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"Dynamically preventing scrolling on selected ViewPager pages" for blog.jakelee.co.uk
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<com.example.LockableViewPager | |
android:id="@+id/pager" | |
android:layout_width="match_parent" | |
android:layout_height="match_parent" /> |
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import android.content.Context | |
import android.support.v4.view.ViewPager | |
import android.util.AttributeSet | |
import android.view.MotionEvent | |
enum class SwipeDirection { BOTH, LEFT, RIGHT, NONE } | |
// https://stackoverflow.com/a/34076649/608312 | |
class LockableViewPager(context: Context, attrs: AttributeSet) : ViewPager(context, attrs) { | |
private var initialXValue: Float = 0f | |
private var direction: SwipeDirection? = null | |
init { | |
this.direction = SwipeDirection.BOTH | |
} | |
override fun onTouchEvent(event: MotionEvent): Boolean { | |
return if (this.isSwipeAllowed(event)) { | |
super.onTouchEvent(event) | |
} else false | |
} | |
override fun onInterceptTouchEvent(event: MotionEvent): Boolean { | |
return if (this.isSwipeAllowed(event)) { | |
super.onInterceptTouchEvent(event) | |
} else false | |
} | |
private fun isSwipeAllowed(event: MotionEvent): Boolean { | |
if (this.direction === SwipeDirection.BOTH) { | |
return true | |
} else if (direction === SwipeDirection.NONE) { | |
return false | |
} | |
if (event.action == MotionEvent.ACTION_DOWN) { | |
initialXValue = event.x | |
return true | |
} | |
if (event.action == MotionEvent.ACTION_MOVE) { | |
try { | |
val diffX = event.x - initialXValue | |
if (diffX > 0 && direction === SwipeDirection.RIGHT) { | |
// swipe from left to right detected | |
return false | |
} else if (diffX < 0 && direction === SwipeDirection.LEFT) { | |
// swipe from right to left detected | |
return false | |
} | |
} catch (e: Exception) { | |
e.printStackTrace() | |
} | |
} | |
return true | |
} | |
fun setAllowedSwipeDirection(direction: SwipeDirection) { | |
this.direction = direction | |
} | |
} |
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private fun pageChangeListener(): ViewPager.SimpleOnPageChangeListener = | |
object : ViewPager.SimpleOnPageChangeListener() { | |
override fun onPageSelected(position: Int) { | |
setSwipeability() | |
} | |
} | |
private fun setSwipeability() { | |
pager.setAllowedSwipeDirection(getSwipeDirection(pager)) | |
} | |
override fun getSwipeDirection(pager: LockableViewPager): SwipeDirection { | |
if (isUserRequired(pager.currentItem)) { | |
return SwipeDirection.NONE | |
} | |
val isFirstUser = pager.currentItem == 0 | |
val isLastUser = pager.currentItem == pager.adapter!!.count - 1 | |
val isUserToLeft = !isFirstUser && pager.currentItem > 0 | |
val isUserToRight = !isLastUser && pager.currentItem < pager.adapter!!.count - 1 | |
val isOptionalUserOnLeft = isUserToLeft && !isUserRequired(pager.currentItem - 1) | |
val isOptionalUserOnRight = isUserToRight && !isUserRequired(pager.currentItem + 1) | |
if (isOptionalUserOnLeft && isOptionalUserOnRight) { | |
return SwipeDirection.BOTH | |
} else if (isOptionalUserOnLeft) { | |
return SwipeDirection.LEFT | |
} else if (isOptionalUserOnRight) { | |
return SwipeDirection.RIGHT | |
} else { | |
return SwipeDirection.NONE | |
} | |
} |
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