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Passing data from receiver to activity

I am really stuck. After test lots of different approaches. I'm asking this question.
I'm trying to make an app which should alert the users at the specific date and time, like lots of other apps that you have definitely seen before. I'm using BroadcastReceiver as it should. I register it in manifest to activate it the first time the app gets installed and after restarting the phone but the problem is in android 3.1- taskkillers can kill this receiver so I thought it would be better to activate it again each time the app gets opened but The problem is that I don't know how many instance I'm creating so the first question is:
How to get the active receiver?
so I can make a decision upon it. If it is not active so I can active it again.
What I'm doing within onReceive is: getting data from database and comparing the time and date to now. If the app is not open I want to notify the user in notification area and pass extra data to the app' which is working pretty well. But if the app is open I do not want to notify the user in notification area, instead I want to pass data to an activity and alert the user in my app. I made my activity singleTask and used startActivity to pass data to the activity also I used onNewIntent method to handle new data but the problem is what if the user is using another activity. The second and third questions are:
How to know if my app is open? (I used ActivityManager.getRunningTasks but I realized it is not a good solution because it is an api for Task Manger apps.)
how to pass data from receiver to my activity? (I used interface to pass data from fragment to activity so I thought it can be used here but it does not work here)
After a lot of exertion -Reading and Trying- I know i'm still doing wrong So please guide me.

I suggest that you start a ServiceIntent from the Broadcast reciever. and from there you can send an intent that you can catch in the activity

Okay no one answered my question but I got it myself so here is my own answer:
Every receiver has only one instance and you can just enable or disable it. So to ensure that it is working you can enable it in your activity every time it gets run.
Within onReceive instead of doing stuff there, start a service and in your activity bind the activity with this service so in onBind and onUnbind method you can change a Boolean value and make decision upon it. In onBind make the value True which means your app is open and vice versa in onUnBind.
And finally the best way to pass data from service to activity is using Interface.
Now my app is working just like I want. . Hope to be helpful and save someone's time.

how to callback into various activities from a android library

I’ve written a library for Android, upon initialising the library I register for call backs for location updates, subscription status changes, library status changes and various other updates...
Originally, I wanted all these updates to call back to a controller in my android UI app, and then for the controller to launch activity A, pass on the messages from the controller to activity A and so on. Or launch activity B for signing up for a subscription and forward messages to this etc
However, it appears that there isn’t a way to achieve this - Because each activity is in isolation? Unless I’m mistaken?
So what are my options here? It sounds like I either have to use one activity for the whole app and swap the UI’s which after looking into it doesn’t appear to be the way to go?
I did try to subclass Application, which worked and gave me access to my library from an activity – but I want it the other way around. Is this possible? would wrapping the library in a service achieve what I want to do?

You could use broadcasts and send them from your library. Each of your activities would have to register a BroadcastReceiver in their onResume() method and unregister it in their onPause() method. This would be comparatively easy when you use a common base class for your activities. You could then send commands from your library to whatever activity is currently active.

Is there a way to know why your application was not given priority as a receiver

I'm trying to override the default incoming screen, something that I know is possible in all edition of Android as fullscreencallerid does it (and well).
If I register a receiver and start an activity, I successfully replace the view with my activity. If however I start filtering by EXTRA_STATE, the default incoming call screen appears.
I suppose what would help is somehow seeing what the hell is android thinking at that point, and why it preferred the default receiver.
Is there a way to trace application lifecycle, even if it involves some heavy tweaking (It's purely for learning purposes).
Thank you.

Android StartActivtyForResult() from a Service

First I'm sorry for my english that is not so good :).
I am facing a problem to develop my app.
That is a general architecture scheme of my solution.
http://i.stack.imgur.com/ooTmE.png
To be quick, the app has to decode code bare but with two possible ways:
using exernal device (The constructor provides a sdk containing an android Service to communicate with the device),
use the camera of the mobile using the library Zxing which is possible to manage it with intent.
The goal of my own service is to manage some business code and make transparent the choice of the tool for the user.
I believed that was a good solution but I wanted to implement it and I had different problems.
My main trouble is that I cannot execute StartActivityForResult inside the service.
Do somebody have any suggestions for my problem whether a change in the architecture or a solution for the main problem?
#Laurent' : You have totaly right my service acts as an API adapter.
I will try to make the expected behaviour more clear.
I have an app that needs to recognize (real) objects which have QR codes on their top. This recognition action will be done several times by the user during the life of the app.
The user chooses to launch the recognition by clicking on a button (or otherwise but he knows that the recogntion will start). So no notification is needed.
The thing is he doesn't choose the way to do the recogniton. It is why, as you said, I implement an adapter.
The adapter chooses between :
Camera mobile or external device. The first is an activity coming from the Zxing library. The second one is a service that manages the external device. This service provides an interface to get back result.
One more thing, I need that my whole implementation (adapter and co) can be re-used by other apps that will also need to do recognition.
So my thought was to implement a service as an adapter to answer my two conditions (make transparent the choice for the user - and make the recognition available for other apps).
I hope you understand my problematic.

Given your architecture, your MyOwnService must act as an API adapter : it should provide a unified scanning API and address each external service specificities transparently.
Your expected behaviour is not clear enough to provide a solution that suits your needs but here are a few remarks that can be of some help.
Passive scanning:
Even if there are some workarounds : no activity should be launched from a service (not directly). Never. Bad. Services are background stuff, the most they will be permitted is to hint users with Notifications (this is point 2 of Justin excellent answer).
As a consequence there's nothing as a 'popup Activities' (and that's good!). If you need to continuously scan for barcodes, even when your activity is not run, then the only way to warn users is by using status bar notification.
Active scanning:
Inside your own activity you can bind to your wrapper service and make it start scanning for codebars. When it finds one it has to message your activity. Your Activity message handler has complete access to the UI to inform the user of your findings.
You selected Active Scanning in your edit, your problem is therefore to find a way for your service to actively notify your main application (the one that started the active scanning) that a new item has been scanned successfully.
You do NOT do this by starting a new activity (remember: this is bad) but you can bind to a service and/or use Messages between the wrapper service and the application.
I advice you take the time to read (and more time to comprehend) this android developer article on BoundServices and especially the part about Messengers.
A full example of Two Way Messaging between a Service and an Activity can be found in the following android examples : Service & Activity
Warning: designing robust, full blown AIDL-based services is a tough job.

Two ways you could solve this problem.
1) Have MyOwnService do a callback into MainActivity telling it to launch your ScanActivity.
- This is a better approach if MyOwnService's task is only going to be running while MainActivity is running and if the user would expect the ScanActivity to come up automatically.
2) Have MyOwnService create a notification that will let the user access the ScanActivity.
- This is a better approach if MyOwnService's task might be running longer than the life span of MainActivity. That way, you can let the user know, unobstrusively, that they might want to access the ScanActivity.

So finally I changed my architecture.
I make the choice to delete myOwnService and to create an intermediate activity that will be my API Adaptater.
This activity will have a dialog.theme to look like a dialog box indicating that a recognition is under execution.
If the recognition uses the external device this activity will stay at the foreground otherwise the camera activity will start (Being managed by the intermediate activity).
Thank to that I can manage my result from the intermediate activity and do not have an android strange architecture, keeping my business code for the recognition outside my main app.
Service was not the good choice.
Thanks a lot for you help and your time.

movement of phone causes unexpected result in code

I am developing an android app which makes no reference to the sensor aspect of the phone. At a certain pint the program sends an sms and then sleeps for five minutes. If I move the phone during this sleep period a dialog box displayed earlier reappears. I realise this is rather vague without code at this stage but to start with is this something to be expected. I am wondering if one of the broadcast listeners is being triggered by the movement but even if this is so I cant make the connection with the dialog box. Any pointers will be much appreciated.

Fist off, I would take care of the orientation change possibility by forcing the app into an orientation by using the option in the manifest file.
Second, I would look at what other apps are on the device that might have an affect on this functionality. Assuming by your question, your app uses BroadcastReceivers. If this is the case, provided your business logic permits, use explicit intents ( new Intent(this, )) in place of implicit intents and receivers. If this is not possible because of business logic, then perhaps using permissions to protect against accidental implicit intent receive triggers. Ref: http://developer.android.com/guide/topics/manifest/permission-element.html (its a good starting place anyways).
Without more info on your specific business logic or source code I can't go much deeper into the problem, but my first suggestion would probably give the simplest result. Just remember to set this attribute for each activity that this problem affects.
Steve.