当我尝试实现Gson类的fromJson方法时，它会给出错误，说包gson不存在。这是我的模型类和主要活动的代码。
public class MainActivity extends AppCompatActivity {
public static final String Logcat = "vmech";
Button searchButton;
EditText editTextSearch;
TextView textViewDisplayResult;
String newText;
String urlstring;
public static final String MyAPIKey = "Your_Api_Key";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
searchButton = (Button) findViewById(R.id.buttonSerch);
editTextSearch = (EditText) findViewById(R.id.editTextSearch);
textViewDisplayResult = (TextView) findViewById(R.id.textViewDisplayResult);
searchButton.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v) {
newText = editTextSearch.getText().toString();
if(newText.length()>0){
newText = newText.replace(" ", "+");
urlstring = "https://www.googleapis.com/books/v1/volumes?q=";
urlstring = urlstring + newText + "&maxResults=5" + "&key=" + MyAPIKey;
}
else {
Toast.makeText(MainActivity.this, "Please enter a book name to search.", Toast.LENGTH_LONG).show();
}
new JSONTask().execute(urlstring);
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu)
{
MenuInflater inflater=getMenuInflater();
inflater.inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item)
{
Toast.makeText(this, "This is the Settings item", Toast.LENGTH_LONG).show();
return true;
}
public class JSONTask extends AsyncTask<String, String, List<BookInfoModel>>{
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected List<BookInfoModel> doInBackground(String... params) {
HttpURLConnection connection = null;
BufferedReader bufferedReader = null;
try {
URL url = new URL(urlstring);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
InputStream inputstream = connection.getInputStream();
bufferedReader = new BufferedReader(new InputStreamReader(inputstream));
StringBuffer stringbuffer = new StringBuffer();
String line = "";
while ((line = bufferedReader.readLine()) != null) {
stringbuffer.append(line);
}
String finalJson = stringbuffer.toString();
JSONObject parentObject = new JSONObject(finalJson);
JSONArray parentArray = parentObject.getJSONArray("items");
List<BookInfoModel> bookInfoModelList = new ArrayList<>();
String idText = null;
Gson gson = new Gson();
for(int i=0; i<parentArray.length(); i++){
JSONObject finalObject = parentArray.getJSONObject(i);
BookInfoModel bookInfoModel = new gson.fromJson(finalObject.toString(),BookInfoModel.class);
bookInfoModelList.add(bookInfoModel);
}
return bookInfoModelList;
} catch (IOException e){
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
} finally {
if (connection != null)
{
connection.disconnect();
}
try {
if (bufferedReader != null){
bufferedReader.close();
}
}catch (IOException e){
e.printStackTrace();
}
}
return null;
}
@Override
protected void onPostExecute(List<BookInfoModel> result) {
super.onPostExecute(result);
textViewDisplayResult.setText((CharSequence) result);
}
}
}
这是我的JSON数据模型类。
public class BookInfoModel {
private List<Items> items;
private String totalItems;
private String kind;
public List<Items> getItems() {
return items;
}
public void setItems(List<Items> items) {
this.items = items;
}
public String getTotalItems ()
{
return totalItems;
}
public void setTotalItems (String totalItems)
{
this.totalItems = totalItems;
}
public String getKind ()
{
return kind;
}
public void setKind (String kind)
{
this.kind = kind;
}
public class Items
{
private SaleInfo saleInfo;
private String id;
private SearchInfo searchInfo;
private String etag;
private VolumeInfo volumeInfo;
private String selfLink;
private AccessInfo accessInfo;
private String kind;
public SaleInfo getSaleInfo ()
{
return saleInfo;
}
public void setSaleInfo (SaleInfo saleInfo)
{
this.saleInfo = saleInfo;
}
public String getId ()
{
return id;
}
public void setId (String id)
{
this.id = id;
}
public SearchInfo getSearchInfo ()
{
return searchInfo;
}
public void setSearchInfo (SearchInfo searchInfo)
{
this.searchInfo = searchInfo;
}
public String getEtag ()
{
return etag;
}
public void setEtag (String etag)
{
this.etag = etag;
}
public VolumeInfo getVolumeInfo ()
{
return volumeInfo;
}
public void setVolumeInfo (VolumeInfo volumeInfo)
{
this.volumeInfo = volumeInfo;
}
public String getSelfLink ()
{
return selfLink;
}
public void setSelfLink (String selfLink)
{
this.selfLink = selfLink;
}
public AccessInfo getAccessInfo ()
{
return accessInfo;
}
public void setAccessInfo (AccessInfo accessInfo)
{
this.accessInfo = accessInfo;
}
public String getKind ()
{
return kind;
}
public void setKind (String kind)
{
this.kind = kind;
}
public class SearchInfo
{
private String textSnippet;
public String getTextSnippet ()
{
return textSnippet;
}
public void setTextSnippet (String textSnippet)
{
this.textSnippet = textSnippet;
}
}
public class AccessInfo
{
private String webReaderLink;
private String textToSpeechPermission;
private String publicDomain;
private String viewability;
private String accessViewStatus;
private Pdf pdf;
private Epub epub;
private String embeddable;
private String quoteSharingAllowed;
private String country;
public String getWebReaderLink ()
{
return webReaderLink;
}
public void setWebReaderLink (String webReaderLink)
{
this.webReaderLink = webReaderLink;
}
public String getTextToSpeechPermission ()
{
return textToSpeechPermission;
}
public void setTextToSpeechPermission (String textToSpeechPermission)
{
this.textToSpeechPermission = textToSpeechPermission;
}
public String getPublicDomain ()
{
return publicDomain;
}
public void setPublicDomain (String publicDomain)
{
this.publicDomain = publicDomain;
}
public String getViewability ()
{
return viewability;
}
public void setViewability (String viewability)
{
this.viewability = viewability;
}
public String getAccessViewStatus ()
{
return accessViewStatus;
}
public void setAccessViewStatus (String accessViewStatus)
{
this.accessViewStatus = accessViewStatus;
}
public Pdf getPdf ()
{
return pdf;
}
public void setPdf (Pdf pdf)
{
this.pdf = pdf;
}
public Epub getEpub ()
{
return epub;
}
public void setEpub (Epub epub)
{
this.epub = epub;
}
public String getEmbeddable ()
{
return embeddable;
}
public void setEmbeddable (String embeddable)
{
this.embeddable = embeddable;
}
public String getQuoteSharingAllowed ()
{
return quoteSharingAllowed;
}
public void setQuoteSharingAllowed (String quoteSharingAllowed)
{
this.quoteSharingAllowed = quoteSharingAllowed;
}
public String getCountry ()
{
return country;
}
public void setCountry (String country)
{
this.country = country;
}
public class Pdf
{
private String acsTokenLink;
private String isAvailable;
public String getAcsTokenLink ()
{
return acsTokenLink;
}
public void setAcsTokenLink (String acsTokenLink)
{
this.acsTokenLink = acsTokenLink;
}
public String getIsAvailable ()
{
return isAvailable;
}
public void setIsAvailable (String isAvailable)
{
this.isAvailable = isAvailable;
}
}
public class Epub
{
private String acsTokenLink;
private String isAvailable;
public String getAcsTokenLink ()
{
return acsTokenLink;
}
public void setAcsTokenLink (String acsTokenLink)
{
this.acsTokenLink = acsTokenLink;
}
public String getIsAvailable ()
{
return isAvailable;
}
public void setIsAvailable (String isAvailable)
{
this.isAvailable = isAvailable;
}
}
}
public class SaleInfo
{
private RetailPrice retailPrice;
private String saleability;
private ListPrice listPrice;
private Offers[] offers;
private String buyLink;
private String isEbook;
private String country;
public RetailPrice getRetailPrice ()
{
return retailPrice;
}
public void setRetailPrice (RetailPrice retailPrice)
{
this.retailPrice = retailPrice;
}
public String getSaleability ()
{
return saleability;
}
public void setSaleability (String saleability)
{
this.saleability = saleability;
}
public ListPrice getListPrice ()
{
return listPrice;
}
public void setListPrice (ListPrice listPrice)
{
this.listPrice = listPrice;
}
public Offers[] getOffers ()
{
return offers;
}
public void setOffers (Offers[] offers)
{
this.offers = offers;
}
public String getBuyLink ()
{
return buyLink;
}
public void setBuyLink (String buyLink)
{
this.buyLink = buyLink;
}
public String getIsEbook ()
{
return isEbook;
}
public void setIsEbook (String isEbook)
{
this.isEbook = isEbook;
}
public String getCountry ()
{
return country;
}
public void setCountry (String country)
{
this.country = country;
}
public class Offers
{
private RetailPrice retailPrice;
private ListPrice listPrice;
private String finskyOfferType;
public RetailPrice getRetailPrice ()
{
return retailPrice;
}
public void setRetailPrice (RetailPrice retailPrice)
{
this.retailPrice = retailPrice;
}
public ListPrice getListPrice ()
{
return listPrice;
}
public void setListPrice (ListPrice listPrice)
{
this.listPrice = listPrice;
}
public String getFinskyOfferType ()
{
return finskyOfferType;
}
public void setFinskyOfferType (String finskyOfferType)
{
this.finskyOfferType = finskyOfferType;
}
}
public class RetailPrice
{
private String amount;
private String currencyCode;
public String getAmount ()
{
return amount;
}
public void setAmount (String amount)
{
this.amount = amount;
}
public String getCurrencyCode ()
{
return currencyCode;
}
public void setCurrencyCode (String currencyCode)
{
this.currencyCode = currencyCode;
}
}
public class ListPrice
{
private String amount;
private String currencyCode;
public String getAmount ()
{
return amount;
}
public void setAmount (String amount)
{
this.amount = amount;
}
public String getCurrencyCode ()
{
return currencyCode;
}
public void setCurrencyCode (String currencyCode)
{
this.currencyCode = currencyCode;
}
}
}
public class VolumeInfo
{
private String pageCount;
private String averageRating;
private ReadingModes readingModes;
private String infoLink;
private String printType;
private String allowAnonLogging;
private String publisher;
private String[] authors;
private String canonicalVolumeLink;
private String title;
private String previewLink;
private String description;
private String ratingsCount;
private ImageLinks imageLinks;
private String contentVersion;
private String[] categories;
private String language;
private String publishedDate;
private IndustryIdentifiers[] industryIdentifiers;
private String maturityRating;
public String getPageCount ()
{
return pageCount;
}
public void setPageCount (String pageCount)
{
this.pageCount = pageCount;
}
public String getAverageRating ()
{
return averageRating;
}
public void setAverageRating (String averageRating)
{
this.averageRating = averageRating;
}
public ReadingModes getReadingModes ()
{
return readingModes;
}
public void setReadingModes (ReadingModes readingModes)
{
this.readingModes = readingModes;
}
public String getInfoLink ()
{
return infoLink;
}
public void setInfoLink (String infoLink)
{
this.infoLink = infoLink;
}
public String getPrintType ()
{
return printType;
}
public void setPrintType (String printType)
{
this.printType = printType;
}
public String getAllowAnonLogging ()
{
return allowAnonLogging;
}
public void setAllowAnonLogging (String allowAnonLogging)
{
this.allowAnonLogging = allowAnonLogging;
}
public String getPublisher ()
{
return publisher;
}
public void setPublisher (String publisher)
{
this.publisher = publisher;
}
public String[] getAuthors ()
{
return authors;
}
public void setAuthors (String[] authors)
{
this.authors = authors;
}
public String getCanonicalVolumeLink ()
{
return canonicalVolumeLink;
}
public void setCanonicalVolumeLink (String canonicalVolumeLink)
{
this.canonicalVolumeLink = canonicalVolumeLink;
}
public String getTitle ()
{
return title;
}
public void setTitle (String title)
{
this.title = title;
}
public String getPreviewLink ()
{
return previewLink;
}
public void setPreviewLink (String previewLink)
{
this.previewLink = previewLink;
}
public String getDescription ()
{
return description;
}
public void setDescription (String description)
{
this.description = description;
}
public String getRatingsCount ()
{
return ratingsCount;
}
public void setRatingsCount (String ratingsCount)
{
this.ratingsCount = ratingsCount;
}
public ImageLinks getImageLinks ()
{
return imageLinks;
}
public void setImageLinks (ImageLinks imageLinks)
{
this.imageLinks = imageLinks;
}
public String getContentVersion ()
{
return contentVersion;
}
public void setContentVersion (String contentVersion)
{
this.contentVersion = contentVersion;
}
public String[] getCategories ()
{
return categories;
}
public void setCategories (String[] categories)
{
this.categories = categories;
}
public String getLanguage ()
{
return language;
}
public void setLanguage (String language)
{
this.language = language;
}
public String getPublishedDate ()
{
return publishedDate;
}
public void setPublishedDate (String publishedDate)
{
this.publishedDate = publishedDate;
}
public IndustryIdentifiers[] getIndustryIdentifiers ()
{
return industryIdentifiers;
}
public void setIndustryIdentifiers (IndustryIdentifiers[] industryIdentifiers)
{
this.industryIdentifiers = industryIdentifiers;
}
public String getMaturityRating ()
{
return maturityRating;
}
public void setMaturityRating (String maturityRating)
{
this.maturityRating = maturityRating;
}
public class ImageLinks
{
private String thumbnail;
private String smallThumbnail;
public String getThumbnail ()
{
return thumbnail;
}
public void setThumbnail (String thumbnail)
{
this.thumbnail = thumbnail;
}
public String getSmallThumbnail ()
{
return smallThumbnail;
}
public void setSmallThumbnail (String smallThumbnail)
{
this.smallThumbnail = smallThumbnail;
}
}
public class ReadingModes
{
private String text;
private String image;
public String getText ()
{
return text;
}
public void setText (String text)
{
this.text = text;
}
public String getImage ()
{
return image;
}
public void setImage (String image)
{
this.image = image;
}
}
public class IndustryIdentifiers
{
private String type;
private String identifier;
public String getType ()
{
return type;
}
public void setType (String type)
{
this.type = type;
}
public String getIdentifier ()
{
return identifier;
}
public void setIdentifier (String identifier)
{
this.identifier = identifier;
}
}
}
}
}
我不知道什么导致错误。除了创建一个名为fromJson的类或内部类之外，Android Studio并没有提出任何建议。 请帮忙。
答案 0 :(得分：0)
更改以下行：
BookInfoModel bookInfoModel = new gson.fromJson(finalObject.toString(),BookInfoModel.class);
到
BookInfoModel bookInfoModel = gson.fromJson(finalObject.toString(), BookInfoModel.class);
以下是如何使用Gson的简单示例：
Gson gson = new Gson();
// JSON to Java object, read it from a Json String.
String jsonInString = "{'name' : 'dummyName'}";
Staff staff = gson.fromJson(jsonInString, Staff.class);
以下是示例类：
public class Staff {
private String name;
}