WP7 Tpa 09 Web Location Sensors

8/2/2019 WP7 Tpa 09 Web Location Sensors

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TPA - Windows Phone

Web requests, Location services

Phone sensors

Prepared by: Kamil Kowalski


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Agenda

Web Requests

WebClient

HttpWebRequest

Consuming Web Service

Location services

Accelerometer

Compass Gyroscope

Q & A


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Web Requests

WP7 uses the same Web request API as normal .NET Only the asynchronous request methods available

System.Net offers the WebClient class for simple access

For non-trivial data handling the WebClient can cause problems while

it runs in the UI thread, so HttpWebRequest should be preferred

WebClient cannot be used when you need to access the basic HTTP

protocol features

HttpWebRequest is for HTTP requests

Use BeginGetResponse() method to initialize a HTTP GET

The response is available in the Callback method through the

argument

Typical approach is to get the response stream, and read the contents

of the stream


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Web RequestsWebClient

The WebClient does not support concurrent calls You have to manage to wait for the completion of the previous call before

starting another one

The WebClient class provides a number of ways to call an httpresource:

DownloadStringAsync - provides the simplest way of downloading astring resource from the network, like an HTML page, a RSS or ATOMfeed, a plain XML file and so on

UploadStringAsync - it can be used to send strings to a server and it canalso specify the method to be used to make the call.

Probably it is the simplest way of making calls to a REST resource

OpenWriteAsync & OpenReadAsync - these two method allow to sendand receive binary resources to/from the server.

The use is slightly more complex that the other methods but once the callcompletes you can access a binary stream you can read or write directly.


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How to use it the simplest way:


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How to use it beter way:


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Web RequestsHttpWebRequest

Basic scenario: Create an instance of the HttpWebRequest

If you have to post something get the request stream

Then write posted data to the request stream

Get the response (that is actually what starts the call)

Get the response stream

Read returned data from response stream

Close all thing


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How to use it the simplest way:


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How to use it beter way:


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Web RequestsConsuming Web Service

The WebClient and HttpWebRequest are both complete andeasy to use, the problem is that their usage is for sure heavy,

because you need to rely on your own protocol made for

example of XML files.

The process of serializing and deserializing can become very

annoying.

The real answer to this problem are the Web Services - something

that is based on a known protocol (built on top of HTTP) and makes

easy the process of sharing data between client and server, hiding

transport and serialization problems.


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Working with Web Services you have to be aware of threethings that uniquely define the Web Service you want to

consume: Address, Binding and Contract.

Address - says where the service is located, in the form of a Uri

Binding - describes how the client and server will speak each other.

Serialization and deserialization matter is part of the binding but also

the transport: HTTP, HTTPS, and so on.

Contract - the most important part, that describes what the service

can do.

In WCF, a contract is an interface with a bunch of methods - usually called

Operations - and each one do something with some kind of input and output.


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Once you have the Address of the service you have to consume, the firstthing you have to do is creating a Proxy.

The proxy is a client side class that implements the Contract of the

service and hides to the developer the presimageence of a Web Service.

What it happens is that you call a method on the local class and the proxy take care of

serialize request, making the network call, reading the response and deserializes it.

Sample web services:

GeoIP

http://www.webservicex.net/geoipservice.asmx?wsdl

Stock Quote

http://www.webservicex.net/stockquote.asmx?wsdl

Demo Weather

http://www.webservicex.net/globalweather.asmx?WSDL
http://www.webservicex.net/geoipservice.asmx?wsdlhttp://www.webservicex.net/stockquote.asmx?wsdlhttp://www.webservicex.net/globalweather.asmx?WSDLhttp://www.webservicex.net/globalweather.asmx?WSDLhttp://www.webservicex.net/globalweather.asmx?WSDLhttp://www.webservicex.net/globalweather.asmx?WSDLhttp://www.webservicex.net/stockquote.asmx?wsdlhttp://www.webservicex.net/geoipservice.asmx?wsdlhttp://www.webservicex.net/geoipservice.asmx?wsdlhttp://www.webservicex.net/geoipservice.asmx?wsdl


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Location services

Windows Phone uses three technologies for finding yourlocation: GPS, WiFi based location, and Cell Tower based

location (triangulation).


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Location services

GPS technology relies on satellites in orbit and the phone'sability to receive signals from at least three of these

satellites.

The satellites are transmitting all the time from synchronized clocks.

But because of the satellites being different distances from the phone

the time received from the satellites will be slightly different, a user'sposition can be calulated from these time differences.

Cell Tower based location and WiFi based location are similar

to GPS in how they work.

When you use either one of these the phone will try to get theidentifiers for near by WiFi access points and cell towers. The

identifier is sent to a Microsoft service which keeps records of the

general area in which those WiFi access points or cell towers have

been seen and returns that information to the device.


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Location services

Each one of these location technologies differs in theaccuracy of the location that it provides.

GPS is the most accurate with the margin of error being around 10

meters in favourable conditions.

The next most precise location technology is WiFi based location.

WiFi access points don't transmit nearly as far as cell towers.

Cell tower based location is the least precise.

Generally speaking the more precise location technology

(GPS) also has a more significant impact on battery life.


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Location services

Things to Remember Request the Location Services capability in your

WMAppManifest.xml

Ask the user for permission to get their location

Be prepared for the possibility of location services beingdisabled on the phone

Don't transmit the user's location to any service without

their permission

Only use high accuracy location when needed Turn off location services when it is nolonger needed

Nokia Places API for Windows Phone
http://nikovrdoljak.wordpress.com/2012/04/16/nokia-places-api-for-windows-phone/http://nikovrdoljak.wordpress.com/2012/04/16/nokia-places-api-for-windows-phone/


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Accelerometer

The accelerometer is a sensorin the Windows Phone device

that measures the acceleration

on 3 axes (X, Y, Z), relative to

freefall.


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Accelerometer

In addition to a timestamp, the values are expressed in G-forces (1G = 9.81 m/s2).

It this means is that if the phone is lying face-up on a perfectly flat

surface, the Z axis would read1.0, and the other two axes would

read 0.

How to get values from accelerometer basic scenario:

Instantiate a new Accelerometer object.

Create a new ReadingChanged() event handler to monitor the

changes in data.

Pass the results of that event back to our pages thread (the eventfires on a different thread).

Use the data values in application.


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Accelerometer

The emulator emulates accelerometer data byAccelerometertab inAdditional tools window.

Feature introduced in Mango release.

By default the emulator assumes it is standing in portrait position,

lined up on a flat surface.

Other ways to emulate accelerometer data:

use Reactive Extensions to emulate and filter accelerometer data for

Windows Phone (check here)

use accelKit (check here)
http://msdn.microsoft.com/en-us/library/ff637521(VS.92).aspxhttp://tainicom.net/tools/accelkit.aspxhttp://tainicom.net/tools/accelkit.aspxhttp://msdn.microsoft.com/en-us/library/ff637521(VS.92).aspx


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Compass

In traditional terms, a compass is used to determine thedirection of the Earths magnetic north pole.

Mobile phones are using element called magnetometer.

It can still determine the direction of magnetic north, but it can alsodetermine rotation of the device relative to magnetic north.

In addition, it is also capable of detecting magnetic fields around thedevice (which often interfere with those other calculations).

The MagneticHeading is the heading, in degrees, measured clockwisefrom the Earths magnetic north.

The TrueHeading is the heading, in degrees, measured clockwise from

the Earths geographic north. The X, Y, and Z values that you retrieve from API are actually

measured in microteslas, which are a unit of magnetic field strength.

NOTICE: The emulator doesnt emulate compas data!
http://en.wikipedia.org/wiki/Microteslahttp://en.wikipedia.org/wiki/Microtesla


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Gyroscope

According to Wikipedia, a gyroscope is a device for measuringor maintaining orientation.

It has the ability to spin on three axes, the X, Y, and Z axis

While the Accelerometer measures acceleration, the Gyroscope

measures rotational velocity.

The data you receive measures the rotational velocity of the device in

radians per second.

This means that you can more accurately and smoothly measure the

current orientation of the device.

NOTICE: The emulator doesnt emulategyroscope data!
http://en.wikipedia.org/wiki/Gyroscopehttp://en.wikipedia.org/wiki/Gyroscope


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Compas & GyroscopeOptional hardware

Not all Windows Phones will have a Gyroscope and/or

Compas. In fact, only phones that come out after the Mango

release will be capable of having a Gyroscope and/or Compas

It is still an optional piece of hardware. Microsoft has created a Motion class that combines the data

from the Accelerometer, the Compass, and the Gyroscope

into one class that we can use more effectively.


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Q & A

??

Documents

WP7 Tpa 09 Web Location Sensors