didAccelerate doesn't fire?

I can't get didAccelerate to trigger开发者_运维百科. I have the delegate implemented in my header file. I've set a breakpoint in the method:

- (void) accelerometer: (UIAccelerometer *)accelerometer didAccelerate: (UIAcceleration *)acceleration {
    int i = 0;
}

I've tried it with two different apps but still nothing. Any ideas on what I'm doing wrong?

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try to set accelerometer's delegate to self. BTW, did you try to check it on a real device?