RecyclerView滑动到指定Item并置顶

RecyclerView滑动到指定Item并置顶

0x01 TopLinearSmoothScroller

import android.content.Context
import androidx.recyclerview.widget.LinearSmoothScroller

class TopLinearSmoothScroller(context: Context?) : LinearSmoothScroller(context) {
    public override fun getVerticalSnapPreference(): Int {
        return SNAP_TO_START
    }

    override fun getHorizontalSnapPreference(): Int {
        return SNAP_TO_START
    }
}

0x02 TopScrollLinearLayoutManager

import android.content.Context
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView

class TopScrollLinearLayoutManager(context: Context?, orientation: Int, reverseLayout: Boolean) :
    LinearLayoutManager(context, orientation, reverseLayout) {

    override fun smoothScrollToPosition(
        recyclerView: RecyclerView?,
        state: RecyclerView.State?,
        position: Int
    ) {
        val linearSmoothScroller = TopLinearSmoothScroller(recyclerView?.context)
        linearSmoothScroller.targetPosition = position
        startSmoothScroll(linearSmoothScroller)
    }
}

0x03 RecyclerView中使用

设置recyclerView的layoutManager为自定义的TopScrollLinearLayoutManager，然后直接调用 smoothScrollToPosition() 方法就可以滚动到指定的位置并且置顶了。

recyclerView.layoutManager = TopScrollLinearLayoutManager(
    this,
    LinearLayoutManager.HORIZONTAL,
    false
)
// ...
recyclerView.smoothScrollToPosition(1)