从AsyncTask的类返回的数据 [英] Return data from AsyncTask class
本文介绍了从AsyncTask的类返回的数据的处理方法，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
我如何从我的AsyncTask的数据？我MainActivity被调用DataCall.getJSON功能触发AsyncTask的，但我不知道如何让数据恢复到原来的活动。
MainActivity与调用DataCall应该返回一个字符串，并将其保存在 state_data
字符串state_data = DataCall.getJSON（spinnerURL，spinnerContentType）;
DataCall：
公共类DataCall延伸活动{
私有静态最后字符串变量=MyApp的;
私有类DownloadWebPageTask扩展的AsyncTask＆LT;字符串，太虚，字符串＆GT; {
保护字符串doInBackground（字符串...网址）{
串响应=;
对于（字符串网址：网址）{
DefaultHttpClient客户端=新DefaultHttpClient（）;
HTTPGET HTTPGET =新HTTPGET（URL）;
尝试 {
HTT presponse执行= client.execute（HTTPGET）;
InputStream的内容= execute.getEntity（）的getContent（）。
的BufferedReader缓冲=新的BufferedReader（
新InputStreamReader的（内容））;
字符串s =;
而（（S = buffer.readLine（））！= NULL）{
响应+ = S;
}
}赶上（例外五）{
e.printStackTrace（）;
}
}
返回响应;
}
保护无效onPostExecute（字符串结果）{
//这是我需要回到我的数据TO的主要活动。 （我猜测）
}
}
公共无效的getJSON（字符串myUrlString，字符串的contentType）{
DownloadWebPageTask任务=新DownloadWebPageTask（）;
task.execute（新的String [] {http://www.mywebsite.com/+ myUrlString}）;
}
}
解决方案
关键的，我是要创建一个类名为URLWithParams或东西，因为的AsyncTask将允许在只发送1类型，我需要两个URL和PARAMS的HTTP请求。
公共类URLWithParams {
公共字符串URL;
公开名单＆LT;的NameValuePair＆GT; namevaluepairs中;
公共URLWithParams（）
{
namevaluepairs中=新的ArrayList＆LT;的NameValuePair＆GT;（）;
}
}
，然后我将其发送到JSONClient：
公共类JSONClient扩展的AsyncTask＆LT; URLWithParams，太虚，字符串＆GT; {
私人最终静态字符串变量=JSONClient;
ProgressDialog progressDialog;
GetJSONListener getJSONListener;
公共JSONClient（GetJSONListener监听器）{
this.getJSONListener =侦听器;
}
@覆盖
保护字符串doInBackground（URLWithParams ...网址）{
返回连接（网址[0] .URL，网址[0] .nameValuePairs）;
}
公共静态字符串连接（字符串URL，列表和LT;的NameValuePair＆GT;对）
{
HttpClient的HttpClient的=新DefaultHttpClient（）;
如果（网址== NULL）
{
Log.d（TAG，想连接，但网址为空）;
}
其他
{
Log.d（TAG，开始跟URL+网址）;
}
如果（对== NULL）
{
Log.d（TAG，想连接，但对为空）;
}
其他
{
Log.d（TAG，开始跟这么多的对：+ pairs.size（））;
对于（的NameValuePair狗：对）
{
Log.d（TAG，例如：+ dog.toString（））;
}
}
//执行请求
HTT presponse响应;
尝试 {
// prepare请求对象
HttpPost httpPost =新HttpPost（URL）;
httpPost.setEntity（新UrlEn codedFormEntity（对））;
响应= httpclient.execute（httpPost）;
//检查响应状态
Log.i（TAG，response.getStatusLine（）的toString（））;
的BufferedReader读卡器=新的BufferedReader（新的InputStreamReader（response.getEntity（）的getContent（），UTF-8））;
JSON字符串= reader.readLine（）;
返回JSON;
}赶上（ClientProtocolException E）{
// TODO自动生成的catch块
e.printStackTrace（）;
}赶上（IOException异常E）{
// TODO自动生成的catch块
e.printStackTrace（）;
}
返回null;
}
@覆盖
保护无效onPostExecute（JSON字符串）{
getJSONListener.onRemoteCallComplete（JSON）;
}
公共接口GetJSONListener {
公共无效onRemoteCallComplete（字符串jsonFromNet）;
}
}
然后从我的主类像这样把它叫做
公共类BookCatalog实现GetJSONListener {
私人最终字符串变量= this.getClass（）getSimpleName（）。
私人字符串CATALOG_URL =URL;
私人无效getCatalogFromServer（）{
URLWithParams mURLWithParams =新URLWithParams（）;
mURLWithParams.url = CATALOG_URL;
尝试 {
JSONClient asyncPoster =新JSONClient（本）;
asyncPoster.execute（mURLWithParams）;
}赶上（例外五）{
// TODO自动生成的catch块
e.printStackTrace（）;
}
}
@覆盖
公共无效onRemoteCallComplete（字符串jsonBookCatalogList）{
Log.d（TAG，收到的JSON目录：）;
Log.d（TAG，jsonBookCatalogList）;
的JSONObject bookCatalogResult;
尝试 {
bookCatalogResult =（JSONObject的）新JSONTokener（jsonBookCatalogList）.nextValue（）;
JSONArray书= bookCatalogResult.getJSONArray（书）;
如果（书！= NULL）{
ArrayList的＆LT;字符串＆GT; newBookOrdering =新的ArrayList＆LT;字符串＆GT;（）;
INT num_books = books.length（）;
BookCatalogEntry温度;
DebugLog.d（TAG，显然，我们发现+ Integer.toString（num_books）+的书。）;
对于（INT book_id = 0; book_id＆LT; num_books; book_id ++）{
JSONObject的书= books.getJSONObject（book_id）;
字符串标题= book.getString（标题）;
INT版本= book.getInt（代价）;
}
}
}赶上（JSONException E）{
e.printStackTrace（）;
}
}
}
How do I get the data from my AsyncTask? My MainActivity is calling the DataCall.getJSON function that triggers the AsyncTask but I am not sure how to get the data back to the original Activity.
MainActivity with call to DataCall that should return a string and save it in state_data
String state_data = DataCall.getJSON(spinnerURL,spinnerContentType);
DataCall:
public class DataCall extends Activity {
private static final String TAG = "MyApp";
private class DownloadWebPageTask extends AsyncTask<String, Void, String> {
protected String doInBackground(String... urls) {
String response = "";
for (String url : urls) {
DefaultHttpClient client = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
try {
HttpResponse execute = client.execute(httpGet);
InputStream content = execute.getEntity().getContent();
BufferedReader buffer = new BufferedReader(
new InputStreamReader(content));
String s = "";
while ((s = buffer.readLine()) != null) {
response += s;
}
} catch (Exception e) {
e.printStackTrace();
}
}
return response;
}
protected void onPostExecute(String result) {
//THIS IS WHERE I NEED TO RETURN MY DATA TO THE MAIN ACTIVITY. (I am guessing)
}
}
public void getJSON(String myUrlString, String contentType) {
DownloadWebPageTask task = new DownloadWebPageTask();
task.execute(new String[] { "http://www.mywebsite.com/" + myUrlString });
}
}
解决方案
The key for me was to create a class called URLWithParams or something because AsyncTask will allow only 1 type to be sent IN, and I needed both the URL and the params for the HTTP request.
public class URLWithParams {
public String url;
public List<NameValuePair> nameValuePairs;
public URLWithParams()
{
nameValuePairs = new ArrayList<NameValuePair>();
}
}
and then I send it to a JSONClient:
public class JSONClient extends AsyncTask<URLWithParams, Void, String> {
private final static String TAG = "JSONClient";
ProgressDialog progressDialog ;
GetJSONListener getJSONListener;
public JSONClient(GetJSONListener listener){
this.getJSONListener = listener;
}
@Override
protected String doInBackground(URLWithParams... urls) {
return connect(urls[0].url, urls[0].nameValuePairs);
}
public static String connect(String url, List<NameValuePair> pairs)
{
HttpClient httpclient = new DefaultHttpClient();
if(url == null)
{
Log.d(TAG, "want to connect, but url is null");
}
else
{
Log.d(TAG, "starting connect with url " + url);
}
if(pairs == null)
{
Log.d(TAG, "want to connect, though pairs is null");
}
else
{
Log.d(TAG, "starting connect with this many pairs: " + pairs.size());
for(NameValuePair dog : pairs)
{
Log.d(TAG, "example: " + dog.toString());
}
}
// Execute the request
HttpResponse response;
try {
// Prepare a request object
HttpPost httpPost = new HttpPost(url);
httpPost.setEntity(new UrlEncodedFormEntity(pairs));
response = httpclient.execute(httpPost);
// Examine the response status
Log.i(TAG,response.getStatusLine().toString());
BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent(), "UTF-8"));
String json = reader.readLine();
return json;
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(String json ) {
getJSONListener.onRemoteCallComplete(json);
}
public interface GetJSONListener {
public void onRemoteCallComplete(String jsonFromNet);
}
}
Then call it from my main class like this
public class BookCatalog implements GetJSONListener {
private final String TAG = this.getClass().getSimpleName();
private String catalog_url = "URL";
private void getCatalogFromServer() {
URLWithParams mURLWithParams = new URLWithParams();
mURLWithParams.url = catalog_url;
try {
JSONClient asyncPoster = new JSONClient(this);
asyncPoster.execute(mURLWithParams);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
@Override
public void onRemoteCallComplete(String jsonBookCatalogList) {
Log.d(TAG, "received json catalog:");
Log.d(TAG, jsonBookCatalogList);
JSONObject bookCatalogResult;
try {
bookCatalogResult = (JSONObject) new JSONTokener(jsonBookCatalogList).nextValue();
JSONArray books = bookCatalogResult.getJSONArray("books");
if(books != null) {
ArrayList<String> newBookOrdering = new ArrayList<String>();
int num_books = books.length();
BookCatalogEntry temp;
DebugLog.d(TAG, "apparently we found " + Integer.toString(num_books) + " books.");
for(int book_id = 0; book_id < num_books; book_id++) {
JSONObject book = books.getJSONObject(book_id);
String title = book.getString("title");
int version = book.getInt("price");
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}
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