How does the Android phone phone it has been docked in a car holder?

I think the HTC Desire car dock can launch Car Home, but how does the phone known it's been docked?

2 Answers 2


Some Android phones, like the Nexus One, have special contacts that tell the OS when the phone has been docked.

The Desire actually doesn't have these so can't automatically detect that it has been docked. Car Home can still be launched manually.

Another option is to look at an app like Tasker. You could configure Car Home to be launched when certain conditions are met, like the phone is on charge and in a vertical position (so docked). There are many other ways you could use tasker for this.

  • Once the phone is docked, it sends a special 'intent' signal to applications, in this case: android.intent.category.CAR_DOCK
    – Bryce
    Nov 30, 2013 at 5:35

Typically, the phone knows whether it has been docked by the placement of a magnet on a certain area on the back of the phone. You can therefore create your own cheap dock using a magnet and some sort of stand. Here is an example with the Droid.

  • But then you loose your compass functionality... Aug 3, 2011 at 4:51
  • @Denis Most apps that use a compass (let's say while you are driving) will switch from using the magnetometer and accelerometer to using the GPS's velocity after you go faster than say 2mph. (This is what my app, Car Dashboard, does). The magnetic compass is not very accurate to begin with.
    – Bryan Denny
    Aug 3, 2011 at 15:13
  • Agreed, but does a permanent magnet damage the sensor? By magnetizing internal components which are made of metal? I like to go outside and magnetic sensor works quite good for me. I just do not like the idea to run at 15 km/h to get the direction from GPS. And in dense forests GPS does not always work. Aug 3, 2011 at 20:07
  • The Droid one was designed to use a magnet. Depending on which pole is facing the phone, it either activates the car dock or the desk dock. But not all phones use a magnet. Some use pin connectors to the dock to enable the dock mode. Magnets should not damage the phone, you don't have a magnetic HDD in the device like desktop computers. It's all flash memory.
    – Bryan Denny
    Aug 4, 2011 at 13:37
  • I was worried that a magnetic sensor would be damaged by permanent magnet, not flash :) For example electronic compass application reacts, when I place a real magnetic compass (it contains a permanent magnet) near the phone. After I remove the real compass, the reading in electronic compass does not return to what was before. It is offset by 10-15 degrees. If I move a phone around and place it on the same spot in the same orientation, the reading returns to normal. Assuming that the phone uses the same brand of magnetic sensor as in Droid it should be safe to use permanent magnet around... Aug 4, 2011 at 16:47

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