我找不到通过JSON获取实时更新到listview的方法。
我的活动是从网页请求JSON数据，代码是：
public class Second extends Activity {
static final String Li_nk = "LinkName:";
static final String Image_name = "ImageName:";
ListView list;
public final static String AUTH = "authentication";
static final String KEY_THUMB_URL = "thumb_image"; // Uri.decode("http://zeesms.info/android_app_images/Koala.jpg");
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Intent i2 = getIntent();
String wrd = i2.getStringExtra("entrd");
Log.v("keyis", wrd);
// if(wrd.equalsIgnoreCase("test")){
JSONObject j2 = JSONfunctions.getJSONfromURL("/webservice_search.php?keyword=" + wrd + "&format=json");
ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();
try {
JSONArray jray = j2.getJSONArray("listings");
for (int i = 0; i < jray.length(); i++) {
Log.v("state", "json data being read");
JSONObject j3 = jray.getJSONObject(i);
String first = j3.getString("listing");
Log.v("sublist", first);
JSONObject j4 = j3.getJSONObject("listing");
String sec = j4.getString("links");
int maxLength = (sec.length() < 30) ? sec.length() : 27;
sec.substring(0, maxLength);
String cutsec = sec.substring(0, maxLength);
Log.v("links are", cutsec);
String img = j4.getString("image_name");
Log.v("image name is ", img);
// Uri
// dimg=Uri.parse("http://zeesms.info/android_app_images/Koala.jpg");
HashMap<String, String> map = new HashMap<String, String>();
map.put("Id", String.valueOf(i));
map.put(Li_nk, cutsec);
map.put(Image_name, j4.getString("image_name"));
map.put(KEY_THUMB_URL, "http://zeesms.info/android_app_images/" + img);
mylist.add(map);
}
}
catch (JSONException e) {
alertbox();
Log.e("loG_tag", "Error parsing" + e.toString());
}
list = (ListView) findViewById(R.id.lv1);
this.list.setEmptyView(findViewById(R.id.empty));
list.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
// Toast.makeText(getApplicationContext(),"Click ListItem Number "
// + position, Toast.LENGTH_LONG).show();
Intent myIntent = new Intent(Intent.ACTION_VIEW, Uri.parse("http://www.riffre.com/"));
startActivity(myIntent);
}
});
LazyAdapter adapter = new LazyAdapter(this, mylist);
list.setAdapter(adapter);
list.setItemsCanFocus(false);
// }
/*
* else{ alertbox(); }
*/
}
/*
* public void register(View view) { Log.w("C2DM",
* "start registration process"); Intent intent = new
* Intent("com.google.android.c2dm.intent.REGISTER");
* intent.putExtra("app", PendingIntent.getBroadcast(this, 0, new
* Intent(), 0)); // Sender currently not used intent.putExtra("sender",
* "nonsenses@gmail.com"); startService(intent); }
*
* public void showRegistrationId(View view) { SharedPreferences prefs =
* PreferenceManager .getDefaultSharedPreferences(this); String string =
* prefs.getString(AUTH, "n/a"); Toast.makeText(this, string,
* Toast.LENGTH_LONG).show(); Log.d("C2DM RegId", string);
*
* }
*/
public void alertbox() {
new AlertDialog.Builder(this).setMessage("Invalid Keyword,No Results found").setTitle("Alert").setCancelable(true).setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
finish();
}
}).show();
}
}
我正在使用自定义适配器，代码如下：
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());
}
@Override
public int getCount() {
// TODO Auto-generated method stub
return data.size();
}
@Override
public Object getItem(int position) {
// TODO Auto-generated method stub
return position;
}
@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View vi=convertView;
if(convertView==null)
vi = inflater.inflate(R.layout.custom_row_view1, null);
TextView title = (TextView)vi.findViewById(R.id.linkname); // merchnts name
TextView artist = (TextView)vi.findViewById(R.id.imagename); // address
//TextView duration = (TextView)vi.findViewById(R.id); // distance
ImageView thumb_image=(ImageView)vi.findViewById(R.id.mClogo); // logo
HashMap<String, String> jsn = new HashMap<String, String>();
jsn = data.get(position);
// Setting all values in listview
title.setText(jsn.get(Second.Li_nk));
artist.setText(jsn.get(Second.Image_name));
//duration.setText(song.get(CustomizedListView.KEY_DURATION));
imageLoader.DisplayImage(jsn.get(Second.KEY_THUMB_URL), thumb_image);
return vi;
}
}
我想要的是应用程序每分钟左右用数据更新listview。此外，列表中的最新条目应保持最佳状态。
最好的方法是什么？
答案 0 :(得分：2)
如果上面的代码有效，您应该可以通过以下步骤实现目标：
答案 1 :(得分：2)
将您的JSON解析代码放在一个单独的函数中，而不是try..catch中。{/ p>
所以每分钟都可以轻松调用该部分。假设函数名onCreate()每次还要添加一行LoadData()来更新适配器/列表。
现在在onCreate（）中，编写此代码每隔一分钟调用一次该函数，
adapter.notifyDataSetChanged()现在第二个问题，在顶部添加新数据..
我现在正想着写一个循环，在调用适配器通知更改之前将其添加到您的功能中，例如
final Handler handler = new Handler();
Runnable runable = new Runnable() {
@Override
public void run() {
//call the function
LoadData();
//also call the same runnable
handler.postDelayed(this, 1000);
}
};
handler.postDelayed(runable, 1000);
答案 2 :(得分：2)
这是onCreate（）方法的一种可能实现，它将每分钟运行一次更新任务：
public class JSON_AndroidActivity extends Activity {
/** Called when the activity is first created. */
private JSONLoaderTask mJSONLoaderTask;
private Handler mHandler;
private ArrayAdapter<String> mArrayAdapter;
private Runnable mRefresher = new Runnable() {
@Override
public void run() {
mJSONLoaderTask = new JSONLoaderTask(JSON_AndroidActivity.this, mArrayAdapter);
mJSONLoaderTask.execute("");
mHandler.postDelayed(this, 1000);
}
};
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mHandler.postDelayed(mRefresher, 1000);
}
}
这是一个可能的任务的船体实现，您可以在其中执行繁重的加载并更新适配器以获取列表：
public class JSONLoaderTask extends AsyncTask<String, String, String> {
private Context context;
private ProgressDialog progressDialog;
private final ArrayAdapter<String> mArrayAdapter;
public JSONLoaderTask(Context pContext, ArrayAdapter<String> pArrayAdapter) {
this.context = pContext;
this.mArrayAdapter = pArrayAdapter;
}
@Override
protected void onPreExecute() {
progressDialog = new ProgressDialog(context);
progressDialog.show();
}
@Override
protected String doInBackground(String... params) {
String result = getJSONStream();
return result;
}
private String getJSONStream() {
//load your string here
return "";
}
@Override
protected void onPostExecute(String result) {
progressDialog.dismiss();
// Update your ArrayAdapter
}
}