I am calling a Master/Detail activity in android by clicking on a button placed in another activity (UserActivity). The strange thing is, that if i click the back button in the Master/Detail activity, I loose the Data in the state of the UserActivity. It wants to execute the onCreate Method again.
If I click on the login-button in the LoginActivity where i am redirected to the UserActivitiy and i go back with the Back-Button of the "Smartphone", the username and password i typed are still there. So there i do not loose the data.
Is there a difference between the back-button of the Smartphone and the back-button at the top of the program? I am a bit confused now and i know how to persist the state of the Activity. But my question is, why i am having this behavior on the one side and on the other not.
Just in case you will leave the question like this and don't add code:
What will probably help is checking for the amount of items that are already there. When I ran into this issue, the onStart() got called so quickly that it seemed to me that the Activity has lost the data. Actually it DID have the data, but calling onCreate/onStart (I'm in a Fragment) NULLed it.
What I did to avoid this is to check if there is a need to load items in the list. If there is, it calls a method that contains what the old onCreate/onStart did. If there is no need to load data, it will just skip the step and live with the "old" data happily for the rest of its life.
#Override
public void onStart() {
super.onStart();
if(DummyContent.ITEMS.size()<3){
initializeApp();
}
}
void initializeApp(){
videoTitles=new ArrayList<String>();
videoUrls=new ArrayList<String>();
. . .
}
Related
i have two simple questions (hope so).
First i want to close my app, when the user hits the homebutton in my HomeFragment, because there is a counter (Days,Hours) and when I click the home Button and come back later there is still the old value.
Then i have to close the app via backbutton and start again. So i want my app to get killed, when I hit the home button.
Then i have a button to delete the last value, on which the counter is based. When I hit the button i want to run my homeFragment again. Should i just create a funnction which calls, the homefragment.onCreate again?
When I hit the button i want to run my homeFragment again. Should i just create a funnction which calls, the homefragment.onCreate again?
No, these functions are meant to be called by the system.
You are probably looking for the onStop() method (also called by the system)
protected void onStop()
{
super.onStop();
// clear counter e.g.
myCounter.setText("");
}
Other than this, it's kind of hard to tell what you want. Feel free to add more (if not all) of your code.
I have a ViewPager with a FragmentStatePagerAdapter and the starting page should be somewhere in the middle. But when the user goes to another Activity and then comes back, the page number should be saved, so that he returns to the same page. There is probably an easy way to get this done, but I can't find the solution.
Usually the current page number will be saved, so this is not the point. The problem is that I don't know where to put the code that sets the starting page at first, because when I put it in onCreate, the starting page will be shown even if I come back from a different Activity.
I also tried saving the number in a variable in the onPause method:
this.currentPageNumber = viewPager.getCurrentItem();
But next time when onStart() is called, the variable currentPageNumber is null, so it seems that variables are not saved after onDestroy().
I could use a static variable, but it feels wrong. Is there a better solution?
EDIT: Sorry, I didn't make clear enough, that I want the saved page only be opened, if I come back to this Activity after I launched it. Every time I start the Activity from the launcher, the starting page should be shown and not the saved page.
EDIT 2: The behaviour I want to have is exactly the same as the Google Calendar app has when you open the day or week perspective. If I open this app, the current day will be shown. If I swipe to another day, then open settings, then press back, this other day is still be shown. But if I restart the app, again today will be shown.
After you have initialised your viewpager, use this method :
viewPager.setCurrentItem(int position)
Or this :
viewPager.setCurrentItem(int position, boolean withAnimation)
You can save the last position by using SharedPreference in the onPageSelect() method where you can get the position of each page. You have to implement the OnPageChangeListner in order to have this method.
Edit
Your question wasn't clear :
Sorry, maybe I didn't express my problem well enough. I want the starting page to appear everytime I start my app. But if I enter the activity by the back-button (for example if I opened my settings activity and then go back) the last viewed page should be shown. The solution provided in the link will lead to the safed page everytime I open the app
I don't know why you want to change this, it's a normal behavior, read this.
But if you insist, you can always use setCurrentItem() method in the onResume of your Activity/Fragment, thus the first page will always be shown after your Activity/Fragment gets resumed.
Edit 2
That can still be done by setCurrentItem. In your adapter, try to detect the index of the page of the current day. Create a method that returns that field from outside the adapter. And then after you have initialised your ViewPager,
viewpager = (ViewPager) findViewById(R.id.viewpager);
viewpager.setAdapter(adapter);
setCurrentItem(adapter.getCurrentDayPosition()) // or something like that ...
The method in the adapter :
public int getCurrentDayPosition() {
return this.currentDayPosition // this a field of the adapter.
}
I have the same requirement to show the default page whenever the onCreate of the ViewPager hosting Activity is called and show the current page for all the other cases including the motivating case: when user navigate back from the Activity started from the current page (onCreate won't be called in this case). My solution is based on the time spend between onCreate and onResume.
If the time between onCreate and onResume is shorter then a threshold (I use 1s assuming onCreate could be finished within 1s which we really wanted for the good programming practice), then we believe this is the first time the onStart/onResume is called right after the onCreate, otherwise we believe it is about all the other cases including our motivating case.
Then we only need to set the current timestamp in onCreate and do the time comparison in onResume to make the decision to set the current item of ViewPager to default or current. Note that we need to save the current page number in onPause in SharedPreference.
I am not claiming this idea is perfect but it works fine for me so far. Let me know if you are interested in the implementation and I will post my code upon your request.
i think this solve your problem , because first time you launch your activity there is no instance saved (savedInstanceState) ...
read comments in the post ...Android :Save View Pager State ...
I'm running into a bit of a problem.
I have a PreferenceActivity with a list of headers, each pointing to a fragment. Those fragments are shown as a single pane (small display).
In order to exit a header fragment and go back to the list of headers of the PreferenceActivity itself, I press the back button (as a user), or call getActivity().onBackPressed() if I need to get back to the list after the user pressed a button on the UI.
This brings me back to the header list PreferenceActivity, but it also calls the onDestroy() method of that activity.
This is what I don't understand:
Why does it call the onDestroy() when the activity itself is clearly visible? And why doesn't it call the onCreate() after that, again, since the activity is visible?
This also has a side effect of calling the onReset() of a loader I use to create the list of data that produces the headers in the first place. That in turn makes it look like the header list hasn't changed, even when I have removed an item from the list, and thus reduced the number of headers. If I actually close and reopen the PreferenceActivity, the header list will be correct, which shows that the loader itself is working.
I don't fully understand what is happening here without code. But from the sounds of it you are calling onBackPressed() for the activity, thus what happens happens irrespective of fragments. Try overriding onBackPressed() in the activity and handle your fragment transactions there.
Headers launch new activities in single pane mode. That is likely why you are seeing onDestroy() for the same named activity, as it launches the same activity with a different intent it seems.
For future readers.
In my app I have situations where I need to get a user back to some activity that preceded(not necessarilly directly) the current one. All of those previous acitivities might need Intent parameters in onCreate.
So, my question is there any easy way to get user back to an activity that might not be the direct previous activity he's been on and is it possible to avoid manual workaround of saving/restoring those previous activities' intent parameters ?
Consider an example: there's a global search-bar that can provide users with suggestions on products; once they hit one of suggested items they get moved on a product-view activity where they can reload this activity with another product - walk through. After a couple of such reloads they might decide to go back to the activity where the search was initiated, but it might not the closest to the current one.
UPD: There also should be a possibility to go back in B activities sequence.
Using startActivityForResult() while loading a new activity and using finish() to close the launched activity on back press can solve your problem.
Today I was testing my app (wich is a very simple note application) but some strange behaviour occur .
The app consists of a big ListView which displays all the notes and a button to make a new note (activity A).
When I press the button to "Add new note",it takes me to the activity B
(with all the fields like title and text).
When I press "Add" ,it take me back to the activity A and displays ok
the new Note .
The thing is that I started pressing BACK and it began to take me "back in time" where some notes were still not created,until it reached the time they were 0 notes .
Since I am new to Android devel ,is this normal or is it something wrong with my app ?
When you go from one activity to another then you should finish your activity and then start new activity.
Try the below code:
finish();
startActivity(new Intent(CurrentActivity.this,NewActivity.class));
You probably need to implement some sort of refresh method to update your ListView. Depending on how you are persisting the data, you could create a method that retrieves the latest data and then updates the adapter for the ListView. Once you have that implemented, you should call the method in onResume().