I am using this class to download txt file
class RetreiveFeedTask extends AsyncTask<String, Void,String> {
#Override
protected ArrayList<Item> doInBackground(String... params) {
try{
URL url = new URL("myurl");
InputStream is = url.openStream();
BufferedReader in = new BufferedReader(new InputStreamReader(is));
String str;
while ((str = in.readLine()) != null){
}
in.close();
return str;
}
catch (MalformedURLException e){}
catch (IOException e){}
return null;
}
protected void onPostExecute(Strin str) {
}
this is how i call this class from my activity:
new RetreiveFeedTask().execute();
And i want to know if there is a way to pass out this result to the activity that make the call.
You can create a listener which you'll pass in the constructor of your AsyncTask. In your onPostExecute you just call this listener.
Something like that:
public interface OnTaskCompleteListener {
void onTaskComplete(String result);
}
protected void onPostExecute(String str) {
onTaskCompleteListener.onTaskComplete(str);
}
Related
I have declared a private field in the MainActivity Class with getter and setter method. Now I want to setText from another class in this field. But after running the device the app is crushing. I want to fetch some json data by using this code. I am not getting how to call this field from another class and how to set the value to run the app smoothly. My code looks like this.
public class MainActivity extends AppCompatActivity {
private TextView tvData;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button btnHit=(Button)findViewById(R.id.btnHit);
tvData=(TextView)findViewById(R.id.tvJsonItem);
btnHit.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
JSONTask jsonTask=new JSONTask("https://jsonparsingdemo-cec5b.firebaseapp.com/jsonData/moviesDemoItem.txt"); //error showing this cannot be applied
jsonTask.execute();
}
});
}
The another class is
public class JSONTask extends AsyncTask<String,String,String>{
private TextView tvData;
public JSONTask(TextView tvData) {
this.tvData =tvData;
}
#Override
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);
}
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);
tvData.setText(result);
}
}
Make your AsyncTask like this:
class JSONTask extends AsyncTask<String ,String,String>{
private TextView textView;
public JSONTask(TextView textView) {
this.textView = textView;
}
#Override
protected String doInBackground(String... params) {
return null;
}
#Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
textView.setText(s);
}
}
now call this class from MainActivity
JSONTask jsonTask = new JSONTask(yourTextView);
jsonTask.execute();
Hope it will work for you .
#override
protected void onPostExecute(String result){
super.onPostExecute(result);
new MainActivity().setTvData().setText(result);
Use setTvData().setText() to set the value if you only one data in your json string .
I have created a class and extend with AsyncTask , now i want to return me a string to another activity throw this class . its getting jsonstring from mysql mDatabase
enter code here
public class GetJson extends AsyncTask<Void,Void,String> {
String JSON_STRING;
String json_url;
public String pasString;
Activity ab;
#Override
protected void onPreExecute() {
json_url="https://XXXXXXX.000webhostapp.com/Json_getData_Survey.php";
}
public GetJson(Activity b) {
ab=b;
}
#Override
protected String doInBackground(Void... params) {
try {
URL url =new URL(json_url);
HttpURLConnection httpURLConnection =(HttpURLConnection) url.openConnection();
InputStream inputStream =httpURLConnection.getInputStream();
BufferedReader bufferedReader=new BufferedReader(new InputStreamReader(inputStream));
StringBuilder stringBuilder=new StringBuilder();
while ((JSON_STRING=bufferedReader.readLine())!=null)
{
stringBuilder.append(JSON_STRING+"\n");
}
bufferedReader.close();
inputStream.close();
httpURLConnection.disconnect();
String strings =stringBuilder.toString().trim();
return strings;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
#Override
protected void onProgressUpdate(Void... values) {
super.onProgressUpdate(values);
}
#Override
protected void onPostExecute(String result) {
pasString=result;
// Toast.makeText(ab,pasString,Toast.LENGTH_LONG).show();
// json_string1=result;
}
}
i just need to return string1 to my another Activity , i have creaetd a another mehtod in GetJson class to return this string but when i display this it show nothing in it. please help
its Quite simple
make an interface class as following
public interface ResponseListener() {
void onResponseReceive(String data);
}
and add instance of this class in you GetJson class like this
public class GetJson extends AsyncTask<Void,Void,String> {
String JSON_STRING;
String json_url;
public String pasString;
Activity ab;
// this is new code
ResponseListener listener;
public void setOnResponseListener(ResponseListener listener) {
this.listener = listener;
}
#Override
protected void onPreExecute() {
json_url="https://XXXXXXX.000webhostapp.com/Json_getData_Survey.php";
}
// now add this code in onPost function
#Override
protected void onPostExecute(String result) {
pasString=result;
listener.onResponseReceive(pasString);
// Toast.makeText(ab,pasString,Toast.LENGTH_LONG).show();
// json_string1=result;
}
now when you call GetJson from your activity, just simple do that;
GetJson json = new GetJson(Activity.this);
json.setOnResponseListener(new ResponseListener() {
#Override
public void onResponseReceived(String data) {
// here you will get your response
}
});
hope you will understand. :)
Try using activity results. You can set the return value on the one activity, and get it when that activity terminates.
https://developer.android.com/training/basics/intents/result.html
i want to get the result form AsyncTask , i can show with system.out.println(), but i want keep that result and save on a new attribute, outside from AsyncTask;
OnTaskFinished.java
public interface OnTaskFinished
{
public void onFeedRetrieved(String feeds);
}
RetrieveFeedTask.java
class RetrieveFeedTask extends AsyncTask<String, Void, String>
{
String HTML_response= "";
String VideoLink;
public String getVideoLink() {
return VideoLink;
}
public void setVideoLink(String videoLink) {
this.VideoLink = videoLink;
}
OnTaskFinished onOurTaskFinished;
public RetrieveFeedTask(OnTaskFinished onTaskFinished)
{
onOurTaskFinished = onTaskFinished;
}
#Override
protected void onPreExecute()
{
super.onPreExecute();
}
#Override
protected String doInBackground(String... urls)
{
try
{
URL url = new URL(urls[0]); // enter your url here which to download
URLConnection conn = url.openConnection();
// open the stream and put it into BufferedReader
BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
String inputLine;
while ((inputLine = br.readLine()) != null)
{
//System.out.println(inputLine);
if(inputLine.toString().contains("<meta property='og:image'"))
{
String str =inputLine;
str = str.replace("<meta property='og:image' content=\"", "");
//System.out.println(str);
VideoLink=str;
setVideoLink(str);
inputLine=str;
}
HTML_response += inputLine;
}
br.close();
//System.out.println("Done");
}
catch (MalformedURLException e)
{
e.printStackTrace();
}
catch (IOException e)
{
e.printStackTrace();
}
return VideoLink;
}
#Override
protected void onPostExecute(String feed)
{
onOurTaskFinished.onFeedRetrieved(feed);
}
}
and here is how i call
Main.java
String data;
....
new RetrieveFeedTask(new OnTaskFinished()
{
#Override
public void onFeedRetrieved(String feeds)
{
System.out.println(feeds);
}
}).execute(VideoUrl);
i want that feeds get out and set on a diferente value outside from RetrieveFeedTask
on this case set the result on data;
this is the class for reading json string from web
{
public class JSONmethod extends AsyncTask<String,String,String>
{
public String result_string;
#Override
protected void onPreExecute() {
super.onPreExecute();
}
#Override
protected String doInBackground(String... params) {
BufferedReader reader = null;
HttpURLConnection connection = null;
StringBuffer buffer;
try {
URL url;
url = new URL(params[0]);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
InputStream stream = connection.getInputStream();
reader = new BufferedReader(new InputStreamReader(stream));
String line= "";
buffer = new StringBuffer();
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);
result_string=result;
}
public String result_string_josn()
{
return result_string;
}
}
method "result_string_json()" return null string
i want to use this class frequntly for reading the json string from the web
so i made this method for return string which will returns from onPostExecute
this is the class where i want that value which is generate in post execute through method or anything else
simple.java
package com.bhatti.bis;
import android.app.Activity;
import android.os.Bundle;
import android.widget.Toast;
public class simple extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.simple);
JSONmethod j = new JSONmethod();
j.execute("here is json string");
Toast.makeText(this,j.result_string_josn(),Toast.LENGTH_LONG).show();
}
}
Use EventBus library. It's very easy to use and will perfectly fix your problem:
First create a simple class for your Event:
public class MyEvent{
private String data;
public MyEvent(String data) {
this.data = data;
}
public String getData() {
return data;
}
public void setData(String data) {
this.data = data;
}
Then in your Activity or wherever, register and unregister the EventBus, as explained in the docs.
Now post the appropriate event:
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
EventBus.getDefault().post(new MyEvent(jsonArray.toString()));
}
All that's left for you to do is to listen for that event wherever you want (in another Activity, Fragment, Service - that's what makes EventBus great):
#Subscribe
public void onMyEvent(MyEvent myEvent){
String data = myEvent.getData();
//do whatever you wish with the text (e.g. make a toast, write it somewhere)
}
Async Task is asynchronous task, please read https://en.wikipedia.org/wiki/Asynchrony_%28computer_programming%29
Remove Toast just after :
JSONmethod j = new JSONmethod();
j.execute("here is json string");
And put it in onPostExecute :
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
Toast.makeText(this,result,Toast.LENGTH_LONG).show();
}
Android handles input events/tasks with a single User Interface (UI) thread and the thread is called Main thread. Main thread cannot handle concurrent operations as it handles only one event/operation at a time.For detail read this tutorials
JSONmethod jSONmethod = new JSONmethod();
jSONmethod.execute("Your json string");
public class JSONmethod extends AsyncTask<String,String,String>
{
public String result_string;
#Override
protected void onPreExecute() {
super.onPreExecute();
}
#Override
protected String doInBackground(String... params) {
BufferedReader reader = null;
HttpURLConnection connection = null;
StringBuffer buffer;
try {
URL url;
url = new URL(params[0]);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
InputStream stream = connection.getInputStream();
reader = new BufferedReader(new InputStreamReader(stream));
String line= "";
buffer = new StringBuffer();
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);
Log.d("JSONmethod","result = "+result);
}
}
I have a main activity with launch mode set as "singleTask". When I bring it to the foreground and the onNewIntent method is called, it runs an AsyncTask containing a while loop which reads lines from a text file.
Part way into this loop, the value of one of my integer variables changes to 0. This doesn't always happen in the same stage in the loop cycle and the loop has nothing to do with this variable at all so I don't understand why this is happening.
Here's an image that might better explain the problem:
http://i.stack.imgur.com/ogLQh.jpg
EDIT: Code as requested:
private class ReadFile extends AsyncTask<String, String, String> implements DialogInterface.OnCancelListener {
protected void onPreExecute() {
//Launch dialog
}
protected String doInBackground(String... path) {
try {
File f = new File(path[0]);
FileInputStream in = new FileInputStream(f);
InputStreamReader ir;
ir = new InputStreamReader(in);
BufferedReader br = new BufferedReader(ir);
StringBuffer sb = new StringBuffer();
String str = new String();
while ((str = br.readLine()) != null) {
Log.i("My Variable",Integer.toString(myVariable));
sb.append(str);
sb.append("\n\n");
}
br.close();
myTextFile = sb.toString();
} catch (IOException e) {
e.printStackTrace();
}
return "";
}
protected void onProgressUpdate(String... progress) {
//Nothing here
}
protected void onPostExecute(final String unusedString) {
//Dismiss dialog
}
protected void onCancelled() {
finish();
}
public void onCancel(DialogInterface dialog) {
cancel(true);
}
}
myVariable seems to be changed from UI thread (activity thread). Try to add logging in each place where you modify myVariable.