Develop Reference

Two background service android

In my acivity, i need to run two background service.
main background service:
class loadingTask extends AsyncTask<Void, Void,Void> {
#Override
protected void onPreExecute() {
// TODO Auto-generated method stub
pd = ProgressDialog.show(context, "", "Chargement en cours..", true, false);
super.onPreExecute();
}
#Override
protected void onPostExecute(Void result) {
// TODO Auto-generated method stub
super.onPostExecute(result);
pd.dismiss();
}
...
#Override
protected Void doInBackground(Void... params) {
// TODO Auto-generated method stub
getxml = Util.CallWebService("");
return null;
}
}
Second background service.
class mloadingTask extends AsyncTask<String, Void, String> {
protected String doInBackground(String... urls) {
SAXHelper sh = null;
try {
sh = new SAXHelper(urls[0]);
} catch (MalformedURLException e) {
e.printStackTrace();
}
sh.parseContent("");
return "";
}
protected void onPostExecute(String s) {
pd.dismiss();
}
}
In my onCreate() method I want to call the first background and when it finished loading the second background service starts. Part of my background service is as follows.
AsyncTask<Void, Void,Void> loadTask = new loadingTask().execute();
if(loadTask.getStatus()==AsyncTask.Status.FINISHED){
new mloadingTask().execute(getxml);
System.out.println("getxml: "+getxml);
}
However the second background service doesn't seem to start. i am not getting the a print also. I think I miss a step or android doesn't allow more than one background service in the same activity. A help please.

AsyncTask<Void, Void,Void> loadTask = new loadingTask().execute();
if(loadTask.getStatus()==AsyncTask.Status.FINISHED){
new mloadingTask().execute(getxml);
System.out.println("getxml: "+getxml);
}
there is a 99% chance that the if() block will never pass.
You first execute the first asyncTask named loadTask and RIGHT after check if it finished.
Small chance that it actually finishes by then.
The easy approach:
Use only one async task. You want to finish asyncTask 1 and then fire asyncTask 2, its exactly the same as having only one asyncTask doing both operations.
class loadingTask extends AsyncTask<Void, Void,Void> {
#Override
protected void onPreExecute() {
// TODO Auto-generated method stub
pd = ProgressDialog.show(context, "", "Chargement en cours..", true, false);
super.onPreExecute();
}
#Override
protected void onPostExecute(Void result) {
// TODO Auto-generated method stub
super.onPostExecute(result);
pd.dismiss();
}
...
#Override
protected Void doInBackground(Void... params) {
// TODO Auto-generated method stub
getxml = Util.CallWebService("");
SAXHelper sh = null;
try {
sh = new SAXHelper(urls[0]);
} catch (MalformedURLException e) {
e.printStackTrace();
}
sh.parseContent("");
return null;
}
}
The difficult approach:
How I solve this kind of thing is(our situation is different, but it should do)
Create an interface, with one method. for example:
public interface OnDataChangedListner {
void dataChanged(Class listener);
}
Then somewhere (i use my repository classes)
write a method to add and remove entires to a list of OnDataChangedListener interfaces
private ArrayList<OnDataChangedListner> mOnDataChangedListners;
public void addOnDataChangedListner(OnDataChangedListner onDataChangedListner){
synchronized (mOnDataChangedListners){
mOnDataChangedListners.add(onDataChangedListner);
}
}
public void removeOnDataChangedListner(OnDataChangedListner onyDataChangedListner){
if (mOnDataChangedListners != null){
synchronized (mOnDataChangedListners){
for (Iterator<OnDataChangedListner> it = mOnDataChangedListners.iterator(); it.hasNext();) {
OnDataChangedListner listener = it.next();
if (listener .equals(onDataChangedListner))
it.remove();
}
}
}
}
This might be overkill. But this example should help you with updating the UI while your tasks are running. A free extra! :))
With the above code in place, create an onDataChanged() method in the same class where u defined the add and remove listener methods.
In that code call a handler
// Need handler for callbacks to the UI thread
final static Handler mHandler = new Handler();
// Create runnable for posting
final Runnable mNotifyDataChanged = new Runnable() {
public void run() {
if (mOnDataChangedListners != null){
synchronized (mOnDataChangedListners){
for (Iterator<OnDataChangedListner> it = mOnDataChangedListners.iterator(); it.hasNext();) {
OnDataChangedListner listener = it.next();
if (listener != null)
listener.dataChanged(this.getClass());
else
it.remove();
}
}
}
}
};
/**
* will notify registerred delegates on the main (UI) thread
*/
public void notifyDataChanged(){
mHandler.post(mNotifyDataChanged);
}
Ok, so I ended up giving out an entire sample.
Where you place this code is upto you. But when you call notifyDataChanged() it will fire the handler, which in turn will loop trough all current registered listeners for this class
then in turn it will call the listeners datachanged method.
To make this all work, all you have to do is have a class implement the interface
call addOnDataChangedListener(this);
and implement the method provided in the interface.
Note that this is deffinetly not the easiest way to do things.
I don't know what the easiest way to do what you want is. I never have been in that situation before.
but you can execute the second task in the implemented method. Should work..

AsyncTask is Asynchronous as its name suggest. You need to call your 2nd AsyncTask in onPostExecute of your 1st AsyncTask
OR
Loop and wait till AsyncTask is finished in your activity, but it may take more time and you can get Application Not Responding message.
As soon as you call execute() method, control comes to next statement which loadTask.getStatus(). As task is just started, loadTask.getStatus() will not return FINISH and your 2nd task is never getting executed.

How to waits the thread till another thread completes

I want to show the progress dialog while loading the images in grid view.
The problem i'm facing was the current thread and Progress Dialog thread running simultaniously.
public String Method1(){
String output="";
final ProgressDialog aProgDialogL = ProgressDialog.show(this, "", "Loading...");
Thread thread = new Thread() {
public void run () {
//My codes
aHandlerL.post(new Runnable() {
#Override
public void run() {
//Post Runnable codes
aProgDialogL.dismiss();
}
});
}
};
thread.start();
/*
*
*
* OTHER CODES
*
*
*/
return output;
}
In the above example I need to run the code inside Progress Dialog Thread. After it finish executing i need to run my "OTHER CODES". How to do it?
.
I tried using Async task. Before async task completes method1 gets extcuted and reurning the string.
public String Method1(){
String result="";
new GetImages().execute();
return result;
}
public class GetData extends AsyncTask<Void, Void, Integer>{
#Override
protected void onPreExecute() {
aProgDialogL = ProgressDialog.show(Main.this, "", "Loading...");
}
#Override
protected Integer doInBackground(Void... params) {
//Progress Dialig Code
return null;
}
#Override
protected void onPostExecute(Integer result) {
aProgDialogL.dismiss();
//OTHER CODES
super.onPostExecute(result);
}
}

You can use Async task. http://developer.android.com/reference/android/os/AsyncTask.html. There is a good tutorial here. http://www.vogella.com/articles/AndroidPerformance/article.html.Also have a look at this link
http://developer.android.com/guide/components/processes-and-threads.html. Use asynctask modify it according to your needs.
doInBackground()- For long running operations. Don't update ui here.
onPreExecute()- update ui before running the operatio nin background.
onPostExecute()- update ui after running the operation.

I would suggest you to take somewhat different approach.
Dont involve any threads in Method1() function.Rather your Method1() function should be run under separate thread.
Below snippet will help you.
public class MainActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
((Button) findViewById(R.id.btnPopup))
.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
new Thread() {
public void run() {
String answer = Method1();
runOnUiThread(new Runnable() {
#Override
public void run() {
// Here you will write the code which is
// to be executed on main thread.
}
});
};
}.start();
}
});
}
public String Method1() {
// Write code
return "result";
}
}

Instead of that : What about use Timer After specific Time Stop Your thread and and write your code you want after stop statement Like that :
Timer timer=new Timer();
timer.schedule(new TimerTask() {
#Override
public void run() {
thread.stop;
// Other code }
}, Time You want );

How to run the same asynctask more than once?

I have my asyncTask run when the activity first starts, then if network connectivity is not available then i have a refresh button that tries to run the asyncTask to try again. But i get a debug error saying this..
07-29 18:14:21.290: ERROR/AndroidRuntime(9080): FATAL EXCEPTION: main
07-29 18:14:21.290: ERROR/AndroidRuntime(9080): java.lang.IllegalStateException: Cannot execute task: the task has already been executed (a task can be executed only once)
07-29 18:14:21.290: ERROR/AndroidRuntime(9080): at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:541)
07-29 18:14:21.290: ERROR/AndroidRuntime(9080): at android.os.AsyncTask.execute(AsyncTask.java:499)
07-29 18:14:21.290: ERROR/AndroidRuntime(9080): at com.fttech.gameIT.MainMenu$1.onClick(MainMenu.java:90)
Is there anyway to run this twice?

Just create another instance and execute it.

Just like threads, AsyncTasks can't be reused. You have to create a new instance every time you want to run one.

You can never execute a thread again, not in Java, not in any other language, once the thread is done with the run() method, you cannot restart it, which is why you are getting the IllegalStateException.
You can however still call the methods on that thread but they will run on the thread that is calling them NOT on a different thread. Therefore you will have to create a new one.

You cannot run same instance of an AsyncTask more than once.
Let's assume you have an AsyncTask named MyAsyncTaks and you intend to do something like this,
MyAsyncTask myAsyncTask = new MyAsyncTaks();
myAsyncTask.execute(); // Works as expected
.
.
.
.
myAsyncTask.execute(); // This will throw you exception
The reason for this is, a thread once finishes its 'run' method, cannot be assigned another task. Here, on the first invocation of execute(), your AsyncTask started running and
after doing its job, the thread comes out of run. Naturally, next invocation of execute() will throw you exception.
The simplest way to run this more than once is to create a new instance of MyAsyncTaks and call execute on that.
MyAsyncTask myAsyncTask = new MyAsyncTaks();
myAsyncTask.execute(); // Works as expected
.
.
.
MyAsyncTask myAsyncTask2 = new MyAsyncTaks();
myAsyncTask2.execute(); // Works as expected
Though its not needed to be mentioned here, one must be aware that post Android SDK version Honeycomb, if your run more than one AsyncTask at once, they actually run
sequentially. If you want to run them parallally, use executeOnExecutor instead.

Just make a new call like new asyncTask().execute(); You must create a new object to restart that task.

I just create the asynctask then create a runnable that creates new instances of the asynctask. Then you can submit your runnable over and over again to the handler.
class MyAsyncTask extends AsyncTask<String, Void, String>{ ...}
Runnable myRunner = new Runnable(){
public void run() {
new MyAsyncTask ().execute(...);
}};
myHandler.post(myRunner);

This solved my problem:
public class MainActivity extends AnimationActivity {
MyAsyncTasks asyncTasks = new MyAsyncTasks();
#BindView(R.id.refresh_btn)
Button refreshBtn;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setUnbinder(ButterKnife.bind(this)); // ButterKnife usage
syncTasks(); // run asyncTasks on activity start
refreshBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
syncTasks(); // run asyncTasks on button click
}
});
}
private void syncTasks() {
try {
if (asyncTasks.getStatus() != AsyncTask.Status.RUNNING){ // check if asyncTasks is running
asyncTasks.cancel(true); // asyncTasks not running => cancel it
asyncTasks = new MyAsyncTasks(); // reset task
asyncTasks.execute(); // execute new task (the same task)
}
} catch (Exception e) {
e.printStackTrace();
Log.e("MainActivity_TSK", "Error: "+e.toString());
}
}
}

You can do it like this :
private MyAsyncTask createAsyncTask(){
if (myAsyncTask == null){
return myAsyncTask = new MyAsyncTask();
}
myAsyncTask.cancel(true);
return myAsyncTask = new MyAsyncTask();
}
and then you can use it :
createAsyncTask().execute();
this make a new instance of your background task everytime.

Async tsk only run once as the Exceptions says the task has already been executed..
So you just have to make a new instance of async and then call .execute();
in order to run it again .. thank you

I created an Arraylist of type ProgressUpdater(Name of class which extends AsyncTask) and added the instances into it(in the onClick of a button). So you can execute and cancel these task when needed.
public class MainActivity extends Activity {
ProgressBar progress;
ProgressUpdater task;
ArrayList<ProgressUpdater> pu = new ArrayList<MainActivity.ProgressUpdater>();
int count = 0;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
progress = (ProgressBar) findViewById(R.id.progress);
}
public void onClick(View v) {
switch (v.getId()) {
case R.id.btn:
task = new ProgressUpdater();
pu.add(task);
count++;
pu.get(count - 1).execute(0);
System.out.println("task" + task);
// task.execute(10);
break;
case R.id.btnCancel:
if (count >= 0) {
pu.get(count - 1).cancel(true);
pu.remove(count - 1);
count--;
}
// task.cancel(true);
break;
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
private class ProgressUpdater extends AsyncTask<Integer, Integer, Void> {
#Override
protected void onPreExecute() {
// TODO Auto-generated method stub
super.onPreExecute();
progress = (ProgressBar) findViewById(R.id.progress);
progress.setMax(100);
}
#Override
protected Void doInBackground(Integer... params) {
// TODO Auto-generated method stub
int start = params[0];
for (int i = start; i <= 100; i++) {
try {
boolean cancelled = isCancelled();
if (!cancelled) {
publishProgress(i);
SystemClock.sleep(100);
}
} catch (Exception e) {
e.printStackTrace();
}
}
return null;
}
#Override
protected void onPostExecute(Void result) {
// TODO Auto-generated method stub
super.onPostExecute(result);
Log.v("Progress", "Finished");
}
#Override
protected void onCancelled() {
// TODO Auto-generated method stub
super.onCancelled();
progress.setMax(0);
}
#Override
protected void onProgressUpdate(Integer... values) {
// TODO Auto-generated method stub
super.onProgressUpdate(values);
progress.setProgress(values[0]);
}
}
}

in your MainActivity you can put so this:
LeoAsyncTask leoAsyncTaskGeneric;
public void onClick_AsyncTask(View view) {
LeoAsyncTask leoAsyncTaskInner = new LeoAsyncTask();
leoAsyncTaskInner.execute();
leoAsyncTaskGeneric=leoAsyncTaskInner;
}
/**if you create a space in memory of your AsyncTask class as a generic, then you can create an instance of that same class within the onClick method, and there the equals, so every time you press onClick you will be using a new instance of the Class AsyncTask, it will not give you problems
*/

You could cancel your asyncTask when you press the button and then execute it again.
Inside OnClic method:
asyncTask.cancel();
AsyncTask asyncTask = new AsyncTask();
asyncTask.execute();

#coder_For_Life22 I think am late for the answer ,anyway you can do like
#Override
protected void onPostExecute(Void a) {
myAsyncTask=new MyAsyncTask();
}
in order to start a new AsyncTask after execution :)

Android: TimerTask scheduled for repetition getting fired only once

Ok this is a very weird problem I am having, and I'm pretty sure that I am messing up somewhere, but I can't quite figure out where.
What I am trying is -
Schedule a Timer to execute a TimerTask every five seconds
The TimerTask in turn executes an AsyncTask (which in this case simple sleeps for a second before returning the static count of the number of AsyncTasks).
Finally, the aforementioned count is updated in the UI.
And of course, the appropriate Handlers and Runnables have been used to post asynchronous messages from other threads to the UI.
This code executes only once. I expect it to fire every 5 seconds. Here's the code.
Note: I had no idea what to do with the Looper. I put it there after trial and error!
public class TimerAsyncMixActivity extends Activity {
public static final String TAG = "TimerAsyncMix";
static int executionCount = 0;
Handler mHandler = new Handler();
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
new Timer().schedule(new MyTimerTask(this), 0, 5000);
}
class MyAsyncTask extends AsyncTask<String, Void, Integer>{
#Override
protected Integer doInBackground(String... params) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return ++executionCount;
}
#Override
protected void onPostExecute(Integer result) {
mHandler.post(new UpdateUiThread(TimerAsyncMixActivity.this, result));
super.onPostExecute(result);
}
}
}
class MyTimerTask extends TimerTask{
private TimerAsyncMixActivity tma;
public MyTimerTask(TimerAsyncMixActivity tma) {
this.tma = tma;
}
#Override
public void run() {
Looper.prepare();
Log.d(TimerAsyncMixActivity.TAG, "Timer task fired");
tma.new MyAsyncTask().execute();
Looper.loop();
Looper.myLooper().quit();
}
}
class UpdateUiThread implements Runnable{
int displayCount;
TimerAsyncMixActivity tma;
public UpdateUiThread(TimerAsyncMixActivity tma, int i) {
this.displayCount = i;
this.tma = tma;
}
#Override
public void run() {
TextView tv = (TextView) tma.findViewById(R.id.tvDisplay);
tv.setText("Execution count is : "+displayCount);
}
Can anyone point me to what I'm doing wrong?

techie, this is how I implemented similar things. I'm won't claim that this is the best way, but it has worked for me and doesn't look too bad.
I have the following code in my activity. I create an async task when the activity starts and I stop it onPause. The AsyncTask does whatever it needs to do, and updates the UI on onProgressUpdate() (which is run on the UI thread, so there's no need to use a Handler).
private Task task;
#Override
protected void onPause() {
task.stop();
task = null;
}
#Override
protected void onResume() {
task = new Task();
task.execute();
}
private class Task extends AsyncTask<Void, String, Void> {
private boolean running = true;
#Override
protected Void doInBackground(Void... params) {
while( running ) {
//fetch data from server;
this.publishProgress("updated json");
Thread.sleep(5000); // removed try/catch for readability
}
return null;
}
#Override
protected void onProgressUpdate(String... values) {
if( ! running ) {
return;
}
String json = values[0];
//update views directly, as this is run on the UI thread.
//textView.setText(json);
}
public void stop() {
running = false;
}
}

Do not use a timer. If your phone goes to sleep, the timer is suspended too. Use AlarmManager.

Show Dialog After Thread is Finish

I want show dialog after finish Thread.
In thread I am changing TextView's Value like as 0 to 100...
When TextView Value is reach 100 then i want to show dialog..
What i do for it.
Thanks in advance...
Code Snippet:
final Thread thread = new Thread(new Runnable()
{
#Override
public void run()
{
synchronized (this)
{
try
{
for(int i=0 ; i<speed; i++)
{
final int value=i+1;
wait(3000/speed);
Test.this.runOnUiThread(new Runnable() {#Override public void run()
{
accText.setText(String.valueOf(value));
}});
}
}
catch (InterruptedException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
});
thread.start();
this is asyntask code snippet...
class setTextBackgroundTask extends AsyncTask<String , Integer, Void>
{
#Override
protected void onPreExecute()
{
}
#Override
protected Void doInBackground(String... params)
{
Thread th = new Thread();
int value;
for(int i=0 ; i<speed; i++)
{
value=i+1;
publishProgress(value);
try {
th.sleep(3000/speed);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return null;
}
#Override
protected void onProgressUpdate(Integer... values)
{
accText.setText(String.valueOf(values[0]));
System.out.println("Value=="+values[0]);
super.onProgressUpdate(values);
}
#Override
protected void onPostExecute(Void result)
{
showShareDialog();
}
}

This document explains how you can create dialogs.
Please note that you will have to do any dialog creation code on the UI thread.
You already have code that runs something on the UI thread, just do that outside the loop,but with the dialog creation code inside.

You should use AsyncTask: subclass AsyncTask, override doInBackground() to execute your time consuming action on another thread, and then override onPostExecute() to show your dialog.
Note that you cannot change UI elements from a non-UI (background) thread. AsyncTask takes care of that for you: it calls doInBackground() on a new thread and then calls onPostExecute() on the UI thread as soon as the background task is complete.