1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
|
package ca.allanwang.kau.adapters
import android.support.v7.widget.LinearLayoutManager
import android.support.v7.widget.RecyclerView
import ca.allanwang.kau.utils.withLinearAdapter
import com.mikepenz.fastadapter.IItem
import com.mikepenz.fastadapter.adapters.HeaderAdapter
import com.mikepenz.fastadapter.commons.adapters.FastItemAdapter
import org.jetbrains.anko.collections.forEachReversedWithIndex
import java.util.*
/**
* Created by Allan Wang on 2017-06-27.
*
* Once bounded to a [RecyclerView], this will
* - Chain together a list of [HeaderAdapter]s, backed by a generic [FastItemAdapter]
* - Add a [LinearLayoutManager] to the recycler
* - Add a listener for when a new adapter segment is being used
*/
class ChainedAdapters<T>(vararg items: Pair<T, SectionAdapter<*>>) {
private val chain: MutableList<Pair<T, SectionAdapter<*>>> = mutableListOf(*items)
val baseAdapter: FastItemAdapter<IItem<*, *>> = FastItemAdapter()
private val indexStack = Stack<Int>()
var recycler: RecyclerView? = null
val firstVisibleItemPosition: Int
get() = (recycler?.layoutManager as LinearLayoutManager?)?.findFirstVisibleItemPosition() ?: throw IllegalArgumentException("No recyclerview was bounded to the chain adapters")
fun add(vararg items: Pair<T, SectionAdapter<*>>) = add(items.toList())
fun add(items: Collection<Pair<T, SectionAdapter<*>>>): ChainedAdapters<T> {
if (recycler != null) throw IllegalAccessException("Chain adapter is already bounded to a recycler; cannot add directly.")
items.map { it.second }.forEachIndexed { index, sectionAdapter -> sectionAdapter.sectionOrder = chain.size + 1 + index }
chain.addAll(items)
return this
}
operator fun get(index: Int) = chain[index]
/**
* Attaches the chain to a recycler
* After this stage, any modifications to the adapters must be done through external references
* You may still get the generic header adapters through the get operator
* Binding the recycler also involves supplying a callback, which returns
* the item (T) associated with the adapter,
* the index (Int) of the current adapter
* and the dy (Int) as given by the scroll listener
*/
fun bindRecyclerView(recyclerView: RecyclerView, onAdapterSectionChanged: (item: T, index: Int, dy: Int) -> Unit) {
if (recycler != null) throw IllegalStateException("Chain adapter is already bounded")
if (chain.isEmpty()) throw IllegalArgumentException("No adapters have been added to the adapters list")
//wrap adapters
chain.map { it.second }.forEachReversedWithIndex { i, headerAdapter ->
if (i == chain.size - 1) headerAdapter.wrap(baseAdapter)
else headerAdapter.wrap(chain[i + 1].second)
}
recycler = recyclerView
indexStack.push(0)
with(recyclerView) {
withLinearAdapter(chain.first().second)
addOnScrollListener(object : RecyclerView.OnScrollListener() {
override fun onScrolled(rv: RecyclerView, dx: Int, dy: Int) {
super.onScrolled(rv, dx, dy)
val topPosition = firstVisibleItemPosition
val currentAdapterIndex = indexStack.peek()
if (dy > 0) {
//look ahead from current adapter
val nextAdapterIndex = (currentAdapterIndex until chain.size).asSequence()
.firstOrNull {
val adapter = chain[it].second
adapter.adapterItemCount > 0 && adapter.getGlobalPosition(adapter.adapterItemCount - 1) >= topPosition
} ?: currentAdapterIndex
if (nextAdapterIndex == currentAdapterIndex) return
indexStack.push(nextAdapterIndex)
onAdapterSectionChanged(chain[indexStack.peek()].first, indexStack.peek(), dy)
} else if (currentAdapterIndex == 0) {
return //All adapters may be empty; in this case, if we are already at the beginning, don't bother checking
} else if (chain[currentAdapterIndex].second.getGlobalPosition(0) > topPosition) {
indexStack.pop()
onAdapterSectionChanged(chain[indexStack.peek()].first, indexStack.peek(), dy)
}
}
})
}
}
}
|
