Handler postdelayed is unaffected for less than 10 milliseconds

Handler postdelayed is unaffected for less than 10 milliseconds - android

I have created two TextViews and updating their contents through two different handlers, one for each TextView. I am incremented two counters in both handlers, one in each, and posting their values to respective TextView.
My first handler is ticking according to the value of long speed variable, and second handler is ticking 10 times later.
public class Main extends Activity{
private View root;
private final Context context = this;
private int count1 = 0, count2 = 0;
private TextView view1, view2;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
init();
}
private void init() {
setContentView(R.layout.s_main);
root = findViewById(R.id.root);
view1 = findViewById(R.id.txv1);
view2 = findViewById(R.id.txv2);
//
ViewTreeObserver vto = root.getViewTreeObserver();
vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
#Override
public boolean onPreDraw() {
root.getViewTreeObserver().removeOnPreDrawListener(this);
startRuns();
return true;
}
});
}
private void startRuns() {
try {
final long sleep = 10;
final Handler handler1 = new Handler();
handler1.postDelayed(new Runnable() {
#Override
public void run() {
view1.setText(String.valueOf(count1++));
handler1.postDelayed(this, sleep);
}
}, 1);
final Handler handler2 = new Handler();
handler1.postDelayed(new Runnable() {
#Override
public void run() {
view2.setText(String.valueOf(count2++));
handler2.postDelayed(this, sleep * 10);
}
}, 1);
Threads.run = true;
} catch (Exception ex) {
Alerts.alert(context, ex.getMessage());
}
}
}
This is good till the value of speed is 10 or above, but as soon i set the value of speed to 1, both handlers work with same duration or speed. First handler should work with speed of 1, and second handler should work with speed of 10, but both works with speed of 10 ms.
EDIT
In short, minimum delay on which postDelayed is working is 10 ms, not less than that, not 1, not 5, at least 10. I need to run a runnable with 5 ms delay in a project.
Can you please suggest where I am wrong?

Related

Handler doesn't work correctly

first of all excuse me if my title doesn't describe my question very well but i couldn't find a better one .
there is a simple stopWatch app that has three button start,stop,reset and a textview to display time . app has just one activity like this:
public class StopwatchActivity extends AppCompatActivity {
private int mNumberOfSeconds = 0;
private boolean mRunning = false;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_stopwatch);
//if if uncomment this runner method and delete the runner inside onClickStart everything will work find
//runner()
}
public void onClickStart(View view){
mRunning = true;
runner();
}
public void onClickStop(View view){
mRunning = false;
}
public void onClickReset(View view){
mRunning = false;
mNumberOfSeconds = 0;
}
public void runner(){
final TextView timeView = (TextView) findViewById(R.id.time_view);
final Handler handler = new Handler();
handler.post(new Runnable() {
#Override
public void run() {
int hours = mNumberOfSeconds/3600;
int minutes = (mNumberOfSeconds%3600)/60;
int second = mNumberOfSeconds%60;
String time = String.format("%d:%02d:%02d" , hours , minutes , second );
timeView.setText(time);
if (mRunning){
mNumberOfSeconds++;
}
handler.postDelayed(this , 1000);
}
});
}
}
my problem is when i comment the runner() in onClickStart method and put it in the onCreate method everything is ok . but when i change the code like above the code is still running but after i press stop button and then press start again the second will increment by 4 or 5 very fast.
can anyone explain me what is the difference between this two modes?

declare your handler globally
public void runner(){
timeView = (TextView) findViewById(R.id.time_view);
handler = new Handler();
runnable = new Runnable() {
#Override
public void run() {
int hours = mNumberOfSeconds/3600;
int minutes = (mNumberOfSeconds%3600)/60;
int second = mNumberOfSeconds%60;
String time = String.format("%d:%02d:%02d" , hours , minutes , second );
timeView.setText(time);
if (mRunning){
mNumberOfSeconds++;
}
handler.postDelayed(this , 1000);
}
}
handler.post(runnable);
}
in button function
public void onClickStart(View view){
if(handler != null) {
//restart the handler to avoid duplicate runnable
handler.removeCallbacks(runnable);//or this handler.removeCallbacksAndMessages(null);
}
mRunning = true;
runner();
}
public void onClickStop(View view){
mRunning = false;
handler.removeCallbacks(runnable); // this will stop the handler from working
}

Changing image on Android thread

I've gone through stackoverflow and all the similar answers - but have found them not of use.
Can anyone please point out why this is not working? It should be simple: update the image every 6 seconds (will be every 3 mins but for testing I've put it as 6 seconds).
What the code does is - goes through each of the 4 images step by step but does not change the image. HOWEVER when it gets to the last image - it does change it(??).
Questions:
What's wrong with this?
Why would it only update the last image?
If I start the code with just a "post" to the handler instead of a "postDelayed" - the tablet just stays with a black screen. Why do I have to start the code with a delay to make it work?
int currentIndex = 0;
boolean start = false;
ImageView descriptionImage;
private Runnable timerRunnable;
long startTime = 0;
private Handler handler;
int[] pictureIds = new int[]{R.drawable.hang, R.drawable.dog, R.drawable.coffee, R.drawable.about};
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
pictureDescription = new ArrayList<String>();
handler = new Handler(Looper.getMainLooper());
}
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_picture_test, container, false);
descriptionImage = (ImageView) v.findViewById(R.id.iv_picture);
return v;
}
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
start();
}
private void start() {
start = true;
startTime = System.currentTimeMillis();
loadImage();
timerRunnable = new Runnable() {
#Override
public void run() {
while (start) {
long time = System.currentTimeMillis() - startTime;
float mins = (float) time / (60 * 1000);
if (mins >= 0.1f) {
startTime = System.currentTimeMillis();
if (currentIndex < pictureIds.length) {
currentIndex++;
loadImage();
}
}
}
}
};
handler.postDelayed(timerRunnable, 1000);
}
private void loadImage() {
getActivity().runOnUiThread(new Runnable() {
#Override
public void run() {
if (currentIndex < pictureIds.length) {
descriptionImage.setImageResource(pictureIds[currentIndex]);
} else {
start = false; // finish
}
}
});
}
Thanks!
EDIT: Doesn't work if I post it to the imageview thread either, instead of the handler.
descriptionImage.postDelayed(timerRunnable, 1000);

What's wrong with this?
while the UI Thread is busy ( while (start) ) , waiting to your condition to became true ( if (mins >= 0.1f) { ), it can't take care of the rest (like drawing).
Why would it only update the last image?
because it can draw only when if (currentIndex < pictureIds.length) { is not true, start becomes false, and the UI thread can finally draw
If I start the code with just a "post" to the handler instead of a
"postDelayed" - the tablet just stays with a black screen. Why do I
have to start the code with a delay to make it work?
see point 1.
if you want to change your image every 3 seconds, you could keep using Handler#postDelayed. E.g.
start = true;
startTime = System.currentTimeMillis();
loadImage();
timerRunnable = new Runnable() {
#Override
public void run() {
currentIndex = currentIndex++ % pictureIds.length;
loadImage();
handler.postDelayed(this, 3000);
}
};
handler.postDelayed(timerRunnable, 3000);

The problem you're facing is that your while loop is running on the main thread. This means the UI never has a chance to update until after the while loop ends (thus why you're only seeing the final image). Try this as your start function:
private void start() {
timerRunnable = new Runnable() {
#Override
public void run() {
if (currentIndex < pictureIds.length) {
loadImage();
currentIndex++;
handler.postDelayed(timerRunnable, 6 * 1000);
}
}
};
handler.post(timerRunnable);
}

Update TextView every second in Android [duplicate]

This question already has answers here:
Update TextView Every Second
(11 answers)
Closed 4 years ago.
i want to update my textview every second.
on button click i am calling one method,
loopMethod(milli); //suppose milli= 50000 i.e 50 sec.
so my loopMethod(int m) is as follows:
public void loopMethod(int m){
timer=(TextView) findViewById(R.id.timerText);
if(m>=1000){
try {
timer.setText(""+m);//timer is a textview
System.out.println(m);
m=m-1000;
Thread.sleep(1000);
} catch(InterruptedException ex) {
ex.printStackTrace();
}
loopMethod(m);
}
}
so what i am expecting is, my timer textview should print the value of m every second.
but i am getting only console output i.e system.out.println(m)...
printing value on console working fine...
but its not updating my textview at all

You can use following code:
Runnable updater;
void updateTime(final String timeString) {
timer=(TextView) findViewById(R.id.timerText);
final Handler timerHandler = new Handler();
updater = new Runnable() {
#Override
public void run() {
timer.setText(timeString);
timerHandler.postDelayed(updater,1000);
}
};
timerHandler.post(updater);
}
In this line:
timerHandler.post(updater);
time will set for the first time. i.e, updater will execute. After first execution it will be posted after every 1 second time interval. It will update your TextView every one second.
You need to remove it when the activity destroys, else it will leak memory.
#Override
protected void onDestroy() {
super.onDestroy();
timerHandler.removeCallbacks(updater);
}
Hope it will help you.

You should use RxJava library to do so:
Subscription s =
Observable.interval(1, TimeUnit.SECONDS)
.observeOn(AndroidSchedulers.mainThread())
.subscribe(v -> {
// update your ui here
}, e -> {
});
// call when you no longer need an update:
if (s != null && !s.isUnsubscribed()){
s.unsubscribe();
s = null;
}
That's it. Do NOT use .postDelay(), Timer because it is error prone.

You might want to consider using the Chronometer class: https://developer.android.com/reference/android/widget/Chronometer.html
just use timer.start(); on the button click

Using handler can be used like this
TextView timer;
int m =0;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
timer=(TextView) findViewById(R.id.timerText);
Handler handler = new UpdateHandler();
m = 10;
handler.sendEmptyMessageDelayed(1, 1000);//start after 1000
}
class UpdateHandler extends Handler{
#Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
switch (msg.what) {
case 1:
timer=(TextView) findViewById(R.id.timerText);
timer.setText("Text :" +m);
m = m-1000;
sendEmptyMessageDelayed(1, 1000); //seng again after 1000
//add some stop logic
break;
default:
break;
}
}
}

Try this code Initialize textview in
onCreate
timer=(TextView) findViewById(R.id.timerText);
public void loopMethod(int m){
if(m>=1000){
try {
System.out.println(m);
m=m-1000;
final ScheduledThreadPoolExecutor c = new ScheduledThreadPoolExecutor(1);
c.schedule(new Runnable() {
#Override
public void run() {
timer.setText(""+m);//timer is a textview
c.shutdownNow();
}
}, 1, TimeUnit.SECONDS);
} catch(InterruptedException ex) {
ex.printStackTrace();
}
loopMethod(m);
}
}

I've added some logics to stop the Timer. If you have any qyestion, ask freely
private int m = 0;
private int milliseconds = 1000;
public void loopMethod(int m){
timer=(TextView) findViewById(R.id.timerText);
Timer t = new Timer();
//schedule a timer
t.scheduleAtFixedRate(new TimerTask() {
#Override
public void run() {
runOnUiThread(new Runnable() {
#Override
public void run() {
timer.setText(String.valueOf(m));//avoid using composite string in the setText
System.out.println(String.valueOf(m));
//remove from the total the amount of millisecond passed
m=m-milliseconds;
if(m <= milliseconds) { //or <= what you want
//stop the timer repeatitions
t.cancel();
}
}
});
}
//"0" is the amount of time to wait for the timer to start
//"milliseconds" is the duration
},0,milliseconds);
}
Add
For a correct analysis you should add more infos in your question. the problem of not-updating textview might be caused by the setText("" + int) because it's always better to avoid the setText with an int. I edited it with String.valueOf, but if it's not working you should add the xml and the onCreate
Hope this helped

I have created timer for seconds.
public class TimerForSeconds extends AppCompatActivity {
private int seconds = 60;
private TextView tvTimer;
private Handler mHandler;
private Runnable runnable = new Runnable() {
#Override
public void run() {
if(seconds == 0){
mHandler.removeCallbacks(runnable);
}
else{
tvTimer.setText(seconds + "");
seconds--;
mHandler.postDelayed(runnable,1000);
}
}
};
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.test_activity);
tvTimer = (TextView) findViewById(R.id.tv_timer);
mHandler = new Handler();
mHandler.postDelayed(runnable,1000);
}
}
//and also removCallback onDestroy too.

How to make Dynamic change of TextVIew and UI in general?

Good afternoon everyone
So, I'm trying to dynamically change textview's properties.
basically, I defined a Duration. and I want to my handler/runnable to append text to a textView until I reach the duration.
public class Dynamic_testActivity extends Activity
{
public Context context = null;
public TextView view = null;
public Handler mHandler = null;
public long startTime = 0L;
public final int duration_millis = 10000;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
context = getApplicationContext();
view = (TextView) findViewById(R.id.textView1);
view.append("\n");
mHandler = new Handler();
}
#Override
protected void onStart() {
super.onStart();
startTime = System.currentTimeMillis();
mHandler.post(new Runnable() {
#Override
public void run() {
view.append("Hell_yeah_!\n");
// 10 character lenght
}
});
}
}
So yes, it append the text once, because the run do so.
But how could I make some kind of loop, without blocking the UI Thread, and append text until the end of the duration.
That was the first step ...
The second part now ... In fact, I Want to change the color of the text.
using
Spannable WordtoSpan = new SpannableString(view.getText());
WordtoSpan.setSpan(new ForegroundColorSpan(Color.BLUE), 0, view.getText().length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
I want to the color changing to be dynamic for the duration ... like a karaoke ...
So, is it possible to make that in the runnable without having the UI Thread blocked until the end of the duration ? and How ?
If anyone could explain the complet process ? or post some source code
Solved.
Here is a basic example...
There is still a little trouble ... at the very beginning of the application, the whole textview is yellow, and after a second, it updates the display as it should be .
If any one knows why, advices are welcome =)
Note : there's only two simple Textview in the layout... Duration is in milliseconds... and there is 10 character in the dynamic textview to fit the duration ... So basically, one char = one second ...
public class Dynamic_testActivity extends Activity
{
public Context context = null;
public TextView view = null;
public TextView view2 = null;
public Handler handler = null;
public long start_time, current_time, elapsed_time = 0L;
public final int duration = 10000;
public int end = 0;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
context = getApplicationContext();
view = (TextView) findViewById(R.id.textView1);
view2 = (TextView) findViewById(R.id.textView2);
handler = new Handler();
}
#Override
protected void onStart() {
super.onStart();
start_time = Long.valueOf( System.currentTimeMillis() );
current_time = start_time;
handler.postDelayed(new Runnable() {
#Override
public void run() {
current_time = Long.valueOf( System.currentTimeMillis() );
elapsed_time = Long.valueOf(current_time) - Long.valueOf(start_time);
if ( elapsed_time >= duration + 30 ) {
Toast.makeText(context, "Done", Toast.LENGTH_LONG).show();
//finish();
} else {
end = (int) (elapsed_time / 1000);
Spannable WordtoSpan = new SpannableString(view.getText());
WordtoSpan.setSpan(new ForegroundColorSpan(Color.YELLOW), 0, end, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
view.setText(WordtoSpan);
view2.setText("time : " + elapsed_time);
handler.postDelayed(this, 10);
}
}
}, 10);
}
}

In your run() methond, you can call mHandler.post(this) (or use postDelayed to delay it)
There is property change animation in API level 14, but if you are targetting a lower version, use postDelayed repetively to change progressively the color of the text.

How to set a timer in android

What is the proper way to set a timer in android in order to kick off a task (a function that I create which does not change the UI)?
Use this the Java way:
http://docs.oracle.com/javase/1.5.0/docs/api/java/util/Timer.html
Or there is a better way in android (android's handler)?

yes java's timer can be used, but as the question asks for better way (for mobile). Which is explained Here.
For the sake of StackOverflow:
Since Timer creates a new thread it may be considered heavy,
if all you need is to get is a call back while the activity is running a Handler can be used in conjunction with a
Runnable:
private final int interval = 1000; // 1 Second
private Handler handler = new Handler();
private Runnable runnable = new Runnable(){
public void run() {
Toast.makeText(MyActivity.this, "C'Mom no hands!", Toast.LENGTH_SHORT).show();
}
};
...
handler.postAtTime(runnable, System.currentTimeMillis()+interval);
handler.postDelayed(runnable, interval);
or a Message
private final int EVENT1 = 1;
private Handler handler = new Handler() {
#Override
public void handleMessage(Message msg) {
switch (msg.what) {
case Event1:
Toast.makeText(MyActivity.this, "Event 1", Toast.LENGTH_SHORT).show();
break;
default:
Toast.makeText(MyActivity.this, "Unhandled", Toast.LENGTH_SHORT).show();
break;
}
}
};
...
Message msg = handler.obtainMessage(EVENT1);
handler.sendMessageAtTime(msg, System.currentTimeMillis()+interval);
handler.sendMessageDelayed(msg, interval);
on a side note this approach can be used, if you want to run a piece of code in the UI thread from an another thread.
WARNING: Handler's timer (or whatever controls delays) gets paused whenever the CPU goes to deep-sleep, but will continue once CPU wakes up (from where it was paused).
if you need to get a call back even if your activity is not running then, you can use an AlarmManager.

Standard Java way to use timers via java.util.Timer and java.util.TimerTask works fine in Android, but you should be aware that this method creates a new thread.
You may consider using the very convenient Handler class (android.os.Handler) and send messages to the handler via sendMessageAtTime(android.os.Message, long) or sendMessageDelayed(android.os.Message, long). Once you receive a message, you can run desired tasks. Second option would be to create a Runnable object and schedule it via Handler's functions postAtTime(java.lang.Runnable, long) or postDelayed(java.lang.Runnable, long).

As I have seen it, java.util.Timer is the most used for implementing a timer.
For a repeating task:
new Timer().scheduleAtFixedRate(task, after, interval);
For a single run of a task:
new Timer().schedule(task, after);
task being the method to be executed
after the time to initial execution
(interval the time for repeating the execution)

I hope this one is helpful and may take less efforts to implement,
Android CountDownTimer class
e.g.
new CountDownTimer(30000, 1000) {
public void onTick(long millisUntilFinished) {
mTextField.setText("seconds remaining: " + millisUntilFinished / 1000);
}
public void onFinish() {
mTextField.setText("done!");
}
}.start();

Probably Timerconcept
new CountDownTimer(40000, 1000) { //40000 milli seconds is total time, 1000 milli seconds is time interval
public void onTick(long millisUntilFinished) {
}
public void onFinish() {
}
}.start();
or
Method 2 ::
Program the timer
Add a new variable of int named time. Set it to 0.
Add the following code to onCreate function in MainActivity.java.
//Declare the timer
Timer t = new Timer();
//Set the schedule function and rate
t.scheduleAtFixedRate(new TimerTask() {
#Override
public void run() {
//Called each time when 1000 milliseconds (1 second) (the period parameter)
}
},
//Set how long before to start calling the TimerTask (in milliseconds)
0,
//Set the amount of time between each execution (in milliseconds)
1000);
Go into the run method and add the following code.
//We must use this function in order to change the text view text
runOnUiThread(new Runnable() {
#Override
public void run() {
TextView tv = (TextView) findViewById(R.id.main_timer_text);
tv.setText(String.valueOf(time));
time += 1;
}
});

It is situational.
The Android documentation suggests that you should use AlarmManager to register an Intent that will fire at the specified time if your application may not be running.
Otherwise, you should use Handler.
Note: The Alarm Manager is intended
for cases where you want to have your
application code run at a specific
time, even if your application is not
currently running. For normal timing
operations (ticks, timeouts, etc) it
is easier and much more efficient to
use Handler.

Here we go.. We will need two classes. I am posting a code which changes mobile audio profile after each 5 seconds (5000 mili seconds) ...
Our 1st Class
public class ChangeProfileActivityMain extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
Timer timer = new Timer();
TimerTask updateProfile = new CustomTimerTask(ChangeProfileActivityMain.this);
timer.scheduleAtFixedRate(updateProfile, 0, 5000);
}
}
Our 2nd Class
public class CustomTimerTask extends TimerTask {
private AudioManager audioManager;
private Context context;
private Handler mHandler = new Handler();
// Write Custom Constructor to pass Context
public CustomTimerTask(Context con) {
this.context = con;
}
#Override
public void run() {
// TODO Auto-generated method stub
// your code starts here.
// I have used Thread and Handler as we can not show Toast without starting new thread when we are inside a thread.
// As TimePicker has run() thread running., So We must show Toast through Handler.post in a new Thread. Thats how it works in Android..
new Thread(new Runnable() {
#Override
public void run() {
audioManager = (AudioManager) context.getApplicationContext().getSystemService(Context.AUDIO_SERVICE);
mHandler.post(new Runnable() {
#Override
public void run() {
if(audioManager.getRingerMode() == AudioManager.RINGER_MODE_SILENT) {
audioManager.setRingerMode(AudioManager.RINGER_MODE_NORMAL);
Toast.makeText(context, "Ringer Mode set to Normal", Toast.LENGTH_SHORT).show();
} else {
audioManager.setRingerMode(AudioManager.RINGER_MODE_SILENT);
Toast.makeText(context, "Ringer Mode set to Silent", Toast.LENGTH_SHORT).show();
}
}
});
}
}).start();
}
}

I'm an Android newbie but here is the timer class I created based on the answers above. It works for my app but I welcome any suggestions.
Usage example:
...{
public Handler uiHandler = new Handler();
private Runnable runMethod = new Runnable()
{
public void run()
{
// do something
}
};
timer = new UITimer(handler, runMethod, timeoutSeconds*1000);
timer.start();
}...
public class UITimer
{
private Handler handler;
private Runnable runMethod;
private int intervalMs;
private boolean enabled = false;
private boolean oneTime = false;
public UITimer(Handler handler, Runnable runMethod, int intervalMs)
{
this.handler = handler;
this.runMethod = runMethod;
this.intervalMs = intervalMs;
}
public UITimer(Handler handler, Runnable runMethod, int intervalMs, boolean oneTime)
{
this(handler, runMethod, intervalMs);
this.oneTime = oneTime;
}
public void start()
{
if (enabled)
return;
if (intervalMs < 1)
{
Log.e("timer start", "Invalid interval:" + intervalMs);
return;
}
enabled = true;
handler.postDelayed(timer_tick, intervalMs);
}
public void stop()
{
if (!enabled)
return;
enabled = false;
handler.removeCallbacks(runMethod);
handler.removeCallbacks(timer_tick);
}
public boolean isEnabled()
{
return enabled;
}
private Runnable timer_tick = new Runnable()
{
public void run()
{
if (!enabled)
return;
handler.post(runMethod);
if (oneTime)
{
enabled = false;
return;
}
handler.postDelayed(timer_tick, intervalMs);
}
};
}

I am using a handler and runnable to create a timer. I wrapper this in an abstract class. Just derive/implement it and you are good to go:
public static abstract class SimpleTimer {
abstract void onTimer();
private Runnable runnableCode = null;
private Handler handler = new Handler();
void startDelayed(final int intervalMS, int delayMS) {
runnableCode = new Runnable() {
#Override
public void run() {
handler.postDelayed(runnableCode, intervalMS);
onTimer();
}
};
handler.postDelayed(runnableCode, delayMS);
}
void start(final int intervalMS) {
startDelayed(intervalMS, 0);
}
void stop() {
handler.removeCallbacks(runnableCode);
}
}
Note that the handler.postDelayed is called before the code to be executed - this will make the timer more closed timed as "expected". However in cases were the timer runs to frequently and the task (onTimer()) is long - there might be overlaps. If you want to start counting intervalMS after the task is done, move the onTimer() call a line above.

I believe the way to do this on the android is that you need a background service to be running. In that background application, create the timer. When the timer "ticks" (set the interval for how long you want to wait), launch your activity which you want to start.
http://developer.android.com/guide/topics/fundamentals.html (<-- this article explains the relationship between activities, services, intents and other core fundamentals of Android development)

I used to use (Timer, TimerTask) as well as Handler to kick off (time-consuming) tasks periodically. Now I've switched the whole to RxJava. RxJava provides Observable.timer which is simpler, less error-prone, hassle-free to use.
public class BetterTimerFragment extends Fragment {
public static final String TAG = "BetterTimer";
private TextView timeView;
private Subscription timerSubscription;
#Override
public View onCreateView(LayoutInflater inflater,
#Nullable ViewGroup container,
#Nullable Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_timer, container, false);
}
#Override
public void onViewCreated(View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
timeView = (TextView) view.findViewById(R.id.timeView);
}
#Override
public void onResume() {
super.onResume();
// Right after the app is visible to users, delay 2 seconds
// then kick off a (heavy) task every 10 seconds.
timerSubscription = Observable.timer(2, 10, TimeUnit.SECONDS)
.map(new Func1<Long, String>() {
#Override
public String call(Long unused) {
// TODO: Probably do time-consuming work here.
// This runs on a different thread than the main thread.
return "Time: " + System.currentTimeMillis();
}
})
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Action1<String>() {
#Override
public void call(String timeText) {
// The result will then be propagated back to the main thread.
timeView.setText(timeText);
}
}, new Action1<Throwable>() {
#Override
public void call(Throwable throwable) {
Log.e(TAG, throwable.getMessage(), throwable);
}
});
}
#Override
public void onPause() {
super.onPause();
// Don't kick off tasks when the app gets invisible.
timerSubscription.unsubscribe();
}
}

For timing operation you should use Handler.
If you need to run a background service the AlarmManager is the way to go.

this example start the timer unitl destroyed in Kotlin
private lateinit var timerTask: TimerTask
timerTask = object : TimerTask() {
override fun run() {
Log.d("KTZ", "$minutes:$seconds");
timeRecordingLiveData.postValue("$minutes:$seconds")
seconds += 1;
if (seconds == 60) {
Log.d("KTZ", "$minutes:$seconds");
timeRecordingLiveData.postValue("$minutes:$seconds")
seconds = 0;
minutes += 1;
}
}
}
Cancel the timertask in onDestroy()
timerTask.cancel()

Develop Reference

The Android operating system is a mobile operating system that was developed by Google (GOOGL?) to be primarily used for touchscreen devices, cell phones, and tablets.

Handler postdelayed is unaffected for less than 10 milliseconds - android

Related

Handler doesn't work correctly

Changing image on Android thread

Update TextView every second in Android [duplicate]

How to make Dynamic change of TextVIew and UI in general?

How to set a timer in android

Categories

Resources