OpenSL ES slCreateEngine causes error

I have an OpenSL ES function call that causes no problems in one application, but causes a problem in another application, both run on the same device.

The line is:

result = slCreateEngine(&engineObject, 0, NULL, 0, NULL, NULL);

Where result is of the type SLresult, engineObject is of the type SLObjectItf

The error I seem to get is:

05-19 11:56:27.007: ERROR/libOpenSLES(1425): slCreateEngine while another engine 0x299fa0 is active

It seems this is not logged from my code, but maybe it开发者_如何学Go is caused by it? So what could cause this line to produce an error in one app, but not in the other?

As it happens to be, it was partly Android's Activity life-cycle which caused the error, but mostly my own fault. It was caused by the onCreate() and onResume() methods Android provides for an Activity. I never thought of the fact that onResume() also get's called when an Activity is started. Because of this, I never realized that I had a 2nd call to the slCreateEngine function.....

According to the docs "OpenSL ES for Android supports a single engine per application". I had a quick check of the source for OpenSL an I can see this is enforced by a global storing the current active engine.

So if you want to call slCreateEngine, you must make sure all other engines have been destroyed first. This includes the possibility of any 3rd party code you are linking in too (incase you are linking in something else that is creating an OpenSL engine object before you do).