InputStream from URL in AsyncTask

InputStream from URL in AsyncTask - java

Trying to get a file from URL into InputStream element (with AsyncTask) and then use it, but so far unsuccessful. Are the parameters right for AsyncTask? Can I check InputStream like I did in my code or is it wrong and it will always return null? Any other changes I should make?
My code:
String url = "https://www.example.com/file.txt";
InputStream stream = null;
public void load() {
DownloadTask downloadTask = new DownloadTask();
downloadTask.execute(url);
if (stream == null) {
//fail, stream == null
} else {
//success
}
}
class DownloadTask extends AsyncTask <String, Integer, InputStream> {
#Override
protected void onPreExecute() {
}
#Override
protected InputStream doInBackground(String... params){
try {
URL url = new URL(url);
stream = url.openStream();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return stream;
}
#Override
protected void onPostExecute(InputStream result) {
super.onPostExecute(result);
}
}
EDIT2:
I fixed it.
public void load(){
//some code
DownloadTask dt=new DownloadTask();
dt.execute("www.example.com");
}
private class DownloadTask extends AsyncTask<String,Integer,Void>{
InputStream text;
protected Void doInBackground(String...params){
URL url;
try {
url = new URL(params[0]);
HttpURLConnection con=(HttpURLConnection)url.openConnection();
InputStream is=con.getInputStream();
text = is;
}catch (Exception e) {
e.printStackTrace();
}
return null;
}
protected void onPostExecute(Void result){
//use "text"
}
}

you are using AsyncTask in the wrong way. Do all operations like download or server requests inside doInBackground(String... params) method.
Very important to know, that you should update your UI inside the onPostExecute(..) method. This method get called from UI-Thread.
Here is an example (pseudo code):
class DownloadTask extends AsyncTask <String, Integer, MyDownloadedData> {
private MyDownloadedData getFromStream(InputStream stream){
// TODO
return null;
}
#Override
protected void onPreExecute() {
}
#Override
protected MyDownloadedData doInBackground(String... params){
try {
URL url = new URL(url);
InputStream stream = url.openStream();
MyDownloadedData data = getFromStream(stream);
return data;
} catch (Exception e) {
// do something
}
return stream;
}
#Override
protected void onPostExecute(MyDownloadedData data) {
//
// update your UI in this method. example:
//
someLabel.setText(data.getName());
}
protected void onProgressUpdate(Integer... progress) {
//...
}
}

Related

How to do tasks like HttpURLConnection in the background of a app using Java in Android Studio?

I am basically following a tutorial for learing Android Studio that uses AsyncTask class for doing background tasks like HttpURLConnection. But the thing is that it created a lot of error and later I found out that class was deprecated. So what is the alternative?
(Please provide an example code if you can)
CODE:
public class MainActivity extends AppCompatActivity {
public class DownloadingTask extends AsyncTask<String, Void, String>
{
#Override
protected String doInBackground(String... urls)
{
String result="";
HttpURLConnection urlConnection=null;
URL url;
try{
url=new URL(urls[0]);
urlConnection=(HttpURLConnection)url.openConnection();
InputStream in;
in = urlConnection.getInputStream();
InputStreamReader reader=new InputStreamReader(in);
int data=reader.read();
while (data!=-1)
{
char current=(char) data;
result = result + current;
data=reader.read();
}
return result;
}
catch (Exception e)
{
e.printStackTrace();
return "Failed";
}
}
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
DownloadingTask task= new DownloadingTask();
String s=null;
try {
s = task.execute("http://www.android.com/").get();
}
catch (Exception e)
{
e.printStackTrace();
}
Log.i("Msg",s);
}
}

This is an example that shows how to download an image using AsynkTask.
private class DownLoadImageTask extends AsyncTask<String, Void, Bitmap> {
ImageView imageView;
DownLoadImageTask(ImageView imageView) {
this.imageView = imageView;
}
protected Bitmap doInBackground(String... urls) {
String urlOfImage = urls[0];
Bitmap logo = null;
try {
InputStream is = new URL(urlOfImage).openStream();
logo = BitmapFactory.decodeStream(is);
} catch (Exception e) { // Catch the download exception
Log.v("download", e.getMessage());
}
return logo;
}
protected void onPostExecute(Bitmap result) {
imageView.setImageBitmap(result);
}
}
This is how to run it
new DownLoadImageTask(img).execute(imageUrl);
Any update is done in this method onPostExecute as it runs on the UI Thread.
Yes, You are right. AsynkTask is deprecated. You can use LoderManager and Java Executor
Or Volley, Retrofit libraries
For downloading images, You can use Picasso and Gilde Libraries.

Get JSON value to TextView from HTTP post

I need to do an HTTP post with a cookie, and get the JSON response and put it in a TextView in Android Studio.
The code I have so far:
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (android.os.Build.VERSION.SDK_INT > 9) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
}
new GetDataSync().execute();
try {
postPHP("Hoi");
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}
public class GetDataSync extends AsyncTask<Void, Void, Void> {
#Override
protected Void doInBackground(Void... params) {
try {
getData();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
}
}
private void postPHP (String cookie1) throws IOException, JSONException {
CookieManager cookieManager = CookieManager.getInstance();
String cookieString = cookieManager.getCookie(cookie1);
URL url = new URL("http://piggybank.wordmediavormgever.nl/getSaldo.php");
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setDoOutput(true);
connection.setRequestMethod("POST");
connection.setRequestProperty("thatsallfolks", cookieString);
connection.connect();
OutputStream out = connection.getOutputStream();
out.write(data);
out.flush();
out.close();
}
private void getData() throws IOException, JSONException {
TextView txtUser = (TextView) findViewById(R.id.user);
JSONObject json = readJsonFromUrl("http://piggybank.wordmediavormgever.nl/getSaldo.php");
try {
String response = json.getString("saldo");
Log.e("saldo", response);
response = json.getString("saldo");
txtUser.setText(response);
} catch (JSONException e) {
e.printStackTrace();
}
}
As you can see, the JSON to TextView and HTTP POST request are two seperate pieces of code, that's why I don't get the correct JSON value. I need to combine the two so it first sends the cookie via POST and then puts the JSON response in a TextView, but I don't know how

Change your code as follows:
public class GetDataSync extends AsyncTask<Void, Void, String> {
private final String cookie;
public GetDataSync(String cookie) {
this.cookie = cookie;
}
#Override
protected String doInBackground(Void... voids) {
try {
postPHP();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}
return getData();
}
#Override
protected void onPostExecute(String resposne) {
super.onPostExecute(s);
TextView txtUser = (TextView) findViewById(R.id.user);
txtUser.setText(resposne);
}
private void postPHP () throws IOException, JSONException {
CookieManager cookieManager = CookieManager.getInstance();
String cookieString = cookieManager.getCookie(cookie);
URL url = new URL("http://piggybank.wordmediavormgever.nl/getSaldo.php");
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setDoOutput(true);
connection.setRequestMethod("POST");
connection.setRequestProperty("thatsallfolks", cookieString);
connection.connect();
OutputStream out = connection.getOutputStream();
out.write(data);
out.flush();
out.close();
}
private String getData() {
JSONObject json = readJsonFromUrl("http://piggybank.wordmediavormgever.nl/getSaldo.php");
try {
String response = json.getString("saldo");
Log.e("saldo", response);
response = json.getString("saldo");
return response;
} catch (Exception e) {
return "";
}
}
}
Execute the task in onCreate as follows:
new GetDataSync("Hoi").execute();

Asking the user for a URL to receive a JSON

Just as a practicing exercise i'm trying to make an app that fetches a JSON from a URL.
I found the following code in other thread here in stackoverflow and it works just fine. My problem is that the URL is hardcoded, and i need it to be an input by the user. What should i change/add?
public class MainActivity extends AppCompatActivity {
Button btnHit;
TextView txtJson;
ProgressDialog pd;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btnHit = (Button) findViewById(R.id.btnHit);
txtJson = (TextView) findViewById(R.id.tvJsonItem);
btnHit.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
new JsonTask().execute("Url address here");
}
});
}
private class JsonTask extends AsyncTask<String, String, String> {
protected void onPreExecute() {
super.onPreExecute();
pd = new ProgressDialog(MainActivity.this);
pd.setMessage("Please wait");
pd.setCancelable(false);
pd.show();
}
protected String doInBackground(String... params) {
HttpURLConnection connection = null;
BufferedReader reader = null;
try {
URL url = new URL(params[0]);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
InputStream stream = connection.getInputStream();
reader = new BufferedReader(new InputStreamReader(stream));
StringBuffer buffer = new StringBuffer();
String line = "";
while ((line = reader.readLine()) != null) {
buffer.append(line+"\n");
Log.d("Response: ", "> " + line); //here u ll get whole response..... :-)
}
return buffer.toString();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (connection != null) {
connection.disconnect();
}
try {
if (reader != null) {
reader.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
return null;
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
if (pd.isShowing()){
pd.dismiss();
}
txtJson.setText(result);
}
}
}
This is the thread where i got that code from:
Get JSON Data from URL Using Android?

Create a constructor in your async Task
private class JSONTask extends AsyncTask<String, String, String> {
String url;
public JSONTask(String url){
this.url=url;
}
use the url string in place of params[0]
And wherever you call your async task do it like this
new JSONTask(textView.getText()).execute()
This should solve it.
Else you can directly use the do in background variable params.

So the problem is that you are using a TextView. TextView does not recieve inputs.
EditText does.
Make these Changes:
TextView txtJson;
In your OnCreate change this:
txtJson = (EditText) findViewById(R.id.tvJsonItem);
btnHit.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
new JsonTask().execute(txtJson.getText());
}
});
Now in your xml file change the Button to EditText.
Hope this helps.

Returning result from Asynctask

If I have this background worker file in my android application and it gets data from my database how can I pass the string 'result' to another class?
The background worker connects to my server and then using php it connects to a database.
public class BackgroundWorker extends AsyncTask<String,Void,String> {
Context context;
AlertDialog alertDialog;
BackgroundWorker (Context ctx) {
context = ctx;
}
#Override
public String doInBackground(String... params) {
String type = params[0];
String specials_url = "";
if(type.equals("venue click")) {
try {
//String user_name = params[1];
URL url = new URL(specials_url);
HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();
httpURLConnection.setRequestMethod("POST");
httpURLConnection.setDoOutput(true);
httpURLConnection.setDoInput(true);
OutputStream outputStream = httpURLConnection.getOutputStream();
BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream, "UTF-8"));
// String post_data = URLEncoder.encode("user_name","UTF-8")+"="+URLEncoder.encode(user_name,"UTF-8");
// bufferedWriter.write(post_data);
bufferedWriter.flush();
bufferedWriter.close();
outputStream.close();
InputStream inputStream = httpURLConnection.getInputStream();
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream,"iso-8859-1"));
String result="";
String line="";
while((line = bufferedReader.readLine())!= null) {
result += line;
}
bufferedReader.close();
inputStream.close();
httpURLConnection.disconnect();
return result;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
return null;
}
#Override
protected void onPreExecute() {
alertDialog = new AlertDialog.Builder(context).create();
alertDialog.setTitle("Info");
}
#Override
protected void onPostExecute(String result) {
alertDialog.setMessage(result);
alertDialog.show();
// String temp = "login success";
// if (result.equals(temp)) {
// Intent intent = new Intent(context, Register.class);
// context.startActivity(intent);
// }
}
#Override
protected void onProgressUpdate(Void... values) {
super.onProgressUpdate(values);
}
}

You need a listener. This will allow you to notify back when the AsyncTask is done.
Define the listener by creating an interface, like this:
public interface IListener
{
void onCompletedTask(String result);
}
On the task store a reference to the listener.
private IListener mListener;
// Pass the reference to the constructor.
public BackgroundWorker(IListener listener)
{
mListener = listener;
}
Then you notify the listener like this.
#Override
protected void onPostExecute(String result)
{
mListener.onCompletedTask(result);
}

Best way to get a callback from background thread is to use interfaces as a callback from AsyncTask for example:
create an interface that can be called in onPostExecute()
public interface ResponseCallback {
void onRespond(String result);
}
and before calling asynckTask define it like this:
ResponseCallback cpk = new ResponseCallback() {
#Override
public void onRespond(String result) {
//code to be done after calling it from onPostExecute
}
};
and pass cpk to the constructor of of the asynckTask and call it in onPostExecute like that:
if(cpk!=null){
cpk.onRespond(result);
}
of course you can modify the signature of the interface to what ever you want.

ImageDownload asynctask is getting start before test asynctask complted

public class DetailsActivity extends Activity {
private ArrayAdapter<Imageclass> adapter;
ArrayList<String> imageselect = new ArrayList<String>();
private ArrayList<Imageclass> array1;
private ArrayList<Imageclass> list = new ArrayList<Imageclass>();
//private ArrayList<Imageclass> array;
ArrayList<String> imagetest = new ArrayList<String>();
private TextView textView1;
private TextView textView2;
private TextView textView3;
private TextView textView4;
private TextView textView5;
int id;
int pid;
int val;
int val_new;
double lati;
double longi;
String imagename;
//private ImageView image;
//public static final String URL = "http://theopentutorials.com/totwp331/wp-content/uploads/totlogo.png";
ImageView image;
static Bitmap bm;
ProgressDialog pd;
BitmapFactory.Options bmOptions;
public class test extends AsyncTask<Void, Void, InputStream>{
ArrayList<Imageclass> str;
private DetailsActivity activity;
public test(DetailsActivity activity){
this.activity = activity;
}
#Override
protected InputStream doInBackground(Void... params) {
//String stringURL = "http://192.168.2.104:8088/Image/MyImage" + String.format("?id=%d",id);
Log.e("Checking id",""+id);
String stringURL = "http://megavenues.org/mobile_json/get_images" + String.format("?id=%d",id);
URL url;
try {
stringURL=stringURL.replaceAll(" ", "%20");
url = new URL(stringURL);
Log.e("URL",""+ url);
URLConnection conn= url.openConnection();
Log.e("URLConnection",""+conn );
InputStream stream= conn.getInputStream();
Log.e("URLStream",""+stream );
return stream;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
Log.e("Excepiton", ""+e);
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(InputStream result) {
super.onPostExecute(result);
Log.e("Result", ""+result);
StringBuilder builder = new StringBuilder();
Log.e("Builder", ""+ builder);
BufferedReader reader = new BufferedReader(new InputStreamReader(result));
Log.e("Reader", ""+ reader);
String line = null;
try {
while((line = reader.readLine()) != null) {
Log.e("Result11", ""+ builder.append(line));
builder.append(line);
}
} catch (IOException e) {
e.printStackTrace();
}
String jsonString = builder.toString();
Log.e("image", jsonString);
try {
JSONObject rootObject = new JSONObject(jsonString);
Log.e("JSOnObject",""+ rootObject);
JSONArray jsonArray = rootObject.getJSONArray("tbl_ads_images");
//array1.clear();
ArrayList<String> imagearray = new ArrayList<String>();
for (int index = 0; index < jsonArray.length(); index++) {
Imageclass imageinstance = new Imageclass();
JSONObject object = (JSONObject) jsonArray.get(index);
Log.e("Image test", "" + object);
imageinstance.image = object.getString("file_name");
//### this contain the image name
Log.e("Imageinstance.image",""+imageinstance.image);
imagename = imageinstance.image;
imagearray.add(imageinstance.image);
array1.add(imageinstance);
//array1.add(imagearray);
Log.e("array1","test"+array1);
}
Log.e("IMAGES",""+array1);
activity.setlist(array1);
}
catch (JSONException e) {
Log.e("this Exception",""+ e);
e.printStackTrace();
}
catch (Exception e) {
Log.e("NULL","NULL"+e);
}
// adapter.notifyDataSetChanged();
}
}
public class ImageDownload extends AsyncTask<String, Void, String> {
protected String doInBackground(String... param) {
bmOptions = new BitmapFactory.Options();
bmOptions.inSampleSize = 1;
String imageUrl ="http://megavenues.com/assets/uploads/users/"+val+"/ads/thumbnail/"+Finalname;
Log.e("inside img",""+Finalname);
Log.e("inside img_val",""+val);
Log.e("Check","check"+imageUrl);
loadBitmap(imageUrl, bmOptions);
return imageUrl;
}
protected void onPostExecute(String imageUrl) {
pd.dismiss();
if (!imageUrl.equals("")) {
Log.e("Test","Test"+ imageUrl.equals(""));
image.setImageBitmap(bm);
} else {
Toast.makeText(DetailsActivity.this,
"test", Toast.LENGTH_LONG)
.show();
}
}
}
public static Bitmap loadBitmap(String URL, BitmapFactory.Options options) {
InputStream in = null;
try {
in = OpenHttpConnection(URL);
bm = BitmapFactory.decodeStream(in, null, options);
in.close();
} catch (IOException e1) {
}
return bm;
}
private static InputStream OpenHttpConnection(String strURL)
throws IOException {
InputStream inputStream = null;
URL url = new URL(strURL);
URLConnection conn = url.openConnection();
try {
HttpURLConnection httpConn = (HttpURLConnection) conn;
httpConn.setRequestMethod("GET");
httpConn.connect();
if (httpConn.getResponseCode() == HttpURLConnection.HTTP_OK) {
inputStream = httpConn.getInputStream();
}
} catch (Exception ex) {
}
return inputStream;
}
String Finalname;
//String imageUrl ="http://megavenues.com/assets/uploads/users/220/ads/thumbnail/"+Finalname;
public void setlist(ArrayList<Imageclass> list)
{
this.list= list;
Log.e("LIST",""+ this.list);
String imagename1 = list.toString();
Log.e("image new value",""+imagename1);
this.list= list;
Log.e("testing",""+ this.list);
for (int i=0; i < list.size(); i++)
{
Log.e("new check",""+list.get(i));
//String test2= list.get(i).toString();
imagetest.add(list.get(i).toString());
Finalname = list.get(i).toString();
getimage_name(Finalname);
Log.e("Come",""+list.get(i).toString());
Log.e("Finalname",""+Finalname);
}
}
//String imageUrl ="http://megavenues.com/assets/uploads/users/"+val+"/ads/thumbnail/"+Finalname;
private void getimage_name(String finalname2) {
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_details);
image = (ImageView)findViewById(R.id.imageView2);
// getMenuInflater().inflate(R.menu.details);
//R.id.textDetailPlace
textView1 = (TextView)findViewById(R.id.textDetailPlace);
textView2 = (TextView)findViewById(R.id.textDetailAddress );
textView3 = (TextView)findViewById(R.id.textCapacity);
// textView4 = (TextView)findViewById(R.id.textDetailContactNo);
textView5 = (TextView) findViewById(R.id.textViewDescription);
textView1.setText(getIntent().getExtras().getString("test"));
textView2.setText(getIntent().getExtras().getString("test2"));
textView3.setText(getIntent().getExtras().getString("test3"));
//textView4.setText(getIntent().getExtras().getString("test4"));
textView5.setText(getIntent().getExtras().getString("test5"));
id = getIntent().getExtras().getInt("test6");
Log.e("ID value",""+id);
pid = getIntent().getExtras().getInt("test7");
Log.e("PID value",""+pid);
lati = getIntent().getExtras().getDouble("testlat");
Log.e("long",""+lati);
longi = getIntent().getExtras().getDouble("testlong");
Log.e("long",""+longi);
val=pid;
Log.e("val",""+val);
ActionBar actionBar = getActionBar();
actionBar.hide();
pd = ProgressDialog.show(DetailsActivity.this, null, null,true);
pd.setContentView(R.layout.progress);
array1 = new ArrayList<Imageclass>();
//new test(this).execute();
new test(this).execute();
here test asynctask is called
Log.e("JUST","CHECK");
Log.e("JUST","CHECK");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
here imageDownload asynctask is getting called::
new ImageDownload().execute();
Log.e("imagename",""+imagename);
}
}
here before ImageDownload is start executing before test async task is complete
and i am not able to get the status of the task can u tell how it is done

whatever i understood from this you want to execute your ImageDownload thread after the task thread,so start the ImageDownload Thread from the onPostExecute() of your task thread

When executing an async task a new thread is started, but your current thread keeps running. It immediately runs into your thread.sleep(1000) just after starting test.async.
It looks like your doing some internet downloading in test.async, and as you might have guessed, it takes longer than 1000 milliseconds (1 second). This means 1 second later, your other async is starting, before the first completed.
I assume you want to stagger them. In the postExecute of the first async, you can spawn the second async. A more stylistically correct method would be to implement an interface on your activity that takes a callback on Async completion, then upon receiving the call back, launch your second async.
An example of how to structure this is below.
interface AsyncCallback{
void onAsyncComplete();
}
public class ExampleActivity extends Activity implements AsyncCallback {
....
public void launchFirstAsync(){
new Task(this).execute();
}
#Override
public void onAsyncComplete() {
//todo launch second asyncTask;
}
}
class Task extends AsyncTask<Void, Void, Void>{
AsyncCallback cb;
Task(AsyncCallback cb){
this.cb = cb;
}
#Override
protected Void doInBackground(Void... params) {
// TODO Auto-generated method stub
return null;
}
#Override
protected void onPreExecute() {
// TODO Auto-generated method stub
super.onPreExecute();
cb.onAsyncComplete();
}
}

Have a look here, This Help me for same..Pass your url to GetTemplateImageController and get the result in Bitmap array
GetTemplateImageController Class:
public class GetTemplateImageController extends AsyncTask<String, Void, Bitmap[]>
{
Context mcontext;
private ProgressDialog pDialog;
public static String[] imageurls;
public static Bitmap bm[]=new Bitmap[15];
// URL to get JSON
private static final String url= "http://xxx.xxx.xxx.xxx/image_master.php?";
private static final String TEMPLATE = "Template_images";
private static final String IMAGEURLS = "tempimagename";
// JSONArray
JSONArray loginjsonarray=null;
//result from url
public GetTemplateImageController(Context c) {
this.mcontext=c;
}
protected void onPreExecute() {
// Showing progress dialog
super.onPreExecute();
pDialog=new ProgressDialog(mcontext);
pDialog.setMessage("Loading");
pDialog.setCancelable(true);
pDialog.setIndeterminate(true);
pDialog.show();
}
protected Bitmap[] doInBackground(String... arg) {
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("templateMasterId",arg[0].toString()));
// Creating service handler class instance
ServiceHandler sh = new ServiceHandler();
// Making a request to url and getting response
String jsonstr = sh.makeServiceCall(url, ServiceHandler.POST, params);
Log.d("Response: ", ">"+jsonstr);
if(jsonstr!=null)
{
try {
JSONObject jsonObj =new JSONObject(jsonstr);
loginjsonarray=jsonObj.getJSONArray(TEMPLATE);
imageurls=new String[loginjsonarray.length()];
for(int i=0;i<loginjsonarray.length();i++)
{
JSONObject l=loginjsonarray.getJSONObject(i);
imageurls[i]=l.getString(IMAGEURLS);
}
for(int i=0;i<imageurls.length;i++){
bm[i]=DownloadImage(imageurls[i]);
}
}catch(JSONException e){
e.printStackTrace();
}
}else{
Toast.makeText(mcontext,"Check your Internet Connection",Toast.LENGTH_SHORT).show();
}
return bm;
}
public Bitmap DownloadImage(String STRURL) {
Bitmap bitmap = null;
InputStream in = null;
try {
int response = -1;
URL url = new URL(STRURL);
URLConnection conn = url.openConnection();
if (!(conn instanceof HttpURLConnection))
throw new IOException("Not an HTTP connection");
try{
HttpURLConnection httpConn = (HttpURLConnection) conn;
httpConn.setAllowUserInteraction(false);
httpConn.setInstanceFollowRedirects(true);
httpConn.setRequestMethod("GET");
httpConn.connect();
response = httpConn.getResponseCode();
if (response == HttpURLConnection.HTTP_OK) {
in = httpConn.getInputStream();
}
}catch(Exception ex) {
throw new IOException("Error connecting");
}
bitmap = BitmapFactory.decodeStream(in);
in.close();
}catch (IOException e1) {
e1.printStackTrace();
}
return bitmap;
}
protected void onPostExecute(Integer result) {
// Dismiss the progress dialog
pDialog.dismiss();
if(result != null)
Toast.makeText(mcontext,"Download complete", Toast.LENGTH_SHORT).show();
//}
}
}
ServiceHandler Class:
public class ServiceHandler {
static String response = null;
public final static int GET = 1;
public final static int POST = 2;
public String makeServiceCall(String url, int method) {
return this.makeServiceCall(url, method, null);
}
/**
* Making service call
* #url - url to make request
* #method - http request method
* #params - http request params
* */
public String makeServiceCall(String url, int method, List<NameValuePair> params) {
try {
DefaultHttpClient httpClient=new DefaultHttpClient();
HttpEntity httpEntity=null;
HttpResponse httpResponse=null;
// Checking http request method type
if(method==POST){
HttpPost httpPost=new HttpPost(url);
if(params!=null)
{
//adding post params
httpPost.setEntity(new UrlEncodedFormEntity(params));
}
httpResponse=httpClient.execute(httpPost);
}
else if(method==GET)
{
// appending params to url
if(params!=null)
{
String paramString=URLEncodedUtils.format(params, "utf-8");
url +="?"+paramString;
}
HttpGet httpGet=new HttpGet(url);
httpResponse=httpClient.execute(httpGet);
}
httpEntity=httpResponse.getEntity();
response=EntityUtils.toString(httpEntity);
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return response;
}
}

Over time there have been several changes to the way Android deals with AsyncTasks that run concurrently. In very old Android versions (pre-1.6 afaik) multiple AsyncTasks were executed in sequence. That behavior has been changed to run the AsyncTasks in parallel up until Android 2.3. Beginning with Android 3.0 the the Android team decided that people were not careful enough with synchronizing the tasks that run in parallel and switched the default behavior back to sequential execution. Internally the AsyncTask uses an ExecutionService that can be configured to run in sequence (default) or in parallel as required:
ImageLoader imageLoader = new ImageLoader( imageView );
imageLoader.executeOnExecutor( AsyncTask.THREAD_POOL_EXECUTOR, "http://url.com/image.png" );

Develop Reference

Java is a programming language and computing platform first released by Sun Microsystems in 1995.

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