API's for Android 4.4 screen recording?

问题:

One of the features of Android 4.4 (Kit Kat) is that it provides a way for developers to capture an MP4 video of the screen using adb shell screenrecord. Does Android 4.4 provide any new API's for applications to capture and encode video, or does it just provide the screenrecord utility/binary?

I ask because I would like to do some screen capture work in an application I'm writing. Before anyone asks, yes, the application would have framebuffer access. However, the only Android-provided capturing/encoding API that I've seen (MediaRecorder) seems to be limited to recording video from the device's camera.

The only screen capture solutions I've seen mentioned on StackOverfow seem to revolve around taking screenshots at a regular interval or using JNI to encode the framebuffer with a ported version of ffmpeg. Are there more elegant, native solutions?

回答1:

The screenrecord utility uses private APIs, so you can't do exactly what it does.

The way it works is to create a virtual display, route the virtual display to a video encoder, and then save the output to a file. You can do essentially the same thing, but because you're not running as the "shell" user you'd only be able to see the layers you created. The relevant APIs are designed around creating a Presentation, which may not be exactly what you want.

See the source code for a CTS test with a trivial example (just uses an ImageView).

Of course, if you happen to be a GLES application, you can just record the output directly (see e.g. EncodeAndMuxTest and the "Record GL app" activity in Grafika).

回答2:

Well, AFAIK, i don't see an API support equivalent to capturing what's going on the screen.