Develop Reference

Android Studio: setOnItemClickListener

I have two AppCompatActivitys, both should have an onItemClickListener, but one of them doesn't do anything on click. I've just added a Toast for test reason, later on it should call a function to delete an item from list (with an ajax request)
What am I doing wrong?
I have made custom list and custom adapter for this - I know, I am new to Android Studio, but the other Activity works fine, and I cant find any differences.
public class ActivityListofProducts extends AppCompatActivity {
ProgressDialog pd;
SharedPreferences preferences;
String userid;
String session;
String list_id = "-1"; // or other values
String appVersion = "";
private ArrayList<listProductItem> myProducts = new ArrayList<listProductItem>();
private ArrayList<listProductItem> groceryFilterProducts = new ArrayList<listProductItem>();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
handleIntent(getIntent());
setContentView(R.layout.activity_list_of_products);
this.setTitle(getString(R.string.grocery_list));
Bundle b = getIntent().getExtras();
SwipeRefreshLayout swipeRefreshLayout = (SwipeRefreshLayout) findViewById(R.id.refreshLayout);
if (b != null)
list_id = b.getString("list_id");
Toast.makeText(this, "List to open " + " " + list_id, Toast.LENGTH_SHORT).show();
preferences =
getSharedPreferences(this.getPackageName(), this.MODE_PRIVATE);
userid = preferences.getString("userid", "");
session = preferences.getString("session", "");
appVersion = preferences.getString("appVersion", "");
getData();
swipeRefreshLayout.setOnRefreshListener(
new SwipeRefreshLayout.OnRefreshListener() {
#Override
public void onRefresh() {
getData();
swipeRefreshLayout.setRefreshing(false);
}
}
);
}
public void getData() {
AsyncTask<String, String, String> Task_GetListofProducts = new Task_GetListofProducts();
Task_GetListofProducts.execute("https://get-some-json.com");
}
public void initListofProducts(String jsonString) {
Log.i("jsonString",jsonString);
try {
JSONObject jsonResponse = new JSONObject(jsonString);
JSONObject jsonListMode = jsonResponse.getJSONObject("list");
String ListName = jsonListMode.optString("name");
this.setTitle(ListName);
JSONArray jsonMainNode = jsonResponse.optJSONArray("data");
for (int i = 0; i < jsonMainNode.length(); i++) {
JSONObject jsonChildNode = jsonMainNode.getJSONObject(i);
int item_amount = jsonChildNode.optInt("item_amount");
int id = jsonChildNode.optInt("id");
String item_name = jsonChildNode.optString("item_name",">Name<");
int done = jsonChildNode.optInt("done", 0);
String timestamp = jsonChildNode.optString("timestamp", "");
String item_scale = jsonChildNode.optString("item_scale", "x");
String img = jsonChildNode.optString("img", "x");
double bestprice = jsonChildNode.optDouble("bestprice");
//int oitems = jsonChildNode.optInt("oitems", 0);
//int shared = jsonChildNode.optInt("shared", 0);
String outPut = "item_amount:"+ item_amount +" id:"+ id +" item_name:"+ item_name +" done:"+ done +" timestamp:"+ timestamp +" item_scale:"+ item_scale +" img:"+ img;
Log.i("outPut",outPut);
myProducts.add(new listProductItem(id, item_name, item_amount, item_scale, img, done, timestamp, bestprice));
}
final ListView lv = findViewById(R.id.grocery_list_of_products);
lv.setAdapter(new listofProductsAdapter(this, myProducts));
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> a, View v, int position, long id) {
/*
!! HERE is my problem. This Code seems not to be executed !!
*/
Toast.makeText(ActivityListofProducts.this, "Should handle click now.", Toast.LENGTH_SHORT).show();
}
});
} catch (JSONException e) {
Toast.makeText(getApplicationContext(), "Error" + e.toString(), Toast.LENGTH_SHORT).show();
}
}
public void setProductDone(int pid, int done) {
String url = "put-some-json.com";
new ActivityListofProducts.Task_SetProductDone().execute(url);
}
private class Task_SetProductDone extends AsyncTask<String, String, String> {
protected void onPreExecute() {
super.onPreExecute();
pd = new ProgressDialog(ActivityListofProducts.this);
pd.setMessage("Please wait");
pd.setCancelable(false);
pd.show();
}
protected String doInBackground(String... params) {
HttpURLConnection connection = null;
BufferedReader reader = null;
Log.i("doInBackground",params.toString());
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 you will get whole response...... :-)
}
return buffer.toString();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (UnknownHostException e) {
Toast.makeText(ActivityListofProducts.this, "No Internet?", Toast.LENGTH_SHORT).show();
} 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();
}
Log.i("onPostExecute", result);
}
}
private class Task_GetListofProducts extends AsyncTask<String, String, String> {
protected void onPreExecute() {
super.onPreExecute();
pd = new ProgressDialog(ActivityListofProducts.this);
pd.setMessage("Please wait");
pd.setCancelable(false);
pd.show();
myProducts = new ArrayList<listProductItem>(); //empty list
}
protected String doInBackground(String... params) {
HttpURLConnection connection = null;
BufferedReader reader = null;
Log.i("doInBackground",params.toString());
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 you will 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();
}
initListofProducts(result);
}
}
private class Task_FindProducts extends AsyncTask<String, String, String> {
protected void onPreExecute() {
super.onPreExecute();
pd = new ProgressDialog(ActivityListofProducts.this);
pd.setMessage("Please wait");
pd.setCancelable(false);
pd.show();
myProducts = new ArrayList<listProductItem>(); //empty list
}
protected String doInBackground(String... params) {
HttpURLConnection connection = null;
BufferedReader reader = null;
Log.i("doInBackground",params.toString());
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 you will 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();
}
setFilterProducts(result);
}
}
}

Parsing Integer from JSON not working [duplicate]

This question already has answers here:
How do I parse JSON in Android? [duplicate]
(3 answers)
Closed 6 years ago.
I am attempting to make an app in android studio that gets live currency rates, so I decided to use a JSON to do this. I am currently able to print out the entire JSON as a string, however I would like to be able to set the TextView to the USD conversion rate, however it doesn't work. The TextView does not change. Any help would be greatly appreciated.
public class Converter extends AppCompatActivity {
TextView txtJson;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_converter);
txtJson = (TextView) findViewById(R.id.tvJsonItem);
new JsonTask().execute("https://openexchangerates.org/api/latest.json?app_id=870447ebb4d94379972250a3bdaed73f");
}
private class JsonTask extends AsyncTask<String, String, String> {
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);
}
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
public void onPostExecute(String result) {
super.onPostExecute(result);
try {
JSONObject jObject = new JSONObject(result);
int USD = jObject.getInt("USD");
String strUSD = Integer.toString(USD);
txtJson.setText(strUSD);
} catch (JSONException e) {
e.printStackTrace();
}
}
}}

You need to get the "rates" object before you can access the "USD" value
Also, it's not an integer. It's a double
getJSONObject("rates").getDouble("USD")

Asynctask android return contents "doinBackground

I would like to retrieve the contents of my variable "$content" in my activity.
But I don't know how to use the return value of my doinbackground.
Can you help me ?
thank you in advance
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
String restURL = "https://proxyepn-test.epnbn.net/wsapi/epn";
RestOperation test = new RestOperation();
test.execute(restURL);
}
private class RestOperation extends AsyncTask<String, Void, String> {
//final HttpClient httpClient = new DefaultHttpClient();
String content;
String error;
ProgressDialog progressDialog = new ProgressDialog(MainActivity.this);
String data = "";
TextView serverDataReceived = (TextView)findViewById(R.id.serverDataReceived);
TextView showParsedJSON = (TextView) findViewById(R.id.showParsedJSON);
// EditText userinput = (EditText) findViewById(R.id.userinput);
#Override
protected void onPreExecute() {
super.onPreExecute();
progressDialog.setTitle("Please wait ...");
progressDialog.show();
}
#Override
protected String doInBackground(String... params) {
BufferedReader br = null;
URL url;
try {
url = new URL(params[0]);
URLConnection connection = url.openConnection();
connection.setDoOutput(true);
OutputStreamWriter outputStreamWr = new OutputStreamWriter(connection.getOutputStream());
outputStreamWr.write(data);
outputStreamWr.flush();
br = new BufferedReader(new InputStreamReader(connection.getInputStream()));
StringBuilder sb = new StringBuilder();
String line = null;
while((line = br.readLine())!=null) {
sb.append(line);
sb.append(System.getProperty("line.separator"));
}
content = sb.toString();
} catch (MalformedURLException e) {
error = e.getMessage();
e.printStackTrace();
} catch (IOException e) {
error = e.getMessage();
e.printStackTrace();
} finally {
try {
br.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return content;
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
progressDialog.dismiss();
if(error!=null) {
serverDataReceived.setText("Error " + error);
} else {
serverDataReceived.setText(content);
String output = "";
JSONObject jsonResponse;
try {
jsonResponse = new JSONObject(content);
JSONArray jsonArray = jsonResponse.names();
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject child = jsonArray.getJSONObject(i);
String name = child.getString("name");
String number = child.getString("number");
String time = child.getString("date_added");
output = "Name = " + name + System.getProperty("line.separator") + number + System.getProperty("line.separator") + time;
output += System.getProperty("line.separator");
Log.i("content",content);
}
showParsedJSON.setVisibility(View.INVISIBLE);
showParsedJSON.setText(output);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
}

You can directly call to the method which exist in activity, from onPostExecute method of asynctask by passing "content" value.
#Override
protected void onPostExecute(String content) {
Activity.yourMethod(content);
}
If you want to return the value from asynctask you can use
content = test.execute(url).get();
but it is not a good practice of asynctask, because it is working as serial execution. So it is not fulfill the use of asynctask for palatalization.Because get() will block the UI thread.

Informationparsing from URL-Request not working / Didn't found TextView

i need your help. I want to send a URL Request, get response and create a JSON Object. My first try was totally wrong. Now I found a tutorial and made a new try.
My Activity looks like:
public class Patienten extends Activity {
//Beacon Elemente
private String UUID;
private String Major;
private String Minor;
private TextView output;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_patienten);
output = (TextView) findViewById(R.id.output);
UpdateBeaconInformation();
Button cmdHit = (Button) findViewById(R.id.cmd_hit);
cmdHit.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
new JSONTask().execute("//http://kusber-web.de/JsonTest.txt");
}
});
setTitle(Surname + ", " + FirstName);
// output.setText(output.getText().toString() + "Gefundener Patient:\n" + "Name: " + Surname + ", " + FirstName + "\nGeb.-Dat: " + Birthdate);
}
Then I created a new Java Class and built an asyncTask with it. But I can't access to the textview output in onPostExecute to update it.
public class JSONTask extends AsyncTask<String, String, String> {
#Override
protected String doInBackground(String... urls) {
HttpURLConnection connection = null;
BufferedReader reader = null;
try {
//http://kusber-web.de/JsonTest.txt
//http://nilsbenning.selfhost.me/PatientFinder.php?beacon_comID=5181f8a3-7354-46ac-b22d-952ec395ab06&beacon_major=12&beacon_minor=249
URL url = new URL(urls[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);
}
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);
output.setText(result);
}
}
What is my mistake? Why I can't access to it? I saw it as a solution here but didn't get it to work:
https://stackoverflow.com/a/12252717/5743912
Hope you can help me now! :)

You probably want to fix this (remove leading slashes):
new JSONTask().execute("//http://kusber-web.de/JsonTest.txt");
In your JSONTask you can reference members of Patienten by using Patienten.this. So in onPostExecute you should change this:
output.setText(result);
to:
Patienten.this.output.setText(result);

Android Null pointer exception while using Async Task method [duplicate]

This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 7 years ago.
While executing Async Task in android and getting Json response and while converting response into JSONArray,i am getting NUll pointer Exception.
I am trying fron two days Please help me.
Here is the code to get the Json String.
error is at task.get().
DownloadTask task=new DownloadTask();
task.execute(new String[]{"URL"});
try {
jsonArr=new JSONArray(task.get());
Toast.makeText(getApplicationContext(), jsonArr.toString(), Toast.LENGTH_LONG).show();
for (int i = 0; i < jsonArr.length(); i++) {
obj = jsonArr.getJSONObject(i);
name = obj.getString("name");
phno = obj.getString("phone");
dcount = obj.getString("count");
}
} catch (JSONException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
Here Is the Async task code.
class DownloadTask extends AsyncTask<String,Void,String>{
private ProgressDialog mProgressDialog=new ProgressDialog(MainActivity.this);
#Override
protected void onPreExecute(){
mProgressDialog.setMessage("Processing");
mProgressDialog.show();
}
#Override
protected String doInBackground(String... targetURL) {
URL url;
HttpURLConnection connection = null;
try {
url = new URL(targetURL[0]);
connection = (HttpURLConnection)url.openConnection();
connection.setRequestMethod("GET");
connection.setRequestProperty("Content-Type",
"application/json");
connection.setUseCaches (false);
connection.setDoInput(true);
connection.setDoOutput(true);
/* //Send request
DataOutputStream wr = new DataOutputStream (
connection.getOutputStream ());
wr.writeBytes("BID1");
wr.flush();
wr.close();*/
//Get Response
InputStream is = connection.getInputStream();
BufferedReader rd = new BufferedReader(new InputStreamReader(is));
String line;
StringBuffer response = new StringBuffer();
while((line = rd.readLine()) != null) {
response.append(line);
response.append('\r');
}
rd.close();
return response.toString();
} catch (Exception e) {
e.printStackTrace();
return null;
} finally {
if(connection != null) {
connection.disconnect();
}
}
}
#Override
protected void onPostExecute(String result) {
Toast.makeText(getApplicationContext(),result, Toast.LENGTH_SHORT);
mProgressDialog.dismiss();
}
}

You are forgot to call the super method of the onPostExecute
It should be like this
#Override
protected void onPostExecute(String result) {
Toast.makeText(getApplicationContext(),result, Toast.LENGTH_SHORT);
mProgressDialog.dismiss();
super.onPostExecute(result);
}
Other Solution
You can use an interface for your callback
ICallback.java
public interface ICallback {
void onResult(String result);
}
DownloadTask
class DownloadTask extends AsyncTask<String, Void, String> {
private ProgressDialog mProgressDialog = new ProgressDialog(MainActivity.this);
private ICallback callback;
public DownloadTask(ICallback callback) {
this.callback = callback;
}
#Override
protected void onPreExecute() {
//Your Codes Here
}
#Override
protected String doInBackground(String... targetURL) {
//Your Codes Here
}
#Override
protected void onPostExecute(String result) {
//Your Codes Here
callback.onResult(result)
}
}
How to use it
DownloadTask task = new DownloadTask(new ICallback() {
#Override
public void onResult(String result) {
try {
jsonArr=new JSONArray(result);
Toast.makeText(getApplicationContext(), jsonArr.toString(), Toast.LENGTH_LONG).show();
for (int i = 0; i < jsonArr.length(); i++) {
obj = jsonArr.getJSONObject(i);
name = obj.getString("name");
phno = obj.getString("phone");
dcount = obj.getString("count");
}
} catch (JSONException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
}
});
task.execute(new String[]{"URL"});