【发布时间】：2021-03-10 14:28:57
【问题描述】：
我正在制作一个应用程序，其中有一个 RecyclerView，其中包含一些在创建应用程序后立即添加的固定元素。
我想要做的是，当按下Button 时，一个元素被添加到RecyclerView 中，当关闭它并再次启动它时，这个新元素仍然存在。
除此之外，我使用IndicatorView 滚动查看recyclerview 的元素。当我使用 Button 添加一些元素时，发生在我身上的问题是创建了新元素，RecyclerView 的大小增加了，但 IndicatorView 没有增加，我无法滚动查看添加的新元素，除此之外，当重新启动应用程序时，这些通过按钮添加的新元素会自行删除。
向RecyclerView 添加新元素时如何增加IndicatorView 的大小？
如何在Button 上使用 onClick 将元素永久添加到 RecyclerView？
我的代码：
MainActivity.kt：
class MainActivity : AppCompatActivity() {
private lateinit var viewPager: ViewPager
private lateinit var pagerAdapter: PageAdapter
private val animalList = arrayListOf<String>()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
animalList.add("1")
animalList.add("2")
animalList.add("3")
animalList.add("4")
animalList.add("5")
animalList.add("6")
animalList.add("7")
animalList.add("8")
animalList.add("9")
animalList.add("10")
animalList.add("11")
animalList.add("12")
animalList.add("13")
animalList.add("14")
animalList.add("15")
animalList.add("16")
animalList.add("17")
var size = animalList.size / 4
if ((animalList.size % 4 ) > 0)
size += 1
pagerAdapter = PageAdapter(supportFragmentManager, size, animalList)
ADDbutton.setOnClickListener {
animalList.add("lol")
animalList.add("añadido jaja")
Log.i("AAA","Added: "+ animalList +" SIZE: " + animalList.size)
pagerAdapter.notifyDataSetChanged()
}
viewPager = findViewById(R.id.view_pager)
pagerAdapter = PageAdapter(supportFragmentManager, size, animalList)
viewPager.adapter = pagerAdapter
}
}
ItemFragment.kt：
class ItemFragment : Fragment() {
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
// Creates the view controlled by the fragment
val view = inflater.inflate(R.layout.page, container, false)
val recycler = view.findViewById<RecyclerView>(R.id.recycler)
// Retrieve and display the movie data from the Bundle
val args = arguments
recycler.layoutManager = GridLayoutManager(activity,2,GridLayoutManager.VERTICAL,false)
recycler.adapter = ItemAdapter(args?.getStringArrayList("items")!!, this.activity!!)
return view
}
companion object {
fun newInstance(items: ArrayList<String>): ItemFragment {
val args = Bundle()
args.putStringArrayList("items", items)
val fragment = ItemFragment()
fragment.arguments = args
return fragment
}
}
}
PageAdapter.kt：
class PageAdapter(fragmentManager: FragmentManager, private val size: Int, private val items: ArrayList<String>) :
FragmentStatePagerAdapter(fragmentManager) {
override fun getItem(position: Int): Fragment {
val firstItem = ((position + 1) * 4) - 3
val lastItem = ((position + 1) * 4)
val itemSet = arrayListOf<String>()
for (i in firstItem..lastItem) {
if (i <= items.size)
itemSet.add(items[i - 1])
}
return ItemFragment.newInstance(itemSet)
}
override fun getCount(): Int {
return size
}
}
ItemAdapter.kt：
class ItemAdapter(private val items: ArrayList<String>, private val context: Context) : RecyclerView.Adapter<ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
return ViewHolder(LayoutInflater.from(context).inflate(R.layout.item, parent, false))
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder?.title?.text = items.get(position)
}
override fun getItemCount(): Int {
return items.size
}
}
class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {
val title: TextView = view.title_view
val item: RelativeLayout = view.item_view
}
布局：
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:attrs="http://schemas.android.com/tools"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<androidx.viewpager.widget.ViewPager
android:id="@+id/view_pager"
android:layout_width="wrap_content"
android:layout_height="0dp"
android:layout_marginBottom="32dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="@+id/guideline2">
</androidx.viewpager.widget.ViewPager>
<com.rd.PageIndicatorView
android:id="@+id/pageIndicatorView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/view_pager"
app:piv_animationType="worm"
app:piv_dynamicCount="true"
app:piv_interactiveAnimation="true"
app:piv_radius="8dp"
app:piv_selectedColor="#000000"
app:piv_unselectedColor="#999999"
app:piv_viewPager="@id/view_pager"
attrs:piv_padding="8dp" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintGuide_begin="251dp"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="@+id/ADDbutton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button"
app:layout_constraintBottom_toTopOf="@+id/view_pager"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>item.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/item_view"
android:layout_width="match_parent"
android:layout_height="100dp"
android:layout_margin="10dp"
android:background="@color/teal_700">
<TextView
android:id="@+id/title_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_centerInParent="true"
android:gravity="center"
android:textColor="@android:color/white"
android:textSize="18sp"
android:textStyle="bold" />
</RelativeLayout>page.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.recyclerview.widget.RecyclerView
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:id="@+id/recycler"
android:layout_height="match_parent"/>【问题讨论】：
标签： android android-studio kotlin android-recyclerview