Develop Reference

Easier way to publish an APK to Google Play on behalf of public clients

There are a lot of answers out there for how to publish an APK on Google Play, they involve the following:
Creating a Google Play Developer account and pay $25
Create a Google Developer App Project
Enable the Google Play Developer API is enabled on the project
Create a service account on the project and ensure that a role is selected during that process (got tripped up here myself when I didn't add a role)
Link the Google Developer App project to my Google Play Developer account and select the service account.
All this seems very technical and complicated when I'm trying to create a service where my clients can go to my site, create a simple mobile app and publish it on Google Play. I'm not expecting my clients to be technically minded so expecting them to do all this seems like a stretch too far.
Is it possible for me to get my clients to sign in with their google play developer account and do the other parts on their behalf for them? Or is there a more simpler way? Or can I publish their APK's on my Google Play Developer account and manage them for them?

Pushing apps to Google Play on behalf of clients is specifically forbidden by Google Play policy. You should carefully review the Play Policy on repetitive content otherwise your clients may not be happy when their apps are taken down.
"Apps that are created by an automated tool, wizard service, or based on templates and submitted to Google Play by the operator of that service on behalf of other persons are not allowed. Such apps are only permissible if they are published by an individually registered developer account belonging to the user of the automated tool, not the operator of the service."

You want the Google Play publishing API. See https://developers.google.com/android-publisher/#publishing

Update Android app in COSU device

I am working of app support COSU app android. The app is working fine for me but I am not understand how user will update our app, because COSU app user can't access any other application even google play store. So now the question is that how user will update our application without google play access.
I have one solutin download app from our server, but in this case user will lose save data like the data we are storing in SharedPreference. Please guide me if you have any other solution for that. Thank in advence

According to Google's docs on COSU (Google Play app management), it is possible to "install, update, and uninstall apps using the Play EMM API". Under "Google-hosted private app management" it describes the ability to host private apps through Play that your users can install/update:
Simplifies the Google-hosted private app publishing and update
workflows available to all admins through managed Google Play, by
enabling admins to update Google-hosted private apps through the EMM console instead of through the Google Play console.
Enterprise admin can upload new versions of apps that are already published privately to the enterprise using the Google Play Developer Publishing API.
If you don't want to use Play for this functionality you can read the "Self-hosted private app management" section.
You can also look at "Managed Google Play" to publish private apps for your users: https://support.google.com/googleplay/work/topic/6145152
After you register for a Google Play Developer account and set up the correct administrator privileges to upload and publish the app to managed Google Play, you can use the Enterprise Mobility Management (EMM) console to distribute the app to users.
Going the EMM route will let you update apps with the same functionality as regular Google Play apps where updates don't cause users to lose data. Unfortunately Google's documentation isn't detailed or centralized for this feature. Going through Google will also require that all of your devices are signed in to Google account in order to install apps or receive updates that you deploy though the EMM console.
Another option is to use a mobile device management (MDM) solution. If you have Samsung devices you can look into Samsung Knox which has a much simpler method for distributing your app: https://www.samsungknox.com/en/article/manage-apps
Another MDM option for single use apps is Mason (https://bymason.com/). Mason lets you upload your app, select any or all of your devices, and then deploy your APK to your users. When updating your app, all you have to do is increment your app version and the update functionality will be the same as a regular Google Play update. Your users also don't have to be signed in to a Google account.
If this sounds useful to you feel free to reach out to me trevor # bymason.com
DISCLAIMER: I work at Mason

Does using google FCM for business App requires registration fee?

I want to use FCM(Firebase Cloud Messaging) in my organization's internal App which is not going to be hosted on google play. Does it require any kind of payment? I searched about it, all the searches pointed to google play developer console which charges $25 as one time registration fees. I assume registering on google play developer console is required when we want to host an App on google play. Correct me if I am wrong.
Currently I am able to use FCM in the App just by signing in using my gmail account. I want to know whether payment is necessary for using google FCM service in the App.

As already mentioned in the comments by #jankigadhiya, FCM service is free of charge, though there are premium packages, as seen in the Firebase Pricings page.
The $25 registration fee for the Google Play Dev Console is only necessary IF you are planning to publish your app via the Google Play Store, as described:
Google Play Developer Console enables developers to easily publish and distribute their applications directly to users of Android-compatible phones.
Most of the perks/advantage when registering are for apps who's target is the public market. Since you're app is for internal use only, the advantage I think you can make use of should you choose to register for a Google Play Dev Console is Viewing the App Performance Statistics.
This How to use the Google Play Dev Console help doc should prove helpful.

Android "The publisher cannot purchase the item"

I'm not testing my in app purchase !
I have download my app from google play store and I still can't buy any of my In App purchase within the application.
I have the following error : "The publisher cannot purchase the item".
All my In App purchase are also valid and active.
I'm using the same google account than in my google play developer console.
I have read on google that it's normal that developer can't buy it's own items in testing mode (alpha or beta) but here i'm using the official version and I still can't do it !! (It's my first android application)
What did I do wrong ?
Thanks,

if you have the same account configured on the device (the one which you are using for developer console) make sure it is removed. Google Play will allow switching between all google accounts added on device. Also, before removing try switching directly in google play first to an account that is not your developer account and then do the purchase. If that doesn't work you'll probably need to remove the developer account for the device if you want to make a purchase fro your own app.

Google Play can't sell apps

I have created game using Unity game engine. It works perfectly fine. I want to upload it to Google Play, I am new to Google Play Developer Console and to this whole Google Play thing actually. I managed to upload .apk and filled all the necessary info. Now it is in beta test. The game will be pai. And that's where my problem is. When I(or other testers) try to buy the game, error pops up. If I try to buy the game via PC or phone, error is this:
An error occurred while getting the status of your purchase.
As far as I understand it's caused by my Google Wallet. I've filled my payment settings in Google Wallet and payment method(wire transfer(I'm from Ukraine)) in Google Wallet Merchant, my buisness address and address. I searched all over the net to find similar problems and solutions to the them, but couldn't find. Please help.
Oh and recently I've found out that there is also a Google Wallet Merchant for Digital Goods. Do I need it to sell apps? Because it's not supported in Ukraine.

Sounds like you have entered faulty info. Otherwise try contacting help services, I'm sure they have already encountered similar problems.

Try clearing your cache/data on your Play Store App (Settings -> Apps -> Google Play Store) or the cache/cookies on your browser. Else, you can check out the Google Wallet Help Center for more troubleshooting help.

Go to google payment ---> you will have multiple payment mode updated and your primary card or payment might be blocked or expired, change this to new added payment card or mode