本文介绍了volley json缓存图像无法脱机工作的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
你好，我是初学者。我创建了导航抽屉和碎片。我可以使用url从json获取数据。它在网上工作。但离线时手机我正在无法解决主机错误。我想在离线时使用json从url获取数据。这不是缓存
Hello i'm beginner in anroid. I created navigation drawer and fragments. I can getting data from json with url. It's working while online. But phone when offline i'm getting "unable to resolve host" error. I want to get data from url with json while offline. It's not cachingenter image description here
片段
private static final String jsonUrl = "http://sunumsitesi.com/json.php";
private ProgressDialog pDialog;
private List<Urun> urunList = new ArrayList<Urun>();
private ListView listView;
private CustomListAdapter adapter;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
View root = inflater.inflate(R.layout.fragment_yemek, container, false);
return root;
}
@Override
public void onActivityCreated(Bundle savedInstanceState)
{
super.onActivityCreated(savedInstanceState);
View v = getView();
if(v!=null)
{
listView = (ListView) v.findViewById(R.id.yemekList);
adapter = new CustomListAdapter(getActivity(), urunList);
listView.setAdapter(adapter);
pDialog = new ProgressDialog(getActivity());
pDialog.setMessage("Loading...");
pDialog.show();
JsonArrayRequest urunReq = new JsonArrayRequest(jsonUrl, new Response.Listener<JSONArray>()
{
@Override
public void onResponse(JSONArray response)
{
hidePDialog();
for (int i = 0; i < response.length(); i++)
{
try
{
JSONObject obj = response.getJSONObject(i);
Urun urun = new Urun();
urun.setUrun_adi(obj.getString("urun_adi"));
urun.setUrl("http://www.iremdeveci.com/ornekler/resimler/resim.png");//example
urunList.add(urun);
} catch (JSONException ex)
{
ex.printStackTrace();
}
}
adapter.notifyDataSetChanged();
}
}, new Response.ErrorListener()
{
@Override
public void onErrorResponse(VolleyError volleyError)
{
Toast.makeText(getActivity(), volleyError.getMessage(), Toast.LENGTH_LONG).show();
}
});
AppController.getmInstance().addToRequestQueue(urunReq);
}
}
@Override
public void onDestroy()
{
super.onDestroy();
hidePDialog();
}
private void hidePDialog()
{
if(pDialog!=null)
{
pDialog.dismiss();
pDialog=null;
}
}
和CustomListAdapter（扩展BaseAdapter）
and CustomListAdapter(extend BaseAdapter)
private Activity activity;
private LayoutInflater inflater;
private List<Urun> urunItems;
ImageLoader imageLoader = AppController.getmInstance().getmImageLoader();
public CustomListAdapter(Activity activity,List<Urun> urunItems)
{
this.activity=activity;
this.urunItems=urunItems;
}
@Override
public int getCount()
{
return urunItems.size();
}
@Override
public Object getItem(int location)
{
return urunItems.get(location);
}
@Override
public long getItemId(int position)
{
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent)
{
if (inflater==null)
{
inflater=(LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
if (convertView==null)
{
convertView=inflater.inflate(R.layout.list_row,null);
}
if (imageLoader==null)
{
imageLoader=AppController.getmInstance().getmImageLoader();
}
NetworkImageView urunResim=(NetworkImageView)convertView.findViewById(R.id.urunResim);
TextView urun_adi= (TextView)convertView.findViewById(R.id.urun_adi);
Urun u = urunItems.get(position);
urunResim.setImageUrl(u.getUrl(),imageLoader);
urun_adi.setText(u.getUrun_adi());
return convertView;
}
LruBitmapCache.java
LruBitmapCache.java
public static int getDefaultLruCacheSize()
{
final int maxMemory=(int)(Runtime.getRuntime().maxMemory()/1024);
final int cacheSize= maxMemory/8;
return cacheSize;
}
public LruBitmapCache()
{
this(getDefaultLruCacheSize());
}
public LruBitmapCache(int sizeInKiloBytes)
{
super(sizeInKiloBytes);
}
@Override
protected int sizeOf(String key, Bitmap value)
{
return value.getRowBytes() * value.getHeight()/1024;
}
@Override
public Bitmap getBitmap(String url)
{
return get(url);
}
@Override
public void putBitmap(String url, Bitmap bitmap)
{
put(url,bitmap);
}
推荐答案
你的照片（）似乎要正确缓存，因为它有etag和缓存标题。
your pictures(http://www.iremdeveci.com/ornekler/resimler/resim.png) seems to be cached correctly as the have etag and cache headers.
但是你提出的第一个请求（）似乎既没有返回缓存头也没有返回etag。因此，您有错误甚至无法到达图片部分。
However the very first request you make (http://sunumsitesi.com/json.php) doesn't seems to return neither cache headers nor etag. Thus you have the error you dont even reach the picture part.
您可以从服务器修复它或使Volley全部缓存，您需要为此创建自定义请求和覆盖
You can either fix that from the server or make Volley cache it all, for which you need to create custom request and override
protected Response<String> parseNetworkResponse(NetworkResponse response)
您可以检查我的答案。
在你的代码就像这样......
In your code this would be smth like
JsonArrayRequest urunReq = new JsonArrayRequest(jsonUrl, new Response.Listener<JSONArray>()
{
@Override
public void onResponse(JSONArray response)
{
String dosyakonum = "http://www.pukkaliving.concept.com/upload/galeri/buyuk/";
hidePDialog();
for (int i = 0; i < response.length(); i++)
{
try
{
JSONObject obj = response.getJSONObject(i);
Urun urun = new Urun();
urun.setUrun_adi(obj.getString("urun_adi"));
urun.setUrl("http://www.iremdeveci.com/ornekler/resimler/resim.png");//example
urunList.add(urun);
} catch (JSONException ex)
{
ex.printStackTrace();
}
}
adapter.notifyDataSetChanged();
}
}, new Response.ErrorListener()
{
@Override
public void onErrorResponse(VolleyError volleyError)
{
Toast.makeText(getActivity(), volleyError.getMessage(), Toast.LENGTH_LONG).show();
}
}) {
@Override
protected Response<JSONArray> parseNetworkResponse(NetworkResponse response) {
try {
String jsonString =
new String(response.data, HttpHeaderParser.parseCharset(response.headers));
long now = System.currentTimeMillis();
Cache.Entry entry = HttpHeaderParser.parseCacheHeaders(response);
entry.ttl = now + 30l * 24 * 60 * 60 * 1000; //keeps cache for 30 days
entry.softTtl = now + 1 * 24 * 60 * 60 * 1000; //will not try to refresh for 1 day
return Response.success(new JSONArray(jsonString), entry);
} catch (UnsupportedEncodingException e) {
return Response.error(new ParseError(e));
} catch (JSONException je) {
return Response.error(new ParseError(je));
}
}
};
AppController.getmInstance().addToRequestQueue(urunReq);
但是对于NetworkImage视图，您必须自定义 as this this是创建图像请求的那个，然后逻辑是相同的。你必须覆盖makeImageRequest。
however for NetworkImage view you have to customize ImageLoader as this is the one creating the image requests and then the logic is the same. You have to override "makeImageRequest".
ex：
...
mImageLoader = new ImageLoader(this.mRequestQueue,
new LruBitmapCache()) {
@Override
protected Request<Bitmap> makeImageRequest(String requestUrl, int maxWidth, int maxHeight,
ScaleType scaleType, final String cacheKey) {
return new ImageRequest(requestUrl, new Listener<Bitmap>() {
@Override
public void onResponse(Bitmap response) {
onGetImageSuccess(cacheKey, response);
}
}, maxWidth, maxHeight, scaleType, Config.RGB_565, new ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
onGetImageError(cacheKey, error);
}
}){
@Override
public Response<Bitmap> parseNetworkResponse(NetworkResponse response) {
Response<Bitmap> resp = super.parseNetworkResponse(response);
if(!resp.isSuccess()) {
return resp;
}
long now = System.currentTimeMillis();
Cache.Entry entry = resp.cacheEntry;
entry.ttl = now + 30l * 24 * 60 * 60 * 1000; //keeps cache for 30 days
return Response.success(resp.result, entry);
}
};
}
};
...
这篇关于volley json缓存图像无法脱机工作的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！