ANativeWindow_acquire usage

[Ratamovic]

Hi all,

There is a function ANativeWindow_acquire in native_window.h that allows acquiring a reference to an Android Surface. However, I never see it called in the NDK samples except the native-media-jni example which uses ANativeWindow_fromSurface() (which itself acquires a reference).

So when should acquire() be used and when it is not required? What's the right practice, more specifically when using the window given to NativeActivity?

Thanks in advance.

[Philippe Simons]

ANativeWindow_acquire is for access to the Surface pixel buffer.

It can be used if you want to draw something by "editing" the buffer.

If you want to draw something using OGLES, you don't have to use this function.

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[Ratamovic]

Hi Philippe,

Thanks for your answer. Actually I'm not really interested in OpenGL ES, just in understanding the ANativeWindow API :-).
Are you talking about ANativeWindow_acquire or ANativeWindow_lock?

Because I agree that ANativeWindow_lock gives access to the surface.
But ANativeWindow_acquire seems to only increment the reference counter. But it doesn't seem "required" as I don't see it often used, for example, with the window given by a NativeActivity.
The only example I found is in the native-media-jni.

Is it a bad practice not to use it? Or are there some cases were it is really not needed? (I guess the answer is when we have a guarantee the Surface will be released after native code has done its job... But when does this kind of cases happens?)

Thanks again.

[J Decker]

I'll toss out, I don't think it's required.

Only api I use is get with/height/format and set width/height/format then when I'm drawing, lock and postandupdate.

Think the aquire is more for internal use (part of the nativeactivity setup)