如何从另一个函数获取java中的hashmap键和值
我有一个类似这样的json解析如何从另一个函数获取java中的hashmap键和值,java,android,json,hashmap,Java,Android,Json,Hashmap,我有一个类似这样的json解析 public class SecondFragment extends Fragment implements OnClickListener { // URL to get contacts JSON private static String contestUrl = "http://api.apps.com/contest"; // JSON Node names private static final String TAG_ITEM_ID = "i
public class SecondFragment extends Fragment implements OnClickListener {
// URL to get contacts JSON
private static String contestUrl = "http://api.apps.com/contest";
// JSON Node names
private static final String TAG_ITEM_ID = "id";
private static final String TAG_URL = "url";
private static final String TAG_START_DATE = "start_date";
private static final String TAG_END_DATE = "end_date";
// contacts JSONArray
JSONArray foods = null;
// Hashmap for ListView
ArrayList<HashMap<String, String>> foodslist;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onActivityCreated(savedInstanceState);
foodslist = new ArrayList<HashMap<String, String>>();
// Calling async task to get json
new GetContacts().execute();
}
/**
* Async task class to get json by making HTTP call
* */
private class GetContacts extends AsyncTask<Void, Void, Void> {
@Override
protected Void doInBackground(Void... arg0) {
// Creating service handler class instance
ServiceHandler sh = new ServiceHandler();
// Making a request to url and getting response
String jsonStr = sh.makeServiceCall(contestUrl, ServiceHandler.GET);
Log.d("Response: ", "> " + jsonStr);
if (jsonStr != null) {
try {
foods = new JSONArray(jsonStr);
// looping through All Contacts
for (int i = 0; i < foods.length(); i++) {
JSONObject c = foods.getJSONObject(i);
String id = c.getString(TAG_ITEM_ID);
String name = c.getString(TAG_URL);
String email = c.getString(TAG_START_DATE);
String address = c.getString(TAG_END_DATE);
// tmp hashmap for single contact
HashMap<String, String> contact = new HashMap<String, String>();
// adding each child node to HashMap key => value
contact.put(TAG_ITEM_ID, id);
contact.put(TAG_URL, name);
contact.put(TAG_START_DATE, email);
contact.put(TAG_END_DATE, address);
String start_date = (String)contact.get(TAG_ITEM_ID);
// adding contact to contact list
foodslist.add(contact);
}
} catch (JSONException e) {
e.printStackTrace();
}
} else {
Log.e("ServiceHandler", "Couldn't get any data from the url");
}
return null;
}
}
public类SecondFragment扩展了片段实现OnClickListener{
//获取联系人JSON的URL
专用静态字符串URL=”http://api.apps.com/contest";
//JSON节点名称
私有静态最终字符串标记\u ITEM\u ID=“ID”;
私有静态最终字符串标记_URL=“URL”;
私有静态最终字符串标记\u START\u DATE=“START\u DATE”;
私有静态最终字符串标记\u END\u DATE=“END\u DATE”;
//联系JSONArray
JSONArray食品=空;
//ListView的Hashmap
ArrayList Foodlist;
}
@凌驾
已创建ActivityState上的公共无效(Bundle savedInstanceState){
//TODO自动生成的方法存根
super.onActivityCreated(savedInstanceState);
FoodList=新的ArrayList();
//调用异步任务以获取json
新建GetContacts().execute();
}
/**
*异步任务类通过HTTP调用获取json
* */
私有类GetContacts扩展异步任务{
@凌驾
受保护的Void doInBackground(Void…arg0){
//创建服务处理程序类实例
ServiceHandler sh=新的ServiceHandler();
//向url发出请求并获得响应
字符串jsonStr=sh.makeServiceCall(contestUrl,ServiceHandler.GET);
Log.d(“响应:”、“>”+jsonStr);
if(jsonStr!=null){
试一试{
食品=新JSONArray(jsonStr);
//通过所有触点循环
对于(int i=0;ivalue
联系人。放置(标签项目ID,ID);
contact.put(TAG_URL,name);
联系人。放置(标记开始日期、电子邮件);
联系方式(标签、结束日期、地址);
字符串start\u date=(字符串)contact.get(TAG\u ITEM\u ID);
//将联系人添加到联系人列表
添加(联系人);
}
}捕获(JSONException e){
e、 printStackTrace();
}
}否则{
Log.e(“ServiceHandler”,“无法从url获取任何数据”);
}
返回null;
}
}
}
我有两个功能,onCreate
和GetContacts
。在onCreate
的末尾,它调用GetContacts
并调用这个json
我的问题是,如何获得GetContacts
上的Hashmap
值,以便在onCreate上使用它
到目前为止,我得到这个值是为了得到Hashmap
String start\u date=(String)contact.get(TAG\u ITEM\u ID)代码>
但是,它只在GetContacts
上起作用。
有人能帮我吗
谢谢你的光临
List<Map<String,String>> foodslist = ...;
你可以打电话
String id = xxx.getAttr( i, TAG_ITEM_ID );
所以返回数据
public List<Map<String, String>> getContacts() {
if (foodslist != null && foodslist.isEmpty()) {
return foodslist;
}
foodslist = new ArrayList<Map<String, String>>();
try {
foods = new JSONArray(jsonStr);
// looping through All Contacts
for (int i = 0; i < foods.length(); i++) {
JSONObject c = foods.getJSONObject(i);
String id = c.getString(TAG_ITEM_ID);
String name = c.getString(TAG_URL);
String email = c.getString(TAG_START_DATE);
String address = c.getString(TAG_END_DATE);
// tmp hashmap for single contact
HashMap<String, String> contact = new HashMap<String, String>();
// adding each child node to HashMap key => value
contact.put(TAG_ITEM_ID, id);
contact.put(TAG_URL, name);
contact.put(TAG_START_DATE, email);
contact.put(TAG_END_DATE, address);
// adding contact to contact list
foodslist.add(contact);
}
return foodslist;
}
public List getContacts(){
if(foodList!=null&&foodList.isEmpty()){
返回食物列表;
}
FoodList=新的ArrayList();
试一试{
食品=新JSONArray(jsonStr);
//通过所有触点循环
对于(int i=0;ivalue
联系人。放置(标签项目ID,ID);
contact.put(TAG_URL,name);
联系人。放置(标记开始日期、电子邮件);
联系方式(标签、结束日期、地址);
//将联系人添加到联系人列表
添加(联系人);
}
返回食物列表;
}
虽然我不知道为什么这个变量被称为foodList,如果它应该包含联系人。有两种方法:
Way-1:
创建HashMap联系人的实例变量(类级别),然后可以在类中的任何位置使用它,包括onCreate和getContacts方法
package stackoverflow.q_25034927;
import java.util.HashMap;
import java.util.Map;
public class PassVariable {
private static Map<String, String> contact = new HashMap<String, String>();
public void onCreate() {
//populate contact object as per your logic
getContacts();
}
private void getContacts() {
//Use contact object directly which was pre-populby onCreate method.
}
}
要回答下面的#3,变量s在NotInner类中不可访问:
package com.test;
public class Test {
static String s = "";
}
class NotInner {
public static void main(String[] args) {
System.out.println(s); //Compilation error: s cannot be resolved to a variable
}
}
不确定,这里到底是什么问题。您正在将hashmapcontact
添加到FoodList
中。什么类型是FoodList
?如果您从类中的多个方法访问它,为什么不能返回它或使它成为类成员?请发布完整的代码或至少是带有简要描述的方法API,以提供更多信息清晰性。你能检查我的问题吗?我编辑了我的代码。但是如果我从你的答案中看到,我错过了onCreate
中的for循环吗?我说得对吗?“}”onActivityCreated(Bundle)方法之前的括号会生成编译时错误。|2.FoodList作为实例变量是完全正确的3.GetContacts类应该作为内部类在SecondFragment类中。对不起,您能解释更多关于第三点的信息吗?我真的不明白,请检查我编辑的答案,您需要内部类来访问GetContacts中的'FoodList'变量。
package stackoverflow.q_25034927;
import java.util.HashMap;
import java.util.Map;
public class PassVariable {
private static Map<String, String> contact = new HashMap<String, String>();
public void onCreate() {
//populate contact object as per your logic
getContacts();
}
private void getContacts() {
//Use contact object directly which was pre-populby onCreate method.
}
}
package stackoverflow.q_25034927;
import java.util.HashMap;
import java.util.Map;
public class PassVariable {
public void onCreate() {
final Map<String, String> contact = new HashMap<String, String>();
//populate contact object as per your logic.
getContacts(contact);
}
private void getContacts(Map<String, String> contact) {
//Use contact object which is passed as argument.
}
}
String email = c.getString(TAG_START_DATE);
String address = c.getString(TAG_END_DATE);
package com.test;
public class Test {
static String s = "";
}
class NotInner {
public static void main(String[] args) {
System.out.println(s); //Compilation error: s cannot be resolved to a variable
}
}