How to display a Dialog from a Service?

Question

I have read really a lot of posts about this topic, however nothing works for me (or doesn't have the effect I wish).

I have a an application, that after logging in starts a background Service (implementation of the Service class). This service syncs itself with a Server and if a new order comes, it creates a notification.

So far, everything works great, I have the notification and the Toast message. However, I would like to have a dialog, that notifies the user about the new order.

As I understood, you can start an activity from within the service, which displays the dialog. This works, but the activity starts on top of the current activity stack and displays the dialog. I have an activity with no view attached and it correctly displays the dialog, however, on a black background.

What I want is to display the dialog on the current activity, causing the actual background(the running activity) to fade and display the dialog.

Is this somehow possible?

Answer 1

We can show dialog from service only if it is a system alert dialog. So, set TYPE_SYSTEM_ALERT window layout parameter to Dialog as follows:

dialog.getWindow().setType(WindowManager.LayoutParams.TYPE_SYSTEM_ALERT); 

But, it needs SYSTEM_ALERT_WINDOW permission. So, don't forget to add this permissin in Manifest file.

<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/> 

Edit: Better option to show dialog is to start activity as one of the below ways.

1. Start Activity with Dialog Theme (android:theme="@android:style/Theme.Dialog") -(or)
2. Start Translucent Activity and show Dialog in it.

Note: You should add Intent.FLAG_ACTIVITY_NEW_TASK to intent

Answer 2

I highly, highly, HIGHLY recommend that you DON'T do this (it goes against Android design and UI guidelines). Notifications are the preferred way to accomplish what you are doing (which it sounds as if you have already accomplished).

That being said, if you must do it, I would recommend just using a Dialog themed activity. That way you don't have to start up a separate dialog. Please see http://developer.android.com/guide/topics/ui/themes.html#ApplyATheme for how to do this.