Android Json使用Gson解析

Question

我想將使用Gson的json數據從URL映射到我的java類。這是類代碼：

public class Sessions { 
public Boolean active; 
public String contributor_covu_id; 
public String created_at; 
public String key; 
public String status; 

public Boolean getActive() { 
    return active; 
} 
public void setActive(Boolean active) { 
    this.active = active; 
} 
public String getContributor_covu_id() { 
    return contributor_covu_id; 
} 
public void setContributor_covu_id(String contributor_covu_id) { 
    this.contributor_covu_id = contributor_covu_id; 
} 
public String getCreated_at() { 
    return created_at; 
} 
public void setCreated_at(String created_at) { 
    this.created_at = created_at; 
} 
public String getKey() { 
    return key; 
} 
public void setKey(String key) { 
    this.key = key; 
} 
public String getStatus() { 
    return status; 
} 
public void setStatus(String status) { 
    this.status = status; 
} 
public String getType() { 
    return type; 
} 
public void setType(String type) { 
    this.type = type; 
} 
public String type; 

}

，這是調用服務和地圖JSON

public static List<Sessions> getSessions(String urlString) 
     throws IOException { 

    Sessions[] sessions; 
    List<Sessions> tempList = null; 
    URL url = new URL(urlString); 
    HttpURLConnection conn = (HttpURLConnection) url.openConnection(); 
    GsonBuilder gsonb = new GsonBuilder(); 
    Gson gson = gsonb.create(); 
    StringBuilder sb = new StringBuilder(); 
    String line; 

    // Response response = null; 
    JSONObject j = null; 

    if (conn.getResponseCode() != 200) { 
     throw new IOException(conn.getResponseMessage()); 
    } 

    BufferedReader bufferedReader = new BufferedReader(
      new InputStreamReader(conn.getInputStream())); 

    while ((line = bufferedReader.readLine()) != null) { 
     sb.append(line); 
    } 
    bufferedReader.close(); 
    conn.disconnect(); 

    try { 
     j = new JSONObject(sb.toString()); 
     sessions = gson.fromJson(j.toString(), Sessions[].class); 
     tempList = Arrays.asList(sessions); 

     // response = gson.fromJson(j.toString(), Response.class); 
     // tempList.add(response); 

    } catch (JSONException e) { 
     e.printStackTrace(); 
    } 
    return tempList; 
} 

雖然代碼是正確的，我得到的類的代碼一個Gson異常「無法爲類com.test.Sessions調用無參數構造函數;使用Gson爲此類型註冊一個InstanceCreator可能會解決此問題」

如何解決此問題d將Gson作爲ArrayList返回？

Answer 1

解決的辦法是：

public class Sessions { 

private String status; 
private List<Session> sessions; 

public String getStatus() { 
    return status; 
} 

public void setStatus(String status) { 
    this.status = status; 
} 

public List<Session> getSessions() { 
    return sessions; 
} 

public void setSessions(List<Session> sessions) { 
    this.sessions = sessions; 
} 

public static class Session { 
    public Boolean active; 
    public String contributor_covu_id; 
    public String created_at; 
    public String key; 
    public String status; 
    public String name; 

}; 

}

Answer 2

一個構造函數添加到您的Sessions類：

public class Sessions { 
    public Boolean active; 
    public String contributor_covu_id; 
    public String created_at; 
    public String key; 
    public String status; 

    void Sessions() 
    { 
    } 
    . 
    . 
    . 
}