Android：如何通过单击按钮重新启动方法

Question

我有一个按钮，它从微调器中获取月份和年份，然后调用异步任务，该任务读取json数据。 那部分工作正常，但是如果我尝试更改月份和年份，然后再次单击该按钮，则无济于事。 我必须按返回以重新加载页面，然后再次单击该按钮才能获得不同的结果。 这是我的代码。 你们中任何一个聪明的人可以帮我吗。

package com.app.simplictyPortal;


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.List;

import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import com.app.simplicityPortal.adapter.InvoiceAdapter;

import android.app.Fragment;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Spinner;



public class InvoiceFragment extends Fragment {
    public InvoiceFragment(){}
    Button load;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        View rootView = inflater.inflate(R.layout.fragment_invoice, container, false);
        ArrayList<String> years = new ArrayList<String>();
        int thisYear = Calendar.getInstance().get(Calendar.YEAR);
        int currentMonth = Calendar.getInstance().get(Calendar.MONTH);
        for (int i = 2013; i <= thisYear; i++)
        {
            years.add(Integer.toString(i));
        }

        //String tmonth = Integer.toString(currentMonth);
        String tyear = Integer.toString(thisYear);
        final Spinner year = (Spinner)rootView.findViewById(R.id.spinner1);
        final Spinner month = (Spinner)rootView.findViewById(R.id.spinner2);
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity(),
                android.R.layout.simple_spinner_item, years);



        // Specify the layout to use when the list of choices appears
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

        // Apply the adapter to the spinner
        year.setAdapter(adapter);
        year.setSelection(adapter.getPosition(tyear));

        ArrayAdapter<CharSequence> adapter2 = ArrayAdapter.createFromResource(getActivity(),
                R.array.month, android.R.layout.simple_spinner_item);
        // Specify the layout to use when the list of choices appears
        adapter2.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        // Apply the adapter to the spinner
        month.setAdapter(adapter2);
        month.setSelection(currentMonth);
        load=(Button)rootView.findViewById(R.id.button1);
        load.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub

                String y = (String) year.getSelectedItem();
                int im = month.getSelectedItemPosition();
                String m =  Integer.toString(im +1);

                final GlobalClass globalVariable = (GlobalClass) getActivity().getApplicationContext();

                final String Compid = globalVariable.getCompid();
                new InvoiceAsyncTask().execute("http://dev-sql1:8080/api/invoice/getall/"+Compid+"?m="+m+"&y="+y);

            }
        }); 


        return rootView;

    }


    public void invoice(JSONArray jArray) {

        ListView lv = (ListView) getView().findViewById(R.id.listView1);
        List<ListViewItem> items = new ArrayList<InvoiceFragment.ListViewItem>();
        try {
            for (int i = 0; i <jArray.length(); i++) { 
                final JSONObject json_data = jArray.getJSONObject(i);
                    items.add(new ListViewItem()
                    {{
                        Vendor=  json_data.optString("CarrierName");
                        Bill =  "$ " + json_data.optString("BillAmount");
                        Serviceacct = json_data.optString("ServiceAccountNumber");
                        Date = json_data.optString("ReceivedDate");                     
                    }});


                }


    } catch (JSONException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();


}




        InvoiceAdapter adapter = new InvoiceAdapter(getActivity(), items);
        lv.setAdapter(adapter);


        // TODO Auto-generated method stub

    }


public class ListViewItem
{

    public String Vendor;
    public String Bill;
    public String Serviceacct;
    public String Date;

}   public static String GET(String url){
    InputStream inputStream = null;
    String result = "";
    try {

        // create HttpClient
        HttpClient httpclient = new DefaultHttpClient();

        // make GET request to the given URL
        HttpResponse httpResponse = httpclient.execute(new HttpGet(url));

        // receive response as inputStream
        inputStream = httpResponse.getEntity().getContent();

        // convert inputstream to string
        if(inputStream != null)
            result = convertInputStreamToString(inputStream);
        else
            result = "Did not work!";

    } catch (Exception e) {
        Log.d("InputStream", e.getLocalizedMessage());
    }

    return result;
}

private static String convertInputStreamToString(InputStream inputStream) throws IOException{
    BufferedReader bufferedReader = new BufferedReader( new InputStreamReader(inputStream));
    String line = "";
    String result = "";
    while((line = bufferedReader.readLine()) != null)
        result += line;

    inputStream.close();
    return result;

}


public class InvoiceAsyncTask extends AsyncTask<String, Void, String> {
    @Override
    protected String doInBackground(String... urls) {

        return GET(urls[0]);

    }
    // onPostExecute displays the results of the AsyncTask.
    @Override
    protected void onPostExecute(String result) {
        try {
            JSONArray jArray = new JSONArray(result);

                invoice(jArray);

        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();

    }

}

}


    }

Answer 1

您如何处理InvoiceAsyncTask的结果？ 您是否实现了从AsyncTask的onPostExecute（）到活动的回调？

也许下面的示例将为您提供帮助。

首先，使用回调接口实现AsyncTask类：

public class ServerRequestAsyncTask extends AsyncTask<String, Void, ServerResponseDetails> {

public ServerRequestAsyncTask(Fragment fragment, ServerRequestDetails request) {
    mFragment = fragment;
    mRequest = request;
}

public interface OnServerRequestAsyncTaskCompletedListener {
    void onServerRequestAsyncTaskCompleted(ServerResponseDetails response);
}

public void cancel() {
    if (mHttpGet != null && !mHttpGet.isAborted()) mHttpGet.abort();
    cancel(true);
}

并添加onPostExecute（）：

@Override
protected void onPostExecute(ServerResponseDetails response) {
    if (mFragment != null) mFragment.onServerRequestAsyncTaskCompleted(response);
}

我从Fragment调用AsyncTask，但是您可以将其与Activity结合使用。 然后，在“活动”中实现接口：

@Override
public void onServerRequestAsyncTaskCompleted(ServerResponseDetails response) {
    // do what you need here, then 'finish' task by setting mServerRequest to null
    mServerRequest = null;
}

并执行AsyncTask：

protected ServerRequestAsyncTask mServerRequest = null;

public boolean isServerRequestRunning() {
    return (mServerRequest != null);
}

public void cancelServerRequest() {
    mServerRequest.cancel();
}

public void sendServerRequest(Fragment fragment, ServerRequestDetails request) {
    if (Application.isNetworkAvailable()) {
        if (!isServerRequestRunning()) {
            mServerRequest = new ServerRequestAsyncTask(fragment, request);
            mServerRequest.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR,
                    {params});
        }
    }
}

mServerRequest变量保存对当前执行任务的引用。 如果需要中止，可以调用mServerRequest.cancel（）。

Answer 2

谢谢大家，但我已经弄清楚了。 我需要在post execute方法中取消Async任务。

@Override
    protected void onPostExecute(String result) {
        try {
            JSONArray jArray = new JSONArray(result);

                invoice(jArray);
                cancel(true);
                isCancelled();

        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();

    }