用gallery展示图片，实现中间图片稍大，两边较小的效果

实现原理：在onItemSelected事件中，选中galerry中的图片时，把选中的图片放大，把没有选中的缩小。

以下是关键代码

 1     public void onItemSelected(AdapterView<?> parent, View view, int position,
 2             long id) {
 3         // 选中Gallery中某个图像时，放大显示该图像
 4         ImageView imageview = (ImageView)view;
 5         ((ImageView) view).setImageDrawable((Drawable) product_image_list.get(position));
 6         view.setLayoutParams(new Gallery.LayoutParams(520 / 2, 318 / 2));
 7         title.setText((String)product_title.get(position));
 8         info.setText((String)product_info.get(position));
 9         for(int i=0; i<parent.getChildCount();i++){
10             //缩小选中图片旁边的图片
11             ImageView local_imageview = (ImageView)parent.getChildAt(i);
12             if(local_imageview!=imageview){
13                 local_imageview.setLayoutParams(new Gallery.LayoutParams(520/4, 318/4));
14                 local_imageview.setScaleType(ImageView.ScaleType.FIT_CENTER);
15             }
16         }
17     }
18     
19     public void onNothingSelected(AdapterView<?> parent)
20     {
21     }
22     
23     public class ImageAdapter extends BaseAdapter
24     {
25         int mGalleryItemBackground;
26         private Context mContext;
27 
28         public ImageAdapter(Context context)
29         {
30             mContext = context;
31 //            TypedArray typedArray = obtainStyledAttributes(R.styleable.Gallery);
32 //            mGalleryItemBackground = typedArray.getResourceId(
33 //                    R.styleable.Gallery_android_galleryItemBackground, 0);                        
34         }
35         
36         public int getCount()
37         {
38             return product_image_list.size();
39         }
40 
41         public Object getItem(int position)
42         {
43             return position;
44         }
45 
46         public long getItemId(int position)
47         {
48             return position;
49         }
50  
51         public View getView(int position, View convertView, ViewGroup parent)
52         {
53             ImageView imageView = new ImageView(mContext);
54             imageView.setLayoutParams(new Gallery.LayoutParams(520/4, 318/4));//默认都是大图
55             imageView.setImageDrawable((Drawable) product_image_list.get(position));
56             imageView.setScaleType(ImageView.ScaleType.FIT_CENTER);
57             return imageView;
58         }
59     }