我正在使用Retrofit来调用FlickR API，并且我已成功设置了所有模型类。
我正在尝试访问Photos数组中每张Photo的m_url值。不幸的是，Retrofit响应正在生成一个空对象：
我正在使用Retrofit和FlickRAPI查询FlickR数据库中的照片。
型号：
照片：
public class Photos {
@SerializedName("page")
@Expose
private int page;
@SerializedName("pages")
@Expose
private int pages;
@SerializedName("perpage")
@Expose
private int perpage;
@SerializedName("total")
@Expose
private String total;
@SerializedName("photo")
@Expose
private List<Photo> photo = new ArrayList<Photo>();
/**
*
* @return
* The page
*/
public int getPage() {
return page;
}
/**
*
* @param page
* The page
*/
public void setPage(int page) {
this.page = page;
}
/**
*
* @return
* The pages
*/
public int getPages() {
return pages;
}
/**
*
* @param pages
* The pages
*/
public void setPages(int pages) {
this.pages = pages;
}
/**
*
* @return
* The perpage
*/
public int getPerpage() {
return perpage;
}
/**
*
* @param perpage
* The perpage
*/
public void setPerpage(int perpage) {
this.perpage = perpage;
}
/**
*
* @return
* The total
*/
public String getTotal() {
return total;
}
/**
*
* @param total
* The total
*/
public void setTotal(String total) {
this.total = total;
}
/**
*
* @return
* The photo
*/
public List<Photo> getPhoto() {
return photo;
}
/**
*
* @param photo
* The photo
*/
public void setPhoto(List<Photo> photo) {
this.photo = photo;
}
}
照片：
public class Photo {
@SerializedName("id")
@Expose
private String id;
@SerializedName("owner")
@Expose
private String owner;
@SerializedName("secret")
@Expose
private String secret;
@SerializedName("server")
@Expose
private String server;
@SerializedName("farm")
@Expose
private int farm;
@SerializedName("title")
@Expose
private String title;
@SerializedName("ispublic")
@Expose
private int ispublic;
@SerializedName("isfriend")
@Expose
private int isfriend;
@SerializedName("isfamily")
@Expose
private int isfamily;
@SerializedName("url_m")
@Expose
private String urlM;
@SerializedName("height_m")
@Expose
private String heightM;
@SerializedName("width_m")
@Expose
private String widthM;
/**
* @return The id
*/
public String getId() {
return id;
}
/**
* @param id The id
*/
public void setId(String id) {
this.id = id;
}
/**
* @return The owner
*/
public String getOwner() {
return owner;
}
/**
* @param owner The owner
*/
public void setOwner(String owner) {
this.owner = owner;
}
/**
* @return The secret
*/
public String getSecret() {
return secret;
}
/**
* @param secret The secret
*/
public void setSecret(String secret) {
this.secret = secret;
}
/**
* @return The server
*/
public String getServer() {
return server;
}
/**
* @param server The server
*/
public void setServer(String server) {
this.server = server;
}
/**
* @return The farm
*/
public int getFarm() {
return farm;
}
/**
* @param farm The farm
*/
public void setFarm(int farm) {
this.farm = farm;
}
/**
* @return The title
*/
public String getTitle() {
return title;
}
/**
* @param title The title
*/
public void setTitle(String title) {
this.title = title;
}
/**
* @return The ispublic
*/
public int getIspublic() {
return ispublic;
}
/**
* @param ispublic The ispublic
*/
public void setIspublic(int ispublic) {
this.ispublic = ispublic;
}
/**
* @return The isfriend
*/
public int getIsfriend() {
return isfriend;
}
/**
* @param isfriend The isfriend
*/
public void setIsfriend(int isfriend) {
this.isfriend = isfriend;
}
/**
* @return The isfamily
*/
public int getIsfamily() {
return isfamily;
}
/**
* @param isfamily The isfamily
*/
public void setIsfamily(int isfamily) {
this.isfamily = isfamily;
}
/**
* @return The urlM
*/
public String getUrlM() {
return urlM;
}
/**
* @param urlM The url_m
*/
public void setUrlM(String urlM) {
this.urlM = urlM;
}
/**
* @return The heightM
*/
public String getHeightM() {
return heightM;
}
/**
* @param heightM The height_m
*/
public void setHeightM(String heightM) {
this.heightM = heightM;
}
/**
* @return The widthM
*/
public String getWidthM() {
return widthM;
}
/**
* @param widthM The width_m
*/
public void setWidthM(String widthM) {
this.widthM = widthM;
}
}
JSON响应：
{
photos: {
page: 1,
pages: 3683,
perpage: 100,
total: "368270",
photo: [
{
id: "29264707352",
owner: "84316756@N02",
secret: "9ed355a86e",
server: "8603",
farm: 9,
title: "Tercer Patio de los Claustros de la Compañía/ Arequipa",
ispublic: 1,
isfriend: 0,
isfamily: 0,
url_m: "https://farm9.staticflickr.com/8603/29264707352_9ed355a86e.jpg",
height_m: "500",
width_m: "333"
},
{
id: "29339070436",
owner: "146617764@N02",
secret: "b52f1e9914",
server: "8509",
farm: 9,
title: "2016-04-17 09.24.07",
ispublic: 1,
isfriend: 0,
isfamily: 0,
url_m: "https://farm9.staticflickr.com/8509/29339070436_b52f1e9914.jpg",
height_m: "281",
width_m: "500"
},
最终，我想得到照片的url_m，这是我的代码：
call.enqueue(new Callback<Photos>() {
@Override
public void onResponse(Call<Photos> call, Response<Photos> response) {
Log.v("RESPONSE_CALLED", "ON_RESPONSE_CALLED");
List<Photo> photoResults = response.body().getPhoto();
Log.v("PHOTO_TOTALS", response.body().getTotal());
for (Photo photo : photoResults) {
Log.v("PHOTO_URL:", photo.getUrlM()
);
}
}
@Override
public void onFailure(Call<Photos> call, Throwable t) {
}
});
现在，我收到一个NullPointer：
08-31 21:31:39.425 2526-2526/com.troychuinard.flickr_test E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.troychuinard.flickr_test, PID: 2526
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.String.toString()' on a null object reference
at com.troychuinard.flickr_test.MainActivity$1$1.onResponse(MainActivity.java:65)
at retrofit2.ExecutorCallAdapterFactory$ExecutorCallbackCall$1$1.run(ExecutorCallAdapterFactory.java:68)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)