Develop Reference

How to make a phone call without switching activities to a default calling app in android?

I'm trying to make a phone call from my app in a way it does not need to switch activities, But every guide I find has the following code snippet,
Intent callIntent = new Intent(Intent.ACTION_CALL);
callIntent.setData(Uri.parse("tel:XXXXXXXXX"));
startActivity(callIntent);
which switches the activity I start the call from to another activity (in this case to an activity in a different app). Is there a way to stop this from happening? I managed to do it with a third party library called "sinch" but I'm wondering if there is a native way to do it or maybe a better library?
Ps- the app I'm building it for myself, basically, I'm building a voice assistant that can make calls via voice commands, hence I can't let it switch activities. I have no intention of publishing it on the app store and I have no difficulty giving dangerous permissions :) My plan is to run it on a separate piece of hardware in the future.

This link can help you, but as Xavier Rubio Jansana wrote previously, Google hardly accepts applications that do not use intents to make phone calls :
https://google-developer-training.github.io/android-developer-phone-sms-course/Lesson%201/1_c_phone_calls.html
Google wants any programmer to use an intent to make the user view the default phone application handle the phone call.
If your app does not need to be available on Google Play Store then it would be ok for you to make the phone call directly.

To elaborate on what I was talking about earlier, it is talked about in this stack overflow question (perhaps upvote their answers if they are helpful). How to make a phone call using intent in Android?.
From memory, ACTION_DIAL will bring up the dialler and pre-populate the number.. it requires no special permission because it requires the user to actually place the call.
On the other hand, ACTION_CALL will actually initiate the call and requires special permissions.
If returning focus (bringing your app back to the foreground) is a concern, you could try using a scheduled intent to (re) launch your activity (maybe using alarm manager or similar) some time after invoking the dialler. You can retain state with a little care around launch modes in the intent and/or a special "do nothing" activity published in your app manifest which does nothing but re-activate your app.

Android Conditional PendingIntent in Notification?

My application currently has two activities: a splash activity which displays the app logo and loads the user’s data from a remote database, and then the main activity that houses all my fragments. I’ve reached a bit of an impasse right now with notifications. I’m using FCM to deliver the notifications and have that working fine, but don’t really know what to do with the pending intents of the notifications. If the app is closed, I don’t want it to launch the main activity since I load the data from the DB in the splash activity. Thus the main activity would have missing data (it currently crashes due to null pointer exceptions everywhere). But if the app is still running, I don’t want the splash screen to be launched again. Is there some type of way to have a conditional intent baked into the notification?
Alternatively, is this just bad practice to do what I’m doing with launching the activities from the notifications? I’m by no means an android expert so there might indeed be a better way. I would prefer to keep my current activity flow however where the splash screen is responsible for the initial loading of data. I was hoping there was some way to just broadcast a message on the click of the notification and if any activities have an active listener then it would just consume that data.

The solution I have come up with is to have a single activity whose sole purpose is to process notifications and then pass them to the appropriate activity either through a new intent (if app is terminated) or through a broadcast (if app is resumed). Not sure if this is bad practice (would appreciate anyone telling me if this violates any type of software principle).
It's working like a charm so far and is honestly really nice to have all that logic in one activity anyway - all the service has to do is pass in the data from the notification and the action and the activity does the rest.

How to detect is application been showing?

I have been developing Android application that use Activity with "download" button and Service for executing downloading in the background. And I have following task: to show message about downloading if application is currently displayed. How can I detect it? Is there standard Android OS functions for it? Thank you.

You can do this at the activity level, not for the application as a whole. Check out the description of the activity lifecycle. (Also see "Managing the Activity Lifecycle" in the Activities framework topic.) When your activity becomes visible, the framework will call it's onStart() method. When the user can interact with the activity, the framework will call the onResume() method. You can override one of these to know when your activity is showing or actually interacting with the user.
Note that, as described in the documentation, things work a little differently starting in Honeycomb (3.0).

The basic method is to use Broadcast receiver to share information between a service and an application. If your requirement is to update the status/progress of download on the main activity, you can use it.
Here is a simple tutorial about how to share information between a service and an activity. You can update the progress of download. It works for the activity that is currently running.
To check for it as the activity starts, you should override the onCreate, onStart() or onResume() functions.
Also there is a very neat solution presented in another question and i recommend that you should try to use that. It involves extending the Application class to store the information, and use its instance to check for updates. See this

How do I determine what app is currently in the foreground?

I need a way to log what app is currently running in the foreground, preferably without requiring root access or using the NDK. Is there any way to do this?

If I remember correctly, onResume() gets triggered any time an activity gets on foreground. If your app contains more than one activity, you should check all of them.
You can check activities lifecycle here

Android: how to have my app open automatically?

Basically I want my app to start running in the background when the ACTION_MEDIA_BUTTON is clicked. I've seen other apps do this, so it must be possible. I just don't know how it is possible. Some kind of special manifest code?
Currently my app can receive intents from the ACTION_MEDIA_BUTTON when it has been opened (and even running in the background) via intentfilter that I register in Java code of the main activity (when the app is first opened). But how would I have this button just... open up the app?
For reference, the following app can already do this functionality: https://market.android.com/details?id=com.kober.headset
Much appreciated, thanks.

Use a BroadcastReceiver and register for the intent. See this Android Developers Blog post for more details.