I am trying to create a service which does something every 5 seconds.
The problem is the moment I put the while(true) it gives me an error.
I imagine this is just not allowed. If so, what is a better way to implement a repetitive method?
public class repService extends Service {
#Override
public IBinder onBind(Intent intent) {
// TODO Auto-generated method stub
return null;
}
while(true){
Thread timer = new Thread(){
public void run(){
try {
sleep(5000);
// do something
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
// do something
}
}
};
timer.start();
}
}
You cannot put statements outside of a method to run. Put the while loop inside onCreate or onStartCommand methods of your service. These methods are guaranteed to called once your service is launched.
And for implementing a repetitive task, use HandlerThread, Looper, Handler and handler's postDelayed method to make good use of it.
Timer timer = new Timer();
timer.scheduleAtFixedRate(new TimerTask() {
#Override
public void run() {
// do something
}
}, 0, 5000);
which every 5 seconds does something
You can use Timer().schedule to repeat task every 5 seconds.
new Timer().schedule(new TimerTask() {
#Override
public void run() {
//Do your task here
}
}, System.currentTimeMillis(), 5000);
If you need to modify or play on UI part then make sure to write than code in runOnUiThread
Related
I want to listen sql server database for know whether there are changes of data in android so I want to send request to web service every 5 second to know of new data value.How can I do this? Can you give a example about it?
You can do it with AsyncTask,
public void callAsynchronousTask() {
final Handler handler = new Handler();
Timer timer = new Timer();
TimerTask doAsynchronousTask = new TimerTask() {
#Override
public void run() {
handler.post(new Runnable() {
public void run() {
try {
PerformBackgroundTask performBackgroundTask = new PerformBackgroundTask();
// PerformBackgroundTask this class is the class that extends AsynchTask
performBackgroundTask.execute();
} catch (Exception e) {
// TODO Auto-generated catch block
}
}
});
}
};
timer.schedule(doAsynchronousTask, 0, 50000); //execute in every 50000 ms
}
More: How to execute Async task repeatedly after fixed time intervals
Use Service class and within the service class implement thread scheduler that will send request every 5 seconds. Below is th ecode snippet:
public class ProcessingService extends Service {
private Timer timer = new Timer();
#Override
public IBinder onBind(Intent intent) {
return null;
}
#Override
public void onCreate() {
super.onCreate();
timer.scheduleAtFixedRate(new TimerTask() {
#Override
public void run() {
sendRequest();
}
}, 0, 5000;//5 Seconds
}
#Override
public void onDestroy() {
super.onDestroy();
shutdownService();
}
}
Use this Code:
ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor();
scheduler.scheduleAtFixedRate(new Runnable() {
#Override
public void run() {
// TODO Auto-generated method stub
// Hit WebService
}
}, 0, 5, TimeUnit.SECONDS);
Polling is generally not a good idea. Because it creates unnecessary load in server. In your case, 20 requests per minute per user.
So go for Push Mechanism. So the idea will be like this, whenever you get a push message you will call the web service to get the latest data.
This link will help you : Push, Don’t Poll – How to Use GCM to Update App
I'm trying to make a timer that will do a certain thing after a certain amount of time:
int delay = 1000;
int period = 1000;
Timer timer = new Timer();
timer.scheduleAtFixedRate(new TimerTask() {
public void run() {
//Does stuff
}
}, delay, period);
However, the app crashes after the wait period. This is Java code, so it might not be entirely compatible with Android (like while loops). Is there something I'm doing wrong?
Something like this should work, create a handler, and wait 1 second :) This is generally the best way of doing it, its the most tidy and also probably the best on memory too as its not really doing too much, plus as it's only doing it once it is the most simple solution.
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
public void run() {
// do your stuff
}
}, 1000);
If you would like something to run every one second then something like this would be best:
Thread thread = new Thread()
{
#Override
public void run() {
try {
while(true) {
sleep(1000);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
thread.start();
If you want a GUI thread then something like this should work:
ActivityName.this.runOnUiThread(new Runnable()
{
public void run(){
try {
while(true) {
sleep(1000);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
If your app is crashing after the wait period, then your timer task is doing its job and executing your code on schedule. The problem must then be in your code where run() occurs (for example, you may be trying to update UI elements in a background thread).
If you post more code and your logcat, I can probably be more specific about the error you are getting, but your question was in regards to TimerTask.
Timer and also you can run your code on UI thread:
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.main);
myTimer = new Timer();
myTimer.schedule(new TimerTask() {
#Override
public void run() {
timerMethod();
}
}, 0, 1000);
}
private void timerMethod(){
// This method is called directly by the timer
// and runs in the same thread as the timer.
// We call the method that will work with the UI
// through the runOnUiThread method.
this.runOnUiThread(timerTick);
}
private Runnable timerTick = new Runnable() {
public void run() {
// This method runs in the same thread as the UI.
// Do something to the UI thread here
}
};
i am using below code to run my getLatLngWrkr(); function after 3 seconds but when timer starts and getLatLngWrkr();gets call the code which places Marker does not work.But when i run the function getLatLngWrkr() without Timer it works properly.
here is the some line to place marker to map and it does not work if i call the function through Timer
marker=googleMap.addMarker(new MarkerOptions().position(newLatLng(Double.parseDouble(lati), Double.parseDouble(longi))).title( lati+longi));
Here is Timer Function
Timer time = new Timer();
time.schedule(new TimerTask() {
#Override
public void run() {
// TODO Auto-generated method stub
Log.e("test","tiemr");
getLatLngWrkr();
}
},0, 3000);
When you use a TimerTask the task is performed on a separate thread and not the ui thread. You need to call getLatLngWrkr using runOnUiThread:
Timer time = new Timer();
time.schedule(new TimerTask() {
#Override
public void run() {
// TODO Auto-generated method stub
Log.e("test","tiemr");
MainActivity.this.runOnUiThread(new Runnable() {
#Override
public void run() {
getLatLngWrkr();
}
});
}
},0, 3000);
Replace MainActviity with the name of your activity.
I have this code where I want to try to send an e-mail report every hour (in the example to every second). If there is no coverage, try again within an hour etc. Somehow I managed to break the timer in sendUnsendedReports(): it fires only once. If I remove the call to sendUnsendedReports() than the timer is working perfectly. Even with the try-catch block around it, the timer only fires once. Please advice.
private void createAndScheduleSendReport() {
delayedSendTimer = new Timer();
delayedSendTimer.schedule(new TimerTask() {
#Override
public void run() {
Log.w("UrenRegistratie", "Try to send e-mail...");
try{
sendUnsendedReports();
}
catch(Exception e){
// added try catch block to be sure of uninterupted execution
}
Log.w("UrenRegistratie", "Mail scheduler goes to sleep.");
}
}, 0, 1000);
}
It seems that sometimes timer doesn't works well as it should be. The alternative of this is use of Handler instead TimerTask.
You can use it like :
private Handler handler = new Handler();
handler.postDelayed(runnable, 1000);
private Runnable runnable = new Runnable() {
#Override
public void run() {
try{
sendUnsendedReports();
}
catch(Exception e){
// added try catch block to be sure of uninterupted execution
}
/* and here comes the "trick" */
handler.postDelayed(this, 1000);
}
};
Check out this link for more detail. :)
schedule() can be called in various ways, depending on if you want the task to execute once, or periodically.
To execute the task only once:
timer.schedule(new TimerTask() {
#Override
public void run() {
}
}, 3000);
To execute the task every second after 3 s.
timer.schedule(new TimerTask() {
#Override
public void run() {
}
}, 3000, 1000);
More example usages can be found in the method headers
public void schedule(TimerTask task, Date when) {
// ...
}
public void schedule(TimerTask task, long delay) {
// ...
}
public void schedule(TimerTask task, long delay, long period) {
// ...
}
public void schedule(TimerTask task, Date when, long period) {
// ...
}
It is clearly that you hit the exception and get out of the Timer run method, thus interrupting the timer restart.
I have to display some data after every 10 seconds. Can anyone tell me how to do that?
There is an another way also that you can use to update the UI on specific time interval. Above two options are correct but depends on the situation you can use alternate ways to update the UI on specific time interval.
First declare one global varialbe for Handler to update the UI control from Thread, like below
Handler mHandler = new Handler();
Now create one Thread and use while loop to periodically perform the task using the sleep method of the thread.
new Thread(new Runnable() {
#Override
public void run() {
// TODO Auto-generated method stub
while (true) {
try {
Thread.sleep(10000);
mHandler.post(new Runnable() {
#Override
public void run() {
// TODO Auto-generated method stub
// Write your code here to update the UI.
}
});
} catch (Exception e) {
// TODO: handle exception
}
}
}
}).start();
Probably the simplest thing to do is this:
while(needToDisplayData)
{
displayData(); // display the data
Thread.sleep(10000); // sleep for 10 seconds
}
Alternately you can use a Timer:
int delay = 1000; // delay for 1 sec.
int period = 10000; // repeat every 10 sec.
Timer timer = new Timer();
timer.scheduleAtFixedRate(new TimerTask()
{
public void run()
{
displayData(); // display the data
}
}, delay, period);
Andrahu was on the right track with defining a handler. If you have a handler that calls your update functions you can simply delay the message sent to the handler for 10 seconds.
In this way you don't need to start your own thread or something like that that will lead to strange errors, debugging and maintenance problems.
Just call:
Handler myHandler = new MyUpdateHandler(GUI to refresh); <- You need to define a own handler that simply calls a update function on your gui.
myHandler.sendMessageDelayed(message, 10000);
Now your handleMessage function will be called after 10 seconds. You could just send another message in your update function causing the whole cycle to run over and over
There is Also Another way by Using Handler
final int intervalTime = 10000; // 10 sec
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
#Override
public void run() {
//Display Data here
}
}, intervalTime);
There is a Simple way to display some data after every 10 seconds.
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_launcher);
ActionStartsHere();
}
public void ActionStartsHere() {
againStartGPSAndSendFile();
}
public void againStartGPSAndSendFile() {
new CountDownTimer(11000,10000) {
#Override
public void onTick(long millisUntilFinished) {
// Display Data by Every Ten Second
}
#Override
public void onFinish() {
ActionStartsHere();
}
}.start();
}
Every 10 seconds automatically refreshed your app screen or activity refreshed
create inside onCreate() method i tried this code will work for me
Thread t = new Thread() {
#Override
public void run() {
try {
while (!isInterrupted()) {
Thread.sleep(1000);
runOnUiThread(new Runnable() {
#Override
public void run() {
//CALL ANY METHOD OR ANY URL OR FUNCTION or any view
}
});
}
} catch (InterruptedException e) {
}
}
};t.start();