Android开发之使用GridView展示图片的方法

<GridView
    android:id="@+id/topMerchants"
    style="@style/CustomGridView"
    android:layout_width="fill_parent"
    android:layout_height="0dip"
    android:layout_marginTop="0dip"
    android:layout_weight="1"
    android:columnWidth="50dip"
    android:gravity="center"
    android:horizontalSpacing="5dip"
    android:numColumns="3"
    android:paddingTop="5dip"
    android:stretchMode="columnWidth"
    android:verticalSpacing="5dip"
    android:minHeight="50dip"
    />

public class TopMerchantGridAdapter extends BaseAdapter {
  private List<? extends Object> list;
  private AsyncImageLoader asyncImageLoader;
  private Context context;
  private static int getViewTimes = 0;
  private String TAG = TopMerchantGridAdapter.class.getName();
  public TopMerchantGridAdapter(List<? extends Object> list, Context context) {
    this.list = list;
    this.context = context;
    asyncImageLoader = new AsyncImageLoader();
  }
  @Override
  public int getCount() {
    return list.size();
  }
  @Override
  public Object getItem(int position) {
    return list.get(position);
  }
  @Override
  public long getItemId(int position) {
    return position;
  }
  @Override
  public View getView(int position, View convertView, ViewGroup parent) {
    final ImageView imageView;
    QuhaoLog.i(TAG, "getView times : " + (getViewTimes++));
    QuhaoLog.i(TAG, "getView " + position + " " + convertView);
    Drawable cachedImage = null;
    TopMerchant topMerchant = (TopMerchant) this.getItem(position);
    final int defaultWidth = PhoneTool.getScreenWidth() / 3; // 屏幕宽度的1/3
    final int defaultHight = PhoneTool.getScreenHeight() / 7; // 屏幕高度的1/7
    if (null == convertView) {
      imageView = new ImageView(context);
      imageView.setLayoutParams(new GridView.LayoutParams(defaultWidth, defaultHight));
      imageView.setPadding(8, 8, 8, 8);
    } else {
      imageView = (ImageView) convertView;
    }
    imageView.setScaleType(ImageView.ScaleType.FIT_XY);
    // no content on top merchant grid
    if (StringUtils.isNull(topMerchant.id)) {
      imageView.setImageResource(R.drawable.no_logo);
      return imageView;
    }
    String imageUrl = topMerchant.url;
    QuhaoLog.d(TAG, "asyncImageLoader, the imageUrl is : " + imageUrl);
    if (StringUtils.isNotNull(imageUrl)) {
      cachedImage = asyncImageLoader.loadDrawable(imageUrl, position); //这里是从网络获取图片
      imageView.setImageDrawable(cachedImage);
    }
    return imageView;
  }
  class ViewHolder {
    ImageView img;
    TextView itemView;
    TextView countView;
  }
}

GridView categorysGird = (GridView) findViewById(R.id.categorys);
// 获取到GridView
ListAdapter adapter = new TopMerchantGridAdapter(topMerchants, MainActivity.this);
topMerchantsGird.setAdapter(adapter);
// 设置GridView的数据