装载的ListView在Android的使用AsyncTask的JSON数据 [英] Loading ListView with JSON data using AsyncTask in Android
本文介绍了装载的ListView在Android的使用AsyncTask的JSON数据的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我想从这个网址 http://inspirontrance.com/tpb.json 解析JSON数据。我的code加载一定次数后作品，未经AsyncTask的，但启用了AsyncTask的，应用程序崩溃。虽然我的codeS似乎确定，但不知该应用程序在异步过程冻结。
下面是我的code，
公共类AndroidJSONParsingActivity扩展ListActivity { // URL使请求
私有静态字符串URL =http://inspirontrance.com/tpb.json; // JSON节点名称
私有静态最后弦乐TAG_UPLOADS =上传;
私有静态最后弦乐TAG_ID =ID;
私有静态最后弦乐TAG_NAME =名;
私有静态最后弦乐TAG_DATE =日期; ProgressDialog pDialog; // JSONArray
JSONArray上传= NULL; @覆盖
公共无效的onCreate（捆绑savedInstanceState）{
super.onCreate（savedInstanceState）;
的setContentView（R.layout.main）; 新MyAsyncTask（）执行（URL）;
//发送HTTP请求之前，显示进度对话框
pDialog =新ProgressDialog（本）;
pDialog.setMessage（请稍候...）;
pDialog.setIndeterminate（真）;
pDialog.setCancelable（假）;
pDialog.show（）;
} 类MyAsyncTask扩展
AsyncTask的＆LT;字符串，整数的ArrayList＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT;＆GT; { //为哈希映射的ListView
ArrayList的＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT; UploadsList =新的ArrayList＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT;（）; @覆盖
保护的ArrayList＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT; doInBackground（
串... PARAMS）{ //创建JSON解析器实例
JSONParser jParser =新JSONParser（）; // URL从获取JSON字符串
JSONObject的JSON = jParser.getJSONFromUrl（URL）; 尝试{
//获取上传的数组
上传= json.getJSONArray（TAG_UPLOADS）; //通过所有上传循环
的for（int i = 0; I＆LT; uploads.length（）;我++）{
JSONObject的C = uploads.getJSONObject（I） //存储在变量中的每个JSON项目
字符串ID = c.getString（TAG_ID）;
字符串名称= c.getString（TAG_NAME）;
字符串日期= c.getString（TAG_DATE）; //创建新的HashMap
HashMap的＆LT;字符串，字符串＆GT;地图=新的HashMap＆LT;字符串，字符串＆GT;（）; //将每个子节点的HashMap键=＆GT;值
map.put（TAG_ID，身份证）;
map.put（TAG_NAME，名）;
map.put（TAG_DATE，日期）; //添加HashList到ArrayList的
UploadsList.add（地图）;
}
}赶上（JSONException E）{
e.printStackTrace（）;
} 返回UploadsList;
} } 保护无效onPostExecute（ArrayList的＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT;的结果）{ pDialog.dismiss（）; ListAdapter适配器=新SimpleAdapter（这一点，因此，
R.layout.list_item，
新的String [] {TAG_NAME，TAG_ID，TAG_DATE}，新的INT [] {
R.id.name，R.id.id，R.id.date}）; setListAdapter（适配器）;
}
}
解决方案
下面就是我会做。这是很好的进入你的任务中做你的pre /岗位工作的习惯。
类MyAsyncTask扩展
AsyncTask的＆LT;字符串，整数的ArrayList＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT;＆GT; { //为哈希映射的ListView
ArrayList的＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT; UploadsList =新的ArrayList＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT;（）; @覆盖
在preExecute保护无效（）{
//发送HTTP请求之前，显示进度对话框
pDialog =新ProgressDialog（本）;
pDialog.setMessage（请稍候...）;
pDialog.setIndeterminate（真）;
pDialog.setCancelable（假）;
pDialog.show（）; } @覆盖
保护的ArrayList＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT; doInBackground（
串... PARAMS）{ //创建JSON解析器实例
JSONParser jParser =新JSONParser（）; // URL从获取JSON字符串
JSONObject的JSON = jParser.getJSONFromUrl（URL）; 尝试{
//获取上传的数组
上传= json.getJSONArray（TAG_UPLOADS）; //通过所有上传循环
的for（int i = 0; I＆LT; uploads.length（）;我++）{
JSONObject的C = uploads.getJSONObject（I） //存储在变量中的每个JSON项目
字符串ID = c.getString（TAG_ID）;
字符串名称= c.getString（TAG_NAME）;
字符串日期= c.getString（TAG_DATE）; //创建新的HashMap
HashMap的＆LT;字符串，字符串＆GT;地图=新的HashMap＆LT;字符串，字符串＆GT;（）; //将每个子节点的HashMap键=＆GT;值
map.put（TAG_ID，身份证）;
map.put（TAG_NAME，名）;
map.put（TAG_DATE，日期）; //添加HashList到ArrayList的
UploadsList.add（地图）;
}
}赶上（JSONException E）{
e.printStackTrace（）;
} 返回UploadsList;
} @覆盖
保护无效onPostExecute（ArrayList的＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT;的结果）{ pDialog.dismiss（）; ListAdapter适配器=新SimpleAdapter（这一点，因此，
R.layout.list_item，
新的String [] {TAG_NAME，TAG_ID，TAG_DATE}，新的INT [] {
R.id.name，R.id.id，R.id.date}）; setListAdapter（适配器）;
}
}
I want to parse JSON data from this url http://inspirontrance.com/tpb.json. My code works without the AsyncTask but with the AsyncTask enabled, app crashes after loading for a certain number of times. Although my codes seems ok but somehow the app freezes during the async process.
Here is my code,
public class AndroidJSONParsingActivity extends ListActivity {
// url to make request
private static String url = "http://inspirontrance.com/tpb.json";
// JSON Node names
private static final String TAG_UPLOADS = "uploads";
private static final String TAG_ID = "id";
private static final String TAG_NAME = "name";
private static final String TAG_DATE = "date";
ProgressDialog pDialog;
// JSONArray
JSONArray uploads = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
new MyAsyncTask().execute(url);
// Showing progress dialog before sending http request
pDialog = new ProgressDialog(this);
pDialog.setMessage("Please wait..");
pDialog.setIndeterminate(true);
pDialog.setCancelable(false);
pDialog.show();
}
class MyAsyncTask extends
AsyncTask<String, Integer, ArrayList<HashMap<String, String>>> {
// Hashmap for ListView
ArrayList<HashMap<String, String>> UploadsList = new ArrayList<HashMap<String, String>>();
@Override
protected ArrayList<HashMap<String, String>> doInBackground(
String... params) {
// Creating JSON Parser instance
JSONParser jParser = new JSONParser();
// getting JSON string from URL
JSONObject json = jParser.getJSONFromUrl(url);
try {
// Getting Array of Uploads
uploads = json.getJSONArray(TAG_UPLOADS);
// looping through All Uploads
for (int i = 0; i < uploads.length(); i++) {
JSONObject c = uploads.getJSONObject(i);
// Storing each json item in variable
String id = c.getString(TAG_ID);
String name = c.getString(TAG_NAME);
String date = c.getString(TAG_DATE);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_ID, id);
map.put(TAG_NAME, name);
map.put(TAG_DATE, date);
// adding HashList to ArrayList
UploadsList.add(map);
}
} catch (JSONException e) {
e.printStackTrace();
}
return UploadsList;
}
}
protected void onPostExecute(ArrayList<HashMap<String, String>> result) {
pDialog.dismiss();
ListAdapter adapter = new SimpleAdapter(this, result,
R.layout.list_item,
new String[] { TAG_NAME, TAG_ID, TAG_DATE }, new int[] {
R.id.name, R.id.id, R.id.date });
setListAdapter(adapter);
}
}
解决方案
Here's how I'd do it. It's good to get into the habit of doing your pre/post work within your task.
class MyAsyncTask extends
AsyncTask<String, Integer, ArrayList<HashMap<String, String>>> {
// Hashmap for ListView
ArrayList<HashMap<String, String>> UploadsList = new ArrayList<HashMap<String, String>>();
@Override
protected void onPreExecute() {
// Showing progress dialog before sending http request
pDialog = new ProgressDialog(this);
pDialog.setMessage("Please wait..");
pDialog.setIndeterminate(true);
pDialog.setCancelable(false);
pDialog.show(); }
@Override
protected ArrayList<HashMap<String, String>> doInBackground(
String... params) {
// Creating JSON Parser instance
JSONParser jParser = new JSONParser();
// getting JSON string from URL
JSONObject json = jParser.getJSONFromUrl(url);
try {
// Getting Array of Uploads
uploads = json.getJSONArray(TAG_UPLOADS);
// looping through All Uploads
for (int i = 0; i < uploads.length(); i++) {
JSONObject c = uploads.getJSONObject(i);
// Storing each json item in variable
String id = c.getString(TAG_ID);
String name = c.getString(TAG_NAME);
String date = c.getString(TAG_DATE);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_ID, id);
map.put(TAG_NAME, name);
map.put(TAG_DATE, date);
// adding HashList to ArrayList
UploadsList.add(map);
}
} catch (JSONException e) {
e.printStackTrace();
}
return UploadsList;
}
@Override
protected void onPostExecute(ArrayList<HashMap<String, String>> result) {
pDialog.dismiss();
ListAdapter adapter = new SimpleAdapter(this, result,
R.layout.list_item,
new String[] { TAG_NAME, TAG_ID, TAG_DATE }, new int[] {
R.id.name, R.id.id, R.id.date });
setListAdapter(adapter);
}
}
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