java - Android:如何通过单击按钮重新启动方法

Question

我有一个按钮，可以从微调器获取月份和年份，然后调用异步任务，该任务读取 json 数据。该部分工作正常，但如果我尝试更改月份和年份，然后再次单击按钮，它不会执行任何操作。我必须按回键重新加载页面才能再次单击该按钮才能获得不同的结果。这是我的代码。各位聪明人可以帮助我吗？

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

如何处理 InvoiceAsyncTask 的结果？您是否实现了从 AsyncTask 的 onPostExecute() 到 Activity 的回调？

也许下面的示例会对您有所帮助。

首先，实现带有回调接口(interface)的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，但您可以将其与 Activity 一起使用。然后，在您的 Activity 中实现接口(interface):

@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()。