Develop Reference

Load more option in list view did not show previous list in android

i have parsed Json data from the server. On which im showing all the data in listview and i have Load more option below the ListView. Now when i click load more option, this application reload whole list and did not show previous list data. Please help me find out the solution. Here is footer view click listener :
lFooter.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
page += 1;
new ParseIssues().execute();
listView.removeFooterView(v);
}
});
in above code ParseIssues class parse json values and displays all the data in ListView Here is code for onPostExecute of AsynkTask class :
#Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
if(page < totalPage){
listView.addFooterView(v);
}
listAdapter = new ListAdapterForSearch(activity, mainList);
listView.setAdapter(listAdapter);
// get listview current position - used to maintain scroll position
int currentPosition = listView.getFirstVisiblePosition();
listView.setSelection(currentPosition);
}
Here is BaseAdapter class:
public class ListAdapterForSearch extends BaseAdapter {
private Activity activity;
private ArrayList<HashMap<String, String>> data;
private static LayoutInflater inflater = null;
public ListAdapterForSearch(Activity a, ArrayList<HashMap<String, String>> d) {
activity = a;
data = d;
inflater = LayoutInflater.from(activity);
}
#Override
public int getCount() {
return data.size();
}
#Override
public Object getItem(int position) {
return data.get(position);
}
#Override
public long getItemId(int position) {
return position;
}
#Override
public View getView(final int position, View convertView, final ViewGroup parent) {
View vi = convertView;
if (convertView == null) {
vi = inflater.inflate(R.layout.list_row_item, null);
}
TextView title = (TextView)vi.findViewById(R.id.title);
HashMap<String, String> hash = new HashMap<String, String>();
hash = data.get(position);
title.setText(hash.get("title"));
return vi;
}
}

The answer to your question lies with the variable "mainList", which the adapter uses. You need to add the new data to it, basically this list needs to contain all the data you want to show in your ListView.

You should set adapter on create, after that first add loaded data to mainlist(add new loaded data) & then after loading notify adapter like listadapter.notifydatachange()
Edit: Because every time you are creating adapter that's why you are facing this problem, instead after loading just notify your adapter..

Check in your code you may have clear your mainList.

AsyncTask to get xml

I want to use AsynTask to do custom list with xml from url. I am novice so I don´t know how to structure this properly. When the fragment start doesn´t display nothing. I am using Swipe views with fragments but I don´t know how correct the issue
public class UltimasFragment extends Fragment {
static final String URL = "http://myurl.com/songs";
// XML node keys
static final String KEY_SONG = "songs"; // parent node
static final String KEY_ID = "id_song";
static final String KEY_TITLE = "name";
static final String KEY_THUMB_URL = "picture";
static final String KEY_ARTIST = "duration";
View view;
ListView list;
LazyAdapter adapter;
private ProgressDialog dialog;
public ArrayList<HashMap<String, String>> songsList = new ArrayList<HashMap<String, String>>();
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.ultimas, container, false);
new MiTarea().execute();
list=(ListView) view.findViewById(R.id.lista);
// Getting adapter by passing xml data ArrayList
//adapter=new LazyAdapter(this, songsList);
adapter=new LazyAdapter(getActivity(), songsList);
list.setAdapter(adapter);
// Click event for single list row
list.setOnItemClickListener(new OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
String idrecibida =songsList.get(+position).get("id_song");
String nombrerecibido =songsList.get(+position).get("name");
String caratularecibida =songsList.get(+position).get("picture");
String nuestraoprecibida =songsList.get(+position).get("duration");
}
});
return view;
}
private class MiTarea extends AsyncTask<String, String, String>{
protected void onPreExecute() {
dialog = new ProgressDialog(getActivity());
dialog.setMessage("Actualizando...");
dialog.setIndeterminate(false);
dialog.setCancelable(true);
dialog.show();
}
protected String doInBackground(String... args) {
XMLParser parser = new XMLParser();
String xml = parser.getXmlFromUrl(URL); // getting XML from URL
Document doc = parser.getDomElement(xml); // getting DOM element
NodeList nl = doc.getElementsByTagName(KEY_SONG);
// looping through all song nodes <song>
for (int i = 0; i < nl.getLength(); i++) {
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
Element e = (Element) nl.item(i);
// adding each child node to HashMap key => value
map.put(KEY_ID, parser.getValue(e, KEY_ID));
map.put(KEY_TITLE, parser.getValue(e, KEY_TITLE));
map.put(KEY_THUMB_URL, parser.getValue(e, KEY_THUMB_URL));
map.put(KEY_ARTIST, parser.getValue(e, KEY_ARTIST));
songsList.add(map);
}
return xml;
}
protected void onPostExecute(String bytes) {
dialog.dismiss();
// adding HashList to ArrayList
}
}
}

Here is how to impement async task
http://developer.android.com/reference/android/os/AsyncTask.html
The preExecute method allow you to perform operations before starting the job you want to do asyncronously.
the doInBackground method is here to do your async job.
the on postExecute method will receive what doInBackground returns if it returns something.
if you need to pass parameters to your class like a context, my advice is to make a constructor and passing parameters to it ;)
hope it helped.
regards.

The three parameters are: the parameter type of doInBackground, the parameter type of onProgressUpdate and the parameter type of onPostExecute.
See here the usage:
http://developer.android.com/reference/android/os/AsyncTask.html
Remember to call setReteainInstance(true) in the fragment in this case, because if the fragment is remove you lost the reference to the AsyncTask.

Android How to dynamically update a listview?

I have an app that loads the traffic report from a server and shows it in a timeline (like twitter), the app is configured to load the data from the server every 10 seconds using this code:
#Override
public void onResume() {
super.onResume();
autoUpdate = new Timer();
autoUpdate.schedule(new TimerTask() {
#Override
public void run() {
runOnUiThread(new Runnable() {
public void run() {
new DownloadJSON2().execute(); // this is the class that downloads the data from the server.
}
});
}
}, 0, 10000); // updates each 10 secs
}
#Override
public void onPause() {
autoUpdate.cancel();
super.onPause();
}
The problem is that if I scroll down the list and I'm reading the older posts, the list refreshes and send me to the top of it. I want to download that data like ajax and append it to the top. Or just to tell me that is X new reports and a button to show it.
How can I acomplish this?
BTW I'm extremely new to android programming.
Thanks in advance.
EDIT: Thanks to Vasily Sochinsky i've added the following:
public class DownloadJSON extends AsyncTask<Void, Void, Void> {
#Override
protected void onPreExecute() {
super.onPreExecute();
// Create a progressdialog
mProgressDialog = new ProgressDialog(MainActivity.this);
// Set progressdialog title
mProgressDialog.setTitle("Cargando reportes en tiempo real");
// Set progressdialog message
mProgressDialog.setMessage("Por favor espere");
mProgressDialog.setIndeterminate(false);
// Show progressdialog
mProgressDialog.show();
}
#Override
protected Void doInBackground(Void... params) {
// Create an array
arraylist = new ArrayList<HashMap<String, String>>();
// Retrieve JSON Objects from the given URL address
jsonobject = JSONfunctions
.getJSONfromURL("http://server.com/timeline.php");
try {
// Locate the array name in JSON
jsonarray = jsonobject.getJSONArray("datos");
for (int i = 0; i < jsonarray.length(); i++) {
HashMap<String, String> map = new HashMap<String, String>();
jsonobject = jsonarray.getJSONObject(i);
// Retrive JSON Objects
// jsonobject1 = jsonobject.getJSONObject("contenido");
map.put("imagen", jsonobject.getString("imagen"));
map.put("quien", jsonobject.getString("quien"));
map.put("fecha", jsonobject.getString("fecha"));
map.put("reporte", jsonobject.getString("reporte"));
// map.put("imgs", jsonobject1.getString("imgs"));
// map.put("video", jsonobject1.getString("video"));
// Set the JSON Objects into the array
arraylist.add(map);
}
} catch (JSONException e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(Void args) {
// Locate the listview in listview_main.xml
listview = (ListView) findViewById(R.id.listview);
// Pass the results into ListViewAdapter.java
adapter = new ListViewAdapter(MainActivity.this, arraylist);
// Set the adapter to the ListView
listview.setAdapter(adapter);
adapter.notifyDataSetChanged();
// Close the progressdialog
mProgressDialog.dismiss();
}
}
But the listview is not updating with the new data, how can i achieve this?
EDIT 2: Thanks to cogentapps that gave me a solution, but i still can not add it to the code, where should i add it?
I've tried this but eclipse shows many errors:
protected void onPostExecute(Void args) {
// Locate the listview in listview_main.xml
listview = (ListView) findViewById(R.id.listview);
// Pass the results into ListViewAdapter.java
adapter = new ListViewAdapter(MainActivity.this, arraylist);
// Set the adapter to the ListView
adapter.addAll();
listview.notifyDataSetChanged();
// Close the progressdialog
mProgressDialog.dismiss();
}
This is the code from my ListViewAdapter, where should i add the adapter.add()?
public class ListViewAdapter extends BaseAdapter {
// Declare Variables
Context context;
LayoutInflater inflater;
ArrayList<HashMap<String, String>> data;
ImageLoader imageLoader;
HashMap<String, String> resultp = new HashMap<String, String>();
String coment;
public String img;
public int imga;
public ListViewAdapter(Context context,
ArrayList<HashMap<String, String>> arraylist) {
this.context = context;
data = arraylist;
imageLoader = new ImageLoader(context);
}
#Override
public int getCount() {
return data.size();
}
#Override
public Object getItem(int position) {
return null;
}
#Override
public long getItemId(int position) {
return 0;
}
public View getView(final int position, View convertView, ViewGroup parent) {
// Declare Variables
TextView quien;
ImageView imagen;
TextView reporte;
TextView fecha;
inflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View itemView = inflater.inflate(R.layout.listview_item, parent, false);
// Get the position
resultp = data.get(position);
// Locate the TextViews in listview_item.xml
// Locate the ImageView in listview_item.xml
imagen = (ImageView) itemView.findViewById(R.id.imagen);
fecha = (TextView) itemView.findViewById(R.id.fecha);
quien = (TextView) itemView.findViewById(R.id.quien);
reporte = (TextView) itemView.findViewById(R.id.reporte);
// Capture position and set results to the TextViews
// Capture position and set results to the ImageView
// Passes flag images URL into ImageLoader.class
imageLoader.DisplayImage(resultp.get(MainActivity.IMAGEN), imagen);
fecha.setText(resultp.get(MainActivity.FECHA));
reporte.setText(resultp.get(MainActivity.REPORTE));
quien.setText(resultp.get(MainActivity.QUIEN));
// Capture ListView item click
/*
itemView.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
// Get the position
resultp = data.get(position);
Intent intent = new Intent(context, SingleItemView.class);
// Pass all data rank
intent.putExtra("imagen", resultp.get(MainActivity.IMAGEN));
intent.putExtra("quien", resultp.get(MainActivity.QUIEN));
intent.putExtra("fecha", resultp.get(MainActivity.FECHA));
// Start SingleItemView Class
context.startActivity(intent);
}
});
*/
return itemView;
}
}

Take a look at the answer to this question for an explanation / example of how to maintain scroll position after adding items to a list: Retaining position in ListView after calling notifyDataSetChanged
Basically, you make a note of the position and scroll offset of the first visible item in the list before adding new data. Then afterwards, you restore the previous position and scroll offset.
However, because you're adding new items at the top of the list, the position returned by getFirstVisiblePosition() may refer to a different item after refreshing. The item that was at position 0 before refreshing may now be position 10. To fix that, you need to determine the number of new items returned by timeline.php and add it to index, like this:
mList.setSelectionFromTop(index + newItemCount, top);
You could probably determine which items are new by comparing the date field.
(By the way, if timeline.php only returns the most recent set of items, you could run into trouble if the user has scrolled to an older item which is no longer returned by timeline.php. After setting the new data, the old item will no longer be present, so you won't be able to scroll to it.
To fix that, you could keep the old ArrayList around and only add new items to it in doInBackground(). And call notifyDataSetChanged() in doInBackground(). That way, the adapter will still have access to older items.)

onItemClickListener(), how to pass clicked item's data?

I am using onItemClickListener() with a List. I want to pass name of the item clicked on, and an arbitrary number to next instance of the list. How can this be done?
Edit: here is the class:
public class ListViewA extends Activity{
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
ListView lv= (ListView)findViewById(R.id.listview);
// create the grid item mapping
String[] from = new String[] {"col_1"};
int[] to = new int[] {R.id.item2};
// prepare the list of all records
List<HashMap<String, String>> fillMaps = new ArrayList<HashMap<String, String>>();
for(int i = 0; i < 10; i++){
HashMap<String, String> map = new HashMap<String, String>();
map.put("col_1", "col_1_item_" + i);
fillMaps.add(map);
lv.setOnItemClickListener(onListClick);
}
// fill in the grid_item layout
SimpleAdapter adapter = new SimpleAdapter(this, fillMaps, R.layout.grid_item, from, to);
lv.setAdapter(adapter);
}
private AdapterView.OnItemClickListener onListClick=new AdapterView.OnItemClickListener(){
public void onItemClick(AdapterView<?> parent,View view, int position, long id)
{
Intent i=new Intent(ListViewA.this,ListViewA.class);
startActivity(i);
}
};
}

Following example shows you how to pass data onItemClick for particular position.
ListView lv = getListView();
// listening to single list item on click
lv.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// selected item
HERE YOU GOT POSITION FOR PERTICULAR ITEM
// Launching new Activity on selecting single List Item
Intent i = new Intent(getApplicationContext(), SingleListItem.class);
// sending data to new activity
i.putExtra("position", fillMaps.get(position));
startActivity(i);
}
});
And yes you need to declare fillMaps as globally.
public class ListViewA extends Activity{
List<HashMap<String, String>> fillMaps = new ArrayList<HashMap<String, String>>();
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);......

Intent i=new Intent(ListViewA.this,ListViewA.class);
i.putExtra("Key", fillMaps.get(position));
startActivity(i);
You can use above code in your onItemClickListner.

In this method the third agrument is position. So you have to use this eg. The Arraylist you are passing to your listView contains the data shown on listView. so use this kind of code
#Override
public void onItemClick(AdapterView<?> arg0, View arg1, int position, long arg3) {
// TODO Auto-generated method stub
String data= mArrlist.get(position);
}
If you are using the arralist of String type otherwise If you are using arraylist of getter setter class then use
mArralist.get(potion).getName();

You should get item #paticular position
HashMap<String, String> item = adapterview.getAdapter().getItem(position);
check your condition according to requirement and by getting data from item and process further.
Intent i=new Intent(ListViewA.this,ListViewA.class);
i.putExtra("item", item);
startActivity(i);

For adding arbitrary number you can use the Random class of java as below
Random mRandom = new Random();
int random = mRandom.nextInt(mMoveToList.size());
random variable of int type return every time random value.

you can use getItem(int position) of SimpleAdapter
put your SimpleAdapter variable adapter as global
in your ClickListener call adapter.getItem(position)

Android - ListView dynamic Buttons for each row calling dynamic listeners

I'm new to android, i've spent the last 2 days trying previous examples and online solutions but I just can't seem to get my head around it :(
I'm able to display a list view, parse some json from online and store a book title, book description and book ID and display this data in the listview. I want to be able to put a 'download' button in each row for the ListView, each button will correspond to its book ID on Click() and the action listener will download the book by appending that ID to a url.
e.g www.books.com/download_book1 or /download_book2....
Here is my code. Catalogue.java class
public class Catalogue extends ListActivity {
private JSONObject json;
private ListView lv;
private ArrayList<Integer> alKey = new ArrayList<Integer>();
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState); //icicle
setContentView(R.layout.shelflist);
ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();
....
try{
JSONArray entries = json.getJSONArray("entries");
for(int i=0;i<entries.length();i++){
HashMap<String, String> map = new HashMap<String, String>();
JSONObject e = entries.getJSONObject(i);
alKey.add(e.getInt("key"));
map.put("id", String.valueOf(i));
map.put("title", "Title:" + e.getString("title"));
map.put("description", "Description: " + e.getString("description"));
mylist.add(map);
}
}catch(JSONException e) {
Log.e("log_tag", "Error parsing data "+e.toString());
}
ListAdapter adapter = new SimpleAdapter(this, mylist , R.layout.shelfrow,
new String[] { "title", "description" },
new int[] { R.id.item_title, R.id.item_subtitle });
setListAdapter(adapter);
lv = getListView();
lv.setTextFilterEnabled(true);
.....
This is as far as I get. I don't know how to add 1 button per row in the List and assign an action listener to each button.
I also have a shelfrow.xml file (textView, textView for item_title and item_subtitle) and a shelflist.xml file (ListView).
I have a shelf.xml file with

Basically you need to learn the concept of ListAdapter.
Here's the short story: picture an object that holds the data to be displayed inside a list, along with the way to display each line individually. That's your ListAdapter. Now take each individual line: it's a book with a title and an OnClickListener. It's rendered inside a View with a TextView (for the title) and a Button (for the OnClickListener). All you need to do is give one View to the adapter that will be used for each line, and a List of the books you want to be inside the list.
Here's some sample code. I hope it clears things up a bit
private class MyItemModel{ //that's our book
String title; // the book's title
String description;
long id;
OnClickListener listener = new OnClickListener(){ // the book's action
#Override
public void onClick(View v) {
// the default action for all lines
doSomethingWithTheBookTitleOrUniqueId(this);
}
};
}
private class MyListAdapter extends BaseAdapter{
View renderer;
List<MyItemModel> items;
// call this one and pass it layoutInflater.inflate(R.layout.my_list_item)
public MyListAdapter(View renderer) {
this.renderer = renderer;
}
// whenever you need to set the list of items just use this method.
// call it when you have the data ready and want to display it
public void setModel(List<MyItemModel> items){
this.items = items;
notifyDataSetChanged();
}
#Override
public int getCount() {
return items!=null?items.size():0;
}
#Override
public Object getItem(int position) {
return items!=null?items.get(position):null;
}
#Override
public long getItemId(int position) {
return items!=null?items.get(position).id:-1;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
if(convertView==null){
convertView = renderer;
}
MyItemModel item = items.get(position);
// replace those R.ids by the ones inside your custom list_item layout.
TextView label = (TextView)convertView.findViewById(R.id.item_title);
label.setText(item.label);
Button button = (Button)convertView.findViewById(R.id.item_button);
button.setOnClickListener(item.listener);
return convertView;
}
}
In order to pass the List, instead of putting the data inside your list of hashmaps you can do this for instance (be careful, I also updated the MyItemModel and MyListAdapter to your need, added the id and description properties):
List<MyItemModel> myListModel = new ArrayList<MyItemModel>();
try{
JSONArray entries = json.getJSONArray("entries");
for(int i=0;i<entries.length();i++){
MyItemModel item = new MyItemModel();
JSONObject e = entries.getJSONObject(i);
alKey.add(e.getInt("key"));
item.id = i;
item.title = e.getString("title");
item.description = e.getString("description");
// you can change the button action at this point:
// item.onClickListener = new OnClickListener(){...};
myListModel.add(item);
}
}catch(JSONException e) {
Log.e("log_tag", "Error parsing data "+e.toString());
}
ListAdapter adapter = new MyListAdapter(getLayoutInflater().inflate(R.layout.shelfrow, this));
adapter.setModel(myListModel);
setListAdapter(adapter);
lv = getListView();
lv.setTextFilterEnabled(true);

You can create your own class extending ArrayAdapter that will hold your list and set onClickListener to the Button in each row.
But in getView method of your ArrayAdapter you have to create a new view every time.
for example - row layout
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_height="110dp"
android:background="#FFF"
android:layout_width="fill_parent">
<LinearLayout
android:layout_width="fill_parent"
android:background="#FFF"
android:orientation="vertical"
android:padding="2dp"
android:layout_height="110dp">
<TextView android:id="#+id/list_item_title"
android:background="#FFF"
android:layout_width="fill_parent"
android:layout_height="40dp"/>
<Button android:id="#+id/download_button"
android:gravity="center"
android:text="Download"
android:layout_height="35dp"/>
</LinearLayout>
</RelativeLayout>
and getView method in ArrayAdapter
private List<Map<String, String>> jsonMapList;
#Override
public View getView(int position, View convertView, ViewGroup parent) {
LayoutInflater inflater = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View v = inflater.inflate(R.layout.list_item, null);
// here you set textview values (title and description)
// TextView title = (TextView) v.findViewById(R.id.list_item_title);
// title.setText('bla');
// and set OnClickListener
Button button = (Button) v.findViewById(R.id.download_button);
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
downloadFile(getUrl(position));
}
});
return v;
}
// method that downloads file
private void downloadFile(String url) {}
// get url from your list by index
private String getUrl(int index) {
return jsonMapList.get(index).get("url");
}
Usage of Map is unnecessary, you could use any object you prefer.
In activity class
CustomAdapter listAdapter = new CustomAdapter(this, android.R.layout.simple_list_item_single_choice, jsonMapList);
setListAdapter(listAdapter);