android - ListView 项目滚动动画 ("UIKit Dynamics"-like)

Question

我试图在滚动发生时为 ListView 项设置动画。更具体地说，我正在尝试在 iOS 7 上模拟 iMessage 应用程序的滚动动画。我发现了一个类似的示例 online :

为了澄清，我试图在用户滚动时实现项目的“流畅”移动效果，而不是添加新项目时的动画。我试图修改 BaseAdapter 中的 View ，并查看了 AbsListView 源代码，看看是否可以附加 AccelerateInterpolator在某个地方可以调整发送到 subview 的绘制坐标(如果这就是 AbsListView 的设计方式)。到目前为止，我一直无法取得任何进展。

有人知道如何复制这种行为吗？

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为了帮助使用谷歌搜索记录:这在 ios 上称为 “UIKit Dynamics”。

How to replicate Messages bouncing bubbles in iOS 7

它内置于最近的 iOS 版本中。不过使用起来还是有点难度。 (2014) 这是每个人都复制的帖子:widely copied article令人惊讶的是，UIKit Dynamics 仅适用于苹果的“ Collection View ”，而不是苹果的“表格 View ”，因此所有 iOS debs 都必须将内容从表格 View 转换为“ Collection View ”

每个人都使用的库是 BPXLFlowLayout，因为那个人非常擅长复制 iphone 短信应用程序的感觉。事实上，如果你将它移植到 Android，我想你可以使用其中的参数来获得相同的感觉。仅供引用，我在我的 android fone 收藏中注意到，HTC 手机在其 UI 上具有这种效果。希望能帮助到你。 Android 摇滚!

Answer 1

这个实现效果很好。虽然有一些闪烁，可能是因为当适配器将新 View 添加到顶部或底部时更改了索引..这可能通过观察树中的变化并动态移动索引来解决..

public class ElasticListView extends GridView implements AbsListView.OnScrollListener,      View.OnTouchListener {

private static int SCROLLING_UP = 1;
private static int SCROLLING_DOWN = 2;

private int mScrollState;
private int mScrollDirection;
private int mTouchedIndex;

private View mTouchedView;

private int mScrollOffset;
private int mStartScrollOffset;

private boolean mAnimate;

private HashMap<View, ViewPropertyAnimator> animatedItems;


public ElasticListView(Context context) {
    super(context);
    init();
}

public ElasticListView(Context context, AttributeSet attrs) {
    super(context, attrs);
    init();
}

public ElasticListView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    init();
}

private void init() {
    mScrollState = SCROLL_STATE_IDLE;
    mScrollDirection = 0;
    mStartScrollOffset = -1;
    mTouchedIndex = Integer.MAX_VALUE;
    mAnimate = true;
    animatedItems = new HashMap<>();
    this.setOnTouchListener(this);
    this.setOnScrollListener(this);

}


@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
    if (mScrollState != scrollState) {
        mScrollState = scrollState;
        mAnimate = true;

    }
    if (scrollState == SCROLL_STATE_IDLE) {
        mStartScrollOffset = Integer.MAX_VALUE;
        mAnimate = true;
        startAnimations();
    }

}

@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {

    if (mScrollState == SCROLL_STATE_TOUCH_SCROLL) {

        if (mStartScrollOffset == Integer.MAX_VALUE) {
            mTouchedView = getChildAt(mTouchedIndex - getPositionForView(getChildAt(0)));
            if (mTouchedView == null) return;

            mStartScrollOffset = mTouchedView.getTop();
        } else if (mTouchedView == null) return;

        mScrollOffset = mTouchedView.getTop() - mStartScrollOffset;
        int tmpScrollDirection;
        if (mScrollOffset > 0) {

            tmpScrollDirection = SCROLLING_UP;

        } else {
            tmpScrollDirection = SCROLLING_DOWN;
        }

        if (mScrollDirection != tmpScrollDirection) {
            startAnimations();
            mScrollDirection = tmpScrollDirection;
        }


        if (Math.abs(mScrollOffset) > 200) {
            mAnimate = false;
            startAnimations();
        }
        Log.d("test", "direction:" + (mScrollDirection == SCROLLING_UP ? "up" : "down") + ", scrollOffset:" + mScrollOffset + ", toucheId:" + mTouchedIndex + ", fvisible:" + firstVisibleItem + ", " +
            "visibleItemCount:" + visibleItemCount + ", " +
            "totalCount:" + totalItemCount);
        int indexOfLastAnimatedItem = mScrollDirection == SCROLLING_DOWN ?
            getPositionForView(getChildAt(0)) + getChildCount() :
            getPositionForView(getChildAt(0));

        //check for bounds
        if (indexOfLastAnimatedItem >= getChildCount()) {
            indexOfLastAnimatedItem = getChildCount() - 1;
        } else if (indexOfLastAnimatedItem < 0) {
            indexOfLastAnimatedItem = 0;
        }

        if (mScrollDirection == SCROLLING_DOWN) {
            setAnimationForScrollingDown(mTouchedIndex - getPositionForView(getChildAt(0)), indexOfLastAnimatedItem, firstVisibleItem);
        } else {
            setAnimationForScrollingUp(mTouchedIndex - getPositionForView(getChildAt(0)), indexOfLastAnimatedItem, firstVisibleItem);
        }
        if (Math.abs(mScrollOffset) > 200) {
            mAnimate = false;
            startAnimations();
            mTouchedView = null;
            mScrollDirection = 0;
            mStartScrollOffset = -1;
            mTouchedIndex = Integer.MAX_VALUE;
            mAnimate = true;
        }
    }
}

private void startAnimations() {
    for (ViewPropertyAnimator animator : animatedItems.values()) {
        animator.start();
    }
    animatedItems.clear();
}

private void setAnimationForScrollingDown(int indexOfTouchedChild, int indexOflastAnimatedChild, int firstVisibleIndex) {
    for (int i = indexOfTouchedChild + 1; i <= indexOflastAnimatedChild; i++) {
        View v = getChildAt(i);
        v.setTranslationY((-1f * mScrollOffset));
        if (!animatedItems.containsKey(v)) {
            animatedItems.put(v, v.animate().translationY(0).setDuration(300).setStartDelay(50 * i));
        }

    }
}

private void setAnimationForScrollingUp(int indexOfTouchedChild, int indexOflastAnimatedChild, int firstVisibleIndex) {
    for (int i = indexOfTouchedChild - 1; i > 0; i--) {
        View v = getChildAt(i);

        v.setTranslationY((-1 * mScrollOffset));
        if (!animatedItems.containsKey(v)) {
            animatedItems.put(v, v.animate().translationY(0).setDuration(300).setStartDelay(50 * (indexOfTouchedChild - i)));
        }

    }
}


@Override
public boolean onTouch(View v, MotionEvent event) {
    switch (event.getActionMasked()) {
        case MotionEvent.ACTION_DOWN:
            Rect rect = new Rect();
            int childCount = getChildCount();
            int[] listViewCoords = new int[2];
            getLocationOnScreen(listViewCoords);
            int x = (int)event.getRawX() - listViewCoords[0];
            int y = (int)event.getRawY() - listViewCoords[1];
            View child;
            for (int i = 0; i < childCount; i++) {
                child = getChildAt(i);
                child.getHitRect(rect);
                if (rect.contains(x, y)) {
                    mTouchedIndex = getPositionForView(child); 
                    break;
                }
            }
            return false;

    }
    return false;

}

}