动态加载图片的Adapter

package com.example.cc.ecustapp.Adapter;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.graphics.Bitmap;
import android.os.Handler;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.BaseAdapter;
import android.widget.FrameLayout;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.RelativeLayout;
import android.widget.TextView;
import android.view.LayoutInflater;


import com.example.cc.ecustapp.R;
import com.nostra13.universalimageloader.core.ImageLoader;


import java.util.ArrayList;


public class ImageAdapter1 extends BaseAdapter implements OnScrollListener{
    /**
     * 上下文对象的引用 
     */
    private Context context;

    /**
     * Image Url的数组 
     */
    private String [] imageThumbUrls;

    /**
     * GridView对象的应用 
     */
    private NoScrollGridView mGridView;

    /**
     * 记录是否刚打开程序，用于解决进入程序不滚动屏幕，不会下载图片的问题。 
     * 参考http://blog.csdn.net/guolin_blog/article/details/9526203#comments 
     */
    private boolean isFirstEnter = true;

    /**
     * 一屏中第一个item的位置 
     */
    private int mFirstVisibleItem;

    /**
     * 一屏中所有item的个数 
     */
    private int mVisibleItemCount;

    private LayoutInflater mLayoutInflater = null;

    //private ArrayList<ProductEntity> mList=new ArrayList<>();

    private DisplayMetrics displaysMetrics;

    public void setUrls(String[] imageThumbUrls){this.imageThumbUrls=imageThumbUrls;}

    //public void setlist(ArrayList<ProductEntity> list){this.mList=list;}

    public ImageAdapter1(Context context, NoScrollGridView mGridView, String[] imageThumbUrls,DisplayMetrics displayMetrics){
        this.context = context;
        this.mGridView = mGridView;
        this.imageThumbUrls = imageThumbUrls;
     //   this.mList=list;
        isFirstEnter=true;
        mLayoutInflater=LayoutInflater.from(context);
        this.displaysMetrics = displayMetrics;//获取屏幕分辨率
    }

    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) {
        //仅当GridView静止时才去下载图片，GridView滑动时取消所有正在下载的任务
        if(scrollState == AbsListView.OnScrollListener.SCROLL_STATE_IDLE){
            showImage(mFirstVisibleItem, mVisibleItemCount);
        }
    }


    /**
     * GridView滚动的时候调用的方法，刚开始显示GridView也会调用此方法 
     */
    @Override
    public void onScroll(AbsListView view, int firstVisibleItem,
                         int visibleItemCount, int totalItemCount) {
        mFirstVisibleItem = firstVisibleItem;
        mVisibleItemCount = visibleItemCount;
        // 因此在这里为首次进入程序开启下载任务。
        if(isFirstEnter && visibleItemCount > 0){
            showImage(mFirstVisibleItem,mVisibleItemCount);
            isFirstEnter = false;
        }
    }


    @Override
    public int getCount() {
        return imageThumbUrls.length;
    }

    @Override
    public Object getItem(int position) {
        return imageThumbUrls[position];
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, final View convertView, ViewGroup parent) {
        ImageView mImageView;
        TextView tvView;
        final String mImageUrl = imageThumbUrls[position];
      //  final ProductEntity pro;
       // if(!mList.isEmpty()&&mList.get(position)!=null)
       //     pro=mList.get(position);
      //  else
       //     pro=null;
        View view;
        if (convertView == null) {
            view = mLayoutInflater.inflate(R.layout.gridview_item,parent,false);
        } else {
            view = convertView;
        }
        mImageView=(ImageView)view.findViewById(R.id.ItemImage);
        //tvView=(TextView)view.findViewById(R.id.tvTitle);

        //tvView.setText(pro.getProName());
     //   mImageView.setLayoutParams(new RelativeLayout.LayoutParams(displaysMetrics.widthPixels/3,displaysMetrics.heightPixels/5));;
        //给ImageView设置Tag,这里已经是司空见惯了  
        mImageView.setTag(mImageUrl);
        ImageLoader.getInstance().displayImage(mImageUrl, mImageView);
     //   mImageView.setScaleType(ImageView.ScaleType.FIT_XY);
       // mImageView.setOnClickListener(new View.OnClickListener() {
           // @Override
          //  public void onClick(View v) {
            //    Intent intent=new Intent();
         //       intent.putExtra("ProductName",pro.getProName());
          //      intent.setClass(context, ProductdetailActivity.class);
            //    intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            //    context.startActivity(intent);
          //  }
       // });

        return view;
    }

    /**
     * 显示当前屏幕的图片，先会去查找LruCache，LruCache没有就去sd卡或者手机目录查找，在没有就开启线程去下载 
     * @param firstVisibleItem
     * @param visibleItemCount
     */
    public void showImage(int firstVisibleItem, int visibleItemCount){
        for(int i=firstVisibleItem; i<firstVisibleItem + visibleItemCount; i++) {
            final String mImageUrl = imageThumbUrls[i];
            final ImageView mImageView = (ImageView) mGridView.findViewWithTag(mImageUrl);
            ImageLoader.getInstance().displayImage(mImageUrl, mImageView);
        }
    }

}