如何在android中滚动时放大Recycler View中心项目？

Question

在放大滚动时，我必须始终在回收器视图中突出显示中心项目。

Answer 1

您应该遵循此代码，这有助于我在“回收者”视图中放大中心项目。

public class CenterZoomLayoutManager extends LinearLayoutManager {

    private final float mShrinkAmount = 0.15f;
    private final float mShrinkDistance = 0.9f;

    public CenterZoomLayoutManager(Context context) {
        super(context);
    }

    public CenterZoomLayoutManager(Context context, int orientation, boolean reverseLayout) {
        super(context, orientation, reverseLayout);
    }

    @Override
    public int scrollVerticallyBy(int dy, RecyclerView.Recycler recycler, RecyclerView.State state) {
        int orientation = getOrientation();
        if (orientation == VERTICAL) {
            int scrolled = super.scrollVerticallyBy(dy, recycler, state);
            float midpoint = getHeight() / 2.f;
            float d0 = 0.f;
            float d1 = mShrinkDistance * midpoint;
            float s0 = 1.f;
            float s1 = 1.f - mShrinkAmount;
            for (int i = 0; i < getChildCount(); i++) {
                View child = getChildAt(i);
                float childMidpoint =
                        (getDecoratedBottom(child) + getDecoratedTop(child)) / 2.f;
                float d = Math.min(d1, Math.abs(midpoint - childMidpoint));
                float scale = s0 + (s1 - s0) * (d - d0) / (d1 - d0);
                child.setScaleX(scale);
                child.setScaleY(scale);
            }
            return scrolled;
        } else {
            return 0;
        }
    }

    @Override
    public int scrollHorizontallyBy(int dx, RecyclerView.Recycler recycler, RecyclerView.State state) {
        int orientation = getOrientation();
        if (orientation == HORIZONTAL) {
            int scrolled = super.scrollHorizontallyBy(dx, recycler, state);

            float midpoint = getWidth() / 2.f;
            float d0 = 0.f;
            float d1 = mShrinkDistance * midpoint;
            float s0 = 1.f;
            float s1 = 1.f - mShrinkAmount;
            for (int i = 0; i < getChildCount(); i++) {
                View child = getChildAt(i);
                float childMidpoint =
                        (getDecoratedRight(child) + getDecoratedLeft(child)) / 2.f;
                float d = Math.min(d1, Math.abs(midpoint - childMidpoint));
                float scale = s0 + (s1 - s0) * (d - d0) / (d1 - d0);
                child.setScaleX(scale);
                child.setScaleY(scale);
            }
            return scrolled;
        } else {
            return 0;
        }

    }
}

中心水平视图

Answer 2

我缩小了该解决方案，并在onLayoutComplete中添加了初始调整大小。我不需要垂直滚动，因此我将其中的一部分取出了。

class CenterZoomLinearLayoutManager(
    context: Context,
    private val mShrinkDistance: Float = 0.9f,
    val mShrinkAmount: Float = 0.15f
) : LinearLayoutManager(context, LinearLayoutManager.HORIZONTAL, false) {

    override fun onLayoutCompleted(state: RecyclerView.State?) {
        super.onLayoutCompleted(state)
        scaleChildren()
    }

    override fun scrollHorizontallyBy(dx: Int, recycler: RecyclerView.Recycler?, state: RecyclerView.State?): Int {
        return if (orientation == HORIZONTAL) {
            super.scrollHorizontallyBy(dx, recycler, state).also { scaleChildren() }
        } else {
            0
        }
    }

    private fun scaleChildren() {
        val midpoint = width / 2f
        val d1 = mShrinkDistance * midpoint
        for (i in 0 until childCount) {
            val child = getChildAt(i) as View
            val d = Math.min(d1, Math.abs(midpoint - (getDecoratedRight(child) + getDecoratedLeft(child)) / 2f))
            val scale = 1f - mShrinkAmount * d / d1
            child.scaleX = scale
            child.scaleY = scale
        }
    }
}

请参见https://github.com/pcholt/toy-card-carousel

Answer 3

嗯，紧随Anarchofascist和Mayank之后，只需在Mayank代码的开头处添加此替代，以使效果与第一个元素一起使用。

@Override
public void onLayoutCompleted(RecyclerView.State state) {
    super.onLayoutCompleted(state);

    //aqui ele executa o codigo no estado inicial, originalmente ele nao aplicava no inicio
    //este codigo é em horizontal. Para usar em vertical apagar e copiar o codigo
    int orientation = getOrientation();
    if (orientation == HORIZONTAL) {

        float midpoint = getWidth() / 2.f;
        float d0 = 0.f;
        float d1 = mShrinkDistance * midpoint;
        float s0 = 1.f;
        float s1 = 1.f - mShrinkAmount;
        for (int i = 0; i < getChildCount(); i++) {
            View child = getChildAt(i);
            float childMidpoint =
                    (getDecoratedRight(child) + getDecoratedLeft(child)) / 2.f;
            float d = Math.min(d1, Math.abs(midpoint - childMidpoint));
            float scale = s0 + (s1 - s0) * (d - d0) / (d1 - d0);
            child.setScaleX(scale);
            child.setScaleY(scale);
        }

    } else {

        float midpoint = getHeight() / 2.f;
        float d0 = 0.f;
        float d1 = mShrinkDistance * midpoint;
        float s0 = 1.f;
        float s1 = 1.f - mShrinkAmount;
        for (int i = 0; i < getChildCount(); i++) {
            View child = getChildAt(i);
            float childMidpoint =
                    (getDecoratedBottom(child) + getDecoratedTop(child)) / 2.f;
            float d = Math.min(d1, Math.abs(midpoint - childMidpoint));
            float scale = s0 + (s1 - s0) * (d - d0) / (d1 - d0);
            child.setScaleX(scale);
            child.setScaleY(scale);
        }

    }
}