Android点击按钮后刷新 ListView

Question

我正在尝试刷新从 ArrayList<String> 获取文本的 ListView单击按钮后。

点击之前，我的 ListView填充了在 ArrayList 中找到的第一个字符串(我使用 subList(0,1) 做到了)。

我只想在 arrayList 中找到下一个字符串并将其放在 ListView 上.我尝试了以下但它返回错误将适配器放入 onClick方法。

    package com.android.quizzle;

    import java.io.BufferedReader;
    import java.io.InputStream;
    import java.io.InputStreamReader;
    import java.util.*;

    import org.apache.http.HttpEntity;
    import org.apache.http.HttpResponse;
    import org.apache.http.NameValuePair;
    import org.apache.http.client.HttpClient;
    import org.apache.http.client.entity.UrlEncodedFormEntity;
    import org.apache.http.client.methods.HttpPost;
    import org.apache.http.impl.client.DefaultHttpClient;
    import org.apache.http.message.BasicNameValuePair;
    import org.json.JSONArray;
    import org.json.JSONException;
    import org.json.JSONObject;

    import android.app.Activity;
    import android.content.Intent;
    import android.os.Bundle;
    import android.util.Log;
    import android.view.View;
    import android.view.View.OnClickListener;
    import android.widget.ArrayAdapter;
    import android.widget.Button;
    import android.widget.ListView;
    import android.widget.RadioButton;
    import android.widget.RadioGroup;
    import android.widget.TextView;
    import android.widget.Toast;

    public class MainMenuActivity extends Activity {



ListView ls1;

String result = null;

String result2 = null;

InputStream is = null;

StringBuilder sb=null;

StringBuilder sb2=null;

JSONArray jArray;

String domande;

String risposta;

RadioGroup radioGroup;

private RadioButton radio1;

private RadioButton radio2;

private RadioButton radio3;

private RadioButton radio4;

private Button nextQuest;

TextView t1;

ArrayList<String> strings2 = new ArrayList<String>();
ArrayList<String> risposte = new ArrayList<String>();

ArrayList<String> risp = new ArrayList<String>();



@Override
public void onCreate(Bundle icicle)

{
    Bundle b = getIntent().getExtras();
    String user = b.getString("il dato inserito è: " );
    Toast.makeText(getBaseContext(), "Benvenuto: " + user ,
            Toast.LENGTH_LONG).show();

    //array list per memorizzare l'output json


         super.onCreate(icicle);
         setContentView(R.layout.managerdb);
         ls1 = (ListView) findViewById(R.id.list);
         radioGroup = (RadioGroup)findViewById(R.id.radioGroup1);
         radio1 = (RadioButton)findViewById(R.id.radioButton1);
         radio2 = (RadioButton)findViewById(R.id.radioButton2);
         radio3 = (RadioButton)findViewById(R.id.radioButton3);
         radio4 = (RadioButton)findViewById(R.id.radioButton4);
        //prossima domanda
         nextQuest = (Button)findViewById(R.id.buttonNextQuest);
         t1 = (TextView)findViewById(R.id.TextView01);

        nextQuest.setOnClickListener(new OnClickListener() 
        {
            public void onClick(View v) 
            {
                String risp = null;
                ListView ls1;
                if(v == nextQuest)
                {

                if(radio1.isChecked() == true)
                {
                        risp=risposte.get(0);
                        Toast.makeText(getBaseContext(), risp ,
                                Toast.LENGTH_LONG).show();
    //HERE I PUT MY ADAPTER BUT IT GIVES ME ERROR

    ls1.setAdapter(new ArrayAdapter<String>(this,
            android.R.layout.simple_list_item_1,
            strings2.subList(0, 1)));
    ls1.setTextFilterEnabled(true);

                }
                if(radio2.isChecked() == true)
                {
                        risp=risposte.get(1);
                        Toast.makeText(getBaseContext(), risp ,
                                Toast.LENGTH_LONG).show();

                }
                if(radio3.isChecked() == true)
                {
                    risp=risposte.get(3);
                }
                if(radio4.isChecked() == true)
                {
                    risp=risposte.get(4);
                }
                }


            }




         });



    // query post.

    ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
    nameValuePairs.add(new BasicNameValuePair("username", user));


    // http post

    try {
        HttpClient httpclient = new DefaultHttpClient();
        HttpPost httppost = new HttpPost(
                "http://labinform.altervista.org/Android/quiz.php");
        httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
        HttpResponse response = httpclient.execute(httppost);
        HttpEntity entity = response.getEntity();
        is = entity.getContent();
    } catch (Exception e) {
        Log.e("log_tag", "Error in http connection " + e.toString());
    }

    // convert response to string

    try {

        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "iso-8859-1"), 8);
        sb = new StringBuilder();
        sb.append(reader.readLine());
        String line;
        while ((line = reader.readLine()) != null) {
            sb.append(line);

        }
        is.close();
        result = sb.toString();



        if(result.contains("0") || result.contains("1"))
       { 
           Toast.makeText(MainMenuActivity.this, "Seleziona una categoria di apprendimento" , Toast.LENGTH_LONG).show();               
       }
        else{
           Toast.makeText(MainMenuActivity.this, "Non hai ancora compilato un quiz" , Toast.LENGTH_LONG).show();  
                    retrieveArray();
        }}
    catch (Exception e) {
        Log.e("log_tag", "Error converting result " + e.toString());
    }
    }


    private void retrieveArray() {

        //arrayList per memorizzare il profilo

        //nuova connessione alla pagina contenente i quiz.
        ArrayList<NameValuePair> nameValuePairs2 = new ArrayList<NameValuePair>();

        try {
            HttpClient httpclient = new DefaultHttpClient();
            HttpPost httppost = new HttpPost(
                    "http://labinform.altervista.org/Android/tag.php");
            httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs2));
            HttpResponse response = httpclient.execute(httppost);
            HttpEntity entity = response.getEntity();
            is = entity.getContent();
        } catch (Exception e) {
            Log.e("log_tag", "Error in http connection " + e.toString());
        }
        try {

            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    is, "iso-8859-1"), 8);
            sb2 = new StringBuilder();
            sb2.append(reader.readLine());
            String line;
            while ((line = reader.readLine()) != null) {
                sb2.append(line);               
            }
            is.close();
            result2 = sb2.toString();


        }
        catch (Exception e) {
            Log.e("log_tag", "Error in http connection " + e.toString());
        }
        //parsing data to Json


    try{

        JSONObject jObject = new JSONObject(result2);

        jArray = jObject.getJSONArray("domande");
        JSONArray jArray2 = jObject.getJSONArray("risposte");


        for(int i=0;i<jArray.length();i++)
        {                        
            domande=jArray.getString(i);
            strings2.add(domande);     
        }
        for(int k=0;k<jArray2.length();k++){
        risposta = jArray2.getString(k);
        risposte.add(risposta);
        }


    }catch(JSONException e1){

    }catch(Exception e1){
        Log.e("log_tag", "error " + e1.toString());

    } 



    ls1.setAdapter(new ArrayAdapter<String>(this,
            android.R.layout.simple_list_item_1,
            strings2.subList(0, 1)));
    ls1.setTextFilterEnabled(true);


    radio1.setText(risposte.get(0));
    radio2.setText(risposte.get(1));
    radio3.setText(risposte.get(2));
    radio4.setText(risposte.get(3));

}
}

谁能帮帮我？

Answer 1

ls1.setAdapter(new ArrayAdapter<String>(this,
        android.R.layout.simple_list_item_1,
        strings2.subList(0, 1)));

传递应用程序上下文，而不是 this，即 OnClickListener()。

这可以通过在定义监听器之前存储应用程序上下文来实现:

Context context = this;

并传递 context 变量而不是 this。