Arduino not supplying power to Android device and sensor!!!

I have Arduino Mega 2560 ADK..
I have interfaced it with breadboard with PING sensor plugged in.
Whn i give it power through PC via the power cable,the sensor lights up n work perfectly.
But when i plug in the usb cable to the usb port of the arduino to my android device,the sensor stops.it doesnt get power.
but my mobile starts charging..
Why is that happenging??
Its switching the powr supply between sensor n device.
Arduino shud be able to supply pwer to breadboard n android device simultaneously.isnt it? Plz give me an idea..wht can be the reason??
Here is the circuit diagram..Blue block is arduino mega adk

Whn i give it power through PC via the power cable,the sensor lights up n work perfectly.

What power cable are you talking about? The only cable between the PC and the Arduino is usually the USB cable, which does supply power but also allows the exchange of data.

But when i plug in the usb cable to the usb port of the arduino to my android device

I know what a USB cable is, and that the Arduino has a USB port. I'm having a hard time figuring out where you are putting the other end of the cable, though.

Arduino shud be able to supply pwer to breadboard n android device simultaneously.isnt it?

The Arduino is not a power supply. Where did you get that idea? It consumes power. Your phone might be supplying power to the Arduino, or might not. But, the Arduino is not powering the phone.

Here is the circuit diagram..Blue block is arduino mega adk

That is not a circuit diagram. Post a picture where the wiring can be clearly seen.

I have arduino mega adk..it has 2 usb ports(type A and type B)
type B is the squarish one.to which the printer cable is connected.(cable havin square port on one side and usb on another)
i have connected arduino TYPE B port and PC'S usb port via the printer cable
and the left out port on the board which is TYPE A port(usb port) is conncted to android device via simple usb cable
and device never powers the arduino.it is possible only if the device supports host mode.
m implementing communication thorugh ADB i.e. TCP protocol(microbridge) where arduino powers the device.
I think their is power shortage or the usb is providing less current to the board.therefore board is not able to transmit current to both the andorid device n sensor simultaneously..
here is the photo