使用RecyclerView实现抖音纵向滚动ViewPager效果

重写LinearLayoutManager，在onAttachedToWindow方法中使用 PagerSnapHelper设置RecyclerView条目加载方式为每次滚动加载一页

class MyLinearLayoutManager : LinearLayoutManager {    private lateinit var mPagerSnapHelper: PagerSnapHelper    private var mOnViewPagerListener: OnViewPagerListener? = null    private lateinit var mRecyclerView: RecyclerView    private var mDrift: Int = 0//位移，用来判断移动方向    constructor(context: Context) : this(context, OrientationHelper.VERTICAL)    constructor(context: Context, orientation: Int) : this(context, orientation, false)    constructor(context: Context, orientation: Int, reverseLayout: Boolean) : super(context, orientation, reverseLayout) { mPagerSnapHelper = PagerSnapHelper()    }    override fun onAttachedToWindow(view: RecyclerView) { super.onAttachedToWindow(view) mPagerSnapHelper.attachToRecyclerView(view)//设置RecyclerView每次滚动一页 mRecyclerView = view mRecyclerView.addOnChildAttachStateChangeListener(mChildAttachStateChangeListener)    }    /**     * 滑动状态的改变     * 缓慢拖拽-> SCROLL_STATE_DRAGGING     * 快速滚动-> SCROLL_STATE_SETTLING     * 空闲状态-> SCROLL_STATE_IDLE     * @param state     */    override fun onScrollStateChanged(state: Int) { if (state == RecyclerView.SCROLL_STATE_IDLE){     val viewIdle = mPagerSnapHelper.findSnapView(this)     val positionIdle = getPosition(viewIdle!!)     if (mOnViewPagerListener != null && childCount == 1) {  mOnViewPagerListener!!.onPageSelected(positionIdle, positionIdle == itemCount - 1)     } }    }    /**     * 布局完成后调用     * @param state     */    override fun onLayoutCompleted(state: RecyclerView.State?) { super.onLayoutCompleted(state) if (mOnViewPagerListener != null) mOnViewPagerListener!!.onLayoutComplete()    }    /**     * 监听竖直方向的相对偏移量     */    override fun scrollVerticallyBy(dy: Int, recycler: RecyclerView.Recycler?, state: RecyclerView.State?): Int { this.mDrift = dy return super.scrollVerticallyBy(dy, recycler, state)    }    /**     * 监听水平方向的相对偏移量     */    override fun scrollHorizontallyBy(dx: Int, recycler: RecyclerView.Recycler?, state: RecyclerView.State?): Int { this.mDrift = dx return super.scrollHorizontallyBy(dx, recycler, state)    }    /**     * 设置监听     * @param listener     */    fun setOnViewPagerListener(listener: OnViewPagerListener) { this.mOnViewPagerListener = listener    }    private val mChildAttachStateChangeListener = object : RecyclerView.OnChildAttachStateChangeListener { override fun onChildViewAttachedToWindow(view: View) { } override fun onChildViewDetachedFromWindow(view: View) {     if (mDrift >= 0) {  if (mOnViewPagerListener != null) mOnViewPagerListener!!.onPageRelease(true, getPosition(view))     } else {  if (mOnViewPagerListener != null) mOnViewPagerListener!!.onPageRelease(false, getPosition(view))     } }    }    interface OnViewPagerListener{ /*释放的监听*/ fun onPageRelease(isNext: Boolean, position: Int) /*选中的监听以及判断是否滑动到底部*/ fun onPageSelected(position: Int, isBottom: Boolean) /*布局完成的监听*/ fun onLayoutComplete()    }}

重写RecyclerView条目内容主布局满屏填充

class MyImageView : ImageView {    constructor(context: Context) : this(context, null!!)    constructor(context: Context, attr: AttributeSet) : this(context, attr, 0)    constructor(context: Context, attr: AttributeSet, defStyleAttr: Int) : super(context, attr, defStyleAttr)    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) { val width = View.getDefaultSize(0, widthMeasureSpec) val height = View.getDefaultSize(0, heightMeasureSpec) setMeasuredDimension(width, height)    }}

注:现在谷歌官方 新控件androidx.viewpager2.widget.ViewPager2可实现类似效果
代码参考:https://github.com/DingMouRen/LayoutManagerGroup

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