/**
* Adapter for grid of coupons.
*/
private static class CouponAdapter extends BaseAdapter { private LayoutInflater mInflater;
private List<Coupon> mAllCoupons; /**
* Constructs a new {@link CouponAdapter}.
*
* @param inflater to create new views
* @param allCoupons for list of all coupons to be displayed
*/
public CouponAdapter(LayoutInflater inflater, List<Coupon> allCoupons) {
if (allCoupons == null) {
throw new IllegalStateException("Can't have null list of coupons");
}
mAllCoupons = allCoupons;
mInflater = inflater;
} @Override
public int getCount() {
return mAllCoupons.size();
} @Override
public Coupon getItem(int position) {
return mAllCoupons.get(position);
} @Override
public long getItemId(int position) {
return position;
} @Override
public View getView(int position, View convertView, ViewGroup parent) { //缓存策略的另外一种写法 View result = convertView;
if (result == null) {
//注意mInflater的来源，是在Activity的setContextView中这样写的：
// Fetch the {@link LayoutInflater} service so that new views can be created
// LayoutInflater inflater = (LayoutInflater) getSystemService(
// Context.LAYOUT_INFLATER_SERVICE);
result = mInflater.inflate(R.layout.grid_item, parent, false);
} // Try to get view cache or create a new one if needed
ViewCache viewCache = (ViewCache) result.getTag();
if (viewCache == null) {
viewCache = new ViewCache(result);
result.setTag(viewCache);
} // Fetch item
Coupon coupon = getItem(position); // Bind the data
viewCache.mTitleView.setText(coupon.mTitle);
viewCache.mSubtitleView.setText(coupon.mSubtitle);
viewCache.mImageView.setImageURI(coupon.mImageUri); return result;
}
} /**
* Cache of views in the grid item view to make recycling of views quicker. This avoids
* additional {@link View#findViewById(int)} calls after the {@link ViewCache} is first
* created for a view. See
* {@link CouponAdapter#getView(int position, View convertView, ViewGroup parent)}.
*/
private static class ViewCache { /** View that displays the title of the coupon */
private final TextView mTitleView; /** View that displays the subtitle of the coupon */
private final TextView mSubtitleView; /** View that displays the image associated with the coupon */
private final ImageView mImageView; /**
* Constructs a new {@link ViewCache}.
*
* @param view which contains children views that should be cached.
*/
private ViewCache(View view) {
mTitleView = (TextView) view.findViewById(R.id.title);
mSubtitleView = (TextView) view.findViewById(R.id.subtitle);
mImageView = (ImageView) view.findViewById(R.id.image);
}
} /**
* 关于适配器里面数据bean对象问题，如果只是纯粹展示，而不需要改变bean对象的属性，那么推荐下面这种方式，如果需要改变
* bean对象的属性，那么还是用常见的get set方法实现.
*/
private static class Coupon { /** Title of the coupon. */
private final String mTitle; /** Description of the coupon. */
private final String mSubtitle; /** Content URI of the image for the coupon. */
private final Uri mImageUri; /**
* Constructs a new {@link Coupon}.
*
* @param titleString is the title
* @param subtitleString is the description
* @param imageAssetFilePath is the file path from the application's assets folder for
* the image associated with this coupon
*/
private Coupon(String titleString, String subtitleString, String imageAssetFilePath) {
mTitle = titleString;
mSubtitle = subtitleString;
mImageUri = Uri.parse("content://" + AssetProvider.CONTENT_URI + "/" +
imageAssetFilePath);
}
}