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I want to pass the string that I got from the string to the onPostExecute method

I am New to the android studio and want to something more. Actually, I am trying to pass the string that I got from the spinner in onCreateMethod and pass to the onPostExecute function. I will be grateful for the help. Bellow is my code.
I tried making a global variable called First and store the string from spinner and pass it on the onPostExecute function.
public class Convert extends AppCompatActivity implements LocationListener
{
Spinner dropdown;
Button btn;
String text;
String first;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_convert);
dropdown = (Spinner) findViewById(R.id.spinner1);
btn = (Button)findViewById(R.id.btn);
String[] items = new String[]{"United States,USD", "Nepal,NPR", "Bangladesh,BDT","Brazil,BRL"};
ArrayAdapter<String> adapter = new ArrayAdapter<>(this, android.R.layout.simple_spinner_dropdown_item, items);
dropdown.setAdapter(adapter);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
text = dropdown.getSelectedItem().toString();
first = text.substring(text.length()-3);
Log.i("her", first);
}
});
new DownloadTask().execute("http://openexchangerates.org/api/latest.json?
app_id=XXXXXXXXXX");
}
public class DownloadTask extends AsyncTask<String, Void, String> {
#Override
protected String doInBackground(String... urls) {
String result = "";
URL url;
HttpURLConnection httpURLConnection = null;
try {
url = new URL(urls[0]);
httpURLConnection = (HttpURLConnection) url.openConnection();
InputStream in = httpURLConnection.getInputStream();
InputStreamReader reader = new InputStreamReader(in);
int data = reader.read();
while (data != -1) {
char counter = (char) data;
result += counter;
data = reader.read();
}
return result;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
try{
JSONObject jsonObject = new JSONObject(result);
JSONObject curr = jsonObject.getJSONObject("rates");
String npr = curr.getString(first);
Log.i("money", npr );
} catch (JSONException e) {
e.printStackTrace();
}
}
}
What I want is to pass the string first on the onPostExecute function.

When you will call your DownloadTask, asyncTask fires with method execute, just pass param though him. Example:
How to pass url
new DownloadTask().execute("url for download");
How to receive url
protected String doInBackground(String... urls) {
String url = urls[0]; // url for download
}
Also you could send and array of params. Also be careful with AsyncTask, do not pass your context/view variable, it could arise memory leaks, read docs.

doInBackground not updating variable

I'm working on a basic android app that makes a POST with HttpURLConnection. I want to return the response Message from my Web API.
My MainActivity.java
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final TextView mTextView = findViewById(R.id.textView);
AsyncExample asyncExample = new AsyncExample();
asyncExample.execute();
mTextView.setText(asyncExample.getResponseMsg());
}
}
My AsyncExample.java
class AsyncExample extends AsyncTask<Void, Void, Void> {
private HttpURLConnection con;
private String responseMsg;
protected void onPreExecute() {
responseMsg = "empty message";
}
#Override
protected Void doInBackground(Void... params) {
String urlParameters = "param1=data1";
byte[] postData = urlParameters.getBytes(Charset.forName("UTF-8"));
int postDataLength = postData.length;
String request = "http://192.168.1.30:6262";
URL url = null;
try {
url = new URL(request);
con = (HttpURLConnection) url.openConnection();
con.setDoOutput(true);
con.setInstanceFollowRedirects(false);
con.setRequestMethod("POST");
con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
con.setRequestProperty("charset", "utf-8");
con.setRequestProperty("Content-Length", Integer.toString(postDataLength));
responseMsg = con.getResponseMessage();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
public String getResponseMsg() {
return responseMsg;
}
}
After running the app, i get empty message in my TextView. Why it is not getting updated my doInBackground? Even if con.getResponseMessage() is null, it should be updated?

The problem is that your AsyncTask is executed asynchronously, while you try to retrieve the value immediately. You need to implement this a little bit differently. Either leverage the API of AsyncTask, sine it posts callbacks for your on the UI thread. You can update your TextView directly in your AsyncTask
class MyAwesomeAsyncTask extends AsyncTask<Void, Void, String> {
#Override
protected void onPreExecute() {
myTextView.setText("progress started");
}
#Override
protected String doInBackground(final Void... voids) {
String s = amazingCallToBackend();
return s;
}
#Override
protected void onPostExecute(final String s) {
myTextView.setText(s);
}
}
Or if you just want the value, you can pass a Callback to your async task that will deliver the value to you, something like that
interface Callback {
void onValueReceived(String value);
void onFailure();
}
class MyAwesomeAsyncTask extends AsyncTask<Void, Void, String> {
private Callback callback;
MyAwesomeAsyncTask(final Callback callback) {
this.callback = callback;
}
#Override
protected String doInBackground(final Void... voids) {
String s = amazingCallToBackend();
return s;
}
#Override
protected void onPostExecute(final String s) {
callback.onValueReceived(s);
}
}
Here's how you create it
Callback callback = new Callback() {
#Override
public void onValueReceived(final String value) {
}
#Override
public void onFailure() {
}
};
new MyAwesomeAsyncTask(callback).execute();
However, be careful because if for some reason your activity/fragment is gone/finished before your AsyncTask is done, this can cause memory leaks.
A quick Google search will tell you all you want about AsyncTask leaking memory :)

Your doInBackground method take time to execute. you are immediately calling mTextView.setText(asyncExample.getResponseMsg()); but asynctask has been not been finished yet. You need to wait until your doInBackground finish and then call that setText you can do it in onPostExecute method.

AsyncTask has 3 default method
1. On preexecute
2. Do in background
3. On post execute
post execute:
The response got from the doinbackground is in the post execute.
Here we can process the result . use the runnable method to update text view ui

Override the onPostExecute() Method to return the text. In the Main Activity create a method to update the TextView after completing the execution of the Async Task. It is coming blank as because the Main Thread is not paused its executing and setting the text View but the Async task has not yet finished executing and hence the String is empty. So wait for the Async Task to finish before setting the text view.
String str_result= new RunInBackGround().execute().get();
Refer to this for more information.

You can do it in a number of ways. I'd try to suggest you a way that would require negligible amount of changes to your existing code.
Declare the mTextView as a Global variable, Override onPostExecute() method inside your AsyncExample and update mTextView inside that onPostExecute() method with the value passed to it by the doInBackground() method [here, notice that responseMsg is returned at the end of doInBackground() ground which is caught as a String value (result) by the onPostExecute() method]. However, I also think that its a good idea to Override your onPreExecute() method.
In order to do so, your MainActivity.java should be as follows:
public class MainActivity extends AppCompatActivity {
TextView mTextView; //declare mTextView outside the onCreate() method as a Global String variable.
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTextView = findViewById(R.id.textView);
AsyncExample asyncExample = new AsyncExample();
asyncExample.execute();
}
}
Please make your asynctask an inner-class of the same activity and edit it as follows:
class AsyncExample extends AsyncTask<Void, Void, Void> {
private HttpURLConnection con;
private String responseMsg;
#Override // Its a good practice to Override the onPreExecute() method.
protected void onPreExecute() {
responseMsg = "empty message";
}
#Override
protected String doInBackground(String... params) {
String urlParameters = "param1=data1";
byte[] postData = urlParameters.getBytes(Charset.forName("UTF-8"));
int postDataLength = postData.length;
String request = "http://192.168.1.30:6262";
URL url = null;
try {
url = new URL(request);
con = (HttpURLConnection) url.openConnection();
con.setDoOutput(true);
con.setInstanceFollowRedirects(false);
con.setRequestMethod("POST");
con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
con.setRequestProperty("charset", "utf-8");
con.setRequestProperty("Content-Length", Integer.toString(postDataLength));
responseMsg = con.getResponseMessage();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return responseMsg; //return the value of responseMsg
}
#Override //override onPostExecute() method
protected void onPostExecute(String result) { //receive the value to be set to mTextView which is returned by the doInBackground() method.
mTextView.setText(result);
}
}

Try to do like this
MainActivity
public class MainActivity extends AppCompatActivity {
TextView mTextView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTextView = findViewById(R.id.textView);
AsyncExample asyncExample = new AsyncExample(this,mTextView);
asyncExample.execute();
}
}
AsyncTask
class AsyncExample extends AsyncTask<Void, Void, Void> {
private HttpURLConnection con;
private String responseMsg;
private MainActivity mContext;
TextView mTextView;
public AsyncExample (MainActivity context, TextView textView) {
mContext = context;
mTextView = textView;
}
protected void onPreExecute() {
responseMsg = "empty message";
}
#RequiresApi(api = Build.VERSION_CODES.KITKAT)
#Override
protected Void doInBackground(Void... params) {
String urlParameters = "param1=data1";
byte[] postData = urlParameters.getBytes(StandardCharsets.UTF_8);
int postDataLength = postData.length;
String request = "http://192.168.1.30:6262";
URL url = null;
try {
url = new URL(request);
con = (HttpURLConnection) url.openConnection();
con.setDoOutput(true);
con.setInstanceFollowRedirects(false);
con.setRequestMethod("POST");
con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
con.setRequestProperty("charset", "utf-8");
con.setRequestProperty("Content-Length", Integer.toString(postDataLength));
responseMsg = con.getResponseMessage();
mContext.runOnUiThread(new Runnable() {
#Override
public void run() {
mTextView.setText(responseMsg);
}
});
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
public String getResponseMsg() {
return responseMsg;
}
}

Android - Send HTTP Request with AsyncTask on Button Click | Problems with delegate

i am about to write a small application. On button click i send a http request in a custom async task class. I want to write this value in a EditText field and in a ListView as item. My problem now is that i want to return the value of the request to the main thread to process it further. I searched around and found a method with an interface. This is my asynctask class:
public class Request extends AsyncTask<String,Void,String> {
public AsyncResponse delegate=null;
private MainActivity mAct;
public Request(MainActivity mainActivity){
this.mAct = mainActivity;
}
#Override
protected String doInBackground(String... url){
String returnString = "";
try {
URL u = new URL(url[0]);
final HttpURLConnection connection = (HttpURLConnection)u.openConnection();
BufferedInputStream bis = new BufferedInputStream(connection.getInputStream());
byte[] content = new byte[1024];
int bytesRead = 0;
String strContent = "";
while((bytesRead = bis.read(content)) != -1){
strContent += new String(content,0,bytesRead);
}
returnString = strContent;
} catch (Exception e){
} finally {
return returnString;
}
}
protected void onPostExecute(String result){
delegate.processFinish(result);
}
}
And this is my MainActivity:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final Button btnSend = (Button)findViewById(R.id.btnSendMessage);
final ListView lv = (ListView)findViewById(R.id.treeView);
final EditText editText = (EditText)findViewById(R.id.txtReqID);
final MainActivity ma = this;
final ArrayList<String> arrList = new ArrayList<String>();
final ArrayAdapter<String> arrAdapter = new ArrayAdapter<String>(getApplicationContext(),R.layout.simple_list_item_1,arrList);
btnSend.setOnClickListener(new View.OnClickListener(){
public void onClick(View v){
String t = new String("http://myhttprequest");
Request r = new Request(ma);
public void onCreate(Bundle savedInstanceState){
r.delegate = this;
}
editText.setText(returnValue);
lv.setAdapter(arrAdapter);
arrList.add(returnValue);
arrAdapter.notifyDataSetChanged();
}
});
}
public interface AsyncResponse{
void processFinish(String output);
}
The problem is that i have to declare every variable as final because i acces them within a function. I don't feel very happy with my code now and i also have no idea how i can make this work. Any help is very much appreciated.
Best regards

Try this way:
btnSend.setOnClickListener(new View.OnClickListener(){
public void onClick(View v){
String t = new String("http://myhttprequest");
Request r = new Request(ma){
protected void onPostExecute(String result){
editText.setText(result);
lv.setAdapter(result);
arrList.add(result);
arrAdapter.result();
}
};
}
});

What you should do I pretty simple.
Create an AsyncTask constructor that takes "delegate" as param
1.1 In case the "delegate" is an Activity (it is in your case) just make sure it's hold in a WeakReference (to avoid memory leaks)
Do you thing with http
When you want to dispatch the callback, just use your "delegate" param (check for null - as it is a WeakReference).
Cheers!

Asynctask unknown type execute

This is my first time with getting APIS to return the result JSON object. I think I have got the async task code right but I just don't know how to execute it. This is my class code.
For my layout all I have is one button with an onClick () method gg, a progress bar and one text view.
This is the async task:
public class MainActivity extends Activity
{
ProgressBar progressBar;
TextView responseView;
EditText emailText;
String URL;
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
progressBar = (ProgressBar) findViewById(R.id.progressBar);
responseView = (TextView) findViewById(R.id.responseView);
emailText = (EditText) findViewById(R.id.emailText);
URL = "https://kgsearch.googleapis.com/v1/entities:search?query=taylor+swift&key=APIKEY&limit=1&indent=True";
}
public void gg(View v)
{
new RetrieveFeedTask.execute();
}
private class RetrieveFeedTask extends AsyncTask<Void, Void, String> {
private Exception exception;
protected void onPreExecute() {
progressBar.setVisibility(View.VISIBLE);
responseView.setText("");
Toast.makeText(MainActivity.this, "pre execute", Toast.LENGTH_LONG).show();
}
protected String doInBackground(Void... urls) {
String email = emailText.getText().toString();
// Do some validation here
try {
URL url = new URL(URL);
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
try {
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
StringBuilder stringBuilder = new StringBuilder();
String line;
while ((line = bufferedReader.readLine()) != null) {
stringBuilder.append(line).append("\n");
}
bufferedReader.close();
return stringBuilder.toString();
}
finally{
urlConnection.disconnect();
}
}
catch(Exception e) {
Log.e("ERROR", e.getMessage(), e);
return null;
}
}
protected void onPostExecute(String response) {
if(response == null) {
response = "THERE WAS AN ERROR";
Toast.makeText(MainActivity.this, "post execute", Toast.LENGTH_LONG).show();
}
progressBar.setVisibility(View.GONE);
Log.i("INFO", response);
responseView.setText(response);
}
}
}
So in the public void gg(View v)
I call the .execute method but it gives me an error
Unknown type execute
Do I have to add some params to the execute method?
If so what?
Thanks.

Try
new RetrieveFeedTask().execute();

Any way to edit a URI based on User Input?

I have an HTTP GET that is receiving information from a URI. The URI is for Google Shopping.
https://www.googleapis.com/shopping/search/v1/public/products?key=key&country=US&q=digital+camera&alt=atom
(Left my key out).
Is there a way that I can change it from
q=digital+camera
to anything a user puts in an EditText?
So basically, I want the EditText to change what is searched on Google Shopping.
First screen, ProductSearchEntry with EditText for search query:
Code for ProductSearchEntry
public class ProductSearchEntry extends Activity{
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.productsearchentry);
Button search = (Button) findViewById(R.id.searchButton);
search.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent searchIntent = new Intent(getApplicationContext(), ProductSearch.class);
startActivity(searchIntent);
}
});
}
}
Then, I have a second class, ProductSearch, with no picture, but just this code:
public class ProductSearch extends Activity{
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.productsearchresults);
EditText searchQuery = (EditText) findViewById(R.id.searchQuery);
ProductSearchMethod test = new ProductSearchMethod();
String entry;
TextView httpStuff = (TextView) findViewById(R.id.httpTextView);
try {
entry = test.getSearchData(searchQuery.getText().toString());
httpStuff.setText(entry);
} catch (Exception e) {
e.printStackTrace();
}
}
}
Which references the ProductSearchMethod class which consists of a TextView that is changed to the code recieved in the HTTP GET:
Code:
public class ProductSearchMethod {
public String getSearchData(String query) throws Exception{
BufferedReader in = null;
String data = null;
try{
HttpClient client = new DefaultHttpClient();
URI site = new URI("https://www.googleapis.com/shopping/search/v1/public/products?key=key&country=US&q="+query.replace(" ","+")+"&alt=atom");
HttpGet request = new HttpGet();
request.setURI(site);
HttpResponse response = client.execute(request);
in = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
StringBuffer sb = new StringBuffer("");
String l = "";
String nl = System.getProperty("line.seperator");
while((l = in.readLine()) !=null){
sb.append(l + nl);
}
in.close();
data = sb.toString();
return data;
}finally{
if (in != null){
try{
in.close();
return data;
}catch (Exception e){
e.printStackTrace();
}
}
}
}
}
ProductSearchMethod comes up great, but it doesn't change the text from "Loading Items" to the website code. I had it working before but then I tried to edit what it searched (all this ^) and now it doesn't change.

Make changes in your code like
public class ProductSearchEntry extends Activity{
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.productsearchentry);
EditText etSearch = (EditText) findViewById(id of your edittext);
Button search = (Button) findViewById(R.id.searchButton);
search.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//while calling intent
Intent searchIntent = new Intent(getApplicationContext(), ProductSearch.class);
searchIntent.putExtra("searchText",etSearch.getText().toString());
startActivity(searchIntent);
}
});
}
}
and another activity like this,
public class ProductSearch extends Activity{
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.productsearchresults);
String searchQuery = getIntent().getStringExtra("searchText");
ProductSearchMethod test = new ProductSearchMethod();
String entry;
TextView httpStuff = (TextView) findViewById(R.id.httpTextView);
try {
entry = test.getSearchData(searchQuery);
httpStuff.setText(entry);
} catch (Exception e) {
e.printStackTrace();
}
}
}

Yeah... Change your getSearchData() method to include a string as a parameter
public String getSearchData(String query) throws Exception{
Then, insert that string into the query URL, replacing spaces with "+". You may want to do further conditioning to the string, for instance URL encoding it.
URI site = new URI("https://www.googleapis.com/shopping/search/v1/public/products?key=key&country=US&q="+query.replace(" ","+")+"&alt=atom");
In your XML, create a button that contains the following line:
android:onClick="search"
In your ProductSearch activity, add the following method, and move the code in onCreate into it. You will also need to create an EditText in your XML for input.
public void search(View v)
{
EditText searchQuery = (EditText) findViewById(R.id.searchQuery);
ProductSearchMethod test = new ProductSearchMethod();
String returned;
try {
returned = test.getSearchData(searchQuery.getText().toString());
httpStuff.setText(returned);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
Finally, you will probably want to read up on running asynchronous tasks so that the query won't freeze your app while performing.

May be I got you wrong, but why don't you just pass it as a parameter in
getSearchData() => getSearchData(string query)
Then you can change the line
URI site = new URI("https://www.googleapis.com/shopping/search/v1/public/products?key=key&country=US&q=digital+camera&alt=atom");
to
URI site = new URI("https://www.googleapis.com/shopping/search/v1/public/products?key=key&country=US&q=+ URLEncoder.encode(query, "UTF-8")+&alt=atom");

Check out http://androidforums.com/developer-101/528924-arduino-android-internet-garage-door-works-but-could-use-input.html I use Asynctask to trigger a get command on a local Arduino server. It appends the Arduino's pin number and, depending on if it's needed, a port number to the end of the URL. I'm sure you could use it to help you out.