Android Sleep/Standby Mode

I have made an app that starts a service, which starts a timer, which fires off a small function after an amount of time. This is working great on the emulator and on the Motorola Droid 1, but it doesn't work on the Droid X when the phone has been put into sleep mode. What I have discovered is that the timer seems to pause when the phone is in sleep. It doesn't seem to do this on the Droid 1, or the emulator. I'm sure the workaround isn't too difficult, so I'm not asking for help(for once) I just want an explanation, to better understand this.

My question is what exactly does "sleep mode" do on android systems? What does it stop, what doesn't it stop, etc. By sleep mode I mean, of course, when you press the power button and the screen goes black. What exactly is happening? Any insight is appreciated.

Solution 1:

I'm sure the workaround isn't too difficult

Using AlarmManager is a bit tricky.

My question is what exactly does "sleep mode" do on android systems?

Primarily, it shuts down the CPU. Along the way, non-essential radios (WiFi, GPS) will have been shut down as well.

What does it stop, what doesn't it stop, etc.

About the only thing you can count on not stopping is the GSM or CDMA radio (for incoming calls, SMSes, and IP packets) and AlarmManager.

By sleep mode I mean, of course, when you press the power button and the screen goes black.

Actually, that's not sleep mode, per se. That is the screen turning off.

The device will go into sleep mode shortly thereafter, if nothing is keeping it awake with a WakeLock. However, there is no guarantee that within a millisecond of you pressing that button and the screen turning off that the CPU is off.