Develop Reference

How to add a sleep timer to my Android app

My project is a radio app and I want to add a sleep timer so that the user can set it to close the app after a specified time.

Please use startTimer(long ms) to start countdown timer and cancel timer to stop. And use wakelock to continue timer after screen off.
CountDownTimer cTimer = null;
void startTimer(long time) {
if(!wakeLock.isHeld()) {
PowerManager mgr = (PowerManager) getApplicationContext().getSystemService(Context.POWER_SERVICE);
wakeLock = mgr.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "SonaHeartLock");
wakeLock.acquire();
}
cTimer = new CountDownTimer(time, 1000) {
public void onTick(long millisUntilFinished) {
timerSync = millisUntilFinished;
}
public void onFinish() {
timerSync = 0;
System.exit(0);
}
};
cTimer.start();
}
//cancel timer
void cancelTimer() {
if (cTimer != null) {
timerSync = 0;
cTimer.cancel();
cTimer=null;
if(wakeLock!=null && wakeLock.isHeld())
wakeLock.release();
}
}

Thread.sleep(2000);
will pause for 2 seconds (i.e 2000 ms). In an Android app I wrote several years ago I actually had:
Thread.currentThread().sleep(2000);
but I'm pretty sure the .currentThread() was not needed. I was just learning Java at the time.
See Oracle's doc.
In more detail, what I actually had was a separate task:
class TimerUpdater extends AsyncTask<String, String, Void>{
}
That periodically checked the time (pausing using Thread.sleep()) and displayed a countdown, and at zero set a flag that the main task periodically checked and ended the game when it saw it was set.
My app was terrible code, but I was learning both Java and Android at the same time as fast as I could, to make an app to help my kid in math class.
Android has changed a lot since then, though.

You can get the time from user and after that you can create one background process which count time everytime and check with user time. If both will match then immediately close your app

timer calling activity after back button is pressed

I am trying to make simple maths game. Aim of the game is to answer so many questions right in a certain time limit.
I have a timer which counts down and calls my final screen to set your highscore. Problem is, when testing the app if the back button is pressed before timer is done, it seems to continue in the background and my highScore screen randomly appears. How can I make this stop?
Here is the code for my timer:
/**
* timer method
*/
public void timer() {
new CountDownTimer(10000, 1000) {
public void onTick(long millisUntilFinished) {
}
public void onFinish() {
Intent i = new Intent(MainActivity.this, HighScoreScreen.class);
i.putExtra("Score", score);
startActivity(i);
resetScore();
finish();
}
}.start();
}

One solution to this very particular problem would be to override onBackPressed and cancel your timer there. On the other hand, if you want to cancel the timer when there is any interruption (e.g. user receives a call while using your app), you could perhaps place the cancel call in a lifecycle method like onStop.

Android Countdown Timer in Broadcast receiver doesn't update TextView

I am creating application which works with SMS service and FTP networking.
If user does not establish connectivity, it will try to reconnect again in 30 seconds.
I am using CountDownTimer with TextView to inform user about time left to reconnnect.
Either it will be successful or it will start counting again.
My problem is, that if counter restarts while activity is in background or the screen is locked, TextView keeps showing number "1" (it won't update) until the timer restarts again in foreground (but updating numbers without timer restart works fine in backround or lock, I am using wakelock in my foreground service).
After counter restarts again (so it won't stop counting) while application is in foreground, everything comes back to normal, TextView updates from freezed "1" to "30" and starts counting down to "1".
I think problem will be somewhere in communication between counter thread and background activity with UI, but I don't know nothing more about it.
I tried several things like:
creating setter and getter for miliseconds and update them in each
tick, then try to update textview from onReume(), didn't work.
create local variable for TextView inside timer, initialize it inside onTick() and
try to update text from there, also didn't work.
Thanks everyone for help, I will appriciate any advices.
Part of code relative to question:
private CountDownTimer cdt = null;
private final TextView getTextView_ActivityMainMenu_Timer(){
return (TextView) findViewById(R.id.ActivityMainMenu_TextView_Timer);
}
private BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
if(intent.getBooleanExtra("KEY_FAILED", false)){
cdt = new CountDownTimer(30000, 1000) {
public void onTick(long millisUntilFinished) {
getTextView_ActivityMainMenu_Timer().setText("" + millisUntilFinished / 1000);
}
public void onFinish() {
;
}
}
.start();
}
else
{
if(cdt != null)
cdt.cancel();
}
}
};

Finally I found solution of this problem. I didn't realize that I am unregistering the receiver in onPause() method. So I had to change it and put registration of broadcast into onResume() and unregister it only in onDestroy() method.

timer.scheduleAtFixedRate does not stop when i call cancel

At onCreate, I run a task that repeats every minute. Here how I do it:
myTimer = new Timer();
int delay = 30000; // delay for 30 sec.
int period = 600000; // repeat every 60 sec.
doThis = new TimerTask() {
public void run() {
Log.v("TImer","repeated");
wv.reload();
}
};
myTimer.scheduleAtFixedRate(doThis, delay, period);
All that code is in onCreate. So, when the app goes off from the screen, I can see in logcat that timer steel runs, and will not stop unless the app will be destroyed. So, in onPause of activity I call myTimer.cancel(); but it didnt help. I still can see updates in logcat, even when the app is not on the screen. So, how to stop timerTask?

Here is your code put into my file, with the values delay and period tweaked so I don't have to wait so long. I run the app. I see the messages in LogCat. I press the home button on my Galaxy S3. Then the messages stop in LogCat.
public class MainActivity extends Activity {
Timer myTimer;
TimerTask doThis;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
myTimer = new Timer();
int delay = 0; // delay for 30 sec.
int period = 1000; // repeat every 60 sec.
doThis = new TimerTask() {
public void run() {
Log.v("TImer","repeated");
}
};
myTimer.scheduleAtFixedRate(doThis, delay, period);
}
#Override
protected void onPause() {
myTimer.cancel();
super.onPause();
}
}

It could be that since the thread has already been sent out, it runs one last time. In the onLoad set a variable to true, then in the onPause set it to false. Then in your timer task only run your code if the variable is true.
Write to the log outside of the new if statement though. If it is indeed running it just one last time, then that might be your solution. But if it is still running it over and over multiple times after the onPause then don't take my solution.

The actual answer is: The onPause method needs to be defined correctly.
The whole story:
The questioner defined the onPause method wrong. That was the reason for asking this question.
I'm writing this because I spent too much time reading question, answers, code and comments. The real answer was hidden in the last comment.

Resuming CountdownTimer after rotation

I have a CountdownTimer that counts down from 60 seconds. This CountdownTimer works by setting a textView to the remaining milliseconds, but whenever i rotate my device, the CountdownTimer gets reset.
I know this happens because the Activity gets restarted on rotation. So i tried saving the time remaining in a bundle and then restoring it, after the Activity was restarted.
long transferValue;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_playtimemode);
Log.d("Debug", "onCreate: " + transferValue);
long setTime = 60000;
long difference = setTime - transferValue;
new CountDownTimer(difference, 1000) {
public void onTick(long millisUntilFinished) {
millisUntilFinishedToSave = millisUntilFinished;
tvCountdown.setText("" + millisUntilFinished / 1000);
}
public void onFinish() {
tvCountdown.setText("done!");
}
}.start();
}
#Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putLong("millisKey", millisUntilFinishedToSave);
}
#Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
transferValue = savedInstanceState.getLong("millisKey");
Log.d("Debug", "onRestoreInstanceState(): " + transferValue);
}
This however doesn't work. I am intializing transferValue at the top of this code (hence it returning 0), but how can i else save the data from the savedInstanceState to the CountdownTimer?
07-06 20:21:30.038: D/Debug(28995): onCreate: 0
07-06 20:21:30.043: D/Debug(28995): onRestoreInstanceState(): 55994

I would give your timer it's own thread. Your timer is being stopped because it's on the UI thread (as you stated) and when the UI redraws the Activity is re-initialized. All long running processes should have their own thread. Rule of thumb: get out of the UI thread as soon as possible.
Here is an example of using a Service. This service will start when called and stay in memory regardless of screen orientation changes or even activity focus changes.
Here is the service:
public class Timer extends Service {
#Override
public IBinder onBind(Intent i) {
return null;
}
#Override
public int onStartCommand(Intent i, int flags, int startId) {
// Put your timer code here
}
}
You will need to add this line to your manifest (somewhere between the application open/close tags):
<service android:name=".Timer" />
Then you can start the service at any time by using this (it's important to note that you can start it over and over again, the recursive calls do not make a new service.):
startService(new Intent(this, Timer.class));

Use System.currentTimeMillis to get the current system time, then add 60000 milliseconds to the time and store that as an end time. Then any time you have to change anything, just compare System.currentTimeMillis to the EndTime.
Endtime = System.currentTimeMillis + 60000;
then on every instance
TimeRemaining = Endtime - System.currentTimeMillis

The accepted answer makes the thing very complex. You can do it in a simpler way. The problem in your code is that Activity gets created on rotation (see Activity Lifecycle), so does the CountdownTimer instance.
I could write the whole example code but there is a nice answer from #Drew here: Android Innerclass TextView reference when activity resumes