最近在学习的时候碰到了ViewPager的无限滑动问题,百度了一下,在一篇文章上看到了一张图,然后恍然大悟,图片在下面,贴上原图地址http://www.cnblogs.com/xinye/archive/2013/06/09/3129140.html
然后下面是我自己写的一个无限滑动的例子,下面这是一个PagerAdapter,需要传进一个图片链接数组
package com.example.admin.kaolafm.discover.adapter;
import android.content.Context;
import android.support.v4.view.PagerAdapter;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import com.nostra13.universalimageloader.core.ImageLoader;
import java.util.ArrayList;
import java.util.List;
/**
* ViewPager的每一页只有一张图片的情况下使用这个adapter
* Created by admin on 2016/8/11.
*/
public class ImageViewAdapter extends PagerAdapter {
//用一个数组来保存imageview,并在imageview设置图片
private List<ImageView> viewList = new ArrayList<>();
private Context context;
private List<String> urlList;
public ImageViewAdapter(Context context, List<String> data) {
this.context = context;
this.urlList = data;
}
@Override
public int getCount() {
return urlList == null ? 0 : (urlList.size() + 2);
}
@Override
public boolean isViewFromObject(View view, Object object) {
return view == object;
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
ImageView imageView;
//这里是为了传数据只需要传图片链接所写的ImageView的创建
if (viewList.size() == (urlList.size() + 2)) {
imageView = viewList.get(position);
} else {
imageView = new ImageView(context);
container.addView(imageView);
if (position == 0) {
ImageLoader.getInstance().displayImage(urlList.get(urlList.size() - 1), imageView);
} else if (position == urlList.size() + 1) {
ImageLoader.getInstance().displayImage(urlList.get(0), imageView);
} else {
ImageLoader.getInstance().displayImage(urlList.get(position - 1), imageView);
}
imageView.setScaleType(ImageView.ScaleType.FIT_XY);
viewList.add(imageView);
}
//如果图片因为网络原因没有下载下来,在这里在此下载
if (viewList.get(position).getDrawable() == null) {
if (position == 0) {
ImageLoader.getInstance().displayImage(urlList.get(urlList.size() - 1), imageView);
} else if (position == urlList.size() + 1) {
ImageLoader.getInstance().displayImage(urlList.get(0), imageView);
} else {
ImageLoader.getInstance().displayImage(urlList.get(position - 1), imageView);
}
}
return imageView;
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
//因为没有一直添加控件,所以不需要移除
// ImageView imageView = viewList.get(position);
// container.removeView((View) object);
}
}
下面是Activity中ViewPager的监听
ImageViewAdapter imagePagerAdapter = new ImageViewAdapter(getContext(), urlList);
viewPager.setAdapter(imagePagerAdapter);
//这里默认显示第一页,ViwePager下标从零开始
viewPager.setCurrentItem(1, false);
viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
//因为这里是采用cabca的形式,所以默认显示a,所以滑动到第二个a的时候让页面无效果跳到第一个a;
// 同理,如果往右滑动,从第一个a滑动到第一个c的时候,需要无跳动效果的跳到第二个c,这样就实现了无限滑动
if (position == urlList.size() + 1) {
viewPager.setCurrentItem(1, false);
//将tabLayout滑块绑定到viewPager
tabLayout.setScrollPosition(0, positionOffset, true);
} else if (position == 0 && positionOffset == 0) {
viewPager.setCurrentItem(urlList.size(), false);
tabLayout.setScrollPosition(urlList.size() + 1, positionOffset, true);
} else {
tabLayout.setScrollPosition(position - 1, positionOffset, true);
}
}
@Override
public void onPageSelected(int position) {
//手动滑动 更新position
playPosition = position;
}
@Override
public void onPageScrollStateChanged(int state) {
}
});
新手写的代码比较渣,还望路过的各路大神指导一下