in java, i'm calling a function which reads a text file's content from the web into a variable, but my problem is that the file's url is hardcoded in the functio. I would like to use this function several times for different files. So how can i manage, to add the file's url when i call the function?
The function is;
public class readtextfile extends AsyncTask<String, Integer, String>{
private TextView description;
public readtextfile(TextView descriptiontext){
this.description = descriptiontext;
}
#Override
protected String doInBackground(String... params) {
URL url = null;
String result ="";
try {
url = new URL("http://example.com/description1.txt");
BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
String line = null;
while ((line = in.readLine()) != null) {
result+=line;
}
in.close();
}
catch (MalformedURLException e) {e.printStackTrace();}
catch (IOException e) {e.printStackTrace();}
return result;
}
protected void onProgressUpdate() {
//called when the background task makes any progress
}
protected void onPreExecute() {
//called before doInBackground() is started
}
#Override
protected void onPostExecute(String result) {
this.description.setText(result);
}
}
Where i'm calling the function:
public class PhotosActivity extends Activity {
TextView description;
String descriptiontext;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.photos_layout);
description = ((TextView)findViewById(R.id.description1));
new readtextfile(description).execute();
}
}
Using AsyncTask for a single task is not a good solution, you should better look to Threads.
But if you want to use AsyncTask, anyway, you can add a constructor like this :
public readtextfile(TextView descriptiontext, String url){
this.description = descriptiontext;
this.url = url;
}
And use this.url in your doInBackground.
Related
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.
When my device Network Connect, execute AsyncTask.
this AsyncTask is get Public Ip.
asyncTask in MainActivity (inner)
I want asyncTask result (result value is public Ip) value from another class.
How to get public ip from another class?
My source
public class MainActivity extends Activity {
static getAsyncPubIp async = new getAsyncPubIp();
public static final class getAsyncPubIp extends AsyncTask<Void, Void, String> {
String result;
TextView pubView;
#Override
public void onPreExecute() {
super.onPreExecute();
}
#Override
protected String doInBackground(Void... params) {
try {
URL pub = new URL("get public ip domain");
BufferedReader in = new BufferedReader(new InputStreamReader(
pub.openStream()));
String strPub = in.readLine();
result = strPub;
} catch (Exception e) {
e.printStackTrace();
}
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
pubView = (TextView) activity.findViewById(R.id.ip);
pubView.setText(result);
async = null;
pubView = null;
}
}
usually, call this asynctask on another class
MainActivity.getAsyncPubIp asyncPub = new MainActivity.getAsyncPubIp();
asyncPub.execute();
but I want only asyncTask result value from another class
How to get this ?
Create a static variable in second activity's java class named SecondClass.java:
public static String public_ip;
Then in your MainActivity:
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
//Add this
SecondClass.public_ip = result;
pubView = (TextView) activity.findViewById(R.id.ip);
pubView.setText(result);
async = null;
pubView = null;
}
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.
I want to show string from another string in my MainActivity, but the string is getting printed in console. Here is my code:
public class MainActivity extends AppCompatActivity {
Button start;
public TextView showText;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
showText= (TextView)findViewById(R.id.textView);
start = (Button)findViewById(R.id.button);
start.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
RetrieveFeedTask click1 = new RetrieveFeedTask();
click1.execute();
showText.setText(click1.getString());
}
});
}
}
And the class:
class RetrieveFeedTask extends AsyncTask<Void, Void, String> {
static final String API_URL = "http://numbersapi.com/random/trivia?json";
private Exception exception;
public String finalString;
protected void onPreExecute() { }
protected String doInBackground(Void... urls) {
try {
URL url = new URL(API_URL );
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
try {
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
StringBuilder stringBuilder = new StringBuilder();
while ((finalString = bufferedReader.readLine()) != null) {
stringBuilder.append(finalString).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";
}
try {
JSONObject object = (JSONObject) new JSONTokener(response).nextValue();
finalString = object.getString("text");
Log.i("Here",finalString);
} catch (JSONException e) {
}
}
public String getString() {
return this.finalString;
}
}
You require the finalString before it's populated with your data. the onPostExecute is executed after the doInBackground so you should pass your text view to your task and set it's value in the onPostExecute
public TextView showText;
public RetrieveFeedTask(TextView showText) { this.showText = showText; }
protected void onPostExecute(String response) {
if(response == null) {
response = "THERE WAS AN ERROR";
}
try {
JSONObject object = (JSONObject) new JSONTokener(response).nextValue();
finalString = object.getString("text");
showText.setText(finalString ); // add this
Log.i("Here",finalString);
} catch (JSONException e) {
}
}
The problem is that showText.setText(click1.getString()); of your activity is called earlier than finalString = object.getString("text"); of your task.
Solution:
Create an interface:
public interface DataCallback {
void onNewData(String data);
}
and implement it in your activity:
public class MainActivity extends ... implements DataCallback
public void onNewData(String data) {
showText.setText(data);
}
Pass the interface to your asynctask when you create it:
RetrieveFeedTask click1 = new RetrieveFeedTask(this);
Call the interface inside the task in onPostExecute() to notify the activity that there is new data:
JSONObject object = (JSONObject) new JSONTokener(response).nextValue();
finalString = object.getString("text");
callback.onNewData(finalString);
Here is my java android code which should pass 'Preferred hotels' string to a php file and later read what have been passed.
sendSubMenuDetail("Preferred hotels");
This is evoked at the activity load. Whose function is below:
public void sendSubMenuDetail(String suggestion){
String urlSuffix = "?suggestion="+suggestion;
class RegisterUser extends AsyncTask<String, Void, String> {
ProgressDialog loading;
#Override
protected void onPreExecute() {
super.onPreExecute();
loading = ProgressDialog.show(ActivitySubMenu.this, "Please Wait",null, true, true);
}
#Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
loading.dismiss();
Toast.makeText(getBaseContext(),s,Toast.LENGTH_LONG).show();
}
#Override
protected String doInBackground(String... params) {
String s = params[0];
BufferedReader bufferedReader = null;
try {
URL url = new URL(address+s);
HttpURLConnection con = (HttpURLConnection) url.openConnection();
bufferedReader = new BufferedReader(new InputStreamReader(con.getInputStream()));
String result;
result = bufferedReader.readLine();
return result;
}catch(Exception e){
return null;
}
}
}
RegisterUser ru = new RegisterUser();
ru.execute(urlSuffix);
}
The output dislayed in a toast here is 'Preferred' instead of 'Preferred hotels'. I tried figuring out what the problem might be with no success.