使用ViewPager打造的3D画廊,先看效果图:
GIF.gif
需求点:
1.中间item放大
2.中间item覆盖在两侧item上
3.点击或者滑动两侧的item可以切换ViewPager的当前展示页面
所以首先我们想到的肯定是ViewGroup的clipChildren属性,设为false,可以让子view突破ViewGroup的限制呈现出来突出来的效果,或者是本文这种ViewPager的覆盖效果,网上也看到用RecyclerView实现类似效果的,有兴趣的自行百度.
下面我们看代码怎么实现:
首先在我的项目中这个3D Gallery是一个RecyclerView的Item,并且外部的界面是可左右滑动切花的Fragment,先说明一下下面有些逻辑会处理滑动冲突.
先看下布局,主界面只有一个RecyclerView就不贴代码了.
看下Gallery的布局吧:
这里可以看出虽然我们的ViewPager看起来是铺满屏幕的,但是其实除了中间的Item两侧是用StarView进行占位的,它的作用是拦截处理点击和触摸两侧可以切换ViewPager的展示Item,但是由于项目中整个界面是可以左右滑动切换的,所以我稍后的代码中拦截了横向滑动,如果不需要请自行忽略.还有个ViewPager的Item的布局也贴一下吧:
简单说下,左后一个ImageView是做两侧小的Item半透明效果的,直接覆盖了一层半透明效果的图片在上面.在ViewPager切换效果的管理类中管理缩放和透明度,看下代码:
package com.bubu.a3dgallerydemo;
import android.content.Context;
import android.support.v4.view.ViewPager;
import android.view.View;
import android.widget.ImageView;
/**
* Fixme
* Author: LWJ
* desc:
* Date: 2017/09/19 10:13
* Copyright (c) 2016 d2cmall. All rights reserved.
*/
public class RotationPageTransformer implements ViewPager.PageTransformer{
private static final float MIN_SCALE=0.85f;
private static final float MIN_ALPHA=0.6f;
public void setContext(Context context) {
mContext = context;
}
private Context mContext;
@Override
public void transformPage(View page, float position) {
float scaleFactor = Math.max(MIN_SCALE,1 - Math.abs(position));
float scaleAlpha = Math.max(MIN_ALPHA,1 - Math.abs(position));
ImageView imageTag= (ImageView) page.findViewById(R.id.iv_cover);
float rotate = 0;
//position小于等于1的时候，代表page已经位于中心item的最左边，
//此时设置为最小的缩放率以及最大的旋转度数
if (position <= -1){
page.setScaleX(MIN_SCALE);
page.setScaleY(MIN_SCALE);
imageTag.setAlpha((float) 1);
}//position从0变化到-1，page逐渐向左滑动
else if (position < 0){
imageTag.setAlpha(Math.abs(position));
page.setScaleX(scaleFactor);
page.setScaleY(scaleFactor);
}//position从0变化到1，page逐渐向右滑动
else if (position >=0 && position < 1){
imageTag.setAlpha(position);
page.setScaleX(scaleFactor);
page.setScaleY(scaleFactor);
}//position大于等于1的时候，代表page已经位于中心item的最右边
else if (position >= 1){
imageTag.setAlpha((float)1);
page.setScaleX(scaleFactor);
page.setScaleY(scaleFactor);
}
}
}
然后看下给ViewPager数据以及拦截左右滑动,贴下代码:
package com.bubu.a3dgallerydemo;
import android.content.Context;
import android.content.Intent;
import android.support.v4.view.ViewPager;
import android.support.v7.widget.RecyclerView;
import android.util.DisplayMetrics;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import java.util.ArrayList;
import java.util.List;
/**
* Created by Administrator on 2018/5/10.
* Description : MainAdapter
*/
public class MainAdapter extends RecyclerView.Adapter {
private Context mContext;
private float downX ; //按下时 的X坐标
private float downY ; //按下时 的Y坐标
private int currentPosition;
private int mOriginSize;
private List dataList=new ArrayList<>();
public MainAdapter(Context context,List list) {
this.mContext=context;
dataList.addAll(list);
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(mContext).inflate(R.layout.layout_main_star1, parent, false);
return new MainStarViewHolder(view);
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
// 所以在空白的左右两侧各填充了透明的View(StarView自定义View拦截左右方向滑动事件),用于交互,左侧View向右滑动和点击ViewPager切换
// ,右侧View向左滑动和点击切换ViewPager,其它不做处理
final MainStarViewHolder mainStarHolder = (MainStarViewHolder) holder;
mainStarHolder.mViewPager.setPageTransformer(true, new RotationPageTransformer());
mainStarHolder.mViewPager.setOffscreenPageLimit(2);
DisplayMetrics dm = mContext.getApplicationContext().getResources().getDisplayMetrics();
//不同分辨率适配
int width = dm.widthPixels;
if (width > 800 && width <= 1080) {
mainStarHolder.mViewPager.setPageMargin(-200);
} else if (width > 1080) {
mainStarHolder.mViewPager.setPageMargin(-280);
} else {
mainStarHolder.mViewPager.setPageMargin(-180);
}
mainStarHolder.viewLeft.setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) { //左侧透明View仅在向右滑时切换ViewPager
float x= event.getX();
float y = event.getY();
switch (event.getAction()){
case MotionEvent.ACTION_DOWN:
//将按下时的坐标存储
downX = x;
downY = y;
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:
//获取到距离差
float dx= x-downX;
float dy = y-downY;
//防止是按下也判断
//通过距离差判断方向
int orientation = getOrientation(dx, dy);
switch (orientation) {
case 'r': //向右滑动
mainStarHolder.mViewPager.setCurrentItem(mainStarHolder.mViewPager.getCurrentItem()-1,true);
return true;
case '0': //点击
mainStarHolder.mViewPager.setCurrentItem(mainStarHolder.mViewPager.getCurrentItem()-1,true);
return true;
case 'l': //向左滑动
return true;
}
break;
}
return true;
}
});
mainStarHolder.viewRight.setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) { //右侧透明View仅在向右滑时切换ViewPager
float x= event.getX();
float y = event.getY();
switch (event.getAction()){
case MotionEvent.ACTION_DOWN:
//将按下时的坐标存储
downX = x;
downY = y;
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:
//获取到距离差
float dx= x-downX;
float dy = y-downY;
//通过距离差判断方向
int orientation = getOrientation(dx, dy);
switch (orientation) {
case 'r': //向右滑动
return true;
case '0': //点击
mainStarHolder.mViewPager.setCurrentItem(mainStarHolder.mViewPager.getCurrentItem()+1,true);
return true;
case 'l': //向左滑动
if(event.getAction()== MotionEvent.ACTION_UP || event.getAction()== MotionEvent.ACTION_CANCEL ){
mainStarHolder.mViewPager.setCurrentItem(mainStarHolder.mViewPager.getCurrentItem()+1,true);
}
return true;
}
break;
}
return true;
}
});
mOriginSize = dataList.size();
initStarAdapter(mainStarHolder, dataList);
mainStarHolder.mViewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
@Override
public void onPageSelected(int position) {
currentPosition = position;
mainStarHolder.mViewPager.setTranslationX(1);
}
@Override
public void onPageScrollStateChanged(int state) {
}
});
}
@Override
public int getItemCount() {
return 1;
}
private void initStarAdapter(MainStarViewHolder mainStarHolder, List dataList) {
final MainStarAdapter mainStarAdapter = new MainStarAdapter(dataList, mContext, mainStarHolder.mViewPager, mOriginSize);
mainStarHolder.mViewPager.setAdapter(mainStarAdapter);
mainStarHolder.mViewPager.setCurrentItem( 20*mOriginSize + currentPosition);
}
//获取滑动方向
private int getOrientation(float dx, float dy) {
if (Math.abs(dx)>Math.abs(dy)){
//X轴移动
if(dx==0){//点击
return '0';
}
return dx>0?'r':'l';
}else{
//Y轴移动
if(dy==0){//点击
return '0';
}
return dy>0?'b':'t';
}
}
}
最核心的逻辑:如果用Android原生的ViewPager来实现你会发现左边的Item会覆盖在中间的Item之上.所以我们要自定义一下ViewPager,重写一下他的排序方法:
import android.content.Context;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.util.SparseArray;
import android.view.View;
import java.util.ArrayList;
import java.util.Collections;
/**
* Created by LWJ.
*/
public class CustomViewPager extends ViewPager {
private ArrayList childCenterXAbs = new ArrayList<>();
private SparseArray childIndex = new SparseArray<>();
public CustomViewPager(Context context) {
super(context);
init();
}
public CustomViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
private void init(){
setClipToPadding(false);
setOverScrollMode(OVER_SCROLL_NEVER);
}
/**
* @param childCount
* @param n
* @return 第n个位置的child 的绘制索引
*/
@Override
protected int getChildDrawingOrder(int childCount, int n) {
if (n == 0 || childIndex.size() != childCount) {
childCenterXAbs.clear();
childIndex.clear();
int viewCenterX = getViewCenterX(this);
for (int i = 0; i < childCount; ++i) {
int indexAbs = Math.abs(viewCenterX - getViewCenterX(getChildAt(i)));
//两个距离相同，后来的那个做自增，从而保持abs不同
if (childIndex.get(indexAbs) != null) {
++indexAbs;
}
childCenterXAbs.add(indexAbs);
childIndex.append(indexAbs, i);
}
Collections.sort(childCenterXAbs);//1,0,2 0,1,2
}
//那个item距离中心点远一些，就先draw它。（最近的就是中间放大的item,最后draw）
return childIndex.get(childCenterXAbs.get(childCount - 1 - n));
}
private int getViewCenterX(View view) {
int[] array = new int[2];
view.getLocationOnScreen(array);
return array[0] + view.getWidth() / 2;
}
}
后续会整理一些项目中比较实用的代码,不喜勿喷.
完整代码请移步github