Q:

Show a float dialog in any screen?

I want to show a dialog in my android phone anywhere. I want to use windowmanager.addView() 
to come true it. But It doesn't work because this function only can add views.How to show a dialog in anywhere?

A:

Refer this links http://developer.android.com/reference/android/Manifest.permission.html#SYSTEM_ALERT_WINDOW
Allows an application to open windows using the type TYPE_SYSTEM_ALERT, shown on top of all other applications. Very few applications should use this permission; these windows are intended for system-level interaction with the user.
Constant Value: "android.permission.SYSTEM_ALERT_WINDOW"
Example projects
https://github.com/fouady/SpotifyTray-Android , https://github.com/henrychuangtw/FB-ChatHead

