/
LoadStateFragmentStateAdapter.kt
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/
LoadStateFragmentStateAdapter.kt
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/*
* Copyright 2021 panpf <panpfpanpf@outlook.com>
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.github.panpf.assemblyadapter.pager2.paging
import androidx.fragment.app.Fragment
import androidx.fragment.app.FragmentActivity
import androidx.fragment.app.FragmentManager
import androidx.lifecycle.Lifecycle
import androidx.paging.LoadState
import androidx.viewpager2.adapter.FragmentStateAdapter
/**
* [Fragment] version of [androidx.paging.LoadStateAdapter]
*
* @see androidx.paging.LoadStateAdapter
*/
abstract class LoadStateFragmentStateAdapter(
fragmentManager: FragmentManager,
lifecycle: Lifecycle
) : FragmentStateAdapter(fragmentManager, lifecycle) {
/**
* Get [FragmentManager] and [Lifecycle] from [FragmentActivity] to create [LoadStateFragmentStateAdapter]
*/
constructor(fragmentActivity: FragmentActivity) : this(
fragmentActivity.supportFragmentManager,
fragmentActivity.lifecycle
)
/**
* Get [FragmentManager] and [Lifecycle] from [Fragment] to create [LoadStateFragmentStateAdapter]
*/
constructor(fragment: Fragment) : this(fragment.childFragmentManager, fragment.lifecycle)
/**
* LoadState to present in the adapter.
*
* Changing this property will immediately notify the Adapter to change the item it's
* presenting.
*/
var loadState: LoadState = LoadState.NotLoading(endOfPaginationReached = false)
set(loadState) {
if (field != loadState) {
val oldItem = displayLoadStateAsItem(field)
val newItem = displayLoadStateAsItem(loadState)
if (oldItem && !newItem) {
notifyItemRemoved(0)
} else if (newItem && !oldItem) {
notifyItemInserted(0)
} else if (oldItem && newItem) {
notifyItemChanged(0)
}
field = loadState
}
}
final override fun getItemViewType(position: Int): Int = getStateViewType(loadState)
final override fun getItemCount(): Int = if (displayLoadStateAsItem(loadState)) 1 else 0
/**
* Override this method to use different view types per LoadState.
*
* By default, this LoadStateAdapter only uses a single view type.
*/
open fun getStateViewType(loadState: LoadState): Int = 0
/**
* Returns true if the LoadState should be displayed as a list item when active.
*
* By default, [LoadState.Loading] and [LoadState.Error] present as list items, others do not.
*/
open fun displayLoadStateAsItem(loadState: LoadState): Boolean {
return loadState is LoadState.Loading || loadState is LoadState.Error
}
override fun createFragment(position: Int): Fragment {
return onCreateFragment(position, loadState)
}
protected abstract fun onCreateFragment(position: Int, loadState: LoadState): Fragment
}