商品IDにlongの代わりにStringを返すことができるように、existing solutionをKotlinに再実装しました。あなたはhere以下それを見つけることができます。
import android.annotation.SuppressLint
import android.os.Bundle
import android.os.Parcelable
import android.support.v4.app.Fragment
import android.support.v4.app.FragmentManager
import android.support.v4.app.FragmentTransaction
import android.view.View
import android.view.ViewGroup
import java.util.HashSet
import java.util.LinkedHashMap
/**
* A PagerAdapter that can withstand item reordering. See
* https://issuetracker.google.com/issues/36956111.
*
* @see android.support.v4.app.FragmentStatePagerAdapter
*/
abstract class MovableFragmentStatePagerAdapter(
private val manager: FragmentManager
) : NullablePagerAdapter() {
private var currentTransaction: FragmentTransaction? = null
private var currentPrimaryItem: Fragment? = null
private val savedStates = LinkedHashMap<String, Fragment.SavedState>()
private val fragmentsToItemIds = LinkedHashMap<Fragment, String>()
private val itemIdsToFragments = LinkedHashMap<String, Fragment>()
private val unusedRestoredFragments = HashSet<Fragment>()
/** @see android.support.v4.app.FragmentStatePagerAdapter.getItem */
abstract fun getItem(position: Int): Fragment
/**
* @return a unique identifier for the item at the given position.
*/
abstract fun getItemId(position: Int): String
/** @see android.support.v4.app.FragmentStatePagerAdapter.startUpdate */
override fun startUpdate(container: ViewGroup) {
check(container.id != View.NO_ID) {
"ViewPager with adapter $this requires a view id."
}
}
/** @see android.support.v4.app.FragmentStatePagerAdapter.instantiateItem */
override fun instantiateItem(container: ViewGroup, position: Int): Any {
val itemId = getItemId(position)
val f = itemIdsToFragments[itemId]
if (f != null) {
unusedRestoredFragments.remove(f)
return f
}
if (currentTransaction == null) {
// We commit the transaction later
@SuppressLint("CommitTransaction")
currentTransaction = manager.beginTransaction()
}
val fragment = getItem(position)
fragmentsToItemIds.put(fragment, itemId)
itemIdsToFragments.put(itemId, fragment)
val fss = savedStates[itemId]
if (fss != null) {
fragment.setInitialSavedState(fss)
}
fragment.setMenuVisibility(false)
fragment.userVisibleHint = false
currentTransaction!!.add(container.id, fragment)
return fragment
}
/** @see android.support.v4.app.FragmentStatePagerAdapter.destroyItem */
override fun destroyItem(container: ViewGroup, position: Int, fragment: Any) {
(fragment as Fragment).destroy()
}
/** @see android.support.v4.app.FragmentStatePagerAdapter.setPrimaryItem */
override fun setPrimaryItem(container: ViewGroup, position: Int, fragment: Any?) {
fragment as Fragment?
if (fragment !== currentPrimaryItem) {
currentPrimaryItem?.let {
it.setMenuVisibility(false)
it.userVisibleHint = false
}
fragment?.setMenuVisibility(true)
fragment?.userVisibleHint = true
currentPrimaryItem = fragment
}
}
/** @see android.support.v4.app.FragmentStatePagerAdapter.finishUpdate */
override fun finishUpdate(container: ViewGroup) {
if (!unusedRestoredFragments.isEmpty()) {
for (fragment in unusedRestoredFragments) fragment.destroy()
unusedRestoredFragments.clear()
}
currentTransaction?.let {
it.commitAllowingStateLoss()
currentTransaction = null
manager.executePendingTransactions()
}
}
/** @see android.support.v4.app.FragmentStatePagerAdapter.isViewFromObject */
override fun isViewFromObject(view: View, fragment: Any): Boolean =
(fragment as Fragment).view === view
/** @see android.support.v4.app.FragmentStatePagerAdapter.saveState */
override fun saveState(): Parcelable? = Bundle().apply {
putStringArrayList(KEY_FRAGMENT_IDS, ArrayList<String>(savedStates.keys))
putParcelableArrayList(
KEY_FRAGMENT_STATES,
ArrayList<Fragment.SavedState>(savedStates.values)
)
for ((f, id) in fragmentsToItemIds.entries) {
if (f.isAdded) {
manager.putFragment(this, "$KEY_FRAGMENT_STATE$id", f)
}
}
}
/** @see android.support.v4.app.FragmentStatePagerAdapter.restoreState */
override fun restoreState(state: Parcelable?, loader: ClassLoader?) {
if ((state as Bundle?)?.apply { classLoader = loader }?.isEmpty == false) {
state!!
fragmentsToItemIds.clear()
itemIdsToFragments.clear()
unusedRestoredFragments.clear()
savedStates.clear()
val fragmentIds: List<String> = state.getStringArrayList(KEY_FRAGMENT_IDS)
val fragmentStates: List<Fragment.SavedState> =
state.getParcelableArrayList(KEY_FRAGMENT_STATES)
for ((index, id) in fragmentIds.withIndex()) {
savedStates.put(id, fragmentStates[index])
}
for (key: String in state.keySet()) {
if (key.startsWith(KEY_FRAGMENT_STATE)) {
val itemId = key.substring(KEY_FRAGMENT_STATE.length)
manager.getFragment(state, key)?.let {
it.setMenuVisibility(false)
fragmentsToItemIds.put(it, itemId)
itemIdsToFragments.put(itemId, it)
}
}
}
unusedRestoredFragments.addAll(fragmentsToItemIds.keys)
}
}
private fun Fragment.destroy() {
if (currentTransaction == null) {
// We commit the transaction later
@SuppressLint("CommitTransaction")
currentTransaction = manager.beginTransaction()
}
val itemId = fragmentsToItemIds.remove(this)
itemIdsToFragments.remove(itemId)
if (itemId != null) {
savedStates.put(itemId, manager.saveFragmentInstanceState(this))
}
currentTransaction!!.remove(this)
}
private companion object {
const val KEY_FRAGMENT_IDS = "fragment_keys_"
const val KEY_FRAGMENT_STATES = "fragment_states_"
const val KEY_FRAGMENT_STATE = "fragment_state_"
}
}
とJavaピース：
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.view.PagerAdapter;
import android.view.ViewGroup;
/**
* A PagerAdapter whose {@link #setPrimaryItem} is overridden with proper nullability annotations.
*/
public abstract class NullablePagerAdapter extends PagerAdapter {
@Override
public void setPrimaryItem(@NonNull ViewGroup container,
int position,
@Nullable Object object) {
// `object` is actually nullable. It's even in the dang source code which is hilariously
// ridiculous:
// `mAdapter.setPrimaryItem(this, mCurItem, curItem != null ? curItem.object : null);`
}
}
私はあなたの固定実装を使用していたが、私は直面しています一つの問題は、ViewPager.Howで隣接フラグメントのNO UPDATIONではありません私はそれを修正することはできますか？ –
あなたは@UgglyNoodleにいると思いますが、並べ替えられたフラグメントを破棄して再作成しても問題がない場合は、順序が変更されたフラグメントに対してはPOSITION_NONEを返し、変更されていないフラグメントについてはPOSTION_UNCHANGEDクラッシュすることなく所望の結果を達成する。 –