我有一个实现监听器的类，这样当另一个具有异步任务的类完成时，可以使用这个监听器返回数据。异步任务正在完成，但在后执行函数中获取数据时，侦听器未传递数据。
异步任务
Public class AdFetcher extends AsyncTask<String,Void,String>
{
private HTTPListener listener;
//sets the listeners
public AdFetcher(HTTPListener listener)
{
this.listener = listener;
}
@Override
protected String doInBackground(String... uri) {
HttpClient httpclient = new DefaultHttpClient();
HttpResponse response;
String responseString = null;
try {
response = httpclient.execute(new HttpGet(uri[0]));
StatusLine statusLine = response.getStatusLine();
if(statusLine.getStatusCode() == HttpStatus.SC_OK){
ByteArrayOutputStream out = new ByteArrayOutputStream();
response.getEntity().writeTo(out);
out.close();
responseString = out.toString();
} else{
//Closes the connection.
response.getEntity().getContent().close();
throw new IOException(statusLine.getReasonPhrase());
}
} catch (ClientProtocolException e) {
//TODO Handle problems..
} catch (IOException e) {
//TODO Handle problems..
}
return responseString;
}
@Override
protected void onPostExecute(String result)
{
//Tries to deserialization and if there is an exception then its added to the Stack Trace.
try
{
JSONObject data = new JSONObject(result);
if(listener==null)
throw new NullPointerException();
//Calls onComplete function in the class/Activity that implemented the listener.
listener.onComplete(data);
}
catch (JSONException e)
{
e.printStackTrace();
}
}
}
听众
public interface HTTPListener{
/**
* Callback function that must be implemented
* to get result from HTTP worker thread.
* @param result
*/
public void onComplete (JSONObject result);
}//end HttpListener interface
类实现监听器
public class AdManager implements HTTPListener
{
//will store the current context of the application.
private Context context;
private Utility utils;
private String url;
private WebView client;
public AdManager(Context context,WebView client)
{
this.client = client;
this.context = context;
}
public void getAd()
{
utils = new Utility();
url = utils.BuildUrl();
new AdFetcher(this).execute(url);
}
public void onComplete(JSONObject result)
{
try
{ Log.e("RESULTS",result.getString("adtype"));
if(result.getString("error") == "null")
{
if(result.getString("adtype") == "banner")
{ //loads the banner image in the webview.
String html = "<a href=\""+result.getString("adclick_url")+"\"><img src=\""+result.getString("adimage")+"\"></a>";
String mime = "text/html";
String encoding = "utf-8";
client.setVisibility(View.VISIBLE);
client.getSettings().setJavaScriptEnabled(true);
client.loadDataWithBaseURL(null, html, mime, encoding, null);
}
}
}
catch (JSONException e)
{
e.printStackTrace();
}
}
}