I have this problem. I'm trying to update my TextView from another thread and it's not letting me.
I have tried a bunch of different solutions and none of those didn't seem to help. In my while loop code is printing that "Started new loop" all the time but it's not continuing from that runOnUiThread.
Can anyone help me figure out how to update TextView from another thread?
//second thread
protected void startKakkosThread() {
Thread t2 = new Thread() {
public void run() {
while (true) {
System.out.println("Started new loop");
runOnUiThread(new Runnable() {
#Override
public void run() {
try {
if(rullaavaNumero >= 0) {
rullaavaNumero--;
System.out.println(rullaavaNumero);
pelaajanPisteetTeksi.setText("" + rullaavaNumero);
sleep(1000);
}else{
rullaavaNumero = 9;
System.out.println(rullaavaNumero);
pelaajanPisteetTeksi.setText("" + rullaavaNumero);
sleep(1000);
}
}catch (InterruptedException e){
e.printStackTrace();
}
}
});
}
}
};
t2.start();
}
Here is a quick fix, you have an infinite loop that runs faster than a thread can have a chance (time) to start. So even thus you have a sleep in side your thread with if statement, if the thread never starts then sleep have no effect.
And your sleep inside a Thread won't work like this. You want to delay your infinite while loop, therefore you need to move sleep on out of the thread in your while loop.
It is still possible to delay your thread by adding extra sleep in it, but all that depends on what you want to achieve.
Your final code would look like this:
protected void startKakkosThread() {
Thread t2 = new Thread() {
public void run() {
while (true) {
System.out.println("Started new loop");
runOnUiThread(new Runnable() {
#Override
public void run() {
if (rullaavaNumero >= 0) {
rullaavaNumero--;
System.out.println(rullaavaNumero);
pelaajanPisteetTeksi.setText("" + rullaavaNumero);
// no need for sleep here
// sleep(1000);
} else {
rullaavaNumero = 9;
System.out.println(rullaavaNumero);
pelaajanPisteetTeksi.setText("" + rullaavaNumero);
// no need for sleep here
// sleep(1000);
}
}
});
// add this part
try {
sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
};
t2.start();
}
I have test it and it works, you could also go what #cricket has suggest.
My eye saw another issue, which is not a part of your question, but good to mention. I assume you want to count from 9 to 0, if that is the case, you need to correct following line by removing = otherwise you get counts till -1, so your code line would look like this:
if(rullaavaNumero > 0) {...
Related
So I'm attempting to create background task that needs to be run every hour in an Android app. Its a rather heavy task that takes around 5 - 10 minutes to finish, and right now it runs on the UI thread which of course isn't good, because it hangs the whole application. I've attempted the following in my MainActivity onCreate:
new Thread(new Runnable() {
private Handler HeavyTaskHandler = new Handler(Looper.getMainLooper());
public void run(){
final TextView updatedTxt = findViewById(R.id.txt);
updatedTxt.post(new Runnable() {
#Override
public void run() {
updatedTxt.setText("Performing cleanup..");
}
});
HeavyTask(); // <-- This method runs for 5 - 10 minutes
updatedTxt.post(new Runnable() {
#Override
public void run() {
updatedTxt.setText("Done..");
}
});
HeavyTaskHandler.postDelayed(this, HeavyTaskCycle);
}
}).start();
I have two issues with the above
It works fine the first time, and the task is performed in the background well without hanging the UI thread. However, after this first time and the next time(s) it is run, the UI thread hangs again when it is run. What am I missing?
Notice that before the HeavyTask() method is called i try to set a TextViews text to "Performing cleanup.." .. This never shows, only the "Done.." which happens after the HeavyTask() method is done. How can i ensure that the message also appears before?
I ended up doing the following from MainActivity which doesn't hang the application
private void CreateCleanUpThread()
{
CleanUpThread = new Thread(new Runnable() {
public void run(){
try {
while(true) {
performingCleanup = true;
final TextView updatedTxt = findViewById(R.id.updated_txt);
runOnUiThread(new Runnable() {
#Override
public void run() {
updatedTxt.setText("Performing database history cleanup..");
}
});
HeavyTask(); // <-- This method runs for 5 - 10 minutes
runOnUiThread(new Runnable() {
#Override
public void run() {
updatedTxt.setText("Done..");
}
});
performingCleanup = false;
Thread.sleep(CleanUpCycle); // 1 hour wait time
}
} catch(Exception ex) {
System.out.println("Error in CreateCleanUpThread : " + ex.getMessage());
}
}
});
}
// onCreate in MainActivity
...
CleanUpThread.start();
Certainly not the best way, but it works and will do for now. Should be moved to a service instead i think.
Consider this example:
Thread thread = new Thread(new Runnable() {
public void run() {
// Sleep for 5000ms
// Show toast message
}
});
Now I will start this thread on button click in MainActivity and right after that I would exit the activity on back button press, but in overided method onBackPressed following code is implemented:
If(thread != null)
thread.interupt();
finish();
After few seconds toast message is shown, why is that?
interrupt, clears the interrupt status of your thread and will cause the InterruptedException to be thrown. So if your thread is sleepin, and while it is asleep, you call interrupt, it will be woken up, and the execution flow will continue from the instruction that follows the catch block. Assuming you have something really simple like:
public void run() {
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackThreace();
}
runOnUiThread(TOAST);
}
or
public void run() {
while(true) {
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackThreace();
}
runOnUiThread(TOAST);
}
}
both will shown the Toast even though you called interrupt()
While blackbelt has already explained the reason why this happens, here is how you can get around the problem.
The best way to interupt a thread is to use a if-boolean-break method.
So if i were to re-write you code it would be along the following lines
onBackPressed:
isBackPressed = true;
inside the thread's run method:
Thread thread = new Thread(new Runnable() {
public void run() {
// Sleep for 5000ms
if(!isBackPressed){
// Show toast message
}
}
});
I have an app that runs 2 threads in loops. 1st one is updating a graph in 1s interval and the second one is updating another graph at 60s interval. The second task is taking a long time since it is quering some server in the internet 3 times that might not always be available and even if it is it will take up to 5-7s to execute.
What is happening is when I launch the second thread it will pause execution of the first one and that is not what I want, I wish both run concurrently. Here in the Youtube video you can see the results of the app running. http://youtu.be/l7K5zSWzlxI
"thread_updater1s" is running a green graph, large readout, and a timer in the corner so you clearly see it stalls for 11 seconds.
1)First of all why is that happening? how to fix it?
2)I'm aware that I might not launch the threads properly at all. I had hard time understanding how to make something to run in a interval loop in Java and my code worked fine for one graph/tread. Now when I have 2 loops in separate threads I don't know why they are not executing concurrently.
Here is the code:
public class LoopExampleActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.main);
thread_updater1s.start();
thread_updater2.start();
}// end of onCreate
final Runnable r1s = new Runnable() {
public void run() {
do_1s_updates(); // those are very quick http calls to the local API server
} // to get data nessessary for some plot.
// They have 1s timeout as well but rarely timeout
};
final Runnable r2 = new Runnable() {
public void run() {
do_large_updates(); //This makes 7 long call over the Internet to the slow https
//server once every 60s. Has 10s timeout and sometimes takes as much as
//7s to execute
}
};
Thread thread_updater1s = new Thread() {
#Override
public void run() {
try {
while (true) {
handler.post(r1s);
sleep(1000);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
Thread thread_updater2 = new Thread() {
#Override
public void run() {
try {
while (true) {
handler2.post(r2);
sleep(60000);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
}
PS. please be forgiving and informative I only code Java for 15 days so far with absolutely no prior experince or lesson.
You need to make the http requests in the threads (not the posted runnables). Then, when you have the data downloaded, you create a runnable with that data that will update the graph and post that runnable to be executed by the UI thread. Here is an example:
public class LoopExampleActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.main);
thread_updater1s.start();
thread_updater2.start();
}// end of onCreate
Thread thread_updater1s = new Thread() {
#Override
public void run() {
try {
while (true) {
final Object data = getDataFromServer1();
handler.post(new Runnable() {
#Override
public void run() {
updateGraph1(data);
}
);
sleep(1000);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
Thread thread_updater2 = new Thread() {
#Override
public void run() {
try {
while (true) {
final Object data = getDataFromServer2();
handler.post(new Runnable() {
#Override
public void run() {
updateGraph2(data);
}
);
sleep(60000);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
Obviously, change that final Object data by the appropriate class that represents your data downloaded.
handler.post pushes the runnable onto the main (UI) thread's message queue for execution on the main thread.
So what you're doing is every sleep interval, you're sending a message to the main thread to run the function. Clearly, the main thread can't run 2 things at once, so that's why one runnable is delayed for the next one.
You probably want to do the work of the runnable in the separate threads - why did you start using a handler? What happens if you call do_1s_updates and do_large_updates directly instead of through the handler & runnable?
I have a litle problem in my Android project.
I would like to do something every 1 second but the problem is that I have something else to do between those 1sec.
I tried to make a while (true) loop with wait(1000) inside but the problem is that this loop blocks all other instructions.
What would be a workaround / solution for this?
I would consider a threading scenario. In case you are working with UI updates, you can use postDelayed so you can update your UI from withing the Runable. You can call the Runable from within a Runable, too.
View.postDelayed(new Runnable() {
public void run() {
// do work
}
}, 1000);
Edit: Based on your comment, this is how you can implement calling back your function repeatedly.
public void PrendrePhoto() {
String nom = "CameraPhoto";
double x;
camera = Camera.open();
capteurBdd = new CapteursBDD(null);
while (true) {
camera.takePicture(null, null, null);
x = 10;
ValeursCapteur capteur = new ValeursCapteur(nom, x, 0, 0);
capteurBdd.insertValeursCapteur(capteur);
Log.i(null, "GPS = " + x);
try {
findViewById(R.id.mainView).postDelayed(predrePhotoRunnable, 1000);
} catch (InterruptedException ex) {
}
}
}
private Runnable predrePhotoRunnable = new Runnable() {
public void run() {
PrendrePhoto();
}
};
You can use async tasks in android.
Hej, I'm trying to create an app that runs on a main thread, but also has a background loop running (to check for a connection).
I just want to call a certain function onCreate, and that function should run in the background...I've tried with the code below, but doesn't seem to work...any suggestions?
void doStuffBackground()
{
Thread testingForBluetooth = new Thread()
{
public void run()
{
try
{
for(int i = 0; i < 100; i++)
{
writeTerminal('x');
sleep(100);
}
}
catch(Exception e)
{
Log.e("Threading", e.toString());
}
finally
{
finish();
}
}
};
}
}
But again...not working?
Thanx in advance
You never started the thread.
Anyway if you need a background task, you could also try a service.