DynamicPageTransformer.java

package com.mogujie.socialsdk.feed.adapter;

import android.graphics.Rect;
import android.support.v4.view.ViewPager;
import android.view.View;
import android.view.ViewGroup;

import com.mogujie.lifetag.TagShowLayout;

import java.util.List;

public class DynamicPageTransformer implements ViewPager.PageTransformer {

    private ViewPager mPager;
    private List<Integer> mHeightList;
    private IndexMultiImageAdapter mAdapter;
    private int pagerWidth;

    public DynamicPageTransformer(ViewPager viewPager, List<Integer> heightList, int pagerWidth) {
        mPager = viewPager;
        mHeightList = heightList;
        setDefaultHeight();
        this.pagerWidth = pagerWidth;
        mAdapter = (IndexMultiImageAdapter) mPager.getAdapter();
    }

    public void setDefaultHeight() {
        ViewGroup.LayoutParams params = mPager.getLayoutParams();
        if (mHeightList != null && mHeightList.size() > 0)
            params.height = mHeightList.get(0);
        mPager.setLayoutParams(params);
    }

    private int getHeight(int position) {
        return position >= 0 && position < mHeightList.size() ? mHeightList.get(position) : 0;
    }

    float lastPosition = -1;
    int base = 0;
    final float valve = 0.5f;
    final int LEFT_SLIDING = -1;
    final int RIGHT_SLIDING = 1;
    final int IDLE = 0;
    int sliding_state = IDLE;

    @Override
    public void transformPage(View page, float position) {
        if (position >= -1 && position <= 0) {
            int curr = mPager.getCurrentItem();
            int gap = 0;

            if (getHeight(curr) > 0) {
                if (lastPosition != 0 && lastPosition != -1 && Math.abs(lastPosition - position) < 0.5f) {

                    if (lastPosition > position) { //左滑 <- 右移
                        if (sliding_state == RIGHT_SLIDING)
                            base = base - 1;
                        if (getHeight(base + 1) != 0 && getHeight(base) != 0)
                            gap = getHeight(base + 1) - getHeight(base);
                        sliding_state = LEFT_SLIDING;
                    } else if (lastPosition < position) {//右滑 -> 左移
                        if (sliding_state == LEFT_SLIDING)
                            base = base + 1;
                        if (getHeight(base - 1) != 0 && getHeight(base) != 0)
                            gap = getHeight(base - 1) - getHeight(base);
                        sliding_state = RIGHT_SLIDING;
                    }
                }
            }

            ViewGroup.LayoutParams params = mPager.getLayoutParams();

            if (position == 0 || position == -1 || Math.abs(lastPosition - position) > valve) {
                base = curr;
                params.height = getHeight(base);
                sliding_state = IDLE;

            } else if (gap != 0) {
                if (Math.abs(lastPosition - position) < valve) {
                    if (lastPosition < position) {
                        params.height = (int) ((1 + position) * gap + getHeight(base));
                    } else if (lastPosition > position) {
                        params.height = (int) ((-position) * gap + getHeight(base));

                    } else
                        lastPosition = 0;
                }
            }

            lastPosition = position;
            mPager.setLayoutParams(params);

            if (mPager.getCurrentItem() >= 0 && mPager.getCurrentItem() < mHeightList.size() && mPager.getCurrentItem() < mAdapter.mViewArray.size()) {
                TagShowLayout itemView = mAdapter.mViewArray.get(mPager.getCurrentItem());
                Rect rect = new Rect(0, 0, pagerWidth, mHeightList.get(mPager.getCurrentItem()));
                itemView.setBoundary(rect);
            }
        }

    }


}