android - 奇怪的 LinearLayoutManager.scrollToPositionWithOffset(...) 行为

Question

我有一个持有两种不同观点的RecyclerViewwith an 。Adapter第一个视图的宽度和高度比后面的视图稍大。

启动包含 的活动时RecyclerView，我想滚动到Adapter. 我通过调用scrollToPositionWithOffset(position, offset)连接LinearLayoutManager到RecyclerView.

以下代码大致描述了设置（没有什么异常）。包含RecyclerView调用的活动Timeline.scrollTo(position)。请耐心等待我发布 Scala 代码。

举办活动RecyclerView

class Activity extends [...] {

    lazy val timeline = findView( TR.layout_screen_transaction_timeline )

    override def onCreate( state: Option[Bundle] ) = {
        super.onCreate( state )

        setContentView( R.layout.screen_transaction_timeline )

        [...]

        timeline.setAdapter( adapter )

        if ( state.isEmpty ) {
            focus.foreach { position ⇒
                new Handler().post { () ⇒
                    timeline.scrollTo( position )
                }
            }
        }
    }

带有 LinearLayoutManager 的 RecyclerView

class Timeline( attributes: AttributeSet = null, style: Int = 0 )( implicit context: Context )
    extends RecyclerView( context, attributes, style ) {
    [...]

    setHasFixedSize( true )
    setLayoutManager( layoutManager )

    def scrollTo( position: Int ) = {
        layoutManager.scrollToPositionWithOffset( position, 0 )
    }

    object layoutManager extends LinearLayoutManager( context, VERTICAL, false )
}

适配器

object adapter extends Adapter[Holder] {
    override def getItemCount = tour.shipments.length + 1

    override def onBindViewHolder( holder: Holder, position: Int ) = holder.view match {
        case collection: widget.transaction.timeline.Header ⇒
            collection.set( tour.collection, tour, tour.state == Tour.State.New )
        case waypoint: widget.transaction.timeline.Waypoint ⇒
            waypoint.set( position, tour.shipments( position - 1 ), focus.contains( position ) )
    }

    override def onCreateViewHolder( parent: ViewGroup, kind: Int ) = Holder {
        val view = kind match {
            case 0 ⇒ new widget.transaction.timeline.Header()
            case 1 ⇒ new widget.transaction.timeline.Waypoint()
        }

        view.setLayoutParams( new RecyclerView.LayoutParams( MATCH_PARENT, WRAP_CONTENT ) )
        view
    }

    override def getItemViewType( position: Int ) = position match {
        case 0 ⇒ 0
        case _ ⇒ 1
    }
}

一切正常，除非我想滚动到最后一个位置。在这种情况下，LinearLayoutManager有时会正确滚动到该位置，有时会以稍微偏离的方式滚动。

更新：我刚刚发现删除包含ActionBar的 Activity 可以RecyclerView解决此问题。不过我需要一个ActionBar...