I'm using the AsyncTask to open a URL, access the server, fetch the content and display them in a list view in the main activity. The content extracted consists of a title of the newspaper and a URL to the website, which will be displayed on a WebView in a second activity, if a "read" button is clicked. I coded out the program straight away and it works, but when I looked back at it, I found something that seems unreasonable, so mainly I want to make clear how the code works. Here is the code for the main activity:
package com.example.newsapp;
public class MainActivity extends Activity {
static final private String LOG_TAG = "main";
private ArrayList<Content> aList;
private class Content{
Content() {};
public String title;
public String url;
}
private class MyAdapter extends ArrayAdapter<Content>{
int resource;
public MyAdapter(Context _context, int _resource, List<Content> titles) {
super(_context, _resource, titles);
resource = _resource;
// this.context = _context;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
LinearLayout newView;
final Content content = getItem(position);
// Inflate a new view if necessary.
if (convertView == null) {
newView = new LinearLayout(getContext());
String inflater = Context.LAYOUT_INFLATER_SERVICE;
LayoutInflater vi = (LayoutInflater) getContext().getSystemService(inflater);
vi.inflate(resource, newView, true);
} else {
newView = (LinearLayout) convertView;
}
// Fills in the view.
TextView tv = (TextView) newView.findViewById(R.id.listText);
ImageButton b = (ImageButton) newView.findViewById(R.id.listButton);
b.setBackgroundResource(0);
tv.setText(content.title);
Typeface type = Typeface.createFromAsset(getAssets(),"LiberationSerif-BoldItalic.ttf");
tv.setTypeface(type);
// Sets a listener for the button, and a tag for the button as well.
b.setTag(Integer.toString(position));
b.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// Reacts to a button press.
Intent intent = new Intent(MainActivity.this, WebPage.class);
Bundle bundle = new Bundle();
bundle.putString("URL", content.url);
intent.putExtras(bundle);
startActivity(intent);
}
});
return newView;
}
}
class MyAsyncTask extends AsyncTask<String, String, String> {
private ProgressDialog progressDialog = new ProgressDialog(MainActivity.this);
InputStream inputStream = null;
String result = "";
Content content;
protected void onPreExecute() {
super.onPreExecute();
progressDialog.setMessage("Downloading the news...");
progressDialog.show();
progressDialog.setOnCancelListener(new OnCancelListener() {
public void onCancel(DialogInterface arg0) {
MyAsyncTask.this.cancel(true);
}
});
}
#Override
protected String doInBackground(String... params) {
String url_select = params[0];
ArrayList<NameValuePair> param = new ArrayList<NameValuePair>();
try {
// Set up HTTP post
// HttpClient is more then less deprecated. Need to change to URLConnection
HttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url_select);
httpPost.setEntity(new UrlEncodedFormEntity(param));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
// Read content & Log
inputStream = httpEntity.getContent();
} catch (UnsupportedEncodingException e1) {
Log.e("UnsupportedEncodingException", e1.toString());
e1.printStackTrace();
} catch (ClientProtocolException e2) {
Log.e("ClientProtocolException", e2.toString());
e2.printStackTrace();
} catch (IllegalStateException e3) {
Log.e("IllegalStateException", e3.toString());
e3.printStackTrace();
} catch (IOException e4) {
Log.e("IOException", e4.toString());
e4.printStackTrace();
}
// Convert response to string using String Builder
try {
BufferedReader bReader = new BufferedReader(new InputStreamReader(inputStream, "iso-8859-1"), 8);
StringBuilder sBuilder = new StringBuilder();
String line = null;
while ((line = bReader.readLine()) != null) {
sBuilder.append(line + "\n");
}
inputStream.close();
result = sBuilder.toString();
} catch (Exception e) {
Log.e("StringBuilding & BufferedReader", "Error converting result " + e.toString());
}
return result;
} // protected Void doInBackground(String... params)
protected void onPostExecute(String result) {
//parse JSON data
try {
super.onPostExecute(result);
Log.i(LOG_TAG, result);
JSONObject object = new JSONObject(result);
JSONArray jArray = object.getJSONArray("sites");
for(int i=0; i < jArray.length(); i++) {
JSONObject jObject = jArray.getJSONObject(i);
content = new Content();
if (jObject.has("title") && jObject.has("url")){
content.title = jObject.getString("title");
content.url = jObject.getString("url");
aList.add(content);
aa.notifyDataSetChanged();
}
} // End Loop
progressDialog.dismiss();
} catch (JSONException e) {
// progressDialog.dismiss();
Log.e("JSONException", "Error: " + e.toString());
}
} // protected void onPostExecute(String result)
}
private MyAdapter aa;
private MyAsyncTask loadTask;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
loadTask = new MyAsyncTask();
loadTask.execute("http://luca-ucsc.appspot.com/jsonnews/default/news_sources.json");
aList = new ArrayList<Content>();
aa = new MyAdapter(this, R.layout.list_element, aList);
ListView myListView = (ListView) findViewById(R.id.listView1);
myListView.setAdapter(aa);
aa.notifyDataSetChanged();
}
public void refresh(View v){
if (loadTask.getStatus() == AsyncTask.Status.FINISHED){
aList.clear();
aa.notifyDataSetChanged();
new MyAsyncTask().execute("http://luca-ucsc.appspot.com/jsonnews/default/news_sources.json");
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}
So you can see that only after loadTask.execute() in onCreate(), do I create the object for alist and aa, but I'm already using them in onPostExecute() in the AsyncTaks class, so I'm not very clear what happens here, because onPostExecute() and the UI are on the same thread, so the code in onPostExecute() should be executed first.
I thought I should put
aList = new ArrayList<Content>();
aa = new MyAdapter(this, R.layout.list_element, aList);
into onPostExecute(), which is more logical to me, but the app crashes this way. Also I think deleting aa.notifyDataSetChanged(); in onPostExecute() shouldn't be a problem because it's also in the onCreate() method, but this actually causes the list view to be blank, without any content. Actually, putting any of the codes after loadTask.execute() into the if block of the onPostExecute() method causes some problem, or crashes the app. That would be great if somebody can give some insight or hint. Thanks for reading.
onPostExecute is called on the UI thread after the background task completes its work. You cannot guarantee the timing of this call in relation to other calls on the UI thread.
Since you are already implementing getView yourself, I recommend you extend BaseAdapter instead of ArrayAdapter and implement the other few required methods. It's not hard and you can use whatever data structure you want to back the adapter. Assuming you use a List<Content> to back the adapter, you can write a method to swap the list in place like so:
public void swapList(List<Content> newList) {
this.list = newList;
notifyDataSetChanged();
}
In your AsyncTask, you have complete control of the Params, Progress, and Result parameterized types. They don't all have to be String. You can do this instead:
private class myAsyncTask extends AsyncTask<String, Void, List<Content>> {
/* ... */
}
The String for Params is the URL (same as you do now). Void for Progress because you don't publish progress anyway. List<Content> for Result because that's the thing you actually want to end up with after doing your task.
You should do ALL of your work in doInBackground. There is no reason to deserialize a String into a JSONArray and mess around with that in onPostExecute, particularly since that is happening on the main thread. Rewrite doInBackground to return a List<Content>, and all you need in onPostExecute is this:
public void onPostExecute(List<Content> result) {
adapter.swapList(result);
}
Now you can create the adapter once (in onCreate()) and just swap the list whenever it's appropriate.
Related
I am trying to update a ListView on previous fragment after back button press. The onResume is called (verified with Toast) and the webservice runs (listView is displayed after it is cleared). The problem is that the ListView is still showing old values and not new value after accessWebService_getUsername is called. I verify the values from MySQL and even though the DB is updated, the ListView only returns old values.
#Override
public void onResume() {
Toast.makeText(getActivity(), "onResume", Toast.LENGTH_SHORT).show();
super.onResume();
adapter.clear();
getIMEI();
accessWebService_getUsername();
adapter.notifyDataSetChanged();
}
Update:
//ListView
ListView lv =(ListView)view.findViewById(R.id.listView);
adapter = new ContactsAdapter(getActivity(), arrRequest_Contact, arrRequest_NameSurname, arrRequest_MessageCount, arrRequest_Time, arrRequest_Image);
lv.setAdapter(adapter);
// Json
private class JsonGetUsername extends AsyncTask<String, Void, String> {
//Pending 01
private ProgressDialog dialog = new ProgressDialog(getActivity());
#Override
protected void onPreExecute() {
this.dialog.setMessage("Loading Contacts, Please Wait");
this.dialog.show();
}
#Override
protected String doInBackground(String... params) {
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(params[0]);
try {
HttpResponse response = httpclient.execute(httppost);
jsonResult = inputStreamToString(response.getEntity().getContent()).toString();
}
catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
private StringBuilder inputStreamToString(InputStream is) {
String rLine = "";
StringBuilder answer = new StringBuilder();
BufferedReader rd = new BufferedReader(new InputStreamReader(is));
try {
while ((rLine = rd.readLine()) != null) {
answer.append(rLine);
}
}
catch (IOException e) {
// e.printStackTrace();
Toast.makeText(getActivity(),"Error..." + e.toString(), Toast.LENGTH_LONG).show();
}
return answer;
}
#Override
protected void onPostExecute(String result) {
//Pending 02
if (dialog.isShowing()) {
dialog.dismiss();
}
adapter.notifyDataSetChanged();
try{
ListDrawer_getUsername(); //has ConnectionException (when it cannot reach server)
}catch (Exception e){
Toast.makeText(getActivity(), "Please check your connection..", Toast.LENGTH_LONG).show();
}
}
}// end async task
public void accessWebService_getUsername() {
JsonGetUsername task = new JsonGetUsername();
// passes values for the urls string array
task.execute(new String[] { "http://mywebsite/php/get_username.php?pIMEI="+IMEI});
}
// build hash set for list view
public void ListDrawer_getUsername() {
try {
JSONObject jsonResponse = new JSONObject(jsonResult);
JSONArray jsonMainNode = jsonResponse.optJSONArray("username_info");
for (int i = 0; i < jsonMainNode.length(); i++) {
JSONObject jsonChildNode = jsonMainNode.getJSONObject(i);
request_username = jsonChildNode.optString("Username");
}
accessWebService_getContacts();
} catch (JSONException e) {
System.out.println("Json Error Rooms" +e.toString());
//Toast.makeText(getApplicationContext(), "No Rooms To Load", Toast.LENGTH_SHORT).show();
}
}
UPDATE 2:
//ContactsAdpater
class ContactsAdapter extends ArrayAdapter<String>
{
Context context;
List<String> Request_Contact;
List<String> Request_NameSurname;
List<String> Request_MessageCount;
List<String> Request_Time;
List<String> Request_Image;
ContactsAdapter(Context c, List<String> Request_Contact, List<String> Request_NameSurname, List<String> Request_MessageCount, List<String> Request_Time, List<String> Request_Image)
{
super(c, R.layout.activity_contacts_single, R.id.textContact, Request_Contact);
this.context=c;
this.Request_Contact=Request_Contact;
this.Request_NameSurname=Request_NameSurname;
this.Request_MessageCount=Request_MessageCount;
this.Request_Time=Request_Time;
this.Request_Image=Request_Image;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
View row=convertView;
if(row==null)
{
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
row = inflater.inflate(R.layout.activity_contacts_single, parent, false);
}
TextView txtContact = (TextView) row.findViewById(R.id.textContact);
TextView txtNameSurname = (TextView) row.findViewById(R.id.textNameSurname);
TextView txtMessageCount = (TextView) row.findViewById(R.id.textMessageCount);
TextView txtTime = (TextView) row.findViewById(R.id.textTime);
ImageView imageView = (ImageView) row.findViewById(R.id.imageView);
txtContact.setText(Request_Contact.get(position));
txtNameSurname.setText(Request_NameSurname.get(position));
txtMessageCount.setText(Request_MessageCount.get(position));
txtTime.setText(Request_Time.get(position));
Picasso.with(context).load(arrRequest_Image.get(position)).transform(new CircleTransform()).placeholder(R.drawable.ic_launcher).into(imageView);
return row;
}
}
You'll need to override the clear method in your ContactsAdapter to actually clear the lists you are storing your data in.
It looks like you'll need to clear all your lists, so if you add this to ContactsAdapter, your code should work as expected:
#Override
public void clear() {
super.clear();
Request_Contact.clear();
Request_NameSurname.clear();
Request_MessageCount.clear();
Request_Time.clear();
Request_Image.clear();
}
I need to delete a list item from listview on clicking a delete button in android eclipse. The list values are populated from mysql database(JSON), so on deleting, I need to delete the same from database also.
Here is my main Activity; I need to delete a listitem from a listview on clicking a delete button on each item in the listview:
public class MainActivity extends Activity implements AsyncResponse2 {
private ProgressDialog dialog;
ListView l1;
//for getting count
TextView count;
private static final String TAG_COUNT = "cnt";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE); //to hide title bar
setContentView(R.layout.activity_main);
l1=(ListView)findViewById(R.id.listView1);
/** Reference to the delete button of the layout main.xml */
Button btnDel = (Button) findViewById(R.id.deleteid);
initView();
//str for getting count
count=(TextView)findViewById(R.id.countid);
//to display count while loading(so outside buttonclick)
String key1 = "saasvaap123";
String signupid1 = "8";
String url2 = "http://gooffers.in/omowebservices/index.php/webservice/Public_User/saved_offers_list?";
//http://gooffers.in/omowebservices/index.php/webservice/Public_User/saved_offers_list?key=saasvaap123&signup_id=8
//put the below lines outside button onclick since we load the values into edittext when opening the app
CustomHttpClient2 task2 = new CustomHttpClient2();
task2.execute(url2,key1,signupid1);
task2.delegate = MainActivity.this;
//end
}
//str getting count
//str customhttp2
private class CustomHttpClient2 extends AsyncTask<String, String, String>{
public AsyncResponse2 delegate=null;
private String msg;
#Override
protected void onPostExecute(String result2) {
// TODO Auto-generated method stub
super.onPostExecute(result2);
delegate.processFinish2(result2);
}
#Override
protected void onPreExecute() {
// TODO Auto-generated method stub
super.onPreExecute();
}
#Override
protected String doInBackground(String... params) {
if(params == null) return null;
// get url from params
String url2 = params[0];
String key1 = params[1];
String signupid1 = params[2];
ArrayList<NameValuePair> postParameters;
postParameters = new ArrayList<NameValuePair>();
postParameters.add(new BasicNameValuePair("key",key1));
postParameters.add(new BasicNameValuePair("signup_id",signupid1));
try {
// create http connection
HttpClient client = new DefaultHttpClient();
HttpPost httppost = new HttpPost(url2);
httppost.setEntity(new UrlEncodedFormEntity(postParameters));
// connect
HttpResponse response = client.execute(httppost);
// get response
HttpEntity entity = response.getEntity();
if(entity != null){
return EntityUtils.toString(entity);
}
else{
return "No string.";
}
}
catch(Exception e){
return "Network problem";
}
}
}
public void processFinish2 (String output2){
Toast.makeText(MainActivity.this,output2, Toast.LENGTH_SHORT).show();
try{
//str
JSONObject jsonResponse = new JSONObject(output2);
JSONArray aJson = jsonResponse.getJSONArray("gen_off");
// create apps list
for(int i=0; i<aJson.length(); i++) {
JSONObject json = aJson.getJSONObject(i);
//end
//str
String strCount = json.getString(TAG_COUNT);
count.setText(strCount);//setting name to original name text
//end
}
}catch (JSONException e) {
Toast.makeText(MainActivity.this,"Exception caught!", Toast.LENGTH_SHORT).show();
}
}
//end getting count
private void initView() {
// show progress dialog
// dialog = ProgressDialog.show(this, "", "Loading...");
String key="saasvaap123";
String signup_id="8";
String url = "http://gooffers.in/omowebservices/index.php/webservice/Public_User/saved_offers_list?";
FetchDataTask task = new FetchDataTask();
task.execute(url,key,signup_id);
}
public class FetchDataTask extends AsyncTask<String, Void, String>{
// private final FetchDataListener listener;
private String msg;
#Override
protected String doInBackground(String... params) {
if(params == null) return null;
// get url from params
String url = params[0];
String key1 = params[1];
String signupid1 = params[2];
ArrayList<NameValuePair> postParameters;
postParameters = new ArrayList<NameValuePair>();
postParameters.add(new BasicNameValuePair("key",key1));
postParameters.add(new BasicNameValuePair("signup_id",signupid1));
//str
try {
// create http connection
HttpClient client = new DefaultHttpClient();
HttpPost httppost = new HttpPost(url);
httppost.setEntity(new UrlEncodedFormEntity(postParameters));
// connect
HttpResponse response = client.execute(httppost);
// get response
HttpEntity entity = response.getEntity();
if(entity != null){
return EntityUtils.toString(entity);
}
else{
return "No string.";
}
}
catch(Exception e){
return "Network problem";
}
}
//end
//
#Override
protected void onPostExecute(String sJson) {
try {
JSONObject jsonResponse = new JSONObject(sJson);
JSONArray aJson = jsonResponse.getJSONArray("gen_off");
Toast.makeText(MainActivity.this, aJson.toString(),Toast.LENGTH_SHORT).show();
// create apps list
List<SavedOffers> apps = new ArrayList<SavedOffers>();
for(int i=0; i<aJson.length(); i++) {
JSONObject json = aJson.getJSONObject(i);
SavedOffers app = new SavedOffers();
app.setTitle(json.getString("title"));
app.setOriginalRate(json.getString("price"));
app.setOfferRate(json.getString("off_price"));
app.setPercentage(json.getString("percent"));
app.setSavings(json.getString("savings"));
app.setUrl(json.getString("image"));
// add the app to apps list
apps.add(app);
}
SavedOffersAdapter adapter = new SavedOffersAdapter(MainActivity.this, apps);
// set the adapter to list
l1.setAdapter(adapter);
//for delete
// adapter.notifyDataSetChanged();
/** Defining a click event listener for the button "Delete" */
Button btnDel = (Button) findViewById(R.id.deleteid);
OnClickListener listenerDel = new OnClickListener() {
#Override
public void onClick(View v) {
/** Getting the checked items from the listview */
SparseBooleanArray checkedItemPositions = l1.getCheckedItemPositions();
int itemCount = l1.getCount();
for(int i=itemCount-1; i >= 0; i--){
if(checkedItemPositions.get(i)){
adapter.remove(l1.get(i));
}
}
checkedItemPositions.clear();
adapter.notifyDataSetChanged();
}
};
/** Setting the event listener for the delete button */
btnDel.setOnClickListener(listenerDel);
/** Setting the adapter to the ListView */
l1.setAdapter(adapter); //end delete
//notify the activity that fetch data has been complete
// if(listener != null) listener.onFetchComplete(apps);
} catch (JSONException e) {
// msg = "Invalid response";
// if(listener != null) listener.onFetchFailure(msg);
// return;
}
}
/**
* This function will convert response stream into json string
* #param is respons string
* #return json string
* #throws IOException
*/
public String streamToString(final InputStream is) throws IOException{
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
StringBuilder sb = new StringBuilder();
String line = null;
try {
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
}
catch (IOException e) {
throw e;
}
finally {
try {
is.close();
}
catch (IOException e) {
throw e;
}
}
return sb.toString();
}
}
}
// this is my adapter class , I think change is only needed in main activity
// , I need to delete a specific list item from listview on clicking the delete button
public class SavedOffersAdapter extends ArrayAdapter<SavedOffers>{
private List<SavedOffers> items;
Bitmap bitmap;
ImageView image;
public SavedOffersAdapter(Context context, List<SavedOffers> items) {
super(context, R.layout.app_custom_list, items);
this.items = items;
}
#Override
public int getCount() {
return items.size();
}
private class ViewHolder {
//TextView laptopTxt;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
// ViewHolder holder;//added
View v = convertView;
if(v == null) {
LayoutInflater li = LayoutInflater.from(getContext());
v = li.inflate(R.layout.app_custom_list, null);
}
SavedOffers app = items.get(position);
if(app != null) {
TextView productName = (TextView)v.findViewById(R.id.nameid);
TextView originalRate = (TextView)v.findViewById(R.id.originalid);
originalRate.setPaintFlags(originalRate.getPaintFlags() | Paint.STRIKE_THRU_TEXT_FLAG);
TextView offerRate = (TextView)v.findViewById(R.id.offerid);
TextView percentage = (TextView)v.findViewById(R.id.discountid);
TextView savings = (TextView)v.findViewById(R.id.savingsid);
image =(ImageView)v.findViewById(R.id.prctimgid);
if(productName != null) productName.setText(app.getTitle());
if(originalRate != null) originalRate.setText(app.getOriginalRate());
if(offerRate != null) offerRate.setText(app. getOfferRate());
if(percentage != null) percentage.setText(app. getPercentage());
if(savings != null) savings.setText(app. getSavings());
if(image!=null){
new DownloadImageTask(image).execute(app.getUrl());
}
}
return v;
}
In your listviews adapter's getView method you link to the button on the layout your inflating and just attach a setOnClickListener... to the button and have it remove that item from your list or array that your adapter uses and then notifyDataHasChanged.
Delete that item from items in that position.
So 1. you want to delete the item from the ListView
2. you want to delete the item from the SQL DB.
The first one is very easy, but you kind of need to know the underlining adapter and how it serves data to your ListView. When you instantiate a BaseAdapter for the ListView you pass in a List or an array. This array will be the data your BaseAdapter serves to your ListView, each view in the listview will be showing an element from the array (done in getView()). If you dynamically delete one of those items, then adjust your array (or just use a List and it's .remove(), and finally notifyDataSetChanged(); your BaseAdapter will refresh your list without that View (or rather that View will be replaced with the new one). So for instance below I pass in a List<WeatherLocation> (WeatherLocation is a containing class that has weather stuff for a particular area (city, zipcode, degree"Biddeford", 04005, 72) to my BaseAdapter.
// Instantiate ListView
ListView lvLocations = (ListView) findViewById(R.id.lvLocations);
// Instantiate our BaseAdapter (pass in the List<WeatherLocation>)
WeatherLocationAdapter mWeatherLocationAdapter = new WeatherLocationAdapter(savedList, this, R.layout.view_weather_location);
lvLocations.setAdapter(mWeatherLocationAdapter);
This is an example of a regular ListView setting an Adapter to a custom BaseAdapter.
The BaseAdapter is so simple, that really the only method you care about (majorly) is the getView() method.
R.layout.view_weather_location is just a `LinearLayout` I made, it has 3 TextViews in it that I tie (show) my data with, by attaching data to those TextViews in the `getView()` method of the `BaseAdapter`. You would put a `Button there and tie it to what you want (to delete the data item)`.
public class WeatherLocationAdapter extends BaseAdapter{
private List <WeatherLocation> mLocations;
private Context mContext;
private int rowForLocationToInflate;
private LayoutInflater inflater;
public WeatherLocationAdapter(List<WeatherLocation> mLocations, Context mContext, int rowForLocationToInflate) {
this.mLocations = mLocations;
this.mContext = mContext;
this.rowForLocationToInflate = rowForLocationToInflate;
inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
//TODO just built up layout now must tie to it.
private void addLocation(WeatherLocation newLocation){
mLocations.add(newLocation);
//TODO maybe invalidate after adding new item.
}
#Override
public int getCount() {
return mLocations.size();
}
#Override
public WeatherLocation getItem(int position) {
return mLocations.get(position);
}
#Override
public long getItemId(int position) {
return 0;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
//TODO build a viewholder
View rowView = inflater.inflate(rowForLocationToInflate, parent, false);
TextView tvZipcode = (TextView) rowView.findViewById(R.id.tvZipCode);
TextView tvCity = (TextView) rowView.findViewById(R.id.tvCity);
TextView tvTemp = (TextView) rowView.findViewById(R.id.tvDegree);
tvZipcode.setText(mLocations.get(position).getZipcode());
tvCity.setText(mLocations.get(position).getCity());
tvTemp.setText(String.valueOf(mLocations.get(position).getTemperature()));
// If you had a Button in your LinearLayout you were attaching to you that you wanted to delete that view/item with, it would look something like this in my case.
Button bDel = (Button) row.findViewById(R.id.bDel);
bDel.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
mLocations.remove(position);
}
});
return rowView;
}
}
In the onClick you would also remove the item from the SQL db. I can show that too, but I feel you have some coding to do as it stands.
I have a list fragment. When I run the app, I see an empty listView.
I don't know what the problem is. Maybe I should use a library?
public class MyEmployeFragment extends ListFragment {
private static final String ATTRIBUTE_ID = "p_id";
private static final String ATTRIBUTE_NAME = "p_name";
private static final String ATTRIBUTE_LAST_NAME = "p_last_name";
ArrayList<spr_item> ret_data;
MyTask task;
SimpleAdapter sAdapter;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
task = new MyTask();
task.execute();
return inflater.inflate(R.layout.my_employe, null);
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
ret_data = new ArrayList<spr_item>();
ArrayList<Map<String, Object>> data = new ArrayList<Map<String, Object>>(
ret_data.size());
Map<String, Object> m;
for (int i = 0; i < ret_data.size(); i++) {
m = new HashMap<String, Object>();
m.put(ATTRIBUTE_ID, ret_data.get(i).getId());
m.put(ATTRIBUTE_NAME, ret_data.get(i).getName());
m.put(ATTRIBUTE_LAST_NAME, ret_data.get(i).getLastName());
data.add(m);
}
// массив имен атрибутов, из которых будут читаться данные
String[] from = {ATTRIBUTE_ID, ATTRIBUTE_NAME, ATTRIBUTE_LAST_NAME};
// массив ID View-компонентов, в которые будут вставлять данные
int[] to = {R.id.tw_employe_id, R.id.tw_employe_name, R.id.tw_employe_last_name};
// создаем адаптер
sAdapter = new SimpleAdapter(getActivity(), data, R.layout.list_item_employee,
from, to);
// определяем список и присваиваем ему адаптер
ListView lvSimple = (ListView) getView().findViewById(android.R.id.list);
lvSimple.setAdapter(sAdapter);
}
class MyTask extends AsyncTask<Void, Void, Void> {
#Override
protected void onPreExecute() {
super.onPreExecute();
}
#Override
protected Void doInBackground(Void... params) {
String s = "5ACACEC6-752B-4EFF-AA50-EEBE58A52113";
// String user_guid = myPrefs.getString("guid", "");
HttpActivity _http = new HttpActivity("192.168.10.11", "80");
_http.set_addr_protocol("/WebSite/P/spr/spr.aspx/");
_http.add_param("query", "spr_employee_get");
// _http.add_param("p_guid", user_guid.toString().trim());
_http.add_param("p_guid", s);
_http.send();
List<spr_item> tempList = _http.getArrayParamValue();
for(int i = 0; i < tempList.size(); i++)
ret_data.add(tempList.get(i));
//employer_name = _http.getArrayParamValue("p_name");
//employer_id = _http.getArrayParamValue("p_id");
//employer_last_name = _http.getArrayParamValue("p_last_name");
return null;
}
protected void onPostExecute(Void result) {
super.onPostExecute(result);
sAdapter.notifyDataSetChanged();
}
}
}
With the above code apart from the Empty list you may have the null pointer exception too if the task is too quick to load. Here onCreate is called first onCreateView next and onActvityCreated next. So it is better to initialise adapter in onCreate set the adapter to listView in onCreateView and set listView listeners in onActvityCreated using getListView() method.
Apart from this if you are using local database to retrieve data you need to use cursorADapter to fetch the data
The adapter's data references (ArrayList, array, etc.), tend to get lost pretty easily. In that case the notfiyDataSetChanged() method will not work. If you are adamant on using this method I suggest you check the references to the adapter's source again. If that is not the case this is the approach I've used in my project. A small warning in advance, the formatting and the closing of brackets is poorly executed, but the approach is still clear enough.
public class MyFragment extends ListFragment {
// For populating the list view.
SomeAdapter adapter;
public MyFragment() {
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
String[] parameters = {"url for request"};
new GetRequestTask().execute(parameters);
}
// The async task to make the HTTP GET requests.
class GetRequestTask extends AsyncTask<String, String, String>{
#Override
protected String doInBackground(String... uri) {
HttpClient httpclient = new DefaultHttpClient();
HttpResponse response;
String responseString = null;
try {
response = httpclient.execute(new HttpGet(uri[0]));
StatusLine statusLine = response.getStatusLine();
if(statusLine.getStatusCode() == HttpStatus.SC_OK){
ByteArrayOutputStream out = new ByteArrayOutputStream();
response.getEntity().writeTo(out);
out.close();
responseString = out.toString();
} else{
//Closes the connection.
response.getEntity().getContent().close();
throw new IOException(statusLine.getReasonPhrase());
}
} catch (ClientProtocolException e) {
Log.e("GetRequestTask", "Client protocol exception.");
e.printStackTrace();
} catch (IOException e) {
Log.e("GetRequestTask", "IO exception.");
e.printStackTrace();
}
return responseString;
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
// Update UI with the new response.
new UpdateUITask().execute(result);
}
}
}
// The async task to update the UI.
class UpdateUITask extends AsyncTask<String, String, ArrayList<Something>>{
#Override
protected ArrayList<Something> doInBackground(String... input) {
ArrayList<Something> someArray = new ArrayList<Something>();
try{
// Do some JSON magic to parse the data.
}
catch(JSONException je){
Log.e("UpdateUITask", "JSON parsing error occured.");
je.printStackTrace();
}
return someArray;
}
#Override
protected void onPostExecute(ArrayList<Something> result) {
super.onPostExecute(result);
Log.i("UpdateUITask", "Updating UI.");
adapter = new SomeAdapter(getActivity(), R.layout.some_list_item, restOfTheParameters);
setListAdapter(adapter);
}
}
}
}
I tried the code below and also tried the AsyncTaskLoader approach. The app crashes when I instantiate the AsyncTask. Pleas advise me on the best approach to load JSON in a list fragment inside tab host.
The code below is the tab fragment (I use action bar tabs in main activity):
public class TabTop extends ListFragment {
Context context = getActivity().getBaseContext();
String API_URL = "http://api.rottentomatoes.com/api/public/v1.0/movies/770672122/similar.json?apikey=crhhxb4accwwa6cy6fxrm8vj&limit=1";
ArrayList<Deal> deals;
DealsListAdapter adapter;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
#SuppressWarnings("unused")
int a = 0;
return super.onCreateView(inflater, container, savedInstanceState);
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
GetTopDeals getTopDeals = new GetTopDeals(context);
getTopDeals.execute(API_URL);
super.onActivityCreated(savedInstanceState);
}
class GetTopDeals extends AsyncTask<String, Void, ArrayList<Deal>>{
ProgressDialog progressDialog;
public GetTopDeals(Context activity) {
this.progressDialog = new ProgressDialog(activity);
}
#Override
protected void onPostExecute(ArrayList<Deal> result) {
adapter = new DealsListAdapter(context, result);
setListAdapter(adapter);
super.onPostExecute(result);
}
#Override
protected void onPreExecute() {
progressDialog.setCancelable(true);
progressDialog.setProgress(0);
progressDialog.setMessage("loading Top deals...");
progressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
super.onPreExecute();
}
#Override
protected ArrayList<Deal> doInBackground(String... urls) {
String response = sendRequest(urls[0]); // make request for json
return processResponse(response); // parse the Json and return ArrayList to postExecute
}
private String sendRequest(String apiUrl) {
BufferedReader input = null; // get the json
HttpURLConnection httpCon = null; // the http connection object
StringBuilder response = new StringBuilder(); // hold all the data from the jason in string separated with "\n"
try {
URL url = new URL(apiUrl);
httpCon = (HttpURLConnection) url.openConnection();
if (httpCon.getResponseCode() != HttpURLConnection.HTTP_OK) { // check for connectivity with server
return null;
}
input = new BufferedReader(new InputStreamReader(httpCon.getInputStream())); // pull all the json from the site
String line;
while ((line = input.readLine()) != null) {
response.append(line + "\n");
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (input != null) {
try {
input.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (httpCon != null) {
httpCon.disconnect();
}
}
return response.toString();
}
}
public ArrayList<Deal> processResponse(String response) {
try {
JSONObject responseObject = new JSONObject(response); // Creates a new JSONObject with name/value mappings from the JSON string.
JSONArray results = responseObject.getJSONArray("movies"); // Returns the value mapped by name if it exists and is a JSONArray.
deals = new ArrayList<Deal>();
for (int i = 0; i < results.length(); i++) { // in this loop i copy the json array to movies arraylist in order to display listView
JSONObject jMovie = results.getJSONObject(i);
int api_id = jMovie.getInt("id");
String name = jMovie.getString("title");
String content = jMovie.getString("synopsis");
JSONObject posters = jMovie.getJSONObject("posters");
String image_url = posters.getString("profile");
}
}catch (JSONException e) {
e.printStackTrace();
}
return deals;
}
#Override
public void onStart() {
super.onStart();
}
#Override
public void onListItemClick(ListView l, View v, int position, long id) {
Intent intent = new Intent(getActivity().getBaseContext(), DealInformation.class);
startActivity(intent);
super.onListItemClick(l, v, position, id);
}
}
Make your asynctask in his own file.
And when your asynctask is finish, implement OnPostExecute which is automatically call. Notify your adapter by a notifyDataSetChanged like that :
#Override
protected void onPostExecute(List<NewItem> list) {
Adapter.getListe().clear();
Adapter.getListe().addAll(list);
Adapter.notifyDataSetChanged();
}
thank you guys,
i want to post my answer. after some research i decided to go with AsyncTaskLoader.
this is my code
public class TabOurPicks extends ListFragment implements LoaderCallbacks<String[]> {
// when activity loads- onActivityCreated() calls the initLoader() who activate onCreateLoader()
#Override
public void onActivityCreated(Bundle savedInstance) {
super.onActivityCreated(savedInstance);
setListAdapter(new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, new String[]{}));
getLoaderManager().initLoader(0, null,this).forceLoad();
}
// onCreateLoader instantiate the asynctaskloaser who work in bg
#Override
public RSSLoader onCreateLoader(int arg0, Bundle arg1) {
return new RSSLoader(getActivity()); //
}
// after bg process invoke onLoadFinished() who work in ui thread
#Override
public void onLoadFinished(Loader<String[]> loader, String[] data) {
setListAdapter(new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, data
) );
}
#Override
public void onLoaderReset(Loader<String[]> arg0) {
// TODO Auto-generated method stub
}
and this is the inner class for the loader:
static public class RSSLoader extends AsyncTaskLoader<String[]>
{
public RSSLoader(Context context) {
super(context);
}
#Override
public String[] loadInBackground() {
String url = "http://api.rottentomatoes.com/api/public/v1.0/movies/770672122/similar.json?apikey=crhhxb4accwwa6cy6fxrm8vj&limit=1";
String response = sendRequest(url);
return processResponse(response);
}
private String sendRequest(String url) {
BufferedReader input = null; // get the json
HttpURLConnection httpCon = null; // the http connection object
StringBuilder response = new StringBuilder(); // hold all the data from the jason in string separated with "\n"
try {
URL apiUrl = new URL(url);
httpCon = (HttpURLConnection) apiUrl.openConnection();
if (httpCon.getResponseCode() != HttpURLConnection.HTTP_OK) { // check for connectivity with server
return null;
}
input = new BufferedReader(new InputStreamReader(httpCon.getInputStream())); // pull all the json from the site
String line;
while ((line = input.readLine()) != null) {
response.append(line + "\n");
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (input != null) {
try {
input.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (httpCon != null) {
httpCon.disconnect();
}
}
return response.toString();
}
private String[] processResponse(String response) {
String[] deals = null;
try {
JSONObject responseObject = new JSONObject(response); // Creates a new JSONObject with name/value mappings from the JSON string.
JSONArray results = responseObject.getJSONArray("movies"); // Returns the value mapped by name if it exists and is a JSONArray.
deals = new String[10];
for (int i = 0; i < 9; i++) { // in this loop i copy the json array to movies arraylist in order to display listView
JSONObject jMovie = results.getJSONObject(i);
String name = jMovie.getString("title");
deals[i] = name;
}
}catch (JSONException e) {
e.printStackTrace();
}
return deals;
}
}
}
It doesn't matter if your asynctask has its own file. You just don't want your activity to extends asynctask as this would make your activity asynchronous - but this is impossible to do anyways due to java's double inheritance rule.
Based on the architecture of your app and your programming style the asyntask can be an inner class in the activity. on the PostExecute method make sure you have given data to your adapter and that the adapter is set to the list, then just run notifyDataSetChanged().
Assuming your asynctask is loading data from cache or the network you are on the right track with your approach to this.
I have read plenty of examples ,but if I wish to maintain my scroll position after a ListView is updated from JSON ,then can I do that without using an AsyncTask instance ???
the code for my list is
String wrd;
//ArrayList<HashMap<String,String>> mylist;
#Override
public void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Intent i2=getIntent();
wrd=i2.getStringExtra("entrd");
Log.v("keyis",wrd);
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, 40000);
}
};
handler.postDelayed(runable, 10);
}public void LoadData(){
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){
Log.e("loG_tag","Error parsing"+e.toString());
}
LazyAdapter adapter = new LazyAdapter(this,mylist);
adapter.notifyDataSetChanged();
ListView list=(ListView)findViewById(R.id.lv1);
list.setEmptyView(findViewById(R.id.empty));
list.setAdapter(adapter);
list.setItemsCanFocus(false);
and my adapter is
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;
}
and finally the class being used for json parsing is
public class JSONfunctions {
public static JSONObject getJSONfromURL(String url){
InputStream is = null;
String result = "";
JSONObject jArray = null;
String str1="http://zeesms.info"+url;
// ArrayList<NameValuePair> namevaluepairs = new ArrayList<NameValuePair>();
Log.v("url result",url);
//namevaluepairs.add(new BasicNameValuePair("location",str1));
//http post
try{
HttpClient httpclient= new DefaultHttpClient();
HttpGet request = new HttpGet();
request.setURI(new URI(str1));
HttpResponse response = httpclient.execute(request);
is = response.getEntity().getContent();
if(is==null){
Log.v("url result","is null");
}
else
{
Log.v("url result","is not null");
}
/* BufferedReader buf = new BufferedReader(new InputStreamReader(is,"UTF-8"));
StringBuilder sb = new StringBuilder();
String s;
while(true )
{
s = buf.readLine();
if(s==null || s.length()==0)
break;
sb.append(s);
}
buf.close();
is.close();
sb.toString(); */
// httppost.setEntity(new UrlEncodedFormEntity(namevaluepairs));
//HttpResponse response=httpclient.execute(httppost);
//HttpEntity entity=response.getEntity();
//is=entity.getContent();
/*
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(url);
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
*/
}catch(Exception e){
Log.v("log_tag", "Error in http connection "+e.toString());
AlertDialog.Builder alert=new AlertDialog.Builder(null);
alert.setMessage("Invalid Keyword").setPositiveButton("Ok", new OnClickListener(){
#Override
public void onClick(DialogInterface arg0, int arg1) {
// TODO Auto-generated method stub
}
});
}
//convert response to string
try{
Log.v("url result","getting result starts");
BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
StringBuilder sb = new StringBuilder();
String line = null;
Log.v("url result","getting result");
while ((line = reader.readLine()) != null) {
Log.v("url result","getting result");
sb.append(line + "\n");
}
is.close();
result=sb.toString();
Log.v("url result",result);
}catch(Exception e){
Log.e("log_tag", "Error converting result "+e.toString());
}
try{
jArray = new JSONObject(result);
}catch(JSONException e){
Log.e("log_tag", "Error parsing data "+e.toString());
}
return jArray;
}
}
along with this if the data is updated from the webpage, what would be the simplest way to show the updated item on top ??
It is easier to maintain scroll position by calling notifydatasetchanged() only. The problem there is that you are creating a new adapter every time the data gets updated... you should do something like this:
if(listView.getAdapter()==null)
listView.setAdapter(myAdapter);
else{
myAdapter.updateData(myNewData); //update adapter's data
myAdapter.notifyDataSetChanged(); //notifies any View reflecting data to refresh
}
This way, your listview will mantain the scrolling position.
In case you want to scroll to a new position, use:
list.smoothScrollToPosition(int position);
In case for some reason you don't want to call notifyDataSetChanged(), the you can maintain the position by using setSelectionFromTop()
Before updating the adaptor:
lastViewedPosition = listView.getFirstVisiblePosition();
//get offset of first visible view
View v = listView.getChildAt(0);
topOffset = (v == null) ? 0 : v.getTop();
After updating the adaptor:
listView.setSelectionFromTop(lastViewedPosition, topOffset);
list.smoothScrollToPosition(int position); //my favorite :)
It may also help you to scroll nice'n'smooth to a particular item
listview.setSelection( i );
this will help you to set particular row at top
For overall picture:
In your API response callback, call this function(example) below:
MyAdapter mAdapter;
ArrayList<Users> mUsers;
private void updateListView(ArrayList<Users> users) {
mUsers.addAll(users);
if(mAdapter == null) {
mAdapter = new MyAdapter(getContext(), mUsers);
mListView.setAdapter(mAdapter);
}
mAdapter.notifyDataSetChanged(); // Add this one
}
If you're using an ArrayAdapter (or a subclass of it), the problem may be caused by that the adapter updates the list when you clean it before adding the new items:
adapter.clear();
adapter.addAll(...);
You can fix it by wrapping the code that modifies the adapter like this:
adapter.setNotifyOnChange(false); // Disable calling notifyDatasetChanged() on modification
adapter.clear();
adapter.addAll(...); // Notify the adapter about that data has changed. Note: it will re-enable notifyOnChange
adapter.notifyDataSetChanged();