Java 从AsyncTask类返回数据
如何从异步任务中获取数据?我的MainActivity正在调用触发AsyncTask的DataCall.getJSON函数,但我不确定如何将数据返回到原始活动 调用DataCall的MainActivity,该调用应返回字符串并将其保存在Java 从AsyncTask类返回数据,java,android,android-asynctask,Java,Android,Android Asynctask,如何从异步任务中获取数据?我的MainActivity正在调用触发AsyncTask的DataCall.getJSON函数,但我不确定如何将数据返回到原始活动 调用DataCall的MainActivity,该调用应返回字符串并将其保存在状态\u data String state_data = DataCall.getJSON(spinnerURL,spinnerContentType); DataCall: public class DataCall extends Activity
状态\u 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 });
}
}
公共类数据调用扩展活动{
私有静态最终字符串TAG=“MyApp”;
私有类下载WebPagetTask扩展异步任务{
受保护的字符串doInBackground(字符串…URL){
字符串响应=”;
for(字符串url:url){
DefaultHttpClient=新的DefaultHttpClient();
HttpGet HttpGet=新的HttpGet(url);
试一试{
HttpResponse execute=client.execute(httpGet);
InputStream内容=execute.getEntity().getContent();
BufferedReader buffer=新的BufferedReader(
新的InputStreamReader(内容));
字符串s=“”;
而((s=buffer.readLine())!=null){
响应+=s;
}
}捕获(例外e){
e、 printStackTrace();
}
}
返回响应;
}
受保护的void onPostExecute(字符串结果){
//这就是我需要将数据返回到主活动的地方。(我猜)
}
}
public void getJSON(字符串myUrlString,字符串contentType){
DownloadWebPagetTask=新建DownloadWebPagetTask();
task.execute(新字符串[]{”http://www.mywebsite.com/“+myUrlString});
}
}
将其序列化,然后读取。我知道的唯一方法是。尽管我不同意为这个简单的任务创建一个新的活动
startActivityForResult()
从另一个活动获取数据
检查。您可以将您的数据存储到Intent的extras中。但是,如果您有大量数据,最好将其写入一个文件,从下载完成的其他活动中获取结果,然后读取该文件。一些选项:
a) 使您的bean实现可序列化的接口,然后您可以通过Intent传递bean
b) 实现
Application
接口(您需要在清单中创建一个条目),在应用程序类中使用setter\getter方法。您可以从AsyncTask
在应用程序中设置bean,然后从活动中检索。修改AsyncTask
,如下所示:
public class GetData extends AsyncTask<String, Void, String>
{
DataDownloadListener dataDownloadListener;
public GetData()
{
//Constructor may be parametric
}
public void setDataDownloadListener(DataDownloadListener dataDownloadListener) {
this.dataDownloadListener = dataDownloadListener;
}
@Override
protected Object doInBackground(Object... param)
{
// do your task...
return null;
}
@Override
protected void onPostExecute(Object results)
{
if(results != null)
{
dataDownloadListener.dataDownloadedSuccessfully(results);
}
else
dataDownloadListener.dataDownloadFailed();
}
public static interface DataDownloadListener {
void dataDownloadedSuccessfully(Object data);
void dataDownloadFailed();
}
}
注意:对于正在阅读此文章的人
请考虑这是最好的,也许是正确的实现。
< P>我的关键是创建一个名为URLWordPARAMS的类或某些东西,因为AssicTebug将只允许发送1种类型,并且我需要URL和PARAMs用于HTTP请求。public class URLWithParams {
public String url;
public List<NameValuePair> nameValuePairs;
public URLWithParams()
{
nameValuePairs = new ArrayList<NameValuePair>();
}
}
公共类URLWithParams{
公共字符串url;
公开名单;
公共URLWithParams()
{
nameValuePairs=新的ArrayList();
}
}
然后我将其发送到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);
}
}
public类JSONClient扩展了异步任务{
私有最终静态字符串TAG=“JSONClient”;
进行对话进行对话;
GetJSONListener GetJSONListener;
公共JSONClient(GetJSONListener侦听器){
this.getJSONListener=listener;
}
@凌驾
受保护的字符串doInBackground(URLWithParams…URL){
返回连接(url[0].url,url[0].nameValuePairs);
}
公共静态字符串连接(字符串url、列表对)
{
HttpClient HttpClient=新的DefaultHttpClient();
如果(url==null)
{
d(标记“想要连接,但url为空”);
}
其他的
{
Log.d(标记“开始连接url”+url);
}
if(pairs==null)
{
d(标记“虽然pairs为null,但想要连接”);
}
其他的
{
Log.d(标记“开始连接这么多对:“+pairs.size()”);
for(NameValuePair狗:对)
{
Log.d(标记,“示例:+dog.toString());
}
}
//执行请求
HttpResponse响应;
试一试{
//准备一个请求对象
HttpPost HttpPost=新的HttpPost(url);
setEntity(新的UrlEncodedFormEntity(对));
response=httpclient.execute(httpPost);
//检查响应状态
Log.i(标记,response.getStatusLine().toString());
BufferedReader=新的BufferedReader(新的InputStreamReader(response.getEntity().getContent(),“UTF-8”);
字符串json=reader.readLine();
返回json;
}捕获(客户端协议例外e){
//TODO自动生成的捕捉块
e、 printStackTrace();
}捕获(IOE异常){
//TODO自动生成的捕捉块
e、 printStackTrace();
}
返回null;
}
@凌驾
受保护的void onPostExecute(字符串json){
onRemoteCallComplete(json);
}
公共接口GetJSONListener{
公共void onRemoteCallComplete(字符串jsonFromNet);
}
}
然后从我的主课上这样叫它
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();
}
}
}
public类BookCatalog实现GetJSONListener{
私有最终字符串标记=this.getClass().getSimpleName();
私有字符串目录\u url=“url”;
私有void getCatalogFromServer(){
URLWithParams mURLWithParams=新的URLWithParams();
mURLWithParams.url=目录\ url;
试一试{
JSONClient asyncPoster=新的JSONClient(此);
asyncPoster.execute(mURLWithParams);
}捕获(例外e){
//TODO自动生成的捕捉块
e、 printStackTrace();
}
}
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();
}
}
}