CWAC-Presentation: Second Screens Supported Succinctly
This project offers a series of classes that wrap around the Presentation
and DisplayManager
of Android 4.2:
-
PresentationHelper
consolidates basicDisplayManager
handling, with a listener to inform you when to show or remove yourPresentation
-
PresentationFragment
extendsDialogFragment
and adds a bit of extra logic to allow it to handle aPresentation
rather than a simpleDialog
-
WebPresentationFragment
simply extendsPresentationFragment
and displays aWebView
in thePresentation
-
MirroringFragment
,MirroringWebViewFragment
, andMirrorPresentationFragment
leverage the mirroring logic from the CWAC-Layouts project to help you display aPresentation
based upon mirrored content from the main screen -
PresentationService
, for showing content on an external display from the background, even if your primary UI is destroyed or otherwise not in the foreground
Installation
This Android library project is available as a JAR. If you wish to use the JAR, you will need to also add the JAR from the CWAC-Layouts project to your project if you wish to use the Mirror*
classes. If you are not using the Mirror*
classes, then the CWAC-Presentation JAR is sufficient.
NOTE: The JAR name, as of v0.4.2, has a cwac-
prefix, to help distinguish it from other JARs.
Also note that if you plan to use this as an Android library project in source form, you will also need to download the CWAC-Layouts project (and, if needed, modify this project's configuration to point to your copy of CWAC-Layouts' library project). Alternatively, download the CWAC-Layouts JAR into the libs/
directory of your clone of this project and remove the dependency on the CWAC-Layouts library project.
This project is also available as an artifact for use with Gradle. To use that, add the following blocks to your build.gradle
file:
repositories {
maven {
url "https://s3.amazonaws.com/repo.commonsware.com"
}
}
dependencies {
compile 'com.commonsware.cwac:presentation:0.5.0'
}
Or, if you cannot use SSL, use http://repo.commonsware.com
for the repository URL. This should automatically pull down the CWAC-Layouts dependency.
Usage: PresentationHelper
PresentationHelper
is designed to be used by an Activity
that wishes to display a Presentation
when a suitable Display
is attached, and stop displaying the Presentation
when any prior such Display
is detached.
To do this:
-
Create an instance of
PresentationHelper
, probably inonCreate()
of the activity. You will need to supply aContext
(probablythis
) and something that implements thePresentationHelper.Listener
interface. -
Forward the
onPause()
andonResume()
events to thePresentationHelper
by calling the same-named methods on the helper. -
Implement the
showPreso()
method on yourListener
. This receives aDisplay
object, and you are now able to display aPresentation
on thatDisplay
. -
Implement the
clearPreso()
method on yourListener
. At this point, you should stop displaying any priorPresentation
, if there was one. You are passed aboolean
value,true
indicating that the activity is going away,false
indicating that we merely lost ourDisplay
. You can use this value to perhaps optimize dealing withDisplay
changes, without destroying all the data.
You can call disable()
and enable()
on the PresentationHelper
. Calling disable()
stops the custom content and reverts the device to normal screen mirroring mode. Calling enable()
reverts a previous disable()
call.
Usage: PresentationFragment
PresentationFragment
is a thin veneer over DialogFragment
to allow it to work with Presentation
objects (which themselves inherit from Dialog
). This allows you to define the content for a Presentation
in the form of a fragment. And, like DialogFragment
, you can elect to either use it for a Presentation
(via a call to show()
) or use it as an ordinary Fragment
in the rest of your UI (via a FragmentTransaction
). This can help you to work both in dual-screen and single-screen scenarios.
Your PresentationFragment
subclass should override onCreateView()
to define the contents of the Presentation
(or what will be shown in the Fragment
when used as a regular fragment). The only significant change over any other Fragment
is that you should use getContext()
, instead of getActivity()
, for any resources you create, such as inflating a layout. This ensures that you get the right Context
for the situation, such as the Context
associated with a secondary screen when used for a Presentation
.
However, when creating the PresentationFragment
, you also need to call setDisplay()
, to provide the Display
object for use when the fragment is shown as a Presentation
. If you are not using it for a Presentation
in the current context, this call is not required. A typical approach for handling setDisplay()
is to use a factory method:
public static YourFragment newInstance(Context ctxt, Display display) {
YourFragment frag=new YourFragment();
frag.setDisplay(ctxt, display);
return(frag);
}
Beyond this, PresentationFragment
is a fairly ordinary Fragment
.
If you wish to display this fragment in a Presentation
, call show()
on the PresentationFragment
, supplying your FragmentManager
and a tag to use for the fragment itself. To get rid of the Presentation
, call dismiss()
on the PresentationFragment
.
Usage: WebPresentationFragment
WebPresentationFragment
is simply a mash-up of PresentationFragment
and WebViewFragment
, to allow a WebView
to be displayed in a Presentation
. You use it just like WebViewFragment
, except for the need to call setDisplay()
(per the PresentationFragment
instructions above). So, for example, getWebView()
returns the WebView
hosted by the WebPresentationFragment
.
Usage: Mirroring Presentation Classes
There are three classes that take advantage of the mirroring support included in the CWAC-Layouts project.
MirroringFragment
works much like a regular Fragment
. However, instead of overriding onCreateView()
, you override onCreateMirroredContent()
. onCreateMirroredContent()
takes the same parameters as does onCreateView()
, and your job is the same: create the content to be displayed by the fragment. The difference is that your returned View
will be wrapped in a MirroringFrameLayout
.
MirroringWebViewFragment
is a mash-up of MirroringFragment
and WebViewFragment
, to allow a WebView
to be mirrored. Use getWebView()
to retrieve the WebView
hosted by this fragment.
MirrorPresentationFragment
is a PresentationFragment
designed to mirror the contents of a MirroringFragment
. To use this, create an instance using the newInstance()
factory method, taking a Context
and the desired Display
as parameters. Then, call setMirror()
on your MirroringFragment
, supplying the MirrorPresentationFragment
. From there, you can show()
and dismiss()
the MirrorPresentationFragment
as you would any other PresentationFragment
. By having the MirroringFragment
on the main screen, and having the MirrorPresentationFragment
on an external display, whatever the user manipulates on the screen is rendered to the external display, ideal for presentation settings (e.g., conferences).
Note that MirroringFragment
suffers the same limitations as does MirroringFrameLayout
, in that it will work with fairly ordinary View
s, plus WebView
, but not SurfaceView
or things that use SurfaceView
(e.g., VideoView
, Maps V2 maps).
Usage: PresentationService
PresentationService
is an abstract base class for you to extend, where PresentationService
handles showing your content on an external display, and you simply manage that content.
In your PresentationService
subclass, you will need to implement two methods:
-
getThemeId()
, which returns the ID of the style resource that you want to use for content being shown on the external display. -
buildPresoView()
, which returns theView
that represents the content to show on the external display. Note that since this is aService
, not anActivity
, you cannot use fragments, only views.buildPresoView()
is passed aContext
and aLayoutInflater
for your use to set up the content to be displayed.
You may optionally override the standard lifecycle methods (though please chain to the superclass!) and buildLayoutParams()
, which returns a WindowManager.LayoutParams
describing how your View
should be applied to the external display. The default implementation of buildLayoutParams()
is probably adequate for your needs.
You may also optionally override the showPreso()
and clearPreso()
methods defined by PresentationHelper.Listener
, though, once again, please chain to the superclass implementations.
You may also optionally override getWindowType()
. This should return the window type int
to be used for the "window" we are going to use for the external display. The stock implementation of getWindowType()
uses TYPE_TOAST
prior to Android 7.1 and TYPE_SYSTEM_ALERT
on Android 7.1+. If you are using Cast Remote Display, you may need to override this method and return TYPE_PRIVATE_PRESENTATION
(untested).
Then, all you need to do is to arrange to start and stop the service as needed. Once started, the service will automatically call buildPresoView()
and show the content, once an external display is detected.
If things that the user does in your UI should affect the behavior of the service and its content, use a message bus implementation, such as:
LocalBroadcastManager
- greenrobot's EventBus
Your PresentationService
can receive bus messages and update the View
accordingly. Note that there is no present means to replace the View
, so you may wish to have buildPresoView()
return a FrameLayout
or something else whose contents you can replace in toto if needed.
Note that it is safe to call startService()
on the service multiple times, if you do not know whether the service is already running and need to ensure that it is running now.
Note that using this on Android 7.1+, where a TYPE_SYSTEM_ALERT
window is used, requires the user to go into Settings and allow your app to draw over other apps.
On Android O and higher, please use multi-display instead of PresentationService
.
JavaDocs
You can browse the JavaDocs for the latest release.
Dependencies
This project depends on Android 4.2 and higher (API Level 17) to actually do its work. It should survive on older devices, simply doing nothing.
This project also depends upon the CWAC-Layouts project.
Version
This is version v0.5.0 of this module, meaning it is coming along nicely.
Demo
In the demo/
sub-project you will find a sample project demonstrating the use of the aforementioned classes, with the exception of PresentationService
. There is a separate demoService/
sub-project with a sample implementation of PresentationService
.
Additional Documentation
The Busy Coder's Guide to Android Development contains a chapter dedicated to the Presentation
API. This chapter walks through a few sample apps that use classes from this library. Another chapter in the book examines a somewhat larger app that supports output on TVs, etc. by a variety of means (e.g., direct-to-TV devices like Android TV and Fire TV) including Presentation
and this library's classes.
License
The code in this project is licensed under the Apache Software License 2.0, per the terms of the included LICENSE file.
Questions
If you have questions regarding the use of this code, please post a question on Stack Overflow tagged with commonsware-cwac
and android
after searching to see if there already is an answer. Be sure to indicate what CWAC module you are having issues with, and be sure to include source code and stack traces if you are encountering crashes.
If you have encountered what is clearly a bug, or if you have a feature request, please post an issue. The contribution guidelines provide some suggestions for how to create a bug report that will get the problem fixed the fastest.
You are also welcome to join the CommonsWare Community and post questions and ideas to the CWAC category.
Do not ask for help via social media.
Also, if you plan on hacking on the code with an eye for contributing something back, please open an issue that we can use for discussing implementation details. Just lobbing a pull request over the fence may work, but it may not. Again, the contribution guidelines provide a bit of guidance here.
Release Notes
- v0.5.0: better
PresentationService
support for Android 7.1+, demo bug fixes - v0.4.6: JavaDocs, sources included in repo; source tree reorg; build files update
- v0.4.5: got
PresentationService
working again on Android 5.1 - v0.4.4: updated for Android Studio 1.0 and new AAR publishing system
- v0.4.3: removed
SYSTEM_ALERT_WINDOW
permission requirement - v0.4.2: updated Gradle, fixed manifest for merging, added
cwac-
prefix to JAR - v0.4.1: tweak for v0.4.0 of CWAC-Layouts
- v0.4.0: added
PresentationService
- v0.3.0: migrated to Gradle
- v0.2.0: handle API level diffs, support enable/disable of
PresentationHelper
- v0.1.0: initial release