package com.lzj.gallery.library.transformer;
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import androidx.viewpager.widget.ViewPager;
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import android.view.View;
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/**
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* Created by Administrator on 2018/11/28.
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* 3D画廊效果其实就是ViewPager的item切换时，进行缩放的动画效果
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*
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*/
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public class ZoomPageTransformer implements ViewPager.PageTransformer {
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private static final float MAX_SCALE = 1.0f;//0缩放
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private static final float MIN_SCALE = 0.85f;//0.85缩放
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private float MIN_ALPHA = 1.0f;//最小透明度
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public ZoomPageTransformer() {
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}
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public ZoomPageTransformer(float MIN_ALPHA) {
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this.MIN_ALPHA = MIN_ALPHA;
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}
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@Override
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public void transformPage(View view, float position) {
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//setScaleY只支持api11以上
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/**
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* (-oo,-1) 相对于左边第一页，其左边的所有页面 **
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* x、y拉伸为MIN_SCALE、透明度MIN_ALPHA
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*/
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if (position < -1) {
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view.setScaleX(MIN_SCALE);
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view.setScaleY(MIN_SCALE);
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view.setAlpha(MIN_ALPHA);
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}
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/**
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* [-1, 1 )当前页的左右第一页
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*/
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else if (position < 1) {
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float scaleFactor = MIN_SCALE + (1 - Math.abs(position)) * (MAX_SCALE - MIN_SCALE);
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//[0, 1 ） 相对于当前选中页，其右边第一页 **
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if (position > 0) {
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view.setTranslationX(-scaleFactor);
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}
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// [-1, 0 ) 相对于当前选中页，其左边的第一页**
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else if (position < 0) {
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view.setTranslationX(scaleFactor);
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}
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view.setScaleY(scaleFactor);
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view.setScaleX(scaleFactor);
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// float alpha = 1f - Math.abs(position) * (1 - );
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float alpha = MIN_ALPHA + (1 - MIN_ALPHA) * (1 - Math.abs(position));
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view.setAlpha(alpha);
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}
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/**
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* [1,+oo） 相对于右边第一页，其右边的所有页面
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* x、y拉伸为MIN_SCALE、透明度MIN_ALPHA
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*/
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else { // (1,+Infinity]
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view.setScaleX(MIN_SCALE);
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view.setScaleY(MIN_SCALE);
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view.setAlpha(MIN_ALPHA);
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}
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}
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}
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