2
我使用LazyAdapter創建了一個listview。Android ListView OnScrollListener清除舊數據
當我滾動到列表的底部時，新數據顯示出來，但它清除了所有的舊數據。
我如何在舊數據下添加新數據？
這是我的主要活動代碼
import java.util.ArrayList;
import java.util.HashMap;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import org.w3c.dom.NodeList;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.sax.Element;
import android.view.View;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;
import android.widget.TextView;
public class AndroidJSONParsingActivity extends Activity {
// url to make request
// JSON Node names
static final String TAG_CONTACTS = "comics";
static final String TAG_ID = "id";
static final String TAG_NAME = "title";
static final String TAG_EMAIL = "id";
static final String TAG_PHONE_MOBILE = "image";
// contacts JSONArray
JSONArray contacts = null;
ListView list;
LazyAdapter adapter;
static int counter = 0;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// call the function
LoadData();
}
public void LoadData(){
String url = "http://myurl.com/?start=" + counter;
// Hashmap for ListView
ArrayList<HashMap<String, String>> contactList = new ArrayList<HashMap<String, String>>();
// Creating JSON Parser instance
JSONParser jParser = new JSONParser();
// getting JSON string from URL
JSONObject json = jParser.getJSONFromUrl(url);
try {
// Getting Array of Contacts
contacts = json.getJSONArray(TAG_CONTACTS);
// looping through All Contacts
for(int i = 0; i < contacts.length(); i++){
JSONObject c = contacts.getJSONObject(i);
// Storing each json item in variable
String id = c.getString(TAG_ID);
String name = c.getString(TAG_NAME);
String email = c.getString(TAG_EMAIL);
String mobile = c.getString(TAG_PHONE_MOBILE);
// Phone number is agin JSON Object
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_ID, id);
map.put(TAG_NAME, name);
map.put(TAG_EMAIL, email);
map.put(TAG_PHONE_MOBILE, mobile);
// adding HashList to ArrayList
contactList.add(map);
}
} catch (JSONException e) {
e.printStackTrace();
}
/**
* Updating parsed JSON data into ListView
* */
list=(ListView)findViewById(R.id.list);
// Getting adapter by passing xml data ArrayList
adapter=new LazyAdapter(this, contactList);
list.setAdapter(adapter);
// Launching new screen on Selecting Single ListItem
list.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// getting values from selected ListItem
String name = ((TextView) view.findViewById(R.id.name)).getText().toString();
String cost = ((TextView) view.findViewById(R.id.email)).getText().toString();
String description = ((TextView) view.findViewById(R.id.mobile)).getText().toString();
// Starting new intent
Intent in = new Intent(getApplicationContext(), SingleMenuItemActivity.class);
in.putExtra(TAG_NAME, name);
in.putExtra(TAG_EMAIL, cost);
in.putExtra(TAG_PHONE_MOBILE, description);
startActivity(in);
}
});
list.setOnScrollListener(new OnScrollListener() {
@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
if (view.getAdapter() != null && ((firstVisibleItem + visibleItemCount) >= totalItemCount)) {
//Log.v(TAG, "onListEnd, extending list");
//mPrevTotalItemCount = totalItemCount;
counter = totalItemCount;
LoadData();
adapter.notifyDataSetChanged();}
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
}
});
}
}
這是我LazyAdapter.java文件
import java.util.ArrayList;
import java.util.HashMap;
import android.app.Activity;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
public class LazyAdapter extends BaseAdapter {
private Activity activity;
private ArrayList<HashMap<String, String>> data;
private static LayoutInflater inflater=null;
public ImageLoader imageLoader;
public LazyAdapter(Activity a, ArrayList<HashMap<String, String>> d) {
activity = a;
data=d;
inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
imageLoader=new ImageLoader(activity.getApplicationContext());
}
public int getCount() {
return data.size();
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
View vi=convertView;
if(convertView==null)
vi = inflater.inflate(R.layout.list_row, null);
TextView title = (TextView)vi.findViewById(R.id.title); // title
TextView artist = (TextView)vi.findViewById(R.id.artist); // artist name
TextView duration = (TextView)vi.findViewById(R.id.duration); // duration
ImageView thumb_image=(ImageView)vi.findViewById(R.id.list_image); // thumb image
HashMap<String, String> song = new HashMap<String, String>();
song = data.get(position);
// Setting all values in listview
title.setText(song.get(AndroidJSONParsingActivity.TAG_NAME));
artist.setText(song.get(AndroidJSONParsingActivity.TAG_ID));
duration.setText(song.get(AndroidJSONParsingActivity.TAG_EMAIL));
imageLoader.DisplayImage(song.get(AndroidJSONParsingActivity.TAG_PHONE_MOBILE), thumb_image);
return vi;
}
}
我在這裏有同樣的問題。我已經閱讀了Joel給出的答案，但我沒有理解這一部分：'然後，只需在現有適配器中添加新的聯繫人列表，這意味着我應該這樣做：'adapter = new LazyAdapter（this，contactList ）'，但他也提到：「那麼你不必再次初始化列表視圖和適配器。」那麼，如何將新的contactList添加到現有的適配器？你是怎麼做到的？ – azizbekian 2012-12-15 21:54:11
我用'加'而不是'初始化'這個詞。當我說添加我的意思是追加。將新值添加到現有適配器。換句話說，修改基本adatper使用的列表，並調用notifyDataSetChanged（）。或者使用一個ArrayAdapter，它有一個add（）方法，可以方便地操縱listview – Joel 2012-12-16 00:22:32