Yuito-app-android/app/src/main/java/com/keylesspalace/tusky/pager/ImagePagerAdapter.kt

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Kotlin
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package com.keylesspalace.tusky.pager
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import androidx.fragment.app.FragmentManager
import androidx.fragment.app.FragmentStatePagerAdapter
import com.keylesspalace.tusky.SharedElementTransitionListener
import com.keylesspalace.tusky.entity.Attachment
import com.keylesspalace.tusky.fragment.ViewMediaFragment
import java.util.*
class ImagePagerAdapter(
fragmentManager: FragmentManager,
private val attachments: List<Attachment>,
private val initialPosition: Int
) : FragmentStatePagerAdapter(fragmentManager), SharedElementTransitionListener {
private var primaryItem: ViewMediaFragment? = null
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private var didTransition = false
override fun setPrimaryItem(container: ViewGroup, position: Int, item: Any) {
super.setPrimaryItem(container, position, item)
this.primaryItem = item as ViewMediaFragment
}
override fun getItem(position: Int): Fragment {
return if (position >= 0 && position < attachments.size) {
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// Fragment should not wait for or start transition if it already happened but we
// instantiate the same fragment again, e.g. open the first photo, scroll to the
// forth photo and then back to the first. The first fragment will trz to start the
// transition and wait until it's over and it will never take place.
ViewMediaFragment.newInstance(
attachment = attachments[position],
shouldStartPostponedTransition = !didTransition && position == initialPosition
)
} else {
throw IllegalStateException()
}
}
override fun getCount(): Int {
return attachments.size
}
override fun getPageTitle(position: Int): CharSequence {
return String.format(Locale.getDefault(), "%d/%d", position + 1, attachments.size)
}
override fun onTransitionEnd() {
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this.didTransition = true
primaryItem?.onTransitionEnd()
}
}