如何在 AsyncTask 完成工作后删除警报对话框

Question

我相信我这样做是正确的，在我调用的活动类中执行警报对话框出现，然后数据加载但警报对话框永远不会消失。这是我的 AsyncTask 代码：

后面是我的活动代码。

public class Worker extends AsyncTask<URL, Integer, Long>{
private Activity ne;
private ProgressDialog progressDialog;
private Handler handler;


public Worker(Handler handler, Activity ne){
this.handler = handler;
this.ne = ne;

}

protected void onPreExecute() {
    progressDialog = ProgressDialog.show(ne,"", "Retrieving News Events", true);
}

protected void onProgressUpdate(Void... progress) {

}

protected void onPostExecute(Void result) {

    progressDialog.dismiss();
}

/* (non-Javadoc)
 * @see android.os.AsyncTask#doInBackground(Params[])
 */
@Override
protected Long doInBackground(URL... urls) {
HttpClient client = new DefaultHttpClient();
HttpGet get;

    try {
            get = new HttpGet(urls[0].toURI());
        ResponseHandler<String> response = new BasicResponseHandler();
        String responseBody = client.execute(get, response);


        String page = responseBody;

        Bundle data = new Bundle();

        data.putString("page",page);
        Message msg = new Message();
        msg.setData(data);

        handler.sendMessage(msg);

    }
    catch (Throwable t) {
        Log.d("UpdateNews", "PROBLEMS");
    }
return null;
}

}

public class NewsEvents extends ListActivity{
private URL JSONNewsEvents;
private ArrayList<NewsEvent> neList;
private ArrayList<String> keyWordList;
private Worker worker;
private TextView selection;
private ProgressDialog progressDialog;
static final int PROGRESS_DIALOG = 0;
public static final String KEYWORDS = "keywords";
private NewsEvents ne;

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.newsevents);
    ne = this;
    neList = new ArrayList<NewsEvent>();
selection=(TextView)findViewById(R.id.selection);

    try {
    JSONNewsEvents = new URL(getString(R.string.jsonnewsevents));
} catch (MalformedURLException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

    worker = new Worker(handler, this);

    setListAdapter(new IconicAdapter());
    getKeywords(); 
    worker.execute(JSONNewsEvents);


}

/**
 * @return
 */

public ArrayList<String> getKeywords(){
try {
    InputStream fi = openFileInput(KEYWORDS);

    if (fi!=null) {
        ObjectInputStream in = new ObjectInputStream(fi);
                keyWordList = (ArrayList<String>) in.readObject();
                in.close();
    }
}
catch (java.io.FileNotFoundException e) {
    // that's OK, we probably haven't created it yet
}
catch (Throwable t) {
    Toast
        .makeText(this, "Exception: "+t.toString(), Toast.LENGTH_LONG)
        .show();
}
if(keyWordList == null){
    keyWordList = new ArrayList<String>();
    return keyWordList;
}

return keyWordList;
}

public void onListItemClick(ListView parent, View v,
    int position, long id) {
startFullNewsEvent(neList.get(position));
}

/**
 * @param newsEvent
 */
public void startFullNewsEvent(NewsEvent ne) {
Intent intent = new Intent(this, FullNewsEvent.class);
intent.putExtra("ne", ne);
this.startActivity(intent);
finish();
}



private Handler handler = new Handler(){
    @Override
    public void handleMessage(Message msg) {
        String page = msg.getData().getString("page");



        try {  
           JSONArray parseArray = new JSONArray(page);  

           for (int i = 0; i < parseArray.length(); i++) {  
               JSONObject jo = parseArray.getJSONObject(i);  

               String title = jo.getString("title");  

               String body =jo.getString("body");

               String pd = jo.getString("postDate");  

               String id = jo.getString("id");


               NewsEvent ne = new NewsEvent(title, pd , body, id);

               boolean unique = true;
               for(NewsEvent ne0 : neList){
               if(ne.getId().equals(ne0.getId())){
                  unique = false;
               }else{
                   unique = true;
               }
               }

               if(unique == true){
               neList.add(ne);
               }
           }  
          } catch (JSONException e) {  
           // TODO Auto-generated catch block  
           e.printStackTrace();  
          }
          ne.setListAdapter(new IconicAdapter());

    }
};

public class IconicAdapter extends ArrayAdapter<NewsEvent> {
IconicAdapter() {
    super(NewsEvents.this, R.layout.rownews, neList);
}

public View getView(int position, View convertView,ViewGroup parent) {
    LayoutInflater inflater=getLayoutInflater();

    View row=inflater.inflate(R.layout.rownews, parent, false);
    TextView label=(TextView)row.findViewById(R.id.label);
    ImageView image= (ImageView)row.findViewById(R.id.icon);

    String body = neList.get(position).getBody();
    body.replaceAll("\\<.*?>", "");
    String title = neList.get(position).getTitle();
    for(String s : keyWordList){
        if(body.contains(s) || body.contains(s.toLowerCase()) ||
            title.contains(s) || title.contains(s.toLowerCase())){
        neList.get(position).setInterested(true);
        }
    }

    if(neList.get(position).isInterested() == true){
        image.setImageResource(R.drawable.star);
    }


    label.setText(neList.get(position).getTitle());

    return(row);
}
}

}

Answer 1

首先更改您的 onPostExecute 以包含 @Override：

@Override
protected void onPostExecute(Void result) { 
  progressDialog.dismiss();
}

在你的类定义中包括：

public class Worker extends AsyncTask<Void, Void, Void>

第一个参数是doInBackground方法的输入类型，第二个参数是onProgressUpdate的输入类型，第三个参数是onPostExecute的输入类型和doInBackground的结果。

您似乎没有使用 doInBackground 方法的输入参数，因此只需将其更改为 Void... 并同时更改返回类型：

protected Void doInBackground(Void... paramArrayOfParams) { ... }

这有帮助吗？

编辑：

我看到您已更改代码以使用 doInBackground 的参数，因此您的类定义中的第一个参数是正确的。但是，尝试将 Void 作为最后两个参数。并将 doInBackground 的返回类型也更改为 Void。

像这样：

public class Worker extends AsyncTask<URL, Void, Void>{
private Activity ne;
private ProgressDialog progressDialog;
private Handler handler;

public Worker(Handler handler, Activity ne){
  this.handler = handler;
  this.ne = ne;

}

@Override
protected void onPreExecute() {
  progressDialog = ProgressDialog.show(ne,"", "Retrieving News Events", true);
}

protected void onProgressUpdate(Void... progress) {
}

@Override
protected void onPostExecute(Void result) {
  progressDialog.dismiss();
}

/* (non-Javadoc)
 * @see android.os.AsyncTask#doInBackground(Params[])
 */
@Override
protected Void doInBackground(URL... urls) {
  HttpClient client = new DefaultHttpClient();
  HttpGet get;

  try {
        get = new HttpGet(urls[0].toURI());
    ResponseHandler<String> response = new BasicResponseHandler();
    String responseBody = client.execute(get, response);


    String page = responseBody;

    Bundle data = new Bundle();

    data.putString("page",page);
    Message msg = new Message();
    msg.setData(data);

    handler.sendMessage(msg);

  }
  catch (Throwable t) {
    Log.d("UpdateNews", "PROBLEMS");
  }
  return null;
}

Answer 2

您没有正确覆盖 asynctask 方法。看一个例子

http://developer.android.com/reference/android/os/AsyncTask.html

注意现在他们声明了他们的异步任务

extends AsyncTask<URL, Integer, Long>