Custom ItemDecoration:
class DemoDecoration(context: Context, left: Float, top: Float, right: Float, bottom: Float) : ItemDecoration() {
companion object {
private const val dividerHeight = 8f
private const val dividerPaddingLeft = 0f
}
private val left: Int
private val top: Int
private val right: Int
private val bottom: Int
private val dividerPaddingRight = 0f
private val dividerPaint: Paint
private val textPaint: Paint
init {
val density = context.resources.displayMetrics.density
this.left = (density * left).toInt()
this.top = (density * top).toInt()
this.right = (density * right).toInt()
this.bottom = (density * bottom).toInt()
dividerPaint = Paint()
dividerPaint.isAntiAlias = true
dividerPaint.style = Paint.Style.FILL
dividerPaint.color = ContextCompat.getColor(context, android.R.color.darker_gray)
textPaint = Paint()
textPaint.isAntiAlias = true
textPaint.style = Paint.Style.FILL
textPaint.textSize = 30f
textPaint.typeface = Typeface.DEFAULT_BOLD
textPaint.color = Color.BLACK
}
override fun onDraw(canvas: Canvas, parent: RecyclerView, state: RecyclerView.State) {
draw(canvas, parent)
}
override fun onDrawOver(canvas: Canvas, parent: RecyclerView, state: RecyclerView.State) {
draw(canvas, parent)
}
private fun draw(canvas: Canvas, parent: RecyclerView) {
if (parent.layoutManager == null) {
return
}
canvas.save()
drawRect(canvas, parent)
canvas.restore()
}
private fun drawRect(canvas: Canvas, parent: RecyclerView) {
val childCount = parent.childCount
val spanCount = getSpanCount(parent)
val space = 0f.coerceAtLeast(((top + bottom).toFloat() - dividerHeight) / 2)
var i = 0
if (i < childCount) {
val view = parent.getChildAt(i)
val position = parent.getChildAdapterPosition(view)
if (position / spanCount % 2 == 0) {
canvas.drawRect(dividerPaddingLeft, view.bottom + space,
parent.right - dividerPaddingRight, view.bottom + space + dividerHeight,
dividerPaint)
}
i += spanCount
}
}
override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) {
if (parent.layoutManager == null) {
return
}
val position = parent.getChildAdapterPosition(view)
val spanCount = getSpanCount(parent)
val index = position / spanCount
if (index > 0 && index % 2 == 0) {
outRect[left, 56, right] = bottom
} else {
outRect[left, top, right] = bottom
}
}
private fun getSpanCount(parent: RecyclerView): Int {
var spanCount = -1
val layoutManager = parent.layoutManager
if (layoutManager is GridLayoutManager) {
spanCount = layoutManager.spanCount
} else if (layoutManager is StaggeredGridLayoutManager) {
spanCount = layoutManager.spanCount
}
return spanCount
}
}
change item position
class MainActivity: AppCompatActivity() {
private lateinit var change: Button
private lateinit var recycler: RecyclerView
private val demoAdapter: DemoAdapter = DemoAdapter()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.main_activity)
change = findViewById(R.id.change)
change.setOnClickListener {
val list = ArrayList(demoAdapter.currentList)
list.add(10, list.removeAt(5))
demoAdapter.submitList(list)
}
recycler = findViewById(R.id.recycler)
recycler.apply {
layoutManager = GridLayoutManager(this@MainActivity, 5)
setHasFixedSize(true)
isNestedScrollingEnabled = false
itemAnimator = DefaultItemAnimator()
addItemDecoration(DemoDecoration(this@MainActivity, 2f, 4f, 2f, 4f))
adapter = demoAdapter
}
val data: MutableList<Model> = ArrayList()
for (i: Int in 0 .. 39) {
when ((1..2).random()) {
1 -> data.add(Model("$i\n\na"))
2 -> data.add(Model("$i\na\nb"))
}
}
demoAdapter.submitList(data)
}
}
adapter
class DemoAdapter: ListAdapter<Model, DemoAdapter.ViewHolder>(TaskDiffCallback()) {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
return ViewHolder(LayoutInflater.from(parent.context).inflate(R.layout.item, parent, false))
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
val model = getItem(position)
holder.text.text = model.text
}
class ViewHolder(view: View): RecyclerView.ViewHolder(view) {
val container: ConstraintLayout
val text: TextView
init {
container = view.findViewById(R.id.container)
text = view.findViewById(R.id.text)
}
}
private class TaskDiffCallback : DiffUtil.ItemCallback<Model>() {
override fun areItemsTheSame(oldItem: Model, newItem: Model): Boolean {
return oldItem == newItem
}
override fun areContentsTheSame(oldItem: Model, newItem: Model): Boolean {
return oldItem == newItem
}
}
}
data class Model(val text: String)
item layout
<?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"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/shape_stroke_black">
<TextView
android:id="@+id/text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center"
android:layout_gravity="center"
android:paddingTop="4dp"
android:paddingBottom="4dp"
android:background="@android:color/holo_blue_light"
android:textColor="@android:color/black"
android:textSize="12sp"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toBottomOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
5-->10
Item height is changed. How can to keep item height unchanged?