listview可见再加载图片

对于，listView如果同时含有大量文字和图片，那么对于用户，如果不需要滑动到后面，那么此时去加载网络图片，显然是耗费流量的。

此时可以做一些优化：

             listView.getRefreshableView().setOnScrollListener(new AbsListView.OnScrollListener() {
                 @Override
                 public void onScrollStateChanged(AbsListView view, int scrollState) {
                     switch (scrollState) {
                         case AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL:   //点按屏幕，准备滚动
                             adapter02.setScrolling(true);
                             //        Log.i(MyConfig.TagMain,"1-scrolling...");
                             //设置ListView的状态
                             break;
                         case AbsListView.OnScrollListener.SCROLL_STATE_FLING:   //滚动中
                             adapter02.setScrolling(true);
                             //        Log.i(MyConfig.TagMain,"2-scrolling...");
                             //设置ListView的状态
                             break;
                         case AbsListView.OnScrollListener.SCROLL_STATE_IDLE:   //滚动结束
                             //获取第一个可见的item的position
                             int first = listView.getRefreshableView().getFirstVisiblePosition();
                             //获取最后一个可见的item的position;
                             int last = listView.getRefreshableView().getLastVisiblePosition();
                             //屏幕上可见的item总数
                             int onScreenCount = listView.getRefreshableView().getChildCount();
                             int total = first + last;
                             Log.i(MyConfig.TagMain,"3-first="+first+",last="+last+"，onScreenCount="+onScreenCount+",total="+total);
                             //adapter.setScrolling(false);
                             adapter02.setPositionRange(first,last);
                             adapter02.setScrolling(false);

                             View child;
                             int position;
                             for (int i = 0 ; i < onScreenCount ; i++) {
                                 position = first + i;
                                 if(adapter02.isInPrevPositionRange(position)) {
                                     Log.i(MyConfig.TagMain, "可见单元位置处在上次滚动可是范围内，无需重新加载图片:"+ position);
                                     continue;
                                 }
                                 //获取可见item子项的视图容器对象
                                 Log.i(MyConfig.TagMain, "now position:"+ position);
                                 child = listView.getRefreshableView().getChildAt(i);
                                 RoundImageView headIco = (RoundImageView) child.findViewById(R.id.iv_hint);
                                 ImageView imageView = (ImageView) child.findViewById(R.id.iv);
                                 Log.i(MyConfig.TagMain, "load image i:"+ position);
                                 adapter02.loadImage(headIco,imageView,channelModels,position);
                             }
                             //设置可见listView的维护表
                             break;
                         default:
                             break;
                     }
                 }

                 @Override
                 public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {

                 }
             });

adapter:

 package com.galaxy.adapter;

 import java.util.ArrayList;
 import java.util.List;

 import com.galaxy.activity.LoginActivity;
 import com.galaxy.activity_group.GroupPersonActivity;
 import com.galaxy.content.MyConfig;
 import com.galaxy.models.ChannelModel;
 import com.galaxy.models.User;
 import com.galaxy.net.GetRequestTask;
 import com.galaxy.net.MyBaseClient;
 import com.galaxy.picture.SetImageUtils;
 import com.galaxy.utils.RoundImageView;
 import com.galaxy.yim.R;

 import android.annotation.SuppressLint;
 import android.content.Context;
 import android.content.Intent;
 import android.graphics.drawable.Drawable;
 import android.util.Log;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.BaseAdapter;
 import android.widget.ImageView;
 import android.widget.TextView;
 import android.widget.Toast;

 public class ChannelListAdapter extends BaseAdapter{
     private Context context;
     private List<ChannelModel> mListData;
     //是否滚动中：
     private boolean isScrolling;

     private int mFirstPosition = 0;
     private int mLastPosition = 0;
     private int mPrevFirstPosition = 0;
     private int mPrevLastPosition = 0;

     /**
      * 记录当前已经出现过的item
      */
     private List<Integer> listPosition = new ArrayList<Integer>();

     /**
      * 记录当前已经点赞的列表
      */
     private List<String> listLikes = new ArrayList<>();

     private CallBackSetLikes callBack;
     /**
      * 定义点赞回调接口
      */
     public interface CallBackSetLikes {
         public void setLikes(int position);
     }

     public ChannelListAdapter(Context context, List<ChannelModel> mListData,CallBackSetLikes callBackSetLikes) {
         super();
         this.context = context;
         this.mListData = mListData;
         this.callBack = callBackSetLikes;
         //设置默认显示前两个item
         listPosition.add(0);
         listPosition.add(1);
     }

     public void setScrolling(boolean isScrolling) {
         this.isScrolling = isScrolling;
     }

     /**
      * 设置点赞标志
      * @param position
      */
     public void setListLikes(int position) {
         listLikes.add(mListData.get(position).getPicurl());
     }

     /**
      * 设置滚动后可见的起止项目序号
      *
      * @param first
      * @param last
      */
     public void setPositionRange(int first, int last) {
         // 保存上次滚动后的可见位置
         this.mPrevFirstPosition = this.mFirstPosition;
         this.mPrevLastPosition = this.mLastPosition;
         // 重置当前可见位置
         this.mFirstPosition = first;
         this.mLastPosition = last;
         Log.i(MyConfig.TagMain, "上次可见first: "+ mPrevFirstPosition +", 上次可见last: "+ mPrevLastPosition +", 当前可见first: "+ mFirstPosition +", 当前可见last: "+ mLastPosition);
     }

     /**
      * 可见单元位置对比是否处在在上次滚动可是范围内
      *
      * @param position
      * @return
      */
     public boolean isInPrevPositionRange(int position) {
         if(!listPosition.contains(position)) {
             listPosition.add(position);
         }
         // 初始化时直接返回 false
         if (this.mPrevLastPosition == 0) return false;
         // 检测当前 item 的位置是否在上次滚动范围内, 是则表示该 item 正处于屏幕可见状态中无需重新加载
         return (position >= this.mPrevFirstPosition && position <= this.mPrevLastPosition) ? true : false;
     }

     @Override
     public int getCount() {
         // TODO Auto-generated method stub
         return mListData.size();
     }

     @Override
     public Object getItem(int position) {
         // TODO Auto-generated method stub
         return mListData.get(position);
     }

     @Override
     public long getItemId(int position) {
         // TODO Auto-generated method stub
         return position;
     }

     @SuppressLint("NewApi") @Override
     public View getView(final int position, View convertView, ViewGroup parent) {
         ViewHolder holder = null;
         if (convertView == null) {
             convertView = LayoutInflater.from(context).inflate(R.layout.item_listview_group_channel_list, null);
             holder = new ViewHolder();
             holder.id = position;
             holder.iv_hint = (RoundImageView) convertView.findViewById(R.id.iv_hint);
             holder.tv_username = (TextView) convertView.findViewById(R.id.tv_username);
             holder.tv_sharecounts = (TextView) convertView.findViewById(R.id.tv_sharecounts);
             holder.tv_date = (TextView) convertView.findViewById(R.id.tv_date);
             holder.tv_title = (TextView) convertView.findViewById(R.id.tv_title);
             holder.iv = (ImageView) convertView.findViewById(R.id.iv);
             holder.tv_address = (TextView) convertView.findViewById(R.id.tv_address);
             holder.tv_likes = (TextView) convertView.findViewById(R.id.tv_likes);
             holder.tv_reply = (TextView) convertView.findViewById(R.id.tv_reply);
             convertView.setTag(holder);
         } else {
             holder = (ViewHolder) convertView.getTag();
         }

         if (mListData.size()>0) {
             final ChannelModel model = mListData.get(position);
             final String nickname = model.getNickname();
             String forwarding = model.getForwarding();
             String date = model.getTime();
             String title = model.getTitle();
             String address = model.getAddress();
             String likes = model.getLikes();
             String reply = model.getComments();

             holder.tv_username.setText(nickname);
             holder.tv_sharecounts.setText(forwarding);
             holder.tv_date.setText(date.substring(0,10));
             holder.tv_title.setText(title);
             holder.tv_address.setText(address);

             if(address == null || address.equals("") || address.equals("所在位置")) {
                 holder.tv_address.setVisibility(View.GONE);
             }else{
                 holder.tv_address.setVisibility(View.VISIBLE);
             }
             holder.tv_likes.setText(likes);
             holder.tv_reply.setText(reply);
             //判断当前图片是否有，没有就设置为空
             if(model.getPicurl().equals("")) {
                 holder.iv.setVisibility(View.GONE);
             }else {
                 holder.iv.setVisibility(View.VISIBLE);
             }

             if(listPosition.contains(position)) {
                 this.loadImage(holder.iv_hint,holder.iv,mListData,position);
             }else{
                 //没曾经出现过的item就设置默认图片
                 holder.iv_hint.setImageResource(R.drawable.icon_person);
                 holder.iv.setImageResource(R.drawable.icon_no_photo);
             }

             //判断男女
             String sex = model.getSex();
             if(sex.equals("女")) {
                 Drawable drawable = context.getDrawable(R.drawable.icon_sex_woman);
                 /// 这一步必须要做,否则不会显示.
                 drawable.setBounds(0, 0, drawable.getMinimumWidth(), drawable.getMinimumHeight());
                 holder.tv_username.setCompoundDrawables(null,null,drawable,null);
             }else if(sex.equals("男")){
                 Drawable drawable = context.getDrawable(R.drawable.icon_sex_man);
                 /// 这一步必须要做,否则不会显示.
                 drawable.setBounds(0, 0, drawable.getMinimumWidth(), drawable.getMinimumHeight());
                 holder.tv_username.setCompoundDrawables(null,null,drawable,null);
             }else{
                 holder.tv_username.setCompoundDrawables(null,null,null,null);
             }

             //判断是否已经点赞
             final String mark = model.getMark();
             if(mark.length()>2 ) {
                 Log.i("main",mark+","+mark.length());
                 listLikes.contains(model.getPicurl());
                 Drawable drawable= context.getResources().getDrawable(R.drawable.icon_likes_pressed);
                 /// 这一步必须要做,否则不会显示.
                 drawable.setBounds(0, 0, drawable.getMinimumWidth(), drawable.getMinimumHeight());
                 //        Log.i("main","已点赞"+position);
                 holder.tv_likes.setCompoundDrawables(drawable,null,null,null);
             }else{
                 Drawable drawable= context.getResources().getDrawable(R.drawable.icon_likes);
                 /// 这一步必须要做,否则不会显示.
                 drawable.setBounds(0, 0, drawable.getMinimumWidth(), drawable.getMinimumHeight());
                 //        Log.i("main","已点赞"+position);
                 holder.tv_likes.setCompoundDrawables(drawable,null,null,null);
             }

             holder.tv_likes.setTag(position);
             holder.tv_likes.setOnClickListener(new View.OnClickListener() {
                 @Override
                 public void onClick(View v) {
             //        Toast.makeText(context,"position="+position+",mark="+mark,Toast.LENGTH_SHORT).show();
                     if((!listLikes.contains(model.getPicurl())) && mark.length()<3) {
                         User user = MyConfig.getUser(context);
                         if(user.getUsername().equals("")) {
                             Toast.makeText(context,"请登录",Toast.LENGTH_SHORT).show();
                             Intent intent = new Intent(context,LoginActivity.class);
                             intent.putExtra(MyConfig.IntentPageTitle, "登录");
                             context.startActivity(intent);
                             return;
                         }
                         int id = Integer.valueOf(((TextView)v).getTag().toString());
                         callBack.setLikes(id);
                         Drawable drawable= context.getResources().getDrawable(R.drawable.icon_likes_pressed);
                         /// 这一步必须要做,否则不会显示.
                         drawable.setBounds(0, 0, drawable.getMinimumWidth(), drawable.getMinimumHeight());
                         //        Log.i("main","已点赞"+position);
                         ((TextView)v).setCompoundDrawables(drawable,null,null,null);
                         //标志图片已经更新
                         listLikes.add(model.getPicurl());
                         mListData.get(position).setLikes(Integer.valueOf(model.getLikes())+1+"");
                         mListData.get(position).setMark(context.getString(R.string.group_likes));
                         ((TextView)v).setText(Integer.valueOf(model.getLikes())+"");
                     }else{
                         Toast.makeText(context,context.getString(R.string.group_likes),Toast.LENGTH_SHORT).show();
                     }
                 }
             });

             holder.iv_hint.setOnClickListener(new View.OnClickListener() {
                 @Override
                 public void onClick(View v) {
                     User user = MyConfig.getUser(context);
                     if(user.getUsername().equals("")) {
                         Toast.makeText(context,"请登录",Toast.LENGTH_SHORT).show();
                         Intent intent = new Intent(context,LoginActivity.class);
                         intent.putExtra(MyConfig.IntentPageTitle, "登录");
                         context.startActivity(intent);
                         return;
                     }
                     Intent intent = new Intent(context, GroupPersonActivity.class);
                     intent.putExtra(MyConfig.IntentPageTitle,nickname);
                     intent.putExtra(MyConfig.IntentUrlPic,model.getPortrait());
                     intent.putExtra("username",model.getUsername());    //点击的头像的username
                     context.startActivity(intent);
                 }
             });
         }
         return convertView;
     }

     public void loadImage(RoundImageView head_ico,ImageView pic,List<ChannelModel> mListData,int position) {
         ChannelModel model = mListData.get(position);
         String icoUrl = model.getPortrait();
         String picUrl = model.getPicurl();
         if(!icoUrl.contains("http")) {
             icoUrl = MyConfig.serviceTest + icoUrl;
         }
         // 通过 tag 来防止图片错位
         SetImageUtils.setImageWithTag(icoUrl,head_ico,context);
         head_ico.setTag(icoUrl);

 //        if (head_ico.getTag() != null && head_ico.getTag().equals(icoUrl)) {
 //            SetImageUtils.setImage(icoUrl,head_ico,context);
 //        }

         String[] pics = picUrl.split("\\|");
         if(!pics[0].contains("http")) {
             pics[0] = MyConfig.serviceTest + pics[0];
         }
         SetImageUtils.setImageWithTag(pics[0],pic,context);
         // 通过 tag 来防止图片错位
         pic.setTag(pics[0]);
 //        if (pic.getTag() != null && pic.getTag().equals(pics[0])) {
 //            SetImageUtils.setImage(pics[0],pic,context);
 //            Log.i(MyConfig.TagMain,"loading..."+position+",pics[0]="+pics[0]);
 //        }

     }

     private class ViewHolder{
         int id;
         RoundImageView iv_hint;
         TextView tv_username;
         TextView tv_sharecounts;
         TextView tv_date;
         TextView tv_title;
         ImageView iv;
         TextView tv_address;
         TextView tv_likes;
         TextView tv_reply;
     }

 }

图片加载工具：

 /**
      * 调用display来加载图片，无闪烁
      * @param pic_url
      * @param imageView
      * @param context
      */
     public static void setImageWithTag(final String pic_url,final ImageView imageView,Context context) {
         if(pic_url != null) {
             String tag = (String) imageView.getTag();
             if(tag == null) {
                 tag = "";
             }
             if(pic_url.equals(imageView.getTag())) {
                 return;
             }
         }
         Log.i("main","loading pic:"+pic_url);
         ImageLoader.getInstance().displayImage(pic_url, new ImageViewAware(imageView), MyApplication.commOptionsCache);
     }

 /**
      *用于显示图片的选项,没过渡时间
      * 用于圈子社区，解决列表图片过多时，出现刷新闪烁的情况
      */
     public static DisplayImageOptions commOptionsCache  = new DisplayImageOptions.Builder()
             .showImageOnLoading(R.drawable.icon_no_photo)
             .showImageOnFail(R.drawable.icon_no_photo)
             .showImageForEmptyUri(R.drawable.icon_no_photo)//设置图片Uri为空或是错误的时候显示的图片
             .cacheInMemory(true)
             .cacheOnDisk(true)
             .bitmapConfig(Bitmap.Config.RGB_565)
             .considerExifParams(true)
             .imageScaleType(ImageScaleType.EXACTLY_STRETCHED)
             .resetViewBeforeLoading(false)
             .displayer(new FadeInBitmapDisplayer(0))
             .build();