Mobile Device Features 2
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Compass
- Certain devices have a built in compass sensor.
- If they do, they call the ondeviceorientation() function when the compass reading changes.
- An event object is passed to the function with the compass reading in evt.webkitCompassHeading.
Function window_ondeviceorientation(evt) TextBox1.value=evt.webkitCompassHeading End Function
- The Compass sample uses this information to rotate an image of a compass.
- The webKitTransform function rotates an image efficiently.
pos="0" Function window_ondeviceorientation(e) imgCompass.style.webkitTransform="rotate(" & pos & "deg)" pos = e.webkitCompassHeading imgCompass.style.webkitTransform="rotate(-" & pos & "deg)" End Function
Geolocation
- Geolocation uses GPS sensors to return the current location of the device.
- The watchPosition() function sets the frequency of the Geolocation events.
- When a Geolocation event is triggered, the function named in the watchPosition function is called.
- The following data is passed to the event:
location.coords.longitude | The current longitude of the device. GPS required. |
location.coords.latitude | The current latitude of the device. GPS required. |
location.coords.altitude | The height of the location. GPS required. |
location.coords.accuracy | The accuracy of the location. GPS required. |
location.coords.altitudeAccuracy | The accuracy of the altitude. GPS required. |
location.coords.heading | Degrees clockwise from North. GPS required. |
location.coords.speed | Speed, meter per second. GPS required. |
location.coords.timestamp | time and date of the observation. GPS required. |
- Here's the code to start generating geolocation events:
Dim gps function btnStart_onclick() options={timeout: 5000, maximumAge: 5000, enableHighAccuracy: True} gps=navigator.geolocation.watchPosition(onGeolocation, errorCallBack, options) End function
- This code will call onGeolocation every 5 seconds.
- If GPS data cannot be obtained, the errorCallBack function is called.
- Cancel it by executing:
navigator.geolocation.clearWatch(gps)
- Here's what the onGeolocation looks like. It gets called every 5 seconds.
function onGeolocation(location) Dim s s = "Longitude: " + location.coords.longitude & vbCRLF s = s & "Latitude: " + location.coords.latitude & vbCRLF s = s & "Speed: " + location.coords.speed & " " s = s & "Altitude: " + location.coords.altitude & vbCRLF s = s & "Accuracy: " + location.coords.accuracy & " " s = s & "Accuracy(altitude): " + location.coords.altitudeAccuracy & " " & vbCRLF 'Convert timestamp if needed. if IsNumeric(location.timestamp) Then gpsDate=new Date(location.timestamp) else gpsDate=location.timestamp End if TextArea1.value = s & "Timestamp: " + gpsDate ShowMap(location.coords.latitude, location.coords.longitude) End function
- This function displays the GPS results in a TextArea.
- The code has to deal with the problem of different browsers returning timestamp in different formats.
- The ShowMap() function near the end displays a map from Google Maps.
function ShowMap(latitude, longitude) if SysInfo(10)-lastRefresh<10000 Then Exit function lastRefresh=SysInfo(10) s = "'https://maps.google.com/maps/api/staticmap?center=" & _ latitude & "," & longitude & _ "&zoom=14&size=300x200&maptype=roadmap&output=embed'" Map.innerHTML="<img width=300 height=200 src=" & s & "></img>" End function
- This function displays a Google map.
- The map is updated every 10 seconds
- More info on Google maps here: http://code.google.com/apis/maps/documentation/staticmaps/
- We pack the latitude and longitude into a URL query string.
- We display the results of the URL in an HTMLview.
Accelerometer
The Accelerometer is a sensor that returns information about the device's movement.
- Results are returned in meters per second squared.
- Results can be with or without taking gravity into effect.
- Whenever motion is detected, the window_ondevicemotion function is called.
Sub window_ondevicemotion(event) ax = event.accelerationIncludingGravity.x; ay = event.accelerationIncludingGravity.y; End Sub
- This code sets a couple of global variables: acceleration in the x direction (horizontal) and the y direction (vertical)
- We can use this data to move a ball around on the screen.
- We will sample the the movement 100 times per second.
- Based on how high the movement rate is, move the ball varying distances.
delay = 10 SetInterval(moveBall, delay)
- SetInterval is an AppStudio function which calls a function repeatedly.
- moveBall is the name of the function to call.
- delay is the time, in milliseconds.
Sub moveBall() vy = vy + -(ay) vx = vx + ax y = parseInt(y + vy * vMultiplier) x = parseInt(x + vx * vMultiplier) 'do bounds checking If x<0 Then x = 0 vx = 0 End if If y<0 Then y = 0 vy = 0 End if If x>document.documentElement.clientWidth-20 Then x = document.documentElement.clientWidth-20 vx = 0 End if If y>document.documentElement.clientHeight-20 Then y = document.documentElement.clientHeight-20 vy = 0 End if ball.style.top = y + "px" ball.style.left = x + "px" End Sub
- The first 4 statements calculate the new position.
- The next section checks to make sure the ball does not roll off the screen.
- The last two statements do the actual movement.
The complete sample is called Accelerometer.