最近在學習的時候碰到了ViewPager的無限滑動問題,百度了一下,在一篇文章上看到了一張圖,然後恍然大悟,圖檔在下面,貼上原圖位址http://www.cnblogs.com/xinye/archive/2013/06/09/3129140.html
然後下面是我自己寫的一個無限滑動的例子,下面這是一個PagerAdapter,需要傳進一個圖檔連結數組
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的每一頁隻有一張圖檔的情況下使用這個adapter
* Created by admin on 2016/8/11.
*/
public class ImageViewAdapter extends PagerAdapter {
//用一個數組來儲存imageview,并在imageview設定圖檔
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;
//這裡是為了傳資料隻需要傳圖檔連結所寫的ImageView的建立
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);
}
//如果圖檔因為網絡原因沒有下載下傳下來,在這裡在此下載下傳
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) {
//因為沒有一直添加控件,是以不需要移除
// ImageView imageView = viewList.get(position);
// container.removeView((View) object);
}
}
下面是Activity中ViewPager的監聽
ImageViewAdapter imagePagerAdapter = new ImageViewAdapter(getContext(), urlList);
viewPager.setAdapter(imagePagerAdapter);
//這裡預設顯示第一頁,ViwePager下标從零開始
viewPager.setCurrentItem(1, false);
viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
//因為這裡是采用cabca的形式,是以預設顯示a,是以滑動到第二個a的時候讓頁面無效果跳到第一個a;
// 同理,如果往右滑動,從第一個a滑動到第一個c的時候,需要無跳動效果的跳到第二個c,這樣就實作了無限滑動
if (position == urlList.size() + 1) {
viewPager.setCurrentItem(1, false);
//将tabLayout滑塊綁定到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) {
//手動滑動 更新position
playPosition = position;
}
@Override
public void onPageScrollStateChanged(int state) {
}
});
新手寫的代碼比較渣,還望路過的各路大神指導一下