Develop Reference

setText of TextView on Async Task complete

I want to return a specific string using ksoap2 web service in my android app.
Web service is returning the correct value but the set text is not getting updated once the task is complete. I need to do something (like trying to open the navigation drawer) then its getting updated. Any ideas??
My code is as follows
// Calling the async class
protected void onResume() {
try {
super.onResume();
new RetrieveTimeWS().execute();
}
catch (Exception e)
{
Log.e("Current Time", e.getMessage());
}
}
Following is the Async Task
class RetrieveTimeWS extends AsyncTask<Void, Void, String> {
protected String doInBackground(Void... params) {
String datetime = "";
try {
TextView TVcurrentTime = (TextView) findViewById(R.id.DateTimeNow);
TVcurrentTime.setText("Loading...");
datetime = getDateTimeClass.getDateTime();
TVcurrentTime.setText(datetime);
} catch (Exception e) {
Log.e("Async Task - GetDateTime ", e.getMessage());
}
return datetime;
}
}
The text field shows "Loading..." only till I touch any component on the screen. How can i change the textview to the required string after the web service returns the text.
Thanks in advance.
Laks.

You can't interact with UI not from UI thread. AsyncTask has onPreExecute and PostExecute methods which called from UI thread and you can change UI in it.
class RetrieveTimeWS extends AsyncTask<Void, Void, String> {
TextView TVcurrentTime = (TextView) findViewById(R.id.DateTimeNow);
Exception e;
#Override
protected void onPreExecute() {
super.onPreExecute();
TVcurrentTime.setText("Loading...");
}
protected String doInBackground(Void... params) {
String datetime = "";
try {
datetime = getDateTimeClass.getDateTime();
} catch (Exception e) {
this.e = e;
Log.e("Async Task - GetDateTime ", e.getMessage());
}
return datetime;
}
#Override
protected void onPostExecute(final String s) {
super.onPostExecute(s);
if (e != null) {
TVcurrentTime.setText(s);
}
}
}

You can not do any UI work in background thread. Do it in onPostExecute() method.
This method runs on main thread. So, you can set text in this method.

Series of AsyncTask does not go for execution instantaneously

My MainActivity has 2 views: TextView and a Button. On button click, I am running an AsyncTask which further creates 10 new AsyncTasks for network operations. Every new task creation is delayed by 1 sec. The code is:
public class MainActivity extends ActionBarActivity
{
TextView tv;
Button t;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tv = (TextView) findViewById(R.id.textView1);
t = (Button) findViewById(R.id.toggleButton1);
t.setOnClickListener(new OnClickListener()
{
#Override
public void onClick(View v)
{
getData();
}
});
}
void getData()
{
SuperNetworkAsyncTask s = new SuperNetworkAsyncTask();
s.execute("");
}
private class SuperNetworkAsyncTask extends AsyncTask<String, Void, String>
{
#Override
protected String doInBackground(String... urls)
{
for(int i=0;i<10;i++)
{
{
nTask = new NetworkAsyncTask();
nTask.execute("");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
return "";
}
#Override
protected void onPostExecute(String result)
{
}
}
private class NetworkAsyncTask extends AsyncTask<String, Void, String>
{
#Override
protected String doInBackground(String... urls)
{
return String.valueOf(System.currentTimeMillis());
}
#Override
protected void onPostExecute(String result)
{
tv.setText(result);
}
}
}
I was expecting that the moment first NetworkAsyncTask execute method is called, it will start execution. But when I run it, I do not find any NetworkAsyncTask begin its execution until the control comes out of SuperNetworkAsyncTask. Is there any way to push the execution of NetworkAsyncTask thread as soon as execute method is called?
Some clarifications:
Why NetworkAsyncTask are created by SuperNetworkAsyncTask? Because If I create the NetworkAsyncTask in main thread, I get my UI freeze for some time.
Why making 10 object? The purpose of NetworkAsyncTask is to read data from a server at interval of 1 sec for n seconds, here n=10.
Part 2: Updates after doing some tests.
Observation 1:
As a fellow Brian shared a way to avoid creating AsyncTasks in nested way, I tried his code:
void getData() {
Runnable runnable = new Runnable() {
#Override
public void run() {
for (int i = 0; i <= 10; i++) {
nTask = new NetworkAsyncTask();
nTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
try {
Thread.sleep(1000);
}
catch (InterruptedException e) {
e.printStackTrace();
}
}
}
};
new Thread(runnable).start();
}
This freezes my UI for few seconds and then the screen is updated in a fraction of second. It is quite surprising to me too.
Observation 2:
With java.lang.Thread, I experimented to make sure that 1) The threads should be executed right away when run() called. 2) The next task will be created only after previous task is finished.
Code:
public static void main(String[] args) {
myThread m;
for (int i=0;i<10;i++)
{
m=new myThread(String.valueOf(i));
m.start();
synchronized (m)
{
try {
m.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
public class myThread extends Thread
{
public String name = "";
public myThread(String n)
{
name = n;
}
public void run()
{
synchronized (this)
{
System.out.println(" Thread Name = " + name);
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
notifyAll();
}
}
}
Output:
Thread Name = 0
Thread Name = 1
Thread Name = 2
Thread Name = 3
Thread Name = 4
Thread Name = 5
Thread Name = 6
Thread Name = 7
Thread Name = 8
Thread Name = 9
Based in this, I updated my NetworkAsyncTask & SuperNetworkAsyncTask as:
private class NetworkAsyncTask extends AsyncTask<String, Void, String>
{
#Override
protected String doInBackground(String... urls)
{
synchronized (this)
{
return String.valueOf(System.currentTimeMillis());
}
}
#Override
protected void onPostExecute(String result)
{
synchronized (this)
{
tv.setText(result);
notifyAll();
}
}
}
private class SuperNetworkAsyncTask extends AsyncTask<String, Void, String>
{
#Override
protected String doInBackground(String... urls)
{
for(int i=0;i<10;i++)
{
nTask = new NetworkAsyncTask();
nTask.execute(url);
synchronized (nTask)
{
try {
nTask.wait();
} catch (InterruptedException e1) {
e1.printStackTrace();
}
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
return "";
}
#Override
protected void onPostExecute(String result)
{
}
}
With this code the wait() keeps on waiting indefinitely.
Finally I replaced:
nTask.execute(url);
with
nTask.executeOnExecutor(THREAD_POOL_EXECUTOR, "");
This worked well as expected.

The UI will be updated only at onPostExecute(). See notes on AsyncTask
Click here! And Try to avoid 10 AysncTasks, it does not make any sense.

You don't need to use a "super async task" use a runnable and then create new async tasks in parallel
void getData() {
Runnable runnable = new Runnable() {
#Override
public void run() {
for (int i = 0; i <= 10; i++) {
nTask = new NetworkAsyncTask();
nTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
try {
Thread.sleep(1000);
}
catch (InterruptedException e) {
e.printStackTrace();
}
}
}
};
new Thread(runnable).start();
}
Post honeycomb you can specify to run async tasks in parallel

An AsyncTask should be started in the UI thread, not on the one doInBackground runs on. You could call publishProgress after every sleep, and spawn each AsyncTask in the resulting calls to onProgressUpdate, which run on the UI thread.

how to handle doInbackGround exception?

i have an asyncTask that downloads an image. sometimes it can't download and give this exception java.lang.RuntimeException: An error occurred while executing doInBackground()
Now i want to handle this and when it occurs stop downloading (because i create a notification bar in onPreExecute that show download progress) and Toast a message that download not completed!
#Override
protected Void doInBackground(Void... unused) {
#Override
protected void onPreExecute() {
mNotifyManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE); //.... to create a notification
}
downloadPackage(IMG_DIR_URL);//my function to download an imagedo some stuff
return null;
}
protected void onProgressUpdate(Integer... progress) {
// setting progress bar on notification area
//fore example mBuilder.setProgress(100, progress[0], false);
}

In similar case as of yours, I opted following approach:
private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {
Exception exception = null;
protected Long doInBackground(URL... urls) {
try{
//downloading code here..
}catch(SomeException e){
exception = e;
}
return totalSize;
}
protected void onPostExecute(Long result) {
if(exception!=null){
// show toast.
// cancel async task. (this.cancel())
}else{
// no exception while downloading, check for result and take corresponding action on result
}
}
}

just put your code in try/catch block and in catch block you can handle exception and app will never crash: use the below code to handle and get the error,it will give you the methid and class name also the line number of exception.
try {
//do your stuff
} catch (Exception e) {
for (int i = 0; i < e.getStackTrace().length; i++) {
StackTraceElement oStackTace = e.getStackTrace()[i];
String ClassName = oStackTace.getClassName();
String MethodName = oStackTace.getMethodName();
StringWriter sw = new StringWriter();
e.printStackTrace(new PrintWriter(sw));
String exceptionAsString = sw.toString();
Log.d("Class Name: " + ClassName + " Method Name: "
+ MethodName, exceptionAsString);
}
}

AsyncTask slow with OnClick

Goodmorning,
I have a button on my android app that launches a search on the web (through google endpoints) through an AsyncTask. My problem is that the button does not "unclick" until the AsyncTask is completed, which may take several seconds. When the internet connection is slow, this even makes the application crash, in any case the application is completely stuck until the AsyncTask is completed. Now the reason for using AsyncTask was exactly to eliminate this problem, so I don't really get what happens!
Here is the OnClickListener:
SearchListener = new OnClickListener() {
#Override
public void onClick(View v) {
String cname=TextCourse.getText().toString();
if (!cname.isEmpty()){
try {
CollectionResponseWine listavini= new QueryWinesTask(messageEndpoint,cname,5).execute().get();
} catch (InterruptedException e) {
showDialog("Errore ricerca");
e.printStackTrace();
} catch (ExecutionException e) {
showDialog("Errore ricerca");
e.printStackTrace();
}
} else{
showDialog("Inserisci un piatto");
}
}
};
and here is the AsyncTask that is being called:
private class QueryWinesTask
extends AsyncTask<Void, Void, CollectionResponseWine> {
Exception exceptionThrown = null;
MessageEndpoint messageEndpoint;
String cname;
Integer limit;
public QueryWinesTask(MessageEndpoint messageEndpoint, String cname, Integer limit) {
this.messageEndpoint = messageEndpoint;
this.cname=cname;
this.limit=limit;
}
#Override
protected CollectionResponseWine doInBackground(Void... params) {
try {
CollectionResponseWine wines = messageEndpoint.listwines().setCoursename(cname).setLimit(limit).execute();
return wines;
} catch (IOException e) {
exceptionThrown = e;
return null;
//Handle exception in PostExecute
}
}
protected void onPostExecute(CollectionResponseWine wines) {
// Check if exception was thrown
if (exceptionThrown != null) {
Log.e(RegisterActivity.class.getName(),
"Exception when listing Messages", exceptionThrown);
showDialog("Non ci sono vini associati al tuo piatto. Aggiungine uno!");
}
else {
messageView.setText("Vini piu' votati per " +
cname + ":\n\n");
for(Wine wine : wines.getItems()) {
messageView.append(wine.getName() + " (" + wine.getScore() + ")\n");
}
}
}
}

...execute().get() is blocking. It makes UI thread wait for Task to complete.
Don't do get(). Use onPostExecute() to get the result (wines) of task and update the UI.

ProgressDialog Android

I am trying to use ProgressDialog. when i run my app the Progress Dialog box show and disappear after 1 second. I want to show it on completion of my process.. Here is my code:
public class MainActivity extends Activity {
android.view.View.OnClickListener mSearchListenerListener;
private ProgressDialog dialog;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new YourCustomAsyncTask().execute(new String[] {null, null});
}
private class YourCustomAsyncTask extends AsyncTask <String, Void, Void> {
protected void onPreExecute() {
dialog = new ProgressDialog(MainActivity.this);
dialog.setMessage("Loading....");
dialog.setIndeterminate(true);
dialog.setCancelable(true);
dialog.show(); //Maybe you should call it in ruinOnUIThread in doInBackGround as suggested from a previous answer
}
protected void doInBackground(String strings) {
try {
// search(strings[0], string[1]);
runOnUiThread(new Runnable() {
public void run() {
// updateMapWithResult(); //Or call it onPostExecute before progressDialog's dismiss. I believe this method updates the UI so it should run on UI thread
}
});
} catch(Exception e) {
}
}
#Override
protected void onPostExecute(Void params) {
dialog.dismiss();
//result
}
#Override
protected Void doInBackground(String... params) {
// TODO Auto-generated method stub
return null;
}
}
}
Updated Question:
#Override
public void onCreate(SQLiteDatabase db) {
mDatabase = db;
Log.i("PATH",""+mDatabase.getPath());
mDatabase.execSQL(FTS_TABLE_CREATE);
loadDictionary();
}
/**
* Starts a thread to load the database table with words
*/
private void loadDictionary() {
new Thread(new Runnable() {
public void run() {
try {
loadWords();
} catch (IOException e) {
throw new RuntimeException(e);
}
}
}).start();
}
private void loadWords() throws IOException {
Log.d(TAG, "Loading words...");
for(int i=0;i<=25;i++)
{ //***//
final Resources resources = mHelperContext.getResources();
InputStream inputStream = resources.openRawResource(raw_textFiles[i]);
//InputStream inputStream = resources.openRawResource(R.raw.definitions);
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
try {
StringBuilder sb = new StringBuilder();
while ((word = reader.readLine()) != null)
{
sb.append(word);
// Log.i("WORD in Parser", ""+word);
}
String contents = sb.toString();
StringTokenizer st = new StringTokenizer(contents, "||");
while (st.hasMoreElements()) {
String row = st.nextElement().toString();
String title = row.substring(0, row.indexOf("$$$"));
String desc = row.substring(row.indexOf("$$$") + 3);
// Log.i("Strings in Database",""+title+""+desc);
long id = addWord(title,desc);
if (id < 0) {
Log.e(TAG, "unable to add word: " + title);
}
}
} finally {
reader.close();
}
}
Log.d(TAG, "DONE loading words.");
}
I want to show ProgressDialogue box untill all words are not entered in the database. This code is in inner calss which extends SQLITEHELPER. so how to can i use ProgressDialogue in that inner class and run my addWords() method in background.

You cannot have this
runOnUiThread(new Runnable() {
public void run() {
// updateMapWithResult(); //Or call it onPostExecute before progressDialog's dismiss. I believe this method updates the UI so it should run on UI thread
}
});
in your doInBackground().
Progress dialog doesn't take priority when there is some other action being performed on the main UI thread. They are intended only when the actions are done in the background. runonUIthread inside doInBackground will not help you. And this is normal behavior for the progressdialog to be visible only for few seconds.

You have two doInBackground() methods inside your AsyncTask Class. Remove the runOnUiThread() from First doInBackground() and move it to second doInBackground() which has #Override annotation.
I don't know whether you wantedly written two doInBackground() methods or by mistake but it is not good to have such confusion between the Method. Your AsyncTask is not calling the first doInBackground() and it will call doInBackground() which has #Override annotation. So your ProgressDialog is dismissed in 1 second of time as it returns null immediately.