数组列表哈希映射空指针异常

Question

我在最后一句话中得到了NullPointerException。请帮忙。

ArrayList<HashMap<String, String>> contactList;
for(int i=0; i < jsonArray.length(); i++){
    JSONObject jsonObject = jsonArray.getJSONObject(i);
    HashMap<String,String> contact = new HashMap<String,String>();
    contact.put(TAG_ID, jsonObject.optString("id").toString());
    contact.put(TAG_NAME,jsonObject.optString("name").toString());
    contact.put(TAG_EXT,jsonObject.optString("extension").toString());
    contactList.add(contact);
}

Answer 1

您尚未初始化联系人列表。

 ArrayList<HashMap<String, String>> contactList = new ArrayList<HashMap<String, String>>();

Answer 2

你必须初始化联系人列表`

ArrayList<HashMap<String, String>> contactList=new ArrayList<HashMap<String, String>>();
 for(int i=0; i < jsonArray.length(); i++){
 JSONObject jsonObject = jsonArray.getJSONObject(i);
 HashMap<String,String> contact = new HashMap<String,String>();
 contact.put(TAG_ID, jsonObject.optString("id").toString());
 contact.put(TAG_NAME,jsonObject.optString("name").toString());
 contact.put(TAG_EXT,jsonObject.optString("extension").toString());
 contactList.add(contact);
}`

Answer 3

你还没有初始化contactList，应该在使用前初始化

ArrayList<HashMap<String, String>> contactList=new ArrayList<HashMap<String, String>>();

Answer 4

ArrayList 应该首先被 iitialized 化。试试这个，

ArrayList<HashMap<String, String>> contactList;
 ArrayList<HashMap<String, String>> contactList=new ArrayList<HashMap<String, String>>();
 for(int i=0; i < jsonArray.length(); i++){
 JSONObject jsonObject = jsonArray.getJSONObject(i);
 HashMap<String,String> contact = new HashMap<String,String>();
 contact.put(TAG_ID, jsonObject.optString("id").toString());
 contact.put(TAG_NAME,jsonObject.optString("name").toString());
 contact.put(TAG_EXT,jsonObject.optString("extension").toString());
 contactList.add(contact);
}