Question

Greetins的编码员！我搜索了论坛，但似乎无法找到我需要的答案。我是一个Android应用程序初学者，所以可以大大使用一些帮助！我有一个从服务器获取的API，我正在尝试反序列化它（使用GSon）并用它填充我的列表视图。我的应用程序下载API但由于某种原因它将gson返回为null，因为我尝试反序列化它。我创建了一类getter（Company.java），对它的响应（Response.java） - [不确定它的结构是否正确]我在MainActivity中调用LoadJsonTask.java。谁能给我一些指示？我非常感谢！（对不起，有这么多代码，但想让我的问题容易理解:)）谢谢！

这是我的代码：公司类：

public class Company {
private String id;
private String name;
private String phone;
private String address;
private String postcode;
private String gps_lat;
private String gps_lng;
private String summary;
private String website;
private String facebook;
private String twitter;
private String webform;
private String email;

public String getId(){
    return id;
}
public String getName() {
    return name;
}

public String getPhone() {
    return phone;
}

public String getAddress() {
    return address;
}

public String getPostcode() {
    return postcode;
}

public String getGps_lat() {
    return gps_lat;
}

public String getGps_lng(){
    return gps_lng;
}

public String getSummary(){
    return summary;
}

public String getWebsite(){
    return website;
}

public String getFacebook(){
    return facebook;
}

public String getTwitter(){
    return twitter;
}

public String getWebform(){
    return webform;
}

public String getEmail(){
    return email;
}
}

我的回复课程：公共课回复{

private List<Company> companies = new ArrayList<Company>();

public List<Company> getCompanies() {
    return companies;
}
}

加载JSonTask：

public class LoadJSONTask extends AsyncTask<String, Void, Response> {

public LoadJSONTask(Listener listener) {

    mListener = listener;
}

public interface Listener {

    void onLoaded(List<Company> androidList);

    void onError();
}

private Listener mListener;

@Override
protected Response doInBackground(String... strings) {
    try {

        String stringResponse = loadJSON(strings[0]);

        List<Company> android = new Gson().fromJson(stringResponse, new TypeToken<ArrayList<Company>>(){}.getType());
        return android;


    } catch (IOException e) {
        e.printStackTrace();
        return null;
    } catch (JsonSyntaxException e) {
        e.printStackTrace();
        return null;
    }
}

@Override
protected void onPostExecute(Response response) {

    if (response != null) {

        mListener.onLoaded(response.getCompanies());

    } else {

        mListener.onError();
    }
}

private String loadJSON(String jsonURL) throws IOException {

    URL url = new URL(jsonURL);
    HttpURLConnection conn = (HttpURLConnection) url.openConnection();
    conn.setReadTimeout(10000);
    conn.setConnectTimeout(15000);
    conn.setRequestMethod("GET");
    conn.setDoInput(true);
    conn.connect();

    BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
    String line;
    StringBuilder response = new StringBuilder();

    while ((line = in.readLine()) != null) {

        response.append(line);
    }

    in.close();
    return response.toString();
}
}

MainActivity类：

public class MainActivity extends AppCompatActivity implements LoadJSONTask.Listener, AdapterView.OnItemClickListener {

private ListView mListView;

public static final String URL = "url_with_api";

private List<HashMap<String, String>> mAndroidMapList = new ArrayList<>();

private static final String KEY_ID = "id";
private static final String KEY_NAME = "name";
private static final String KEY_PHONE = "phone";
private static final String KEY_ADDRESS = "address";
private static final String KEY_POSTCODE = "postcode";
private static final String KEY_GPS_LAT = "gps_lat";
private static final String KEY_GPS_LNG = "gps_lng";
private static final String KEY_SUMMARY = "summary";
private static final String KEY_WEBSITE = "website";
private static final String KEY_FACEBOOK = "facebook";
private static final String KEY_TWITTER = "twitter";
private static final String KEY_WEBFORM = "webform";
private static final String KEY_EMAIL = "email";



@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    mListView = (ListView) findViewById(R.id.list_view);
    mListView.setOnItemClickListener(this);
    new LoadJSONTask(this).execute(URL);
}

@Override
public void onLoaded(List<Company> androidList) {

    for (Company android : androidList) {

        HashMap<String, String> map = new HashMap<>();
        map.put(KEY_ID, android.getId());
        map.put(KEY_NAME, android.getName());
        map.put(KEY_PHONE, android.getPhone());
        map.put(KEY_ADDRESS, android.getAddress());
        map.put(KEY_POSTCODE, android.getPostcode());
        map.put(KEY_GPS_LAT, android.getGps_lat());
        map.put(KEY_GPS_LNG, android.getGps_lng());
        map.put(KEY_SUMMARY, android.getSummary());
        map.put(KEY_WEBSITE, android.getWebsite());
        map.put(KEY_FACEBOOK, android.getFacebook());
        map.put(KEY_TWITTER, android.getTwitter());
        map.put(KEY_WEBFORM, android.getWebform());
        map.put(KEY_EMAIL, android.getEmail());


        mAndroidMapList.add(map);
    }

    loadListView();
}

@Override
public void onError() {

    Toast.makeText(this, "Error !", Toast.LENGTH_SHORT).show();
}

@Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {

    Toast.makeText(this, mAndroidMapList.get(i).get(KEY_NAME),Toast.LENGTH_LONG).show();

}

private void loadListView() {

    ListAdapter adapter = new SimpleAdapter(MainActivity.this, mAndroidMapList, R.layout.list_item,
            new String[] { KEY_ID, KEY_NAME, KEY_PHONE },
            new int[] { R.id.version,R.id.name, R.id.api });

    mListView.setAdapter(adapter);

}

}

我下载的API：

[{"id":4,"name":"Name","phone":"Phone","address":"","postcode":"","gps_lat":null,"gps_lng":null,"summary":"Des.","website":"http:","facebook":"","twitter":"","webform":"","email":"Email"},{"id":8,"name":"Name2","phone":"Phone2","address2":"","postcode":"","gps_lat":null,"gps_lng":null,"summary":"Des2.","website":"http:","facebook":"","twitter":"","webform":"","email":"Email"}]

Answer 1

JSON是Company数组而不是对象{companies:[]}

这意味着您必须使用以下内容反序列化JSON：

Company[] companies =  new Gson().fromJson(json, Company[].class);

而不是

Response response = new Gson().fromJson(json, Response.class);

您可以将异步任务的返回类型更改为List。这就是我的意思：

public class LoadJSONTask extends AsyncTask<String, Void, List<Company>> {

    ...

    @Override
    protected List<Company> doInBackground(String... strings) {
        ...
        List<Company> companies = new Gson().fromJson(stringResponse, new TypeToken<ArrayList<Company>>(){}.getType());
        return companies;
        ...
    }

    @Override
    protected void onPostExecute(List<Company> companies) {
        if (companies != null) {
            mListener.onLoaded(companies);
        } else {
            mListener.onError();
        }
    }
}

在GSon中去除对象数组

1 个答案: