我想用Volley建立我的休息客户端。我找到了一些很好的例子（下面发布），除了缓存之外，它完全符合我的要求。我想将结果缓存到sdcard并在启动应用程序时加载缓存的结果。有关如何修改下面的代码以启用列表视图项的文本和图像的缓存的任何线索吗？
/**
* Demonstrates: 1. ListView which is populated by HTTP paginated requests; 2. Usage of NetworkImageView;
* 3. "Endless" ListView pagination with read-ahead
*
* Please note that for production environment you will need to add functionality like handling rotation,
* showing/hiding (indeterminate) progress indicator while loading, indicating that there are no more records, etc...
*
* @author Ognyan Bankov (ognyan.bankov@bulpros.com)
*
*/
public class Act_NetworkListView extends Activity {
private static final int RESULTS_PAGE_SIZE = 20;
private ListView mLvPicasa;
private boolean mHasData = false;
private boolean mInError = false;
private ArrayList<PicasaEntry> mEntries = new ArrayList<PicasaEntry>();
private PicasaArrayAdapter mAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.act__network_list_view);
mLvPicasa = (ListView) findViewById(R.id.lv_picasa);
mAdapter = new PicasaArrayAdapter(this, 0, mEntries, new ImageLoader(queue, new BitmapCache(4)));
mLvPicasa.setAdapter(mAdapter);
mLvPicasa.setOnScrollListener(new EndlessScrollListener());
}
@Override
protected void onResume() {
super.onResume();
if (!mHasData && !mInError) {
loadPage();
}
}
RequestQueue queue;
private void loadPage() {
queue = MyVolley.getRequestQueue();
int startIndex = 1 + mEntries.size();
JsonObjectRequest myReq = new JsonObjectRequest(Method.GET,
"https://picasaweb.google.com/data/feed/api/all?q=kitten&max-results="
+
RESULTS_PAGE_SIZE
+
"&thumbsize=160&alt=json"
+ "&start-index="
+ startIndex,
null,
createMyReqSuccessListener(),
createMyReqErrorListener());
if (myReq.getCacheEntry().data != null) {
}
queue.add(myReq);
}
private Response.Listener<JSONObject> createMyReqSuccessListener() {
return new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
try {
JSONObject feed = response.getJSONObject("feed");
JSONArray entries = feed.getJSONArray("entry");
JSONObject entry;
for (int i = 0; i < entries.length(); i++) {
entry = entries.getJSONObject(i);
String url = null;
JSONObject media = entry.getJSONObject("media$group");
if (media != null && media.has("media$thumbnail")) {
JSONArray thumbs = media.getJSONArray("media$thumbnail");
if (thumbs != null && thumbs.length() > 0) {
url = thumbs.getJSONObject(0).getString("url");
}
}
mEntries.add(new PicasaEntry(entry.getJSONObject("title").getString("$t"), url));
}
mAdapter.notifyDataSetChanged();
} catch (JSONException e) {
showErrorDialog();
}
}
};
}
private Response.ErrorListener createMyReqErrorListener() {
return new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
showErrorDialog();
}
};
}
private void showErrorDialog() {
mInError = true;
AlertDialog.Builder b = new AlertDialog.Builder(Act_NetworkListView.this);
b.setMessage("Error occured");
b.show();
}
/**
* Detects when user is close to the end of the current page and starts loading the next page
* so the user will not have to wait (that much) for the next entries.
*
* @author Ognyan Bankov (ognyan.bankov@bulpros.com)
*/
public class EndlessScrollListener implements OnScrollListener {
// how many entries earlier to start loading next page
private int visibleThreshold = 5;
private int currentPage = 0;
private int previousTotal = 0;
private boolean loading = true;
public EndlessScrollListener() {
}
public EndlessScrollListener(int visibleThreshold) {
this.visibleThreshold = visibleThreshold;
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
if (loading) {
if (totalItemCount > previousTotal) {
loading = false;
previousTotal = totalItemCount;
currentPage++;
}
}
if (!loading && (totalItemCount - visibleItemCount) <= (firstVisibleItem + visibleThreshold)) {
// I load the next page of gigs using a background task,
// but you can call any function here.
loadPage();
loading = true;
}
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
}
public int getCurrentPage() {
return currentPage;
}
}
适配器：
public class PicasaArrayAdapter extends ArrayAdapter<PicasaEntry> {
private ImageLoader mImageLoader;
public PicasaArrayAdapter(Context context,
int textViewResourceId,
List<PicasaEntry> objects,
ImageLoader imageLoader
) {
super(context, textViewResourceId, objects);
mImageLoader = imageLoader;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View v = convertView;
if (v == null) {
LayoutInflater vi = (LayoutInflater) this.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
v = vi.inflate(R.layout.lv_picasa_row, null);
}
ViewHolder holder = (ViewHolder) v.getTag(R.id.id_holder);
if (holder == null) {
holder = new ViewHolder(v);
v.setTag(R.id.id_holder, holder);
}
PicasaEntry entry = getItem(position);
if (entry.getThumbnailUrl() != null) {
holder.image.setImageUrl(entry.getThumbnailUrl(), mImageLoader);
} else {
holder.image.setImageResource(R.drawable.no_image);
}
holder.title.setText(entry.getTitle());
return v;
}
private class ViewHolder {
NetworkImageView image;
TextView title;
public ViewHolder(View v) {
image = (NetworkImageView) v.findViewById(R.id.iv_thumb);
title = (TextView) v.findViewById(R.id.tv_title);
v.setTag(this);
}
}
}
答案 0 :(得分：2)
使用volley这很容易，因为内置了缓存。您只需要使用请求的url调用getCache。当然要记住，服务器负责设置缓存的最大年龄，如果时间过去，则清除缓存
例如试试这个：
if(queue.getCache().get(url)!=null){
//response exists
String cachedResponse = new String(queue.getCache().get(url).data);
}else{
//no response
queue.add(stringRequest);
}
对于缓存来说，使用VolleyExtended很有用：eu.the4thfloor.volleyextended有更新的Response侦听器，你可以在其中获得额外的布尔值更改，这意味着如果响应与缓存中的最后一个响应不同。在错误响应时，还有其他参数响应（缓存），您可以在服务器或网络外出时使用它。当然，如果它只是缓存。
private class ResponseListenerYYY extends Api.ResponseListener {
@Override
public void onResponse(String response, boolean changed) {
}
@Override
public void onErrorResponse(VolleyError error, String response) {
}
}