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android listview doinbackground can not show anything

I want to do a listview ,and I have lot of data want to insert it.
so I want to use doinbackground.
but when I use doinbackground,my listview never appera anymore,
how can I do ?
this is my code:
public class Listening extends AppCompatActivity {
ArrayList<Listenlist> listenlists = new ArrayList<Listenlist>();
ListView listview;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.listening);
listview = (ListView) findViewById(R.id.list);
}
public void seraechsql2(){
String result = dblisten.executeQuery();
try{
JSONArray jsonArray = new JSONArray(result);
for(int i =0; i < jsonArray.length(); i++)
{
JSONObject jsonData = jsonArray.getJSONObject(i);
track=jsonData.getString("track");
Listenlist team = new Listenlist("T"+track+".mp3");
listenlists.add(team);
final ListenlistAdapter adapter = new ListenlistAdapter(this, R.layout.listenlist, listenlists);
listview.setAdapter(adapter);
}
}
catch(Exception e){}
}
class DownloadFileAsync extends AsyncTask<String, String, String> {
#Override
protected void onPreExecute() {
super.onPreExecute();
}
#Override
protected String doInBackground(String... aurl) {
seraechsql2();// it can not show listview...
return null;
}
protected void onProgressUpdate(String... progress) {}
#Override
protected void onPostExecute(String unused) {}
}
}
thanks.

You shouldn't update UI in doInBackground because it's background thread. It should be update in onPostExecute. Try this code:
public class Listening extends AppCompatActivity {
ArrayList<Listenlist> listenlists = new ArrayList<Listenlist>();
ListView listview;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.listening);
listview = (ListView) findViewById(R.id.list);
}
public void seraechsql2(){
String result = dblisten.executeQuery();
try{
JSONArray jsonArray = new JSONArray(result);
for(int i =0; i < jsonArray.length(); i++)
{
JSONObject jsonData = jsonArray.getJSONObject(i);
track=jsonData.getString("track");
Listenlist team = new Listenlist("T"+track+".mp3");
listenlists.add(team);
}
}
catch(Exception e){}
}
class DownloadFileAsync extends AsyncTask<String, String, ArrayList<Listenlist>> {
#Override
protected void onPreExecute() {
super.onPreExecute();
}
#Override
protected String doInBackground(String... aurl) {
seraechsql2();
return listenlists;
}
protected void onProgressUpdate(String... progress) {}
#Override
protected void onPostExecute(ArrayList<Listenlist> result) {
final ListenlistAdapter adapter = new ListenlistAdapter(this, R.layout.listenlist, result);
listview.setAdapter(adapter);
}
}
}

for(int i =0; i < jsonArray.length(); i++)
{
// each time you create a new adapter and set it !!!
Listenlist team = new Listenlist("T"+track+".mp3");
listenlists.add(team);
final ListenlistAdapter adapter = new ListenlistAdapter(this, R.layout.listenlist, listenlists);
listview.setAdapter(adapter); // HERE!!!
}
I think you should change like this
public class Listening extends AppCompatActivity {
ArrayList<Listenlist> listenlists = new ArrayList<Listenlist>();
ListView listview;
final ListenlistAdapter adapter = new ListenlistAdapter(this, R.layout.listenlist, listenlists); // initilize adapter
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.listening);
listview = (ListView) findViewById(R.id.list);
listview.setAdapter(adapter); // only set once
}
public void seraechsql2(){
String result = dblisten.executeQuery();
try{
JSONArray jsonArray = new JSONArray(result);
for(int i =0; i < jsonArray.length(); i++)
{
JSONObject jsonData = jsonArray.getJSONObject(i);
track=jsonData.getString("track");
Listenlist team = new Listenlist("T"+track+".mp3");
listenlists.add(team);
}
adapter.notifyDataSetChanged();// notify listview that data has changed！
}
catch(Exception e){}
}
}

How to send values from an arraylist from AsyncTask class to another class in Android?

I have the next problem, I tried to send Arraylist<string> values from AsyncTask class to other class call graphics but I don’t know what I do wrong and how to get Arraylist<string> values in the other class, because I have a lot of sintaxis errors I my code
AsyncTask class
public class fetch extends AsyncTask<Void,Void,ArrayList<String>> {
//v funcional
#RequiresApi(api = Build.VERSION_CODES.KITKAT)
#Override
protected ArrayList<String> doInBackground(Void... voids) {
String Id ="";
String Time ="";
String Pressure="";
ArrayList<String> IdArray = new ArrayList<String>();
ArrayList<String> TimeArray = new ArrayList<String>();
ArrayList<String> PressureArray = new ArrayList<String>();
String IdS=""+IdArray;
String TimeS=""+TimeArray;
String PresureS=""+PressureArray;
data.set(1,TimeS);
data.set(2,TimeS);
data.set(3,TimeS);
return data;
}
#Override
protected void onPostExecute(ArrayList<String> result){
super.onPostExecute(result);
Graphics.data.setText(data);
}}
The graphics class
public class Graphics extends AppCompatActivity {
public static TextView data;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.graphics);
Button firstButton = (Button) findViewById(R.id.json);
data = (TextView) findViewById(R.id.msgTxt);
firstButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
fetch process = new fetch();
ArrayList<String> data= process.execute();
data.get(1);
}
});
}

you can create an interface which your "Graphics" implements it , and pass it to your AsyncTask class.
like this
public interface BlaBlaBla {
void doBla(ArrayList<String> myBla);
}
and in your "Graphics" :
class Graphics extends AppCompatActivity implements BlaBlaBla {
fetch process = new fetch(this);
}
and for asyncClass :
public class fetch extends AsyncTask<Void,Void,ArrayList<String>> {
//constructor
BlaBlaBla bla;
public fetch(BlaBlaBla bla){
this.bla=bla;
}
//when your task is complete use bla.doBla(pass your array here);
}

my solution
Fetch class
public class Fetch extends AsyncTask<Void,Void,String[][]> {
public static int KEY = 0;
#RequiresApi(api = Build.VERSION_CODES.KITKAT)
#Override
protected String[][] doInBackground(Void... voids) {
HttpHandler sh = new HttpHandler();
String url = "http:xxxxxxx/xxx.json";
String jsonStr = sh.makeServiceCall(url);
JSONObject jsonObj = null;
try {
jsonObj = new JSONObject(jsonStr);
int nTiempos=jsonObj.length();
String[] IdKeyArray = new String[nTie];
for (int i = 0; i < jsonObj.length(); i++) {
JSONObject c = jsonObj.getJSONObject(String.valueOf(i));
IdKeyArray[i] = c.getString("Key");
String[][] valores={IdKeyArray};
return valores;
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
}
And this is the "call" the other class where I get the values
private String[][] valores;
Fetch process = new Fetch();
process.execute();
try {
valores=process.get();
} catch (ExecutionException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
pm.setText(String.valueOf(valores[Fetch.Key][0]));
}
}
}

Getting data from webservice android studio

I am working on an android application. In this application, I have to retrieve data from a web service and put it in a listview, but it is not retrieving anything. I don't know what I am doing wrong here. Maybe someone can help me with this.
Webservice: http://10.247.240.53/kas/lampen.php
Mainactivity:
`
public class MainActivity extends AppCompatActivity {
ListView listView;
ArrayAdapter<String> adapter;
String[] data;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = findViewById(R.id.listview);
StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder().permitNetwork().build());
getData();
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent intent = new Intent(MainActivity.this, Showdata.class);
intent.putExtra("teeltbed", listView.getItemAtPosition(position).toString());
startActivity(intent);
}
});
}
private void getData()
{
String getData = null;
String dbResult = "empty";
dbConnect database = new dbConnect(this);
try{
String query = "SELECT * FROM Lamp";
getData = "?query=" + URLEncoder.encode(query, "UTF-8");
String link = "http://10.247.240.53/kas/lampen.php";
dbResult = database.execute(link).get();
}
catch (Exception e){
}
try{
JSONArray ja = new JSONArray(dbResult);
JSONObject jo = null;
data = new String[ja.length()];
for (int i = 0; i < ja.length(); i++)
{
jo = ja.getJSONObject(i);
data[i] = jo.getString("teeltbed");
}
adapter = new ArrayAdapter<String>(this, R.layout.layout_list, R.id.list_item, data);
listView.setAdapter(adapter);
}
catch (Exception e)
{
e.printStackTrace();
}
}
}`

.execute cannot be resolved to a type - AsyncTask (Android)

im writing an app which needs to get some json from my DB, i receive the data, but now im trying to also view a icon beside the information which is shown in a listview.
The line which is making trouble is:
mChart.setTag(URL);
new DownloadImagesTask.execute(mChart); <------
MainActivity:
public class MainActivity extends Activity {
ListView list;
TextView icon;
TextView name;
TextView developer;
TextView size;
Button Btngetdata;
ArrayList<HashMap<String, String>> mList = new ArrayList<HashMap<String, String>>();
private static String url = "http://appwhittle.com/getdata.php";
private static final String TAG_ITEM = "app_item";
private static final String TAG_ICON = "app_icon";
private static final String TAG_NAME = "app_name";
private static final String TAG_DEVELOPER = "app_developer";
private static final String TAG_SIZE = "app_size";
JSONArray mJsonArray = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mList = new ArrayList<HashMap<String, String>>();
new JSONParse().execute();
}
private class JSONParse extends AsyncTask<String, String, JSONObject> {
private ProgressDialog pDialog;
#Override
protected void onPreExecute() {
super.onPreExecute();
icon = (TextView)findViewById(R.id.icon);
name = (TextView)findViewById(R.id.name);
size = (TextView)findViewById(R.id.size);
developer = (TextView)findViewById(R.id.developer);
pDialog = new ProgressDialog(MainActivity.this);
pDialog.setMessage("Getting Data ...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
#Override
protected JSONObject doInBackground(String... args) {
JSONParser jParser = new JSONParser();
// Getting JSON from URL
JSONObject json = jParser.getJSONFromUrl(url);
return json;
}
#Override
protected void onPostExecute(JSONObject json) {
pDialog.dismiss();
try {
mJsonArray = json.getJSONArray(TAG_ITEM);
for(int i = 0; i < mJsonArray.length(); i++){
JSONObject c = mJsonArray.getJSONObject(i);
String name = c.getString(TAG_NAME);
String size = c.getString(TAG_SIZE);
String developer = c.getString(TAG_DEVELOPER);
String icon = c.getString(TAG_ICON);
HashMap<String, String> map = new HashMap<String, String>();
map.put(TAG_ICON, icon);
map.put(TAG_NAME, name);
map.put(TAG_DEVELOPER, "Developer: " + developer);
map.put(TAG_SIZE, size + " MB");
mList.add(map);
list=(ListView)findViewById(R.id.list);
ListAdapter adapter = new SimpleAdapter(MainActivity.this, mList,
R.layout.list_v,
new String[] {TAG_NAME, TAG_DEVELOPER, TAG_SIZE }, new int[] {
R.id.name, R.id.developer, R.id.size});
ImageView mChart = (ImageView) findViewById(R.id.icon);
String URL = "http://www...anything ...";
mChart.setTag(URL);
new DownloadImagesTask.execute(mChart);
list.setAdapter(adapter);
list.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
Toast.makeText(MainActivity.this, "You Clicked at "+ mList.get(+position).get(TAG_NAME), Toast.LENGTH_SHORT).show();
}
});
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}
}
DownloadImagesTask:
public class DownloadImagesTask extends AsyncTask<ImageView, Void, Bitmap> {
ImageView imageView = null;
#Override
protected Bitmap doInBackground(ImageView... imageViews) {
this.imageView = imageViews[0];
return download_Image((String)imageView.getTag());
}
#Override
protected void onPostExecute(Bitmap result) {
imageView.setImageBitmap(result);
}
private Bitmap download_Image(String url) {
return null;
}
}
Any help is much appreciated! Thanks in advance!

Replace
new DownloadImagesTask.execute(mChart);
with
new DownloadImagesTask().execute(mChart);
Try this. It will work.

You need to change
new DownloadImagesTask.execute(mChart);
to
new DownloadImagesTask().execute(mChart);.
Check after changing, hopefully it works fine. Happy coding :)

Change:
new DownloadImagesTask.execute(mChart);
to:
new DownloadImagesTask(mChart).execute();

You have not initialized the object of your DownloadImagesTask by calling constructor.
new DownloadImagesTask().execute(mChart); use like this. Call default constructor by putting ().

//Suppose you have a class "DataFetcher" which extends "AsyncTask<Void,Void,Void>{}"
//to execute this class write the code as follows
new DataFetcher().execute(); //done

Matching json parsed value with user entered value

I parsed json to adapt for my autocompleteTextView. I tried to match the value parsed by my json object with the value entered by user.
But some where i am failing. please help me in matching these values.
i have to match the string(acity) that is entered by user with my parsed json value stored in responseList.
This is how i am trying.
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_search);
new HttpGetTask().execute();
Button shwBtn = (Button) findViewById(R.id.showBtn);
shwBtn.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
AutoCompleteTextView city1 = (AutoCompleteTextView) findViewById(R.id.autoCity);
EditText area1 = (EditText) findViewById(R.id.edArea);
String aCity = city1.getText().toString().trim();
String aArea = area1.getText().toString().trim();
//here i have to match acity with all the values in responseList before sending it to next activity
Intent myInt = new Intent(getBaseContext(),
Map1Activity.class);
String city = city1.getText().toString();
String area = area1.getText().toString();
myInt.putExtra("city", city);
myInt.putExtra("area", area);
startActivity(myInt);
}
});
}
private class HttpGetTask extends AsyncTask<Void, Void, String> {
String URL = "xyzz.cities.json?app_id=test";
AndroidHttpClient mClient = AndroidHttpClient.newInstance("");
#Override
protected String doInBackground(Void... params) {
// http stuff
return null;
}
#Override
protected void onPostExecute(String result) {
try {
JSONArray json = new JSONArray(result);
//getting my response(cities)
Log.v("ResponseCity", result);
final List<String> responseList = new ArrayList<String>();
for (int i = 0; i < json.length(); i++) {
final JSONObject e = json.getJSONObject(i);
String name = e.getString("name");
//Adding all values to a stringList
responseList.add(name);
ArrayAdapter<String> adapter;
adapter = new ArrayAdapter<String>(SearchActivity.this,
android.R.layout.simple_dropdown_item_1line,
responseList);
AutoCompleteTextView textView = (AutoCompleteTextView) findViewById(R.id.autoCity);
textView.setAdapter(adapter);
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if (null != mClient)
mClient.close();
}
}

So lets assume you need to match a certain city before you intent to a map :
private final List<String> responseList;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_search);
new HttpGetTask().execute();
Button shwBtn = (Button) findViewById(R.id.showBtn);
shwBtn.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
AutoCompleteTextView city1 = (AutoCompleteTextView) findViewById(R.id.autoCity);
EditText area1 = (EditText) findViewById(R.id.edArea);
String aCity = city1.getText().toString().trim();
String aArea = area1.getText().toString().trim();
//here i have to match acity with all the values in responseList before sending it to next activity
for(int i=0; i<responseList.size(); i++) {
if(responseList.get(i).equals(aCity)) {
Intent myInt = new Intent(getBaseContext(),
Map1Activity.class);
String city = city1.getText().toString();
String area = area1.getText().toString();
myInt.putExtra("city", city);
myInt.putExtra("area", area);
startActivity(myInt);
}
}
}
});
}
private class HttpGetTask extends AsyncTask<Void, Void, String> {
String URL = "xyzz.cities.json?app_id=test";
AndroidHttpClient mClient = AndroidHttpClient.newInstance("");
#Override
protected String doInBackground(Void... params) {
// http stuff
return null;
}
#Override
protected void onPostExecute(String result) {
try {
JSONArray json = new JSONArray(result);
//getting my response(cities)
Log.v("ResponseCity", result);
responseList = new ArrayList<String>();
for (int i = 0; i < json.length(); i++) {
final JSONObject e = json.getJSONObject(i);
String name = e.getString("name");
//Adding all values to a stringList
responseList.add(name);
ArrayAdapter<String> adapter;
adapter = new ArrayAdapter<String>(SearchActivity.this,
android.R.layout.simple_dropdown_item_1line,
responseList);
AutoCompleteTextView textView = (AutoCompleteTextView) findViewById(R.id.autoCity);
textView.setAdapter(adapter);
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if (null != mClient)
mClient.close();
}
}
It should be something like that if I didnt guess your intent wrongly.