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.

Is it possible to know the app which is opened currently?

I am a beginner in android development. I want to know that is it possible to know the app which is opened currently. I came to know that finding the apps which are running currently through Activity Manager (getRunningTasks()) is now removed from the Android studio. So I want to know is there any other way to know? I just want to know the app which is opened and running currently on the mobile but not the apps running in the background Could somebody please help me in this case?

You can use AccessibilityService to get event notification. But AccessibilityService are specifically for accessibility uses. If you use the service for other purposes, then the application will more likely to be downed/removed for PlayStore due to policies. Another viable option is UsageStatsManager, but with some limitations.
UsageStatsManager is not push event based system. You have to poll in few mills(depends upon the use-case)
Usage Access Permission grant/deny is not straight forward. You have to start Setting Activity with Settings#ACTION_USAGE_ACCESS_SETTINGS action and have to rely on the users understanding of how to grant permission(Since permission list may contain other applications).

How to add shortcut on home screen when app gets install

I know it's not the best practice, but it is a requested feature (e.g. for business apps). When the App gets installed, I need to automatically place it on the home screen. I saw a lot of code on the internet, but all of the code only works on button click when the app starts. But I need to place a shortcut on the homescreen immediately after the app is installed and before the app starts. Is there a way I can achieve this?
PS: To make the question more clear: The app will be distributed without Google Play Store, so that's not an option.
Thanks for your help!
Best regards,
Robin

You can't run any code in your application before the user starts your application for first time during to restrictions since Android 3.1. Check this for more information

That's an optional feature of the Market app, not of the apps themselves. When designing an application , it does not receive a broadcast about itself being installed.
the first time the app launched can create it.
You can achieve that by creating a method in your main activity and call this method from oncreate and create a boolean variable andsave it in shared preferences

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

Clearing Activity Stack

I am having trouble clearing my app's activity stack. At the start of my app I make the user login and give them a session id. After they login they are able to continue on using the app. However if there session expires I want to redirect them to the login activity and clear the Activity history so they can't have access to the app. I looked at the Android API and the Intent flag FLAG_ACTIVITY_CLEAR_TASK seems to be want I want but it was just included in API level 11 and no phones have the new OS yet. Does anyone have a solution to this problem. Thanks.

I found my answer here. Turns out that I have to broadcast an intent to tell all of the Activities to call the method finish().

The documentation for FLAG_ACTIVITY_CLEAR_TOP describes the situation you want if you use it in conjunction with FLAG_ACTIVITY_NEW_TASK
http://developer.android.com/reference/android/content/Intent.html#FLAG_ACTIVITY_CLEAR_TOP
"This launch mode can also be used to good effect in conjunction with FLAG_ACTIVITY_NEW_TASK: if used to start the root activity of a task, it will bring any currently running instance of that task to the foreground, and then clear it to its root state. This is especially useful, for example, when launching an activity from the notification manager."