我创建了一个使用 Google Books API 的 Android 应用程序。当我从服务器获得 JSON 响应时,我解析响应并检索标题、作者、类别、出版商、页数、缩略图和一些关于这本书的更多信息。问题是 JSON 响应中的某些书籍没有缩略图键或类别键。当我尝试获取这些 JSON 键值时,程序会抛出一个错误,并因此跳过错误发生后添加其他书籍的代码。
我用嵌套 try catch block 解决了这个问题。例如,如果响应中没有发布者 key ,那么我将返回 null。
String publisher;
try {
publisher = volumeInfo.getString("publisher");
} catch (JSONException e) {
publisher = null;
}
下面是解析 JSON 响应的整个方法的样子:
private List<BookData> parseJsonResponse(String jsonResponse) {
List<BookData> bookData = new ArrayList<>();
try {
JSONObject rootObject = new JSONObject(jsonResponse);
JSONArray itemsArray = rootObject.getJSONArray("items");
for (int i = 0; i < itemsArray.length(); i++) {
JSONObject itemObject = itemsArray.getJSONObject(i);
JSONObject volumeInfo =
itemObject.getJSONObject("volumeInfo");
String title;
try {
title = volumeInfo.getString("title");
} catch (JSONException e) {
title = null;
}
ArrayList<String> authors;
try {
JSONArray authorsArray =
volumeInfo.getJSONArray("authors");
authors = new ArrayList<>();
for (int j = 0; j < authorsArray.length(); j++) {
authors.add(authorsArray.getString(j));
}
} catch (JSONException e) {
authors = null;
}
ArrayList<String> categories;
try {
JSONArray categoriesArray =
volumeInfo.getJSONArray("categories");
categories = new ArrayList<>();
for (int k = 0; k < categoriesArray.length(); k++) {
categories.add(categoriesArray.getString(k));
}
} catch (JSONException e) {
categories = null;
}
String publisher;
try {
publisher = volumeInfo.getString("publisher");
} catch (JSONException e) {
publisher = null;
}
String publishedDate;
try {
publishedDate =
volumeInfo.getString("publishedDate");
} catch (JSONException e) {
publishedDate = null;
}
int pageCount;
try {
pageCount = volumeInfo.getInt("pageCount");
} catch (JSONException e) {
pageCount = 0;
}
String language;
try {
language = volumeInfo.getString("language");
} catch (JSONException e) {
language = null;
}
String description;
try {
description = volumeInfo.getString("description");
} catch (JSONException e) {
description = null;
}
String bookWebsite;
try {
bookWebsite = volumeInfo.getString("infoLink");
} catch (JSONException e) {
bookWebsite = null;
}
Bitmap thumbnail;
try {
JSONObject imageLink =
volumeInfo.getJSONObject("imageLinks");
String thumbnailUrl =
imageLink.getString("thumbnail");
thumbnail = getThumbnailBitmap(thumbnailUrl);
} catch (JSONException e) {
thumbnail = null;
}
// Add a new BookData object to the list
bookData.add(new BookData(title, thumbnail, authors,
categories, publisher, publishedDate,
pageCount, language, description,
bookWebsite));
}
} catch (JSONException e) {
Log.e(LOG_TAG, null, e);
}
return bookData;
}
完成解析后,我必须更新我的 View 。我使用的是 ListView ,因此适配器需要处理 View 膨胀。 我必须添加一个 if 语句来检查变量是否不为空,然后例如设置 TextView 的文本。否则我将文本设置为“Publisher not available”。
TextView publisher = listView.findViewById(R.id.book_publisher);
if (bookData.getPublisher() != null) {
publisher.setText(bookData.getPublisher());
} else {
publisher.setText("Publisher not available");
}
这是整个适配器的样子:
public class BookDataAdapter extends ArrayAdapter<BookData> {
public BookDataAdapter(@NonNull Context context, @NonNull
List<BookData> bookDatas) {
super(context, 0, bookDatas);
}
@NonNull
@Override
public View getView(int position, @Nullable View convertView,
@NonNull ViewGroup parent) {
View listView = convertView;
if (listView == null) {
listView = LayoutInflater.from(getContext())
.inflate(R.layout.book_list_item, parent, false);
}
// Get current BookData object
BookData bookData = getItem(position);
ImageView thumbnail = listView.findViewById(R.id.book_thumbnail);
if (bookData.getThumbnail() != null) {
thumbnail.setImageBitmap(bookData.getThumbnail());
} else {
// Set default thumbnail
thumbnail.setImageResource(R.drawable.default_thumbnail);
}
TextView title = listView.findViewById(R.id.book_title);
if (bookData.getTitle() != null) {
title.setText(bookData.getTitle());
} else {
title.setText("Title not available");
}
TextView author = listView.findViewById(R.id.book_author);
if (bookData.getAuthors() != null) {
author.setText(listToString(bookData.getAuthors()));
} else {
author.setText("Authors not available");
}
TextView category = listView.findViewById(R.id.book_category);
if (bookData.getCategories() != null) {
category.setText("Category: " +
listToString(bookData.getCategories()));
} else {
category.setText("Category not available ");
}
TextView publisher = listView.findViewById(R.id.book_publisher);
if (bookData.getPublisher() != null) {
publisher.setText(bookData.getPublisher() + ", ");
} else {
publisher.setText("Publisher not available, ");
}
TextView publishedDate =
listView.findViewById(R.id.book_published_date);
if (bookData.getPublishedDate() != null) {
publishedDate.setText(bookData.getPublishedDate());
} else {
publishedDate.setText("Published date not available");
}
TextView pageCount = listView.findViewById(R.id.book_page_count);
if (bookData.getPageCount() != 0) {
pageCount.setText("Pages: " + bookData.getPageCount());
} else {
pageCount.setText("Page count not available");
}
TextView language = listView.findViewById(R.id.book_language);
if (bookData.getLanguage() != null) {
language.setText(bookData.getLanguage());
} else {
language.setText("Language not available");
}
TextView description =
listView.findViewById(R.id.book_description);
if (bookData.getDescription() != null) {
description.setText(bookData.getDescription());
} else {
description.setText("Description not available");
}
return listView;
}
private String listToString(List<String> list) {
if (list == null || list.size() == 0) {
return null;
}
StringBuilder builder = new StringBuilder();
for (int i = 0; i < list.size(); i++) {
builder.append(list.get(i));
if (i == (list.size() - 1)) {
break;
}
builder.append(", ");
}
return builder.toString();
}
最后我想问一个问题。有没有更好的方法或更有效的方法来解析具有不同键的 JSON 响应,因为有人说嵌套的 try catch 语句不是一个好的做法?
非常感谢!!
最佳答案
你有两个选择:
使用
.has()
:String publisher = null; if(volumeInfo.has("publisher")){ publisher = volumeInfo.getString("publisher"); }
使用
opt
而不是get
(更好,IMO):String publisher = volumeInfo.optString("publisher");
opt###
方法对于对象默认为 null
,对于基元默认为 0
/false
,因此您不必编写 try/catch
block 或 if
条件。您还可以指定第二个参数作为默认值:
String publisher = volumeInfo.optString("publisher", "no publisher");
// if publisher is not a valid key, "no publisher" will be returned
关于java - 解析具有不同键的 JSON 对象,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/45678050/