Develop Reference

Call activity direct from current activity

Can i call second activity from current activity without use intent? and why use intent, why not call second activity direct from the first activity?.
What does intent do in android?

Because to start any new Activity Android must have to go through the life cycle of an Activity. So it is necessary to use intent.

http://developer.android.com/reference/android/content/Intent.html
you can't ,see this link android is designed in this way to launch another activity

Intent says to Android you need open a new activity. Always when you need open a new Activity, you need "alert" the S.O before. Because of this we use Intent.
Activities doesn't work like a simple class, when we just instantiate.
This link will help you
http://www.vogella.com/tutorials/AndroidIntent/article.html

Android access activity1 from activity2

Hi i am new to Android application development.In my Application i have two activity Activity1 and Activity2.From activity1 i call Activity2 as Intent.I want to access activity1 from this Activity(activity2) without going to first activity is there any posible way?Pls guide me

The only thing which make sence is passing data from Activity 1 to Activity 2. To do it just pass some data through the intent:
intent.putExtra("key", "Your data here");
in second activity:
String data = getIntent().getExtra("key");
If this is not the case, then your task is wrong somewhere. When activity gone background, there is no sence to interact with it.

No, there isn't. Activity1 might even have been shut down.
If you want to pass DATA between the two activities, that's of course doable. Either by passing data on with the intent, by using http://developer.android.com/reference/android/content/SharedPreferences.html or any other storage you can access from both activities.

If from your second activity wants to change something on the previous one, then, instead of using
startActivity(...);
you should use
startActivityForResult(...);
Maybe this link can help.

So you have the scenario where you start activity B from activity A and you want to change some parameters when activity B is done ( your changes can't be propagated in real time because you can't be sure what is the state of activity A ). So the best way to implement this is to use activity result - for more info about it check Android: Capturing the return of an activity

How to stop an Activity from parent Activity?

_alerts = new Intent(homeActivity,Alertss.class);
homeActivity.startActivity(_alerts);
...
...
...
homeActivity.stopService(_alerts);
I need to stop the Activity i created from the object where i created it. I tried it in the way above but it did not work. Can any one suggest me a way to do this.

You can use Activity.startActivityForResult() and then Activity.finishActivity() passing in the same result code you used for starting it.
However, this does sound like something that would be better done just as a Dialog.

Access Activity in a static way

I have an activity which has a static method for updating a textfield. This way I can update this view from another activity.
But now I'm trying to get a Context variable in this static method which is not possible. I've tried declaring a Context variable and initialising it in onCreate ( context = getApplicationContext();)
But still I can't access context in this static method. How is this normally done?
edit: a little bit more information about my situation. I'm starting a countdowntimer in an activity(a) which updates another activity's(b) ``textfield every second. And it does this by accessing b's setTextField in a static way..

How is this normally done?
Accessing a TextView via a static method is not the best way to update the field from another activity. If you want to pass a value to the activity when it starts, you can send data via the intent (i.e. intent.getExtras). If you want to pass data back from a sub-activity, you can use startActivityForResult.

The way you are going is very strange. Why are you trying to change one activity content from another? May be you need to use startActivityForResult to strat a new activity and then return result from it and change views depending on it?

You might want to check some documentation on OO and using static functions. It is not considered a very good approach.
But as we are not talking about a better complete sollution: you can add a parameter with a context to the function, and just give it when you call the function :)

I would suggest the LocalBinder pattern to update the other Activity:
http://developer.android.com/resources/samples/ApiDemos/src/com/example/android/apis/app/LocalService.html

Can you do something like this?
something like this <viewobj>.getContext()
Ref: How can I start an Activity from a non-Activity class?

Whenever you're busy with Activity A, there's no point in updating something on Activity B as it is simply not shown to the user at that point in time.
Seems to me you need to have some kind of global variable here that can be picked up in the onResume of Activity B.
Checkout this question : How to declare global variables in Android?
It shows you how to use the Application class to maintain global application state, accessable from all activities when needed.

Can we create implicit Intent to call our own Activities

Is it possible to create implicit intent to call our own activity? If possible is it useful or better option is Explicit Intent?

please explain your situation more...
If a single Activity is there and you want to call the same activity again from this to have any refresh sort of thing...
Then its not a good idea...
All the views can be updated without calling the same activity again.
And if new view is to be generated then use another activity