When i unlock my device to see my application, the process in onResume() is launched. How do I cancel the events of unlock, to avoid onResume() from processing?
OnResume is always called when your Activity was in background (e.g. other App, Lockscreen, Homescreen... is shown).
Look at the Activity Life Cycle to check if you can move your code from onResume() maybe to onStart() to fix your issue.
To prevent unlock your device use below flag in your activity.
WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
Code
getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
Note :
As stated on the Activity lifecycle docs, onCreate and onResume will always both be called the first time an Activity is started. When going back to Activity, at least onResume will be called
Related
Will my Android Activity always call onResume() when it goes to the foreground?
Yes, based on Activity lifecycle.
First of all, I suggest to look at the Android Activity Life-cycle management.
http://developer.android.com/training/basics/activity-lifecycle/starting.html
The Activity Lifecycle always rest till onResume() method when the screens comes fully visible on the foreground otherwise it may stop at onStart() when the screen view is partially visible possibly blocked by a modal dialog.
My app does a lot of setting up in onCreate and then in onResume.
Is it possible that if a device rotation occurs while onCreate is being performed then onResume won't be called?
I'm asking because I receive many crash logs happening in onPause(). The crashes occur, because in onResume() I ALWAYS register some listeners and in onPause they are ALWAYS unregistered. Exception is thrown when a listener that hasn't been registered is unregistered.
So: is it possible that onResume() is not called at all before onPause()?
is it possible that onResume() is not called at all before onPause()?
No. Never.
onResume() Called just before the activity starts interacting with the user. At this point the activity is at the top of the activity stack, with user input going to it.
Always followed by onPause(). So if onPause() of an Activity is being called means onResume() must called.
Read A summary of the activity lifecycle's callback methods for more details.
Is it possible that if a device rotation occurs while onCreate is being performed then onResume won't be called?
Yes possibly, although it seems highly unlikely. Even if you are doing a lot of stuff in onCreate in relative terms you should never be doing so much that it takes several seconds. In other words, for a user to start your Activity and then rotate the device is going to take some finite 'human reaction' time.
If you believe this is happening then...
Reduce the amount of stuff going on in onCreate
NEVER assume that your listeners are registered - check first. Example, when you register a listener set a boolean and only unregister if it's true and set the boolean to false...
Psuedo code:
// To register
if (!isListenerRegistered) {
register(...);
isListenerRegistered = true;
}
// To unregister
if (isListenerRegistered) {
unregister(...);
isListenerRegistered = false;
}
No, http://developer.android.com/training/basics/activity-lifecycle/pausing.html
the sequence is always onCreate(), onStart(), onResume(), then the user sees the activity in the foreground(totally visible). Once another activity starts, this one goes to onPause(), then onStop().
When the device is rotated the activity gets reloaded, so it goes through the destruction steps depending on when the rotation occured. After onDestroy() is called, the creation starts again with onCreate(). Add log messages in your callbacks to see this:
Log.d("DEBUG", "In Activity A's onCreate()");
You can filter your logcat via the log tag, in this case "DEBUG" and see the lifecycle for yourself. Or just step through with the debugger.
I have read documentation on onResume() and onStart() but one thing I'm still not cleared is under what scenario does onResume() get called without onStart() being called before it?
Please Refer to the Android Activity Lifecycle Documentation.
onStart is called when your application first starts.
If the user click the home button, or another app takes focus, onPause will be called.
If the activity regains focus, while stil running on the device, onResume will be called, and onCreate will NOT be called again.
If the user uses the activity manager to close the application, and then relaunches it, onCreate will be called again.
Note, every time onCreate is called, onResume is also called.
Check below chart:
In case your activity is visible but not active - onPause will be called, and then when you return to this Activity - onResume
One such scenario where onResume() is called without onStart() being called is change of Focus. Think about a dialog popping up on the screen while you're using the application. This is the case when onPause() is called, followed by onResume() after dismissal of dialog.
onStart() gets called once each time the app is launched and is actually called after oncreate()
onResume() gets called instead if the app is already running, just in the background.
if you use onPause(), on Resume will likely get called when you bring your app up again, basically onResume() is a reusable onStart() for when the app is already started.
onResume can sometimes be called when switching activities, onStart only gets called when creating one.
onResume() is called without onStart() when the activity resumes from the background.
Can anyone give me an example that uses onResume() in Android?
Also, if I want to restart the activity at the end of the execution of another, which method is executed—onCreate() or onResume()?
And if I want to update data, how do I put it in onResume()?
Any Activity that restarts has its onResume() method executed first.
To use this method, do this:
#Override
public void onResume(){
super.onResume();
// put your code here...
}
Restarting the app will call OnCreate().
Continuing the app when it is paused will call OnResume(). From the official docs at https://developer.android.com/reference/android/app/Activity.html#ActivityLifecycle here's a diagram of the activity lifecycle.
The best way to understand would be to have all the LifeCycle methods overridden in your activity and placing a breakpoint(if checking in emulator) or a Log in each one of them. You'll get to know which one gets called when.
Just as an spoiler, onCreate() gets called first, then if you paused the activity by either going to home screen or by launching another activity, onPause() gets called. If the OS destroys the activity in the meantime, onDestroy() gets called. If you resume the app and the app already got destroyed, onCreate() will get called, or else onResume() will get called.
Edit: I forgot about onStop(), it gets called before onDestroy().
Do the exercise I mentioned and you'll be having a better understanding.
When you open the app it will go through below states:
onCreate() –> onStart() –> onResume()
When you press the back button and exit the app
onPaused() — > onStop() –> onDestory()
When you press the home button
onPaused() –> onStop()
After pressing the home button, again when you open the app from a recent task list
onRestart() –> onStart() –> onResume()
After dismissing the dialog or back button from the dialog
onResume()
If a phone is ringing and user is using the app
onPause() –> onResume()
After the call ends
onResume()
When your phone screen is off
onPaused() –> onStop()
When your phone screen is turned back on
onRestart() –> onStart() –> onResume()
Happy Coding...#Ambilpura
Most of the previous answers do a good job explaining how, why, and when to use onResume() but I would like to add something about re-creating your Activity.
I want to know if I want to restart the activity at the end of exectuion of an other what method is executed onCreate() or onResume()
The answer is onCreate() However, when deciding to actually re-create it, you should ask yourself how much of the Activity needs to be re-created. If it is data in an adapter, say for a list, then you can call notifyDataChanged() on the adapter to repopulate the adapter and not have to redraw everything.
Also, if you just need to update certain views but not all then it may be more efficient to call invalidate() on the view(s) that need updated. This will only redraw those views and possibly allow your application to run more smoothly. I hope this can help you.
onResume() is one of the methods called throughout the activity lifecycle. onResume() is the counterpart to onPause() which is called anytime an activity is hidden from view, e.g. if you start a new activity that hides it. onResume() is called when the activity that was hidden comes back to view on the screen.
You're question asks abou what method is used to restart an activity. onCreate() is called when the activity is first created. In practice, most activities persist in the background through a series of onPause() and onResume() calls. An activity is only really "restarted" by onRestart() if it is first fully stopped by calling onStop() and then brought back to life. Thus if you are not actually stopping activities with onStop() it is most likley you will be using onResume().
Read the android doc in the above link to get a better understanding of the relationship between the different lifestyle methods. Regardless of which lifecycle method you end up using the general format is the same. You must override the standard method and include your code, i.e. what you want the activity to do at that point, in the commented section.
#Override
public void onResume(){
//will be executed onResume
}
KOTLIN
Any Activity that restarts has its onResume() method executed first.
To use this method, do this:
override fun onResume() {
super.onResume()
// your code here
}
Re-review the Android Activity Lifecycle reference. There is a nice picture, and the table showing what methods get called. reference Link google
https://developer.android.com/reference/android/app/Activity.html
After an activity started, restarted (onRestart() happens before onStart()), or paused (onPause()), onResume() called. When the activity is in the state of onResume(), the activity is ready to be used by the app user.
I have studied the activity lifecycle a little bit, and here's my understanding of this topic:
If you want to restart the activity (A) at the end of the execution of another, there could be a few different cases.
The other activity (B) has been paused and/or stopped or destroyed, and the activity A possibly had been paused (onPause()), in this case, activity A will call onResume()
The activity B has been paused and/or stopped or destroyed, the activity A possibly had been stopped (onStop()) due to memory thing, in this case, activity A will call onRestart() first, onStart() second, then onResume()
The activity B has been paused and/or stopped or destroyed, the activity A has been destroyed, the programmer can call onStart() manually to start the activity first, then onResume() because when an activity is in the destroyed status the activity has not started, and this happens before the activity being completely removed. If the activity is removed, the activity needs to be created again.
Manually calling onStart() I think it's because if the activity not started and it is created, onStart() will be called after onCreate().
If you want to update data, make a data update function and put the function inside the onResume(). Or put a loadData function inside onResume()
It's better to understand the lifecycle with the help of the Activity lifecycle diagram.
I'm having a couple of problems with an alarm app I am developing.
The first thing that I think is a bit weird is that when an alarm goes of and wakes the phone up. These things happend.
oncreate
onresume
onpause
onresume
Why are they run in that order? The last two should not be called? And this is what's causes me big trouble, because when i press home or back on the phone, onPause is run, which I want to call finish() from. And that part works as it should, but that does not work when the phone wakes upp from sleep bacause of the onPause call...
Any ideas?
I also have a similar problem: i create an Activity and a Service in the background. When the service receive some data from the net it will bring-up the activity.
Everything works fine until the activity in in the onStop phase and the screen goes black.
When I have this situation and I request the activity to restart, I have:
onRestart
onStart
onResume
onPause
onNewIntent
onResume
As you can see I have an onResume, onPause and another onResume and the activity came to the user.
Seems that is because we use a singleTop or singleInstance Activity (maybe also appear on singleTask). The problem is that when you send an Intent to an already created singleTop Activity, your new intent active the onNewIntent() method. from the API you can see that:
An activity will always be paused
before receiving a new intent, so you
can count on onResume() being called
after this method.
so maybe this is why you receive onResume-onPause-onResume calls.
However this is a strange behavior!
I would suggest you look at how the official alarm application handles the events:
https://android.googlesource.com/platform/packages/apps/DeskClock
Do you really want to call finish() in onPause()? onPause() is called when the current activity is not in the foreground any more. Maybe you want to call finish() in your onStop() method instead. See the Activity lifecycle for details.