使用Volley加载图片列表

Android开发者可能会使用Universal Image Loader或者Square`s
newer Picasso这些第三方的库去处理图片的加载，那么Volley是怎么加载图片列表的呢，这一篇文章会介绍使用Volley加载图片列表。

在Google I/O介绍Volley的时候，Ficus Kirpatrick讲了很多关于Volley如何的有助于图片加载。但是，你会发现在Volley作为图片加载解决方案的时候，Volley虽然自己处理了L2的缓存，可是它没有处理L1的缓存。它给出了ImageCache接口类，让开发者自己根据自己的需求实现自己L1缓存，这样你可以实现LRU、FIFO等算法的缓存。

Volley加载图片时需要使用ImageLoader，ImageLoader初始化一次。展示图片的View可以使用ImageView或者Volley自定义的NetworkImageView。NetworkImageView可以使用setUrl方法获取图片。下面为两种View加载图片的方式。

使用ImageView：

[java] view
plaincopyprint?

public class VolleyImageViewListAdapter extends BaseAdapter{

private static final String TAG = "VolleyListAdapter";

private Context mContext;

private String[] urlArrays;

private ImageLoader mImageLoader;

public VolleyImageViewListAdapter(Context context, String []url) {

this.mContext = context;

urlArrays = url;

RequestQueue mQueue = Volley.newRequestQueue(context);

mImageLoader = new ImageLoader(mQueue, new BitmapCache());

}

@Override

public int getCount() {

return urlArrays.length;

}

@Override

public Object getItem(int position) {

return position;

}

@Override

public long getItemId(int position) {

return position;

}

@Override

public View getView(int position, View convertView, ViewGroup parent) {

ViewHolder viewHolder = null;

if (convertView == null) {

convertView = LayoutInflater.from(mContext).inflate(

R.layout.volley_image_list_item, null);

viewHolder = new ViewHolder();

viewHolder.mTextView = (TextView) convertView

.findViewById(R.id.tv_tips);

viewHolder.mImageView = (ImageView) convertView

.findViewById(R.id.iv_image);

convertView.setTag(viewHolder);

} else {

viewHolder = (ViewHolder) convertView.getTag();

}

String url = "";

url = urlArrays[position % urlArrays.length];

viewHolder.mTextView.setText(position+"|"+urlArrays.length) ;

ImageListener listener = ImageLoader.getImageListener(viewHolder.mImageView, android.R.drawable.ic_menu_rotate, android.R.drawable.ic_delete);

mImageLoader.get(url, listener);

return convertView;

}

static class ViewHolder {

TextView mTextView;

ImageView mImageView;

}

public class BitmapCache implements ImageCache {

private LruCache<String, Bitmap> mCache;

public BitmapCache() {

int maxSize = 10 * 1024 * 1024;

mCache = new LruCache<String, Bitmap>(maxSize) {

@Override

protected int sizeOf(String key, Bitmap value) {

return value.getRowBytes() * value.getHeight();

}

};

}

@Override

public Bitmap getBitmap(String url) {

return mCache.get(url);

}

@Override

public void putBitmap(String url, Bitmap bitmap) {

mCache.put(url, bitmap);

}

}

}

使用NetworkImageView：

[java] view
plaincopyprint?

public class VolleyListAdapter extends BaseAdapter{

private static final String TAG = "VolleyListAdapter";

private Context mContext;

private String[] urlArrays;

public VolleyListAdapter(Context context, String []url) {

this.mContext = context;

urlArrays = url;

}

@Override

public int getCount() {

return urlArrays.length;

}

@Override

public Object getItem(int position) {

return position;

}

@Override

public long getItemId(int position) {

return position;

}

@Override

public View getView(int position, View convertView, ViewGroup parent) {

ViewHolder viewHolder = null;

if (convertView == null) {

convertView = LayoutInflater.from(mContext).inflate(

R.layout.volley_list_item, null);

viewHolder = new ViewHolder();

viewHolder.mTextView = (TextView) convertView

.findViewById(R.id.tv_tips);

viewHolder.mImageView = (NetworkImageView) convertView

.findViewById(R.id.iv_image);

convertView.setTag(viewHolder);

} else {

viewHolder = (ViewHolder) convertView.getTag();

}

String url = "";

url = urlArrays[position % urlArrays.length];

viewHolder.mTextView.setText(position+"|"+urlArrays.length) ;

viewHolder.mImageView.setImageUrl(url, ImageCacheManager.getInstance().getImageLoader());

return convertView;

}

static class ViewHolder {

TextView mTextView;

NetworkImageView mImageView;

}

}

效果图：