先貼圖

要實(shí)現(xiàn)上面的畫廊效果浇冰，傳統(tǒng)通過ViewPager clipChildren置為false實(shí)現(xiàn)。網(wǎng)上很多教程這個(gè)不多說洋魂，現(xiàn)在說說用RecyclerView實(shí)現(xiàn)上面的效果绷旗。這個(gè)效果分兩步:

1. ViewPager滑動(dòng)最終居中停止
2. 滑動(dòng)過程中縮放

ViewPager滑動(dòng)最終居中停止

Support RecyclerView 24.2.0中增加一個(gè)非常重要的類SnapHelper喜鼓，他的作用是讓RecyclerView滑動(dòng)視圖后使停止位置正好停在某頁(yè)的正中間。使用方式很簡(jiǎn)單
重點(diǎn)在于new LinearSnapHelper().attachToRecyclerView(recyclerView);

LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getContext(), LinearLayoutManager.HORIZONTAL, false);
recyclerView.setLayoutManager(linearLayoutManager);

new LinearSnapHelper().attachToRecyclerView(recyclerView);

一行代碼搞定居中衔肢，LinearSnapHelper的源碼解析查看這里庄岖。

滑動(dòng)過程中縮放

毫無疑問，RecyclerView的滑動(dòng)縮放必須要監(jiān)聽RecyclerView的滑動(dòng)

mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {

    @Override
    public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
        super.onScrolled(recyclerView, dx, dy);
        // dx>0則表示右滑, dx<0表示左滑, dy<0表示上滑, dy>0表示下滑
        mCurrentItemOffset += dx;
        computeCurrentItemPos();
        onScrolledChangedCallback();
    }
});     

mCurrentItemOffset為滑動(dòng)總距離角骤，Card每頁(yè)滑動(dòng)的距離是固定的隅忿，根據(jù)這個(gè)可以計(jì)算出當(dāng)前顯示的位置“钭穑縮放看onScrolledChangedCallback這個(gè)函數(shù)背桐，有了滑動(dòng)位置就能實(shí)時(shí)計(jì)算滑動(dòng)某頁(yè)的百分比
float percent = (float) Math.max(Math.abs(offset) * 1.0 / mOnePageWidth, 0.0001);

得到百分比, 再獲取當(dāng)前位置相鄰的視圖調(diào)用setScaleY函數(shù)實(shí)現(xiàn)縮放

/**
 * RecyclerView位移事件監(jiān)聽, view大小隨位移事件變化
 */
private void onScrolledChangedCallback() {
    int offset = mCurrentItemOffset - mCurrentItemPos * mOnePageWidth;
    float percent = (float) Math.max(Math.abs(offset) * 1.0 / mOnePageWidth, 0.0001);
    
    View leftView = null;
    View currentView;
    View rightView = null;
    if (mCurrentItemPos > 0) {
        leftView = mRecyclerView.getLayoutManager().findViewByPosition(mCurrentItemPos - 1);
    }
    currentView = mRecyclerView.getLayoutManager().findViewByPosition(mCurrentItemPos);
    if (mCurrentItemPos < mRecyclerView.getAdapter().getItemCount() - 1) {
        rightView = mRecyclerView.getLayoutManager().findViewByPosition(mCurrentItemPos + 1);
    }

    if (leftView != null) {
        // y = (1 - mScale)x + mScale
        leftView.setScaleY((1 - mScale) * percent + mScale);
    }
    if (currentView != null) {
        // y = (mScale - 1)x + 1
        currentView.setScaleY((mScale - 1) * percent + 1);
    }
    if (rightView != null) {
        // y = (1 - mScale)x + mScale
        rightView.setScaleY((1 - mScale) * percent + mScale);
    }
}

完整代碼下載

https://github.com/huazhiyuan2008/RecyclerViewCardGallery