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) } }