为什么Volley返回响应对象的空值 [英] Why is Volley returning null value for response object
问题描述
这是我的onResponse
方法
public void onResponse(SongInfo response) {
Log.v("TAG", "Response value is "+String.valueOf(response.artworkUrl30));
// Prints "Response value is null"
}
String.valueOf(response.artworkUrl30))
应该返回一个URL
String.valueOf(response.artworkUrl30))
should return a URL
在这里设置我的请求队列单例
Here I set up my request queue singleton
Static `mRequestQueue` variable and method
public static RequestQueue mRequestQueue;
public static RequestQueue getRequestQueue() {
if (mRequestQueue == null) {
mRequestQueue = Volley.newRequestQueue(MainActivity.getAppContext());
}
return mRequestQueue;
}
我在这里请求获取JSON对象
Here I make the request to get the the JSON object
(实际上, URL 中有多个JSON对象)
(Actually there are multiple JSON object at the URL)
getRequestQueue();
String JSONURL = "https://itunes.apple.com/search?term=michael+jackson";
GsonRequest<SongInfo> myReq = new GsonRequest<SongInfo>(
Request.Method.GET,
JSONURL,
SongInfo.class,
null,
createMyReqSuccessListener(),
createMyReqErrorListener());
mRequestQueue.add(myReq);
这是我使用onResponse
方法的成功响应侦听器
Here is my success response listener with onResponse
method
private Response.Listener<SongInfo> createMyReqSuccessListener() {
return new Response.Listener<SongInfo>() {
@Override
public void onResponse(SongInfo response) {
// Do whatever you want to do with response;
// Like response.tags.getListing_count(); etc. etc.
Log.v("TAG", "This is the value of the string"+String.valueOf(response.artworkUrl30));
}
};
}
这是我的错误监听器
private Response.ErrorListener createMyReqErrorListener() {
return new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
// Do whatever you want to do with error.getMessage();
}
};
}
这是我的GsonRequest
课
public class GsonRequest<T> extends Request<T> {
private final Gson gson = new Gson();
private final Class<T> clazz;
private final Map<String, String> headers;
private final Response.Listener<T> listener; // success listener
/**
* Make a GET request and return a parsed object from JSON.
*
* @param url URL of the request to make
* @param clazz Relevant class object, for Gson's reflection
* @param headers Map of request headers
*/
public GsonRequest(int method,
String url,
Class<T> clazz,
Map<String, String> headers,
Response.Listener<T> listener, // success listener
Response.ErrorListener errorListener) { // error listener
super(method, url, errorListener); // error listener
this.clazz = clazz;
this.headers = headers;
this.listener = listener; // success listener
}
@Override
public Map<String, String> getHeaders() throws AuthFailureError {
return headers != null ? headers : super.getHeaders();
}
@Override
protected void deliverResponse(T response) {
listener.onResponse(response);
}
@Override
protected Response<T> parseNetworkResponse(NetworkResponse response) {
try {
String json = new String(
response.data,
HttpHeaderParser.parseCharset(response.headers));
return Response.success(
gson.fromJson(json, clazz),
HttpHeaderParser.parseCacheHeaders(response));
} catch (UnsupportedEncodingException e) {
return Response.error(new ParseError(e));
} catch (JsonSyntaxException e) {
return Response.error(new ParseError(e));
}
}
}
这是SongInfo
类
public class SongInfo {
public String wrapperType;
public String kind;
public Integer artistId;
public Integer collectionId;
public Integer trackId;
public String artistName;
public String collectionName;
public String trackName;
public String collectionCensoredName;
public String trackCensoredName;
public String artistViewUrl;
public String collectionViewUrl;
public String trackViewUrl;
public String previewUrl;
public String artworkUrl30;
public String artworkUrl60;
public String artworkUrl100;
public Float collectionPrice;
public Float trackPrice;
public String releaseDate;
public String collectionExplicitness;
public String trackExplicitness;
public Integer discCount;
public Integer discNumber;
public Integer trackCount;
public Integer trackNumber;
public Integer trackTimeMillis;
public String country;
public String currency;
public String primaryGenreName;
public String radioStationUrl;
public Boolean isStreamable;
}
推荐答案
我不认为您可以将Json
响应映射为完全平坦,并且所有字段都位于Json
的根层次结构.
I don't think you can just map the Json
response as if it's completely flat, and all fields are located at the root of the Json
hierarchy.
您的SongInfo
模型应该看起来像这样:
Your SongInfo
model should probably look like this:
public class SongInfo {
public int resultCount;
public List<Results> results;
}
您将需要一个Results对象,例如:
And you'll need a Results object, something like:
public class Results {
public String wrapperType;
public String kind;
.
.
.
public String artworkUrl30;
}
这篇关于为什么Volley返回响应对象的空值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IT屋!