Develop Reference

Running for loop periodically

I want to run a for loop every 5 minutes for an Android application. Is there a better method than this where less processing is done
for(;;) {
// code
final long NANOSEC_PER_SEC = 1000 * 1000 * 1000;
long startTime = System.nanoTime();
while ((System.nanoTime() - startTime) < 5 * 60 * NANOSEC_PER_SEC) {
}
}

CountDownTimer is a good class for this kind of work. It looks like this:
long duration = 12345;
long ticksInterval = 5000; // 5 second in millis
new CountDownTimer(duration, ticksInterval){
public void onTick(long remaining) {
// Do something each ticksInterval millis
}
public void onFinish() {
// Do something after duration millis
}
}.start();
That said, I don't think you can use this for an infinite amount of time since it requires an ending time. Though you can hack to restart it once it's finished.

You should go for set Repeat Alert for every 5 Minute and Run your code inside that .
Also you can go for use of Handler like below code .
final int REPEAT_CALL=2;
final int mFIVE_MINUTE=5*60*1000;
private Handler mHandler=new Handler(){
#Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
switch(msg.what){
case REPEAT_CALL:
//This will get execute by every 5 minute so write you for loop code here.
mHandler.sendEmptyMessageDelayed(REPEAT_CALL,mFIVE_MINUTE);
break;
}
}
};
You can start it by calling this :
mHandler.sendEmptyMessageDelayed(REPEAT_CALL,10);
Then after it will call by every 5 minute .
You can cancel this call back by calling below method:
mHandler.removeMessages(REPEAT_CALL);

Automatically refresh image every 2 seconds android

So I am trying to have a picture automatically refresh every 2 seconds. I've tried the handler/timer method, but I'm confused as how to call it and for some reason can not get it to actually refresh...
private void refreshPicture(final String refreshRate, final String userName, final String userPicture) {
final Handler timerHandler = new Handler();
Runnable timerRunnable = new Runnable() {
#Override
public void run() {
long millis = Long.parseLong(refreshRate);
int seconds = (int) (millis / 1000);
int minutes = seconds / 60;
seconds = seconds % 60;
//my method where i refresh image
getUserPicture(userName, userPicture);
timerHandler.postDelayed(this, 500);
}
};
}

You forgot to initiate the first call of the runnable. After defining the timerRunnable, you have to call timerHandler.post(timerRunnable); once. Also, if you want to have it refreshed every 2 seconds, you have to put 2000 instead of 500 as value in postDelayed().
Don’t forget to call timerHandler.removeCallbacks(timerRunnable) when you want to stop refreshing.

Android countdown timer to time in future

I have an activity that receives two values, one for hour and one for minute. A future time, eg: 21:30
How can I set a countdown timer to run from the current time until the future time that was received ?
here is my timer code, currently set to 30sec for testing
CountDownTextView = (TextView) findViewById(R.id.CountDownTextView);
new CountDownTimer(30000, 1000) {
public void onTick(long millisUntilFinished) {
CountDownTextView.setText("" + millisUntilFinished / 1000);
}
public void onFinish() {
CountDownTextView.setText("Unlocking!");
}
}.start();
Many thanks

Calendar targetTime = Calendar.getInstance();
targetTime.set(Calendar.HOUR_OF_DAY, hour);
targetTime.set(Calendar.MINUTE, minute);
new CountDownTimer(targetTime.getTimeInMillis()-System.currentTimeMillis(), 1000) {
// here comes your code
}

First take future timeing then take current timeing calculate difference between it in terms of millisecond then pass this millisecond value as a input to countdown timer class its very easy way to do it

CountDownTimer Check every two seconds

I have one CountDownTimer and i want to do an action for every two wasted seconds.
countdowntimer = new CountDownTimer(10000, 1) {
#Override
public void onTick(long millisUntilFinished) {
}
#Override
public void onFinish() {
}
}.start();
For example when it starts time remaining = 10 seconds
When time remaining = 8 seconds I want to do an action
When time remaining = 6 seconds I want to do an action
and so on......

Just check if it is divisible by 2.
#Override
public void onTick(long millisUntilFinished) {
long seconds = millisUntilFinished/1000;
if ((seconds % 2) == 0)
{ // even number--do some action }
}
This is assuming you are calling the onTick() every second like
countdowntimer = new CountDownTimer(10000, 1000) {
This is probably preferable for you
Setting it up to call every 2 seconds should also work and better but leaving the original answer in case someone needs to call onTick() more often
countdowntimer = new CountDownTimer(10000, 2000) {
then you could just do the action with every call to onTick()
CountDownTimer Docs

Android Handler freezes GUI

I'm trying to port a PC Java program to the Android platform. The PC application uses a Swing.Timer to trigger an update every second. The associated listener, upon being called, gets new data from a database, then updates/redraws the screen using Graphics2D. I've learned how to use Android's Canvas to draw the same things that I do with the PC application. Now I'm trying to learn how to use the equivalent Timer in Android. Unfortunately things don't seem as straightforward on the Android platform. There are Timers, Handlers, AlarmManagers, and AsyncTasks. It would seem that AsyncTasks and AlarmManagers are more appropriate for one time (heavy duty?) tasks (right? wrong?) With regard to Timers and Handlers, I've seen many posts that say don't use Timer, use Handlers instead. I found the approach used in the code below somewhere out there on the web and tried it. It seems like it should do what I want but it hangs the GUI whenever I click the stop button. Does anyone know why it does that?
Thanks times a million
Bill
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
dateFormat = new SimpleDateFormat(dateFormatString);
mHandler = new Handler();
mUpdateTimeTask = new MyRunnable();
Button button = (Button) findViewById(R.id.start_button);
button.setOnClickListener(new MyStartListener());
button = (Button) findViewById(R.id.stop_button);
button.setOnClickListener(new MyStopListener());
}
class MyStartListener implements View.OnClickListener {
public void onClick(View v) {
if (startUptimeMillis == 0L) {
startUptimeMillis = SystemClock.uptimeMillis();
mHandler.removeCallbacks(mUpdateTimeTask);
mHandler.postDelayed(mUpdateTimeTask, 100);
}
}
};
class MyStopListener implements View.OnClickListener {
public void onClick(View v) {
mHandler.removeCallbacks(mUpdateTimeTask);
}
};
class MyRunnable implements Runnable {
public void run() {
final long start = startUptimeMillis;
long millis = SystemClock.uptimeMillis() - start;
int seconds = (int) (millis / 1000);
int minutes = seconds / 60;
seconds = seconds % 60;
Calendar calendar = Calendar.getInstance();
calendar.setTimeInMillis(System.currentTimeMillis());
TextView tv = (TextView) findViewById(R.id.time_textView);
tv.setText(dateFormat.format(calendar.getTime()));
mHandler.postAtTime(this, (((minutes * 60) + seconds + 1) * 1000));
}
};
EDIT:
The problem is that postAtTime needs an absolute time at which to start, not a delay which is what my example is using. (See postAtTime here)
So I replaced all of the timing code above with the below and it does what I want!!:
long millis = SystemClock.uptimeMillis();
mHandler.postAtTime(this, millis+1000);

I don't see how this could hang your app, unless you mean the start button doesn't work any more... Perhaps you want to add this to your stop listener:
public void onClick(View v) {
startUptimeMillis = 0l; // Reset startUptimeMillis
mHandler.removeCallbacks(mUpdateTimeTask);
}
As far as Timers, AsyncsTask, etc... You are correct, the best way to program an event in the near future in Android is with a Handler and Runnable. AlarmManagers are not intended for fast callbacks like in animations and AsyncTasks are better for heavy duty computation.
I would like a to offer a simpler update Runnable:
class MyRunnable implements Runnable {
public void run() {
// You should make this a class variable and initialize it in onCreate(),
// there is no need to search for the same View every second.
TextView tv = (TextView) findViewById(R.id.time_textView);
final long now = System.currentTimeMillis();
tv.setText(dateFormat.format(now));
mHandler.postAtTime(this, 1000 - (now - start) % 1000); // Accounts for millisecond offsets over time
// mHandler.postDelayed(this, 1000); // Effected by minute offsets
}
};