Develop Reference

Wait for thread to finish and then move to next position

i am trying to display a Toast on the screen and when Toast fades off then move to the next question. I have tried with Thread but cannot seem to manage.
My code:
next.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (getUserSelection()){
position = position + 3;
if (position < questionsArray.size()) {
curName = questionsArray.get(position).getName();
curArray = questionsArray.get(position).getAnswers();
curIscorrect = questionsArray.get(position).getIscorrect();
setupQuestionView(curName, curArray, curIscorrect);
} else {
StringGenerator.showToast(QuestionsActivity.this, "Your score : " + score + "/" + (questionsArray.size() / 3));
}
}else {
StringGenerator.showToast(QuestionsActivity.this, getString(R.string.noanswerselected));
}
}
});
and the getUserSelectionMethod:
private boolean getUserSelection() {
correct = (RadioButton)findViewById(group.getCheckedRadioButtonId());
if (correct == null){
return false;
}else {
correctAnswerText = correct.getText().toString();
if (map.get(correctAnswerText).equals(Constants.CORRECTANSWER)) {
score++;
setCorrectMessage();
return true;
} else {
setWrongMessage();
return true;
}
}
}
private void setCorrectMessage() {
correctToast = new Toast(QuestionsActivity.this);
correctToastView = getLayoutInflater().inflate(R.layout.correct, (ViewGroup) findViewById(R.id.correctRootLayout));
correctText = (TextView)correctToastView.findViewById(R.id.correctTextView);
correctText.setText(getString(R.string.correctAnswer));
correctToast.setDuration(Toast.LENGTH_SHORT);
correctToast.setView(correctToastView);
correctToast.show();
correctThread = new Thread(new Runnable() {
#Override
public void run() {
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
correctToast.cancel();
}
});
correctThread.start();
}
private void setWrongMessage() {
wrongToast = new Toast(QuestionsActivity.this);
wrongToastView = getLayoutInflater().inflate(R.layout.wrong, (ViewGroup) findViewById(R.id.wrongRootLayout));
wrongText = (TextView)wrongToastView.findViewById(R.id.wrongTextView);
wrongText.setText(getString(R.string.wrongAnswer));
wrongToast.setDuration(Toast.LENGTH_SHORT);
wrongToast.setView(wrongToastView);
wrongToast.show();
wrongThread = new Thread(new Runnable() {
#Override
public void run() {
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
wrongToast.cancel();
}
});
wrongThread.start();
}
Any suggestion on how to do this?

You can determine the toast visibility:
toast.getView().getWindowToken()
If the result is null, than your toast isn't visible anymore, and than you can run any code you want.

as stated in this answer you can start a thread that waits the duration of the Toast:
Thread thread = new Thread(){
#Override
public void run() {
try {
Thread.sleep(3500); // 3.5seconds!
// Do the stuff you want to be done after the Toast disappeared
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
Toast.LENGTH_SHORT and Toast.LENGTH_LONG are only flags so you have to either hard code the duration or keep them in a constant. The durations are 3.5s (long) and 2s (short).
If you want to manipulate some of your views, you cannot do this in another thread than the "main" UI thread. So you have to implement a kind of callback/polling mechanism to get notified when the SleepThread has finished.
Check this answer to read about a couple of ways to do this. Probably the easiest of them to understand and implement is this:
After you started your Thread you can check if it is still alive and running by calling thread.isAlive(). In this way you can do a while loop that runs while the thread is running:
// start your thread
while(thread.isAlive()){}
// continue the work. The other thread has finished.
Please note that this is NOT the most elegant way to do this! Check the other possibilities in the answer I've mentioned above for more elegant solutions (especially the last one with the listeners is very interesting and worth reading!)

That's because the Thread class is purely executed in the background and you need to manipulate the view in the Main thread. To solve your issue just replace the Thread with AsynTask.
AsyncTask<Void,Void,Void> a = new AsyncTask<Void, Void, Void>() {
#Override
protected Void doInBackground(Void... params) {
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
correctToast.cancel();
}
};
a.execute();
If you look at my code you can see my onPostExecute, this method is called in the Main Thread.

My Error was because i was trying to acess UI Elements through another Thread so modifying the code like this:
Thread thread = new Thread(new Runnable() {
#Override
public void run() {
try {
Thread.sleep(500);
QuestionsActivity.this.runOnUiThread(new Runnable() {
#Override
public void run() {
moveToNextQuestion();
}
});
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
thread.start();
did the trick. I hope my answer helps someone!!!

how to force the AsyncTask to wait

i want the AsyncTask to wait till it finishes. so i wrote the below code and i used .get() method as follows and as shown below in the code
mATDisableBT = new ATDisableBT();
but at run time the .get() doesnt force ATDisableBT to wait, becuase in the logcat i receive mixed order of messages issued from ATDisableBT and ATEnableBT
which means .get() on ATDisableBT did not force it to wait
how to force the AsyncTask to wait
code:
//preparatory step 1
if (this.mBTAdapter.isEnabled()) {
mATDisableBT = new ATDisableBT();
try {
mATDisableBT.execute().get();
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
}
//enable BT.
this.mATEnableBT = new ATEnableBT();
this.mATEnableBT.execute();

You can do this way:
doInBackground of AsyncTask
#Override
protected Void doInBackground(String... params) {
Log.i("doInBackground", "1");
synchronized (this) {
try {
mAsyncTask.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
Log.i("doInBackground", "2");
return null;
}
Outside this function from where you have to nstrong textotify AsyncTask to release from wait state:
new CountDownTimer(2000, 2000) {
#Override
public void onTick(long l) {
}
#Override
public void onFinish() {
synchronized (mAsyncTask) {
mAsyncTask.notify();
}
}
}.start();
Here I have notified AsyncTask by CountDownTimer after 2 seconds.
Hope this will help you.

You should execute AsyncTask on UI thread, so using get() - which will block it makes no sense - it might get you ANR error.
If you are on HONEYCOMB and up, then AsyncTasks are executed on single executor thread, serially - so your mATEnableBT should get executed after mATDisableBT. For more see here:
http://developer.android.com/reference/android/os/AsyncTask.html#execute(Params...)
You might also switch from AsyncTask to Executors. AsyncTask is implemented using executors. By creating single threaded executor you make sure tasks will get executed serially:
ExecutorService executor = Executors.newSingleThreadExecutor();
//...
executor.submit(new Runnable() {
#Override
public void run() {
// your mATDisableBT code
}
});
executor.submit(new Runnable() {
#Override
public void run() {
// your mATEnableBT code
}
});

Stop thread in android application

public class CallEvent extends BroadcastReceiver{
public LEDController ledController = new LEDController();
public ApplicationSettings applicationSettings = new ApplicationSettings();
public boolean ring = false;
#Override
public void onReceive(Context context, Intent intent){
if(intent.getStringExtra(TelephonyManager.EXTRA_STATE).equals(TelephonyManager.EXTRA_STATE_RINGING)){
ring = true;
blink();
}else if(intent.getStringExtra(TelephonyManager.EXTRA_STATE).equals(TelephonyManager.EXTRA_STATE_IDLE) ||
intent.getStringExtra(TelephonyManager.EXTRA_STATE).equals(TelephonyManager.EXTRA_STATE_OFFHOOK)){
ring = false;
}
}
public void blink(){
Runnable r = new Runnable() {
#Override
public void run() {
while(ring){
ledController.turnOnFlash();
try {
Thread.sleep(applicationSettings.getDelayOn());
} catch (InterruptedException e) {
e.printStackTrace();
}
ledController.turnOffFlash();
try {
Thread.sleep(applicationSettings.getDelayOff());
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
};
Thread blinkThread = new Thread(r);
blinkThread.start();
}
}
I want to create led messenger when phone is ring. But I can't stop blinkThread. I dont know it is not working. Led start when call income but don't stop when call decline. Variable ring is changing on 'false' when call decline, but thread still working

In general, you don't forcibly stop threads because it's dangerous. You set a flag that tells the thread in question to exit from it's thread loop under controlled circumstances.
Your thread loop looks something along these lines:
void run() {
while (shouldContinue) {
doThreadWorkUnit();
}
}
And somewhere else you set the shouldContinue variable and wait for the thread to finish:
...
thread.shouldContinue = false;
thread.join();
...
(All this is likely not correct Java, since I don't do Java. View it as pseudo code and modify for your actual language/thread library/etc.)
Source: How to stop a thread?

Android Timed Async Task

Hi currently i have the following code which utilizes Asycn Task and Timer.
My async task is basically trying to send a HTTP GET method from a URL where the response from the server could varies depending on connection and load.
What i would like to do is to have a timed async task. Where, it will schedule an AsyncTask every X second BUT if there is currently an Async Task in progress i would have to kill it first. Then start a new one.
Here is the code that i have at the moment:
private static boolean running = false;
Timer myTimer;
protected void onCreate(Bundle savedInstanceState) {
/* REST OF CODE OMITTED */
MyTimerTask myTask = new MyTimerTask();
myTimer = new Timer();
myTimer.schedule(myTask, 0, 10000);
}
/* REST OF CODE OMITTED */
private class MyTimerTask extends TimerTask {
public void run() {
if(!running){
Log.i("TAG", "NEW TIMER STARTED.");
RetrieveChatMessage task = new RetrieveChatMessage();
task.execute();
running = true;
}else{
running = false;
}
}
}
private class RetrieveChatMessage extends AsyncTask<String, Void, ArrayList<Chat>> {
#Override
protected ArrayList<Chat> doInBackground(String... params) {
// TODO Auto-generated method stub
ArrayList<Chat> cList = null;
String jResult = null;
Log.i("TAG", "RETRIEVING CHAT MESSAGE");
try {
jResult = ((new HttpRetriever())).getChatList(mAccount.email, mAccount.passwd);
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NoSuchAlgorithmException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
if(jResult != null){
Log.i("TAG", "JSON DATA: " + jResult);
cList = (new ChatHandlers()).getChatList(jResult);
}else{
cList = null;
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
Log.e("TAG", "JSON Exception " + e.toString());
}
return cList;
}
#Override
protected void onPostExecute(final ArrayList<Chat> result) {
Log.i("TAG", "ON POST EXECUTE");
if(result != null){
// Do something here
}
}
}
To be honest the code above works with slight issues:
1. It seems to execute the Async randomly, instead of every 10 seconds.
2. When i go to another activity, somewhat it prevents other Async task from doing its job (Which is also trying to retrieve JSON response from server).
I am not too worried about the later problem (and that is not the question i am asking). I just would like to know how to have a proper timed Async Task. Can anyone point me to a direction.
Thank you.
EDIT #1:
after reading #thepoosh comment's i tried the following (i put it in onCreate):
scheduleTaskExecutor= Executors.newScheduledThreadPool(5);
scheduleTaskExecutor.scheduleAtFixedRate(new Runnable() {
public void run() {
// Parsing RSS feed:
// myFeedParser.doSomething();
Log.w("THUMBQOO", "NEW TASK STARTED");
retrieveChat();
}
}, 0, 15, TimeUnit.SECONDS);
Result: i have a consistent execution of Task. However, it seems that retrieveChat(); is never be called after the first execution.

Actually AsyncTask is not used for long operations .Check Here
You should use a Thread that uses a interface to notify UI or you can simply use a Handler which is the most Preffered way in android. Simply you can do a task repeatedly for every 10 seconds by
handler.postDelayed(new Runnable() {
#Override
public void run() {
// do work
handler.postDelayed(10000);
}
}, 10000);

Declare a Handler object to maintain future task executor...
private Handler mTimerHandler = new Handler();
Write a thread which will execute your future task...
private Runnable mTimerExecutor = new Runnable() {
#Override
public void run() {
//write your code what you want to do after the specified time elapsed
if(!running){
RetrieveChatMessage task = new RetrieveChatMessage();
task.execute();
running = true;
}else{
running = false;
}
}
};
Call your future tast executor with time using hanlder...
mTimerHandler.postDelayed(mTimerExecutor, 10000);
You can cancle your future task executor any time by this...
mTimerHandler.removeCallbacks(mTimerExecutor);

I am not sure if this is a very good way of accomplishing this (my answer here below) :
Use a Handler, create a HandlerThread and keep posting messages to this handler.
For the handlers "handleMessage" method, you can do your task and again send a message back to the MessageQueue.
HandlerThread thread = new HandlerThread(<name>);
thread.start();
Looper looper = thread.getLooper();
CustomHandler handler = new CustomHandler(looper);
// The CustomHandler class
class CustomHandler extends Handler {
public CustomHandler(Looper looper) {
super(looper);
}
#Override
public void handleMessage(Message msg) {
//Do your operation here
handler.sendEmptyMessageDelayed(msg, <delayTime>);
}
}

how can I chnage a TextViews text from a thread?

I'm trying to write code to pull a server every second for updated messages. The messages then get displayed in a text view. If I do not change the text in the text view it runs fine. It will crash if I try to change the textview on the thread. IF i change it not on the thread works fine.
I'm assuming the thread cannot access the main threads memory? How can I set the text in the view with the text just loaded over the internet?
In the code below I have a thread that does a endless loop with a sleep. It calls a method called SendMessage. Send Message loads in text over the internet and at the end tries to update the View with it. It causes a exception when this happens.
code:
public class cChat extends cBase implements OnClickListener {
/** Called when the activity is first created. */
TextView mUsers;
TextView mComments;
int i=0;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.chat);
mUsers=( TextView) findViewById(R.id.viewusers);;
mComments=( TextView) findViewById(R.id.viewchats);;
Thread thread = new Thread()
{
#Override
public void run() {
try {
int t=0;
while(true)
{
SendMessage();
sleep(1000*5);
t++;
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
thread.start();
}
public void onClick(View v) {
} // end function
// send a uypdate message to chat server
// return reply in string
void SendMessage()
{
try {
URL url = new URL("http://50.63.66.138:1044/update");
System.out.println("make connection");
URLConnection conn = url.openConnection();
// set timeouts to 5 seconds
conn.setConnectTimeout(1000*5);
conn.setReadTimeout(5*1000);
conn.setDoOutput(true);
BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream()));
// String line;
String strUsers=new String("");
String strComments=new String("");
String line=new String();
int state=0;
while ((line= rd.readLine() ) != null) {
switch(state){
case 0:
if ( line.contains("START USER"))
state=1;
if ( line.contains("START COMMENTS"))
state=2;
break;
case 1:
if ( line.contains("END USER"))
state=0;
else
{
strUsers+=line;
strUsers+="\n";
}
break;
case 2:
if ( line.contains("END COMMENTS"))
state=0;
else {
strComments+=line;
strComments+="\n";
}
break;
} // end switch
} // end loop
// the next line will cause a exception
mUsers.setText(strUsers);
mComments.setText(strComments);
} catch (Exception e) {
i++; // use this to see if it goes here in debugger
// System.out.println("exception");
// System.out.println(e.getMessage());
}
} // end methed
}

use runOnUiThread as
YOUR_CURRENT_ACTIVITY.this.runOnUiThread(new Runnable() {
#Override
public void run() {
// the next line will cause a exception
mUsers.setText(strUsers);
mComments.setText(strComments);
//....YOUR UI ELEMENTS
}
});
EDIT :
see doc runOnUiThread

You can use a handler to post tasks (Runnables) to the UI/Main Thread:
private Handler handler = new Handler();
//...
Thread thread = new Thread()
{
#Override
public void run() {
try {
int t=0;
while(true)
{
handler.post(new Runnable() {
#Override
public void run() {
SendMessage();
}
});
sleep(1000*5);
t++;
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};

You can't touch an UI widget from a thread different than the one used to create it (the UI thread). But if you have a reference to the Activity, you can simply do:
activity.runOnUiThread(new Runnable() {
#Override
public void run() {
mUsers.setText(strUsers);
mComments.setText(strComments);
}
});
which would require strUsers to be accessible by the anonymous class. For that you can simply do:
final String finalUseres = strUsers;
and use finalUsers within run().

Try using a Service to continuously pull/send data to server. This will reduce the load on your UI-Thread.

the Andoid UI toolkit is not thread-safe. So, you
must not manipulate your UI from a worker thread
To fix this problem, Android offers several ways to access the UI thread from other threads. Here is a list of methods that can help:
Activity.runOnUiThread(Runnable)
View.post(Runnable)
View.postDelayed(Runnable, long)
you can also use AsyncTask.
see this tutorial on process and threads in android.