOverScrollX, $maxOverScrollY, $isTouchEvent") | |
return dispatchNestedScroll(0, 0, deltaX, deltaY, null) || super.overScrollBy( | |
deltaX, deltaY, scrollX, scrollY, scrollRangeX, scrollRangeY, maxOverScrollX, maxOverScrollY, isTouchEvent) | |
} | |
override fun onTouchEvent(ev: MotionEvent): Boolean { | |
when (ev.actionMasked) { | |
MotionEvent.ACTION_DOWN -> { | |
parent?.requestDisallowInterceptTouchEvent(true) | |
activePointerId = ev.getPointerId(0) | |
isBeingDragged = true | |
lastMotionX = ev.x | |
lastMotionY = ev.y | |
nestedXOffset = 0f | |
nestedYOffset = 0f | |
startNestedScroll(View.SCROLL_AXIS_VERTICAL) | |
} | |
MotionEvent.ACTION_MOVE -> if (isBeingDragged) { | |
val activePointerIndex = ev.findPointerIndex(activePointerId) | |
if (activePointerIndex == -1) { | |
Log.e(TAG, "Invalid pointerId=$activePointerId in onInterceptTouchEvent") | |
} else { | |
parent?.requestDisallowInterceptTouchEvent(true) | |
val x = ev.getX(activePointerIndex) | |
val y = ev.getY(activePointerIndex) | |
if (dispatchNestedPreScroll((lastMotionX - x).toInt(), (lastMotionY - y).toInt(), scrollConsumed, null)) { | |
// Log.d(TAG, "nested ${scrollConsumed.joinToString()}, $nestedYOffset") | |
nestedXOffset += scrollConsumed[0] | |
nestedYOffset += scrollConsumed[1] | |
} | |
lastMotionX = x | |
lastMotionY = y | |
// dispatchNestedScroll will later be called by overScrollBy, as a result of super.onTouchEvent | |
} | |
} | |
MotionEvent.ACTION_CANCEL, MotionEvent.ACTION_UP -> { | |
activePointerId = ViewDragHelper.INVALID_POINTER | |
isBeingDragged = false | |
stopNestedScroll() | |
nestedXOffset = 0f | |
nestedYOffset = 0f | |
} | |
} | |
val vtev = MotionEvent.obtain(ev) | |
vtev.offsetLocation(nestedXOffset, nestedYOffset) | |
super.onTouchEvent(vtev) | |
return true | |
} | |
} |
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