Develop Reference

Xml Parsing activity force closes if no connection

I am using following code from a tutorial , code works great but the app force closes if there is no connection or incase of slow connection.
public class MainActivity extends Activity {
ListView mListView;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// URL to the XML data
String strUrl = "http://wptrafficanalyzer.in/p/demo1/countries_xml.php/countries/";
// Creating a new non-ui thread task to download xml data
DownloadTask downloadTask = new DownloadTask();
// Starting the download process
downloadTask.execute(strUrl);
// Getting a reference to ListView of activity_main
mListView = (ListView) findViewById(R.id.lv_countries);
}
/** A method to download xml data from url */
private String downloadUrl(String strUrl) throws IOException{
String data = "";
InputStream iStream = null;
try{
URL url = new URL(strUrl);
// Creating an http connection to communicate with url
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
iStream = urlConnection.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(iStream));
StringBuffer sb = new StringBuffer();
String line = "";
while( ( line = br.readLine()) != null){
sb.append(line);
}
data = sb.toString();
br.close();
}catch(Exception e){
Log.d("Exception while downloading url", e.toString());
}finally{
iStream.close();
}
return data;
}
/** AsyncTask to download xml data */
private class DownloadTask extends AsyncTask<String, Integer, String>{
String data = null;
#Override
protected String doInBackground(String... url) {
try{
data = downloadUrl(url[0]);
}catch(Exception e){
Log.d("Background Task",e.toString());
}
return data;
}
#Override
protected void onPostExecute(String result) {
// The parsing of xml data is done in a non-ui thread
ListViewLoaderTask listViewLoaderTask = new ListViewLoaderTask();
// Start parsing xml data
listViewLoaderTask.execute(result);
}
}
/** AsyncTask to parse xml data and load ListView */
private class ListViewLoaderTask extends AsyncTask<String, Void, SimpleAdapter>{
StringReader reader;
// Doing the parsing of xml data in a non-ui thread
#Override
protected SimpleAdapter doInBackground(String... strXml) {
try{
reader = new StringReader(strXml[0]);
}catch(Exception e){
Log.d("XML Exception1",e.toString());
}
// Instantiating xml parser class
CountryXmlParser countryXmlParser = new CountryXmlParser();
// A list object to store the parsed countries list
List<HashMap<String, Object>> countries = null;
try{
// Getting the parsed data as a List construct
countries = countryXmlParser.parse(reader);
}catch(Exception e){
Log.d("Exception",e.toString());
}
// Keys used in Hashmap
String[] from = { "country","flag","details"};
// Ids of views in listview_layout
int[] to = { R.id.tv_country,R.id.iv_flag,R.id.tv_country_details};
// Instantiating an adapter to store each items
// R.layout.listview_layout defines the layout of each item
SimpleAdapter adapter = new SimpleAdapter(getBaseContext(), countries, R.layout.lv_layout, from, to);
return adapter;
}
/** Invoked by the Android when "doInBackground" is executed */
#Override
protected void onPostExecute(SimpleAdapter adapter) {
// Setting adapter for the listview
mListView.setAdapter(adapter);
for(int i=0;i<adapter.getCount();i++){
HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(i);
String imgUrl = (String) hm.get("flag_path");
ImageLoaderTask imageLoaderTask = new ImageLoaderTask();
HashMap<String, Object> hmDownload = new HashMap<String, Object>();
hm.put("flag_path",imgUrl);
hm.put("position", i);
// Starting ImageLoaderTask to download and populate image in the listview
imageLoaderTask.execute(hm);
}
}
}
/** AsyncTask to download and load an image in ListView */
private class ImageLoaderTask extends AsyncTask<HashMap<String, Object>, Void, HashMap<String, Object>>{
#Override
protected HashMap<String, Object> doInBackground(HashMap<String, Object>... hm) {
InputStream iStream=null;
String imgUrl = (String) hm[0].get("flag_path");
int position = (Integer) hm[0].get("position");
URL url;
try {
url = new URL(imgUrl);
// Creating an http connection to communicate with url
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
iStream = urlConnection.getInputStream();
// Getting Caching directory
File cacheDirectory = getBaseContext().getCacheDir();
// Temporary file to store the downloaded image
File tmpFile = new File(cacheDirectory.getPath() + "/wpta_"+position+".png");
// The FileOutputStream to the temporary file
FileOutputStream fOutStream = new FileOutputStream(tmpFile);
// Creating a bitmap from the downloaded inputstream
Bitmap b = BitmapFactory.decodeStream(iStream);
// Writing the bitmap to the temporary file as png file
b.compress(Bitmap.CompressFormat.PNG,100, fOutStream);
// Flush the FileOutputStream
fOutStream.flush();
//Close the FileOutputStream
fOutStream.close();
// Create a hashmap object to store image path and its position in the listview
HashMap<String, Object> hmBitmap = new HashMap<String, Object>();
// Storing the path to the temporary image file
hmBitmap.put("flag",tmpFile.getPath());
// Storing the position of the image in the listview
hmBitmap.put("position",position);
// Returning the HashMap object containing the image path and position
return hmBitmap;
}catch (Exception e) {
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(HashMap<String, Object> result) {
// Getting the path to the downloaded image
String path = (String) result.get("flag");
// Getting the position of the downloaded image
int position = (Integer) result.get("position");
// Getting adapter of the listview
SimpleAdapter adapter = (SimpleAdapter ) mListView.getAdapter();
// Getting the hashmap object at the specified position of the listview
HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(position);
// Overwriting the existing path in the adapter
hm.put("flag",path);
// Noticing listview about the dataset changes
adapter.notifyDataSetChanged();
}
}
}

You're returning null if an exception is thrown during doInBackground(), but then you're accessing result in onPostExecute() and not handling the null case. You need to verify that result is not null before you try to access it. Like so:
#Override
protected void onPostExecute(HashMap<String, Object> result) {
if (result != null) {
// Getting the path to the downloaded image
String path = (String) result.get("flag");

You will have to check if your application has internet access, before making calls that require it.
Following methods check if you have internet access. Use it before you need to do internet calls. If it returns false, show the user a notification saying that internet is required.
public boolean isInternetAvailable() {
try {
InetAddress ipAddr = InetAddress.getByName("google.com"); //You can replace it with your name
if (ipAddr.equals("")) {
return false;
} else {
return true;
}
} catch (Exception e) {
return false;
}
}
Also, add these permissions if you haven't already:
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
Use it like this
if (isInternetAvailable() {
// available network
} else {
// no network
}

ListView with header [Android]

I have a list and I would like to add a 'header'.
I've tried this tutorial and my code final is :
ListView mListView;
#Override
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.lista_producto);
// URL to the JSON data
String strUrl = "http://server/file.php";
// Creating a new non-ui thread task to download json data
DownloadTask downloadTask = new DownloadTask();
// Starting the download process
downloadTask.execute(strUrl);
// Getting a reference to ListView of activity_main
mListView = (ListView) findViewById(R.id.listaJson);
View header = getLayoutInflater().inflate(R.layout.header, null);
mListView.addHeaderView(header);
/*View header = (View)getLayoutInflater().inflate(R.layout.header, null);
mListView.addHeaderView(header);*/
}
/** A method to download json data from url */
private String downloadUrl(String strUrl) throws IOException{
String data = "";
InputStream iStream = null;
try{
URL url = new URL(strUrl);
// Creating an http connection to communicate with url
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
iStream = urlConnection.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(iStream));
StringBuffer sb = new StringBuffer();
String line = "";
while( ( line = br.readLine()) != null){
sb.append(line);
}
data = sb.toString();
br.close();
}catch(Exception e){
Log.d("Exception while downloading url", e.toString());
}finally{
iStream.close();
}
return data;
}
/** AsyncTask to download json data */
private class DownloadTask extends AsyncTask<String, Integer, String>{
String data = null;
#Override
protected String doInBackground(String... url) {
try{
data = downloadUrl(url[0]);
}catch(Exception e){
Log.d("Background Task",e.toString());
}
return data;
}
#Override
protected void onPostExecute(String result) {
// The parsing of the xml data is done in a non-ui thread
ListViewLoaderTask listViewLoaderTask = new ListViewLoaderTask();
// Start parsing xml data
listViewLoaderTask.execute(result);
}
}
/** AsyncTask to parse json data and load ListView */
private class ListViewLoaderTask extends AsyncTask<String, Void, SimpleAdapter>{
JSONObject jObject;
// Doing the parsing of xml data in a non-ui thread
#Override
protected SimpleAdapter doInBackground(String... strJson) {
try{
jObject = new JSONObject(strJson[0]);
JSONParser DealJsonParser = new JSONParser();
DealJsonParser.parse(jObject);
}catch(Exception e){
Log.d("JSON Exception1",e.toString());
}
// Instantiating json parser class
JSONParser DealJsonParser = new JSONParser();
// A list object to store the parsed countries list
List<HashMap<String, Object>> deal = null;
try{
// Getting the parsed data as a List construct
deal = DealJsonParser.parse(jObject);
}catch(Exception e){
Log.d("Exception",e.toString());
}
// Keys used in Hashmap
String[] from = { "nombre","flag","details","precionuevo","descripcion",};
// Ids of views in listview_layout
int[] to = { R.id.price,R.id.dealimage,R.id.details,R.id.price,R.id.descripcion};
// Instantiating an adapter to store each items
// R.layout.listview_layout defines the layout of each item
SimpleAdapter adapter = new SimpleAdapter(getBaseContext(), deal, R.layout.list_view, from, to);
return adapter;
}
/** Invoked by the Android on "doInBackground" is executed */
#Override
protected void onPostExecute(SimpleAdapter adapter) {
// Setting adapter for the listview
/* AÑADIR HEADER?
View header = getLayoutInflater().inflate(R.layout.header, null);
mListView.addHeaderView(header);
*/
mListView.setAdapter(adapter);
for(int i=0;i<adapter.getCount();i++){
HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(i);
String imgUrl = (String) hm.get("flag_path");
ImageLoaderTask imageLoaderTask = new ImageLoaderTask();
HashMap<String, Object> hmDownload = new HashMap<String, Object>();
hm.put("flag_path",imgUrl);
hm.put("position", i);
// Starting ImageLoaderTask to download and populate image in the listview
imageLoaderTask.execute(hm);
}
mListView.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> arg0, View view, int arg2, long arg3) {
// TODO Auto-generated method stub
String URL = ((TextView) view.findViewById(R.id.descripcion)).getText().toString();//this will take the value of the invincible textView
Intent i = new Intent(Lista_productos.this, pruebalista.class);
i.putExtra("URL", URL);
startActivity(i);
}
});
}
/** AsyncTask to download and load an image in ListView */
private class ImageLoaderTask extends AsyncTask<HashMap<String, Object>, Void, HashMap<String, Object>>{
#Override
protected HashMap<String, Object> doInBackground(HashMap<String, Object>... hm) {
InputStream iStream=null;
String imgUrl = (String) hm[0].get("flag_path");
int position = (Integer) hm[0].get("position");
URL url;
try {
url = new URL(imgUrl);
// Creating an http connection to communicate with url
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
iStream = urlConnection.getInputStream();
// Getting Caching directory
File cacheDirectory = getBaseContext().getCacheDir();
// Temporary file to store the downloaded image
File tmpFile = new File(cacheDirectory.getPath() + "/wpta_"+position+".png");
// The FileOutputStream to the temporary file
FileOutputStream fOutStream = new FileOutputStream(tmpFile);
// Creating a bitmap from the downloaded inputstream
Bitmap b = BitmapFactory.decodeStream(iStream);
// Writing the bitmap to the temporary file as png file
b.compress(Bitmap.CompressFormat.PNG,100, fOutStream);
// Flush the FileOutputStream
fOutStream.flush();
//Close the FileOutputStream
fOutStream.close();
// Create a hashmap object to store image path and its position in the listview
HashMap<String, Object> hmBitmap = new HashMap<String, Object>();
// Storing the path to the temporary image file
hmBitmap.put("flag",tmpFile.getPath());
// Storing the position of the image in the listview
hmBitmap.put("position",position);
// Returning the HashMap object containing the image path and position
return hmBitmap;
}catch (Exception e) {
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(HashMap<String, Object> result) {
// Getting the path to the downloaded image
String path = (String) result.get("flag");
// Getting the position of the downloaded image
int position = (Integer) result.get("position");
// Getting adapter of the listview
SimpleAdapter adapter = (SimpleAdapter ) mListView.getAdapter();
// Getting the hashmap object at the specified position of the listview
HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(position);
// Overwriting the existing path in the adapter
hm.put("flag",path);
// Noticing listview about the dataset changes
adapter.notifyDataSetChanged();
/*Toast toast = Toast.makeText(Lista_productos.this, path, Toast.LENGTH_LONG);
toast.show();*/
}
}
}
When you run the application prints the list and the header but after 6 seconds, the app quits unexpectedly showing errors in logcat:
https://www.dropbox.com/s/uj1a3zj64wrtzfy/error3.png

JSON listview OnItemClickListener url (webview)

I got all the data ... But I am not able to use webview url(UrlWeb) , i mean when i click on list item then it will open in web view. when i click any list it should pass corresponding url to the WebView activity.So how to achieve this, how to store corresponding url?? please someone help me..
My MainActivity :
public class MainActivity extends Activity {
ListView mListView;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// URL to the JSON data
String strUrl = "http://www.mulnivasisangh.com/aman/listweb.json";
// Creating a new non-ui thread task to download json data
DownloadTask downloadTask = new DownloadTask();
// Starting the download process
downloadTask.execute(strUrl);
// Getting a reference to ListView of activity_main
mListView = (ListView) findViewById(R.id.lv_countries);
}
/** A method to download json data from url */
private String downloadUrl(String strUrl) throws IOException{
String data = "";
InputStream iStream = null;
try{
URL url = new URL(strUrl);
// Creating an http connection to communicate with url
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
iStream = urlConnection.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(iStream));
StringBuffer sb = new StringBuffer();
String line = "";
while( ( line = br.readLine()) != null){
sb.append(line);
}
data = sb.toString();
br.close();
}catch(Exception e){
Log.d("Exception while downloading url", e.toString());
}finally{
iStream.close();
}
return data;
}
/** AsyncTask to download json data */
private class DownloadTask extends AsyncTask<String, Integer, String>{
String data = null;
#Override
protected String doInBackground(String... url) {
try{
data = downloadUrl(url[0]);
}catch(Exception e){
Log.d("Background Task",e.toString());
}
return data;
}
#Override
protected void onPostExecute(String result) {
// The parsing of the xml data is done in a non-ui thread
ListViewLoaderTask listViewLoaderTask = new ListViewLoaderTask();
// Start parsing xml data
listViewLoaderTask.execute(result);
}
}
/** AsyncTask to parse json data and load ListView */
private class ListViewLoaderTask extends AsyncTask<String, Void, SimpleAdapter>{
JSONObject jObject;
// Doing the parsing of xml data in a non-ui thread
#Override
protected SimpleAdapter doInBackground(String... strJson) {
try{
jObject = new JSONObject(strJson[0]);
CountryJSONParser countryJsonParser = new CountryJSONParser();
countryJsonParser.parse(jObject);
}catch(Exception e){
Log.d("JSON Exception1",e.toString());
}
// Instantiating json parser class
CountryJSONParser countryJsonParser = new CountryJSONParser();
// A list object to store the parsed countries list
List<HashMap<String, Object>> countries = null;
try{
// Getting the parsed data as a List construct
countries = countryJsonParser.parse(jObject);
}catch(Exception e){
Log.d("Exception",e.toString());
}
// Keys used in Hashmap
String[] from = { "country","flag","details", "URL"};
// Ids of views in listview_layout
int[] to = { R.id.tv_country,R.id.iv_flag,R.id.tv_country_details,R.id.tv_URL};
// Instantiating an adapter to store each items
// R.layout.listview_layout defines the layout of each item
SimpleAdapter adapter = new SimpleAdapter(getBaseContext(), countries, R.layout.lv_layout, from, to);
return adapter;
}
/** Invoked by the Android on "doInBackground" is executed */
protected void onPostExecute(SimpleAdapter adapter) {
// Setting adapter for the listview
mListView.setAdapter(adapter);
for(int i=0;i<adapter.getCount();i++){
HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(i);
String imgUrl = (String) hm.get("flag_path");
ImageLoaderTask imageLoaderTask = new ImageLoaderTask();
HashMap<String, Object> hmDownload = new HashMap<String, Object>();
hm.put("flag_path",imgUrl);
hm.put("position", i);
// Starting ImageLoaderTask to download and populate image in the listview
imageLoaderTask.execute(hm);
}
mListView.setOnItemClickListener(new OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> arg0, View view, int arg2,
long arg3) {
// TODO Auto-generated method stub
String URL = ((TextView) view.findViewById(R.id.tv_URL)).getText().toString();//this will take the value of the invincible textView
Intent i = new Intent(MainActivity.this, WebViewActivity.class);
i.putExtra("URL", URL);
startActivity(i);
}
});
}
}
/** AsyncTask to download and load an image in ListView */
private class ImageLoaderTask extends AsyncTask<HashMap<String, Object>, Void, HashMap<String, Object>>{
#Override
protected HashMap<String, Object> doInBackground(HashMap<String, Object>... hm) {
InputStream iStream=null;
String imgUrl = (String) hm[0].get("flag_path");
int position = (Integer) hm[0].get("position");
URL url;
try {
url = new URL(imgUrl);
// Creating an http connection to communicate with url
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
iStream = urlConnection.getInputStream();
// Getting Caching directory
File cacheDirectory = getBaseContext().getCacheDir();
// Temporary file to store the downloaded image
File tmpFile = new File(cacheDirectory.getPath() + "/wpta_"+position+".png");
// The FileOutputStream to the temporary file
FileOutputStream fOutStream = new FileOutputStream(tmpFile);
// Creating a bitmap from the downloaded inputstream
Bitmap b = BitmapFactory.decodeStream(iStream);
// Writing the bitmap to the temporary file as png file
b.compress(Bitmap.CompressFormat.PNG,100, fOutStream);
// Flush the FileOutputStream
fOutStream.flush();
//Close the FileOutputStream
fOutStream.close();
// Create a hashmap object to store image path and its position in the listview
HashMap<String, Object> hmBitmap = new HashMap<String, Object>();
// Storing the path to the temporary image file
hmBitmap.put("flag",tmpFile.getPath());
// Storing the position of the image in the listview
hmBitmap.put("position",position);
// Returning the HashMap object containing the image path and position
return hmBitmap;
}catch (Exception e) {
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(HashMap<String, Object> result) {
// Getting the path to the downloaded image
String path = (String) result.get("flag");
// Getting the position of the downloaded image
int position = (Integer) result.get("position");
// Getting adapter of the listview
SimpleAdapter adapter = (SimpleAdapter ) mListView.getAdapter();
// Getting the hashmap object at the specified position of the listview
HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(position);
// Overwriting the existing path in the adapter
hm.put("flag",path);
// Noticing listview about the dataset changes
adapter.notifyDataSetChanged();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}
My CountryJSONParser :
public class CountryJSONParser {
// Receives a JSONObject and returns a list
public List<HashMap<String,Object>> parse(JSONObject jObject){
JSONArray jCountries = null;
try {
// Retrieves all the elements in the 'countries' array
jCountries = jObject.getJSONArray("webs");
} catch (JSONException e) {
e.printStackTrace();
}
// Invoking getCountries with the array of json object
// where each json object represent a country
return getCountries(jCountries);
}
private List<HashMap<String, Object>> getCountries(JSONArray jCountries){
int countryCount = jCountries.length();
List<HashMap<String, Object>> countryList = new ArrayList<HashMap<String,Object>>();
HashMap<String, Object> country = null;
// Taking each country, parses and adds to list object
for(int i=0; i<countryCount;i++){
try {
// Call getCountry with country JSON object to parse the country
country = getCountry((JSONObject)jCountries.get(i));
countryList.add(country);
} catch (JSONException e) {
e.printStackTrace();
}
}
return countryList;
}
// Parsing the Country JSON object
private HashMap<String, Object> getCountry(JSONObject jCountry){
HashMap<String, Object> country = new HashMap<String, Object>();
String countryName = "";
String flag="";
String language = "";
String capital = "";
String web ="";
try {
countryName = jCountry.getString("Nom");
flag = jCountry.getString("UrlImatge");
language = jCountry.getString("Descripcio");
capital = jCountry.getString("Id");
web = jCountry.getString("UrlWeb");
String details = "Descripcio : " + language + "\n" +
"Id : " + capital + "\n" + "URL: " + web + "\n";
country.put("country", countryName);
country.put("UrlImatge", R.drawable.blank);
country.put("flag_path", flag);
country.put("details", details);
country.put("URL", web);
} catch (JSONException e) {
e.printStackTrace();
}
return country;
}
}
Thanks in advance..

I use this trick when I want to pass data from listview to another activity.
1- I add a textView to my item-list.xml which is R.layout.lv_layout in your case and make its visibility gone. android:visibility="gone"
2- add the URL String to this textView, it wont be shown in the listview, because it has no visibility.
String[] from = { "country","flag","details", "URL"};
// Ids of views in listview_layout
int[] to = { R.id.tv_country,R.id.iv_flag,R.id.tv_country_details, R.id.tv_country_URL};//the forth one is the textView you set it as gone.
3- in OnItemClick function just add the following:
String URL = ((TextView) view.findViewById(R.id.tv_country_URL)).getText().toString();//this will take the value of the invincible textView
Intent i = new Intent(MainActivity.this, WebView.class);
i.putExtra("URL", URL);
startActivity(i);
4- use getIntent in your webView Activity to get the URL and load it.
if it is still vague please inform me. hope you got the idea.
Edit
you dont need getURL function anymore, I thought getCountries doesnt return a hashMap for URL.
so all you have to do is create a invisible textView in your lv_layout and put each URL in it.
follow the 4 steps above.
for step 3 in Post:
protected void onPostExecute(SimpleAdapter adapter) {
// Setting adapter for the listview
mListView.setAdapter(adapter);
for(int i=0;i<adapter.getCount();i++){
HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(i);
String imgUrl = (String) hm.get("flag_path");
ImageLoaderTask imageLoaderTask = new ImageLoaderTask();
HashMap<String, Object> hmDownload = new HashMap<String, Object>();
hm.put("flag_path",imgUrl);
hm.put("position", i);
// Starting ImageLoaderTask to download and populate image in the listview
imageLoaderTask.execute(hm);
}
mListView.setOnItemClickListener(new OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> arg0, View view, int arg2,
long arg3) {
// TODO Auto-generated method stub
String URL = ((TextView) view.findViewById(R.id.tv_URL)).getText().toString();//this will take the value of the invincible textView
Intent i = new Intent(MainActivity.this, WebView.class);
i.putExtra("URL", URL);
startActivity(i);
}
Edit
for webViewActivity you need to get extra from the previous activity as the following:
public class WebViewActivity extends Activity{
private WebView webView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.web_view);
webView = (WebView) findViewById(R.id.webview);
webView.setWebViewClient(new MyWebViewClient());
String url = getIntent().getExtras().getString("URL")
if (null != url) {
webView.getSettings().setJavaScriptEnabled(true);
webView.loadUrl(url);
}
}
private class MyWebViewClient extends WebViewClient {
#Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
view.loadUrl(url);
return true;
}
}
}

i am using gridview in which i am parsing data from json in android,but some time my application runs and some time gives rejected execution eception

public class TopMovie extends Activity
{
GridView lv;
Vibrator vibrator;
private Object params;
public static String movie_Id;
#Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
Log.i("Category", MainActivity.movie_Category);
setContentView(R.layout.new_movie);
LayoutInflater inflater = getLayoutInflater();
View view = inflater.inflate(R.layout.customtoast,
(ViewGroup) findViewById(R.id.custom_toast_layout));
Toast toast = new Toast(getApplicationContext());
toast.setDuration(Toast.LENGTH_LONG);
toast.setGravity(Gravity.CENTER_HORIZONTAL, 0, 0);
toast.setView(view);
toast.show();
vibrator = (Vibrator) getSystemService(Context.VIBRATOR_SERVICE);
lv = (GridView) findViewById(R.id.grid_view);
// URL to the JSON data
String strUrl = "http://vaibhavtech.com/work/android/movie_list.php?category="
+ MainActivity.movie_Category + "&sub_category=other";
DownloadTask downloadTask = new DownloadTask();
downloadTask.execute(strUrl);
lv.setOnItemClickListener(new OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
long arg3) {
// // TODO Auto-generated method stub
vibrator.vibrate(40);
LayoutInflater inflater = getLayoutInflater();
View view = inflater.inflate(R.layout.customtoast,
(ViewGroup) findViewById(R.id.custom_toast_layout));
Toast toast = new Toast(getApplicationContext());
toast.setDuration(Toast.LENGTH_LONG);
toast.setGravity(Gravity.CENTER_HORIZONTAL, 0, 0);
toast.setView(view);
toast.show();
MainActivity.movie_Id = ((TextView) arg1
.findViewById(R.id.tv_girdview_content_id)).getText()
.toString();
Log.i("Name is", MainActivity.movie_Id);
startActivity(new Intent(TopMovie.this, MovieDescription.class));
}
});
}
private String downloadUrl(String strUrl) throws IOException {
String data = "";
InputStream iStream = null;
try {
URL url = new URL(strUrl);
// Creating an http connection to communicate with url
HttpURLConnection urlConnection = (HttpURLConnection) url
.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
iStream = urlConnection.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(
iStream));
StringBuffer sb = new StringBuffer();
String line = "";
while ((line = br.readLine()) != null) {
sb.append(line);
}
data = sb.toString();
br.close();
} catch (Exception e) {
Log.d("Exception while downloading url", e.toString());
} finally {
iStream.close();
}
return data;
}
/** AsyncTask to download json data */
private class DownloadTask extends AsyncTask<String, Integer, String> {
String data = null;
#Override
protected String doInBackground(String... url) {
try {
data = downloadUrl(url[0]);
} catch (Exception e) {
Log.d("Background Task", e.toString());
}
return data;
}
#Override
protected void onPostExecute(String result) {
// The parsing of the xml data is done in a non-ui thread
ListViewLoaderTask listViewLoaderTask = new ListViewLoaderTask();
// Start parsing xml data
listViewLoaderTask.execute(result);
}
}
/** AsyncTask to parse json data and load ListView */
private class ListViewLoaderTask extends
AsyncTask<String, Void, SimpleAdapter> {
JSONObject jObject;
// Doing the parsing of xml data in a non-ui thread
#Override
protected SimpleAdapter doInBackground(String... strJson) {
try {
jObject = new JSONObject(strJson[0]);
MovieParser countryJsonParser = new MovieParser();
countryJsonParser.parse(jObject);
} catch (Exception e) {
Log.d("JSON Exception1", e.toString());
}
// Instantiating json parser class
MovieParser countryJsonParser = new MovieParser();
// A list object to store the parsed countries list
List<HashMap<String, Object>> countries = null;
try {
// Getting the parsed data as a List construct
countries = countryJsonParser.parse(jObject);
} catch (Exception e) {
Log.d("Exception", e.toString());
}
// Keys used in Hashmap
String[] from = { "image", "id", "year", "duration", "name" };
// Ids of views in listview_layout
// int[] to = {
// R.id.iv_radio_data_image,R.id.tv_radio_data_id,R.id.tv_radio_data_like,R.id.tv_radio_data_rating,R.id.tv_radio_data_listner,R.id.tv_radio_data_radio_url,R.id.tv_radio_data_name};
int[] to = { R.id.iv_girdview_content_image,
R.id.tv_girdview_content_id, R.id.tv_girdview_content_like,
R.id.tv_girdview_content_listner,
R.id.tv_girdview_content_name };
SimpleAdapter adapter = new SimpleAdapter(getBaseContext(),
countries, R.layout.grid_view_content, from, to);
return adapter;
}
/** Invoked by the Android on "doInBackground" is executed */
#Override
protected void onPostExecute(SimpleAdapter adapter) {
// Setting adapter for the listview
lv.setAdapter(adapter);
for (int i = 0; i < adapter.getCount(); i++) {
HashMap<String, Object> hm = (HashMap<String, Object>) adapter
.getItem(i);
String imgUrl = (String) hm.get("flag_path");
ImageLoaderTask imageLoaderTask = new ImageLoaderTask();
HashMap<String, Object> hmDownload = new HashMap<String, Object>();
hm.put("flag_path", imgUrl);
hm.put("position", i);
// Starting ImageLoaderTask to download and populate image in
// the listview
imageLoaderTask.execute(hm);
}
}
}
/** AsyncTask to download and load an image in ListView */
private class ImageLoaderTask extends
AsyncTask<HashMap<String, Object>, Void, HashMap<String, Object>> {
#Override
protected HashMap<String, Object> doInBackground(
HashMap<String, Object>... hm) {
InputStream iStream = null;
String imgUrl = (String) hm[0].get("flag_path");
int position = (Integer) hm[0].get("position");
URL url;
try {
url = new URL(imgUrl);
// Creating an http connection to communicate with url
HttpURLConnection urlConnection = (HttpURLConnection) url
.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
iStream = urlConnection.getInputStream();
// Getting Caching directory
File cacheDirectory = getBaseContext().getCacheDir();
// Temporary file to store the downloaded image
File tmpFile = new File(cacheDirectory.getPath() + "/wpta_"
+ position + ".png");
// The FileOutputStream to the temporary file
FileOutputStream fOutStream = new FileOutputStream(tmpFile);
// Creating a bitmap from the downloaded inputstream
Bitmap b = BitmapFactory.decodeStream(iStream);
// Writing the bitmap to the temporary file as png file
b.compress(Bitmap.CompressFormat.PNG, 100, fOutStream);
// Flush the FileOutputStream
fOutStream.flush();
// Close the FileOutputStream
fOutStream.close();
// Create a hashmap object to store image path and its position
// in the listview
HashMap<String, Object> hmBitmap = new HashMap<String, Object>();
// Storing the path to the temporary image file
hmBitmap.put("image", tmpFile.getPath());
// Storing the position of the image in the listview
hmBitmap.put("position", position);
// Returning the HashMap object containing the image path and
// position
return hmBitmap;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(HashMap<String, Object> result) {
// Getting the path to the downloaded image
String path = (String) result.get("image");
// Getting the position of the downloaded image
int position = (Integer) result.get("position");
// Getting adapter of the listview
SimpleAdapter adapter = (SimpleAdapter) lv.getAdapter();
// Getting the hashmap object at the specified position of the
// listview
HashMap<String, Object> hm = (HashMap<String, Object>) adapter
.getItem(position);
// Overwriting the existing path in the adapter
hm.put("image", path);
adapter.notifyDataSetChanged();
}
}
}
My application is debugging but not running.RejectedExecutionException: Task android.os.AsyncTas rejected from java.util.concurrent.
Submitting tasks to a thread-pool gives RejectedExecutionException
how to resolve threadpool exception in gridview android

You can change the executor the asynctask uses if you extend the asynctask class.
Check this example from docs where they download multiple images and use a custom asynctask to control the concurrency.
I had the same problem you are having and used that project to fix it.

Make application load faster with ViewHolder class

I've made gridview application that get path of image from json. it work find but when it load it's so slow. and i try to find solution and they recommended me to use ViewHolder but I don't know how to use in my gridview application.
How can I use ViewHolder in my application? how I speed up my application?
This code work find but it load so slow.
public class MainActivity extends Activity {
String strUrl = "http://192.168.10.104/adchara1/";
GridView gridView;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Creating a new non-ui thread task to download json data
DownloadTask downloadTask = new DownloadTask();
// Starting the download process
downloadTask.execute(strUrl);
gridView = (GridView) findViewById(R.id.lv_countries);
gridView.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View v, int positon,
long id) {
HashMap<String, Object> hm = (HashMap<String, Object>) gridView.getAdapter().getItem(positon);
String imgPath = (String) hm.get("photo"); //get downloaded image path
Intent i = new Intent(MainActivity.this, DisplayActivity.class); //start new Intent to another Activity.
i.putExtra("ClickedImagePath", imgPath ); //put image link in intent.
startActivity(i);
}
});
}
/** A method to download json data from url */
private String downloadUrl(String strUrl) throws IOException{
String data = "";
InputStream iStream = null;
HttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(strUrl);
ArrayList<NameValuePair> param = new ArrayList<NameValuePair>();
try {
httpPost.setEntity(new UrlEncodedFormEntity(param));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
iStream = httpEntity.getContent();
} catch (Exception e) {
Log.e("log_tag", "Error in http connection " + e.toString());
}
try {
BufferedReader br = new BufferedReader(new InputStreamReader(iStream));
StringBuilder sb = new StringBuilder();
String line = "";
while((line = br.readLine()) != null){
sb.append(line + "\n");
}
iStream.close();
data = sb.toString();
} catch (Exception e) {
Log.e("log_tag", "Error converting result " + e.toString());
}
return data;
}
/** AsyncTask to download json data */
private class DownloadTask extends AsyncTask<String, Integer, String>{
String data = null;
#Override
protected String doInBackground(String... url) {
try{
data = downloadUrl(url[0]);
}catch(Exception e){
Log.d("Background Task",e.toString());
}
return data;
}
#Override
protected void onPostExecute(String result) {
// The parsing of the xml data is done in a non-ui thread
GridViewLoaderTask gridViewLoaderTask = new GridViewLoaderTask();
// Start parsing xml data
gridViewLoaderTask.execute(result);
}
}
/** AsyncTask to parse json data and load ListView */
private class GridViewLoaderTask extends AsyncTask<String, Void, SimpleAdapter>{
JSONObject jObject;
// Doing the parsing of xml data in a non-ui thread
#Override
protected SimpleAdapter doInBackground(String... strJson) {
try{
jObject = new JSONObject(strJson[0]);
CountryJSONParser countryJsonParser = new CountryJSONParser();
countryJsonParser.parse(jObject);
}catch(Exception e){
Log.d("JSON Exception1",e.toString());
}
// Instantiating json parser class
CountryJSONParser countryJsonParser = new CountryJSONParser();
// A list object to store the parsed countries list
List<HashMap<String, Object>> countries = null;
try{
// Getting the parsed data as a List construct
countries = countryJsonParser.parse(jObject);
}catch(Exception e){
Log.d("Exception",e.toString());
}
// Keys used in Hashmap
String[] from = { "frame","photo"};
// Ids of views in listview_layout
int[] to = { R.id.iv_frame,R.id.iv_photo};
// Instantiating an adapter to store each items
// R.layout.listview_layout defines the layout of each item
SimpleAdapter adapter = new SimpleAdapter(getBaseContext(), countries, R.layout.lv_layout, from, to);
return adapter;
}
/** Invoked by the Android on "doInBackground" is executed */
#Override
protected void onPostExecute(SimpleAdapter adapter) {
// Setting adapter for the listview
gridView.setAdapter(adapter);
for(int i=0;i<adapter.getCount();i++){
HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(i);
String frameUrl = (String) hm.get("frame_path");
String imgUrl = (String) hm.get("photo_path");
ImageLoaderTask imageLoaderTask = new ImageLoaderTask();
HashMap<String, Object> hmDownload = new HashMap<String, Object>();
hm.put("frame_path", frameUrl);
hm.put("photo_path",imgUrl);
hm.put("position", i);
// Starting ImageLoaderTask to download and populate image in the listview
imageLoaderTask.execute(hm);
}
}
}
/** AsyncTask to download and load an image in ListView */
private class ImageLoaderTask extends AsyncTask<HashMap<String, Object>, Void, HashMap<String, Object>>{
#Override
protected HashMap<String, Object> doInBackground(HashMap<String, Object>... hm) {
InputStream iStream = null;
String imgUrl;
String frameUrl;
imgUrl = (String) hm[0].get("photo_path");
frameUrl = (String) hm[0].get("frame_path");
int position = (Integer) hm[0].get("position");
URL url;
URL urlFrame;
try {
url = new URL(imgUrl);
urlFrame = new URL(frameUrl);
// Creating an http connection to communicate with url
HttpURLConnection urlConnection = (HttpURLConnection) url
.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
iStream = urlConnection.getInputStream();
// Getting Caching directory
File cacheDirectory = getBaseContext().getCacheDir();
// Temporary file to store the downloaded image
File tmpFile = new File(cacheDirectory.getPath() + "/wpta_"+ position + ".png");
// The FileOutputStream to the temporary file
FileOutputStream fOutStream = new FileOutputStream(tmpFile);
// Creating a bitmap from the downloaded inputstream
Bitmap b = BitmapFactory.decodeStream(iStream);
// Writing the bitmap to the temporary file as png file
b.compress(Bitmap.CompressFormat.PNG, 100, fOutStream);
// Flush the FileOutputStream
fOutStream.flush();
// Close the FileOutputStream
fOutStream.close();
// Create a hashmap object to store image path and its position in the listview
HashMap<String, Object> hmBitmap = new HashMap<String, Object>();
// Storing the path to the temporary image file
hmBitmap.put("photo", tmpFile.getPath());
hmBitmap.put("frame", tmpFile.getPath());
// Storing the position of the image in the listview
hmBitmap.put("position", position);
// Returning the HashMap object containing the image path and position
return hmBitmap;
} catch (MalformedURLException e) {
return null;
} catch (FileNotFoundException e) {
return null;
} catch (IOException e) {
return null;
}
}
#Override
protected void onPostExecute(HashMap<String, Object> result) {
// Getting the path to the downloaded image
String path = (String) result.get("photo");
String framePath = (String) result.get("frame");
// Getting the position of the downloaded image
int position = (Integer) result.get("position");
// Getting adapter of the listview
SimpleAdapter adapter = (SimpleAdapter ) gridView.getAdapter();
// Getting the hashmap object at the specified position of the listview
HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(position);
// Overwriting the existing path in the adapter
hm.put("photo",path);
hm.put("frame", framePath);
// Noticing listview about the dataset changes
adapter.notifyDataSetChanged();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}

you should read the slide here to improve the performance.it's contain an example of using ViewHolder.

Take a look at our Google Guys at Google I/O 2010 . They had a session hosted by Google Software Engineer in Android Team, talking about ListView and related stuffs, including how to optimize listview-usage with ViewHolder class.
I think you can learn something from that.
Here is the link Google I/O 2010 - ListView Session