Programming for Mobile III

Android Studio 2.0

• Preview version announced Monday, 11/23/2015
• Adds several improvements including
  • Instant Run feature to reduce time between change in application and change on device/emulator
  • GPU Anaylsis
  • Interface emulate location or a series of locations
• To see some examples in action, watch this talk

Sensor Listener Review

• Event registration for sensors must be handled more responsibly than UI Events
• SensorEventListeners caputre a wide range of sensors and accuracy changes

App Permissions

• Apps running on Android (or any mobile system) are much more tightly controlled in what they can do
• Accessing any resource outside of the app requires permission, including the internet or installing an icon on the phone
  • Many permissions must be specified but are granted by the OS without input from the user
  • Some permissions deal with more sensitive data and require the user agree for the app to access them, such as location or phone calls
• The tag < uses-permision /> in the file AndroidManifest.xml is how permissions are set

Using Location

• When building an app there are two different APIs that can be used for location
  • The android.location package
    • Provides low level access to location API
    • Doesn't require Google Play Services, is soley part of the Android system
  • The com.google.android.gms.location package
    • Higer level API
    • Requires Google approved device
    • Can be updated seperately from the OS

Play Services API Location

• To use location from play services, first request permission for location

  <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
  

• Then a new client is created with specifications for the required API and the behavior on connection to that API

  mGoogleApiClient = new GoogleApiClient.Builder(this)
        .addConnectionCallbacks(this)
        .addOnConnectionFailedListener(this)
        .addApi(LocationServices.API)
        .build();
  

• After it is created, call the connect method (This isn't clear from the online docs!)

mGoogleApiClient.connect();

Play Services API Location Callbacks

• In the prior example the event handler was this for both cases
  • The activity itself implemented both the ConnectionCallbacks and OnConnectionFailedListener interfaces
  • This interface specifies the method onConnected that runs when your application is connected to the API
  • Listening to this event will only get you the location one time.

Location Listener

• To recieve repeated updates, a LocationListener is required
• This is a bit more similar to listening to sensor events
  • A LocationRequest object defines the parameters of the requests, ie update frequency
  • The LocationListener handles the update through the onLocationChange event |

Localization

• How do we make one application that can be deployed around the world in different languages
• Thus far we have abstracted out the design from the code
  • We can further abstract out the text contents from the design?
• Support for this is built in to Android apps

String Resources

• To create a file of string constants, place them in the res/values directory in the file named strings.xml
• The structure of this file looks like:

  <resources>
    <string name="app_name">CMSC331Ex</string>
    <string name="action_settings">Settings</string>
  </resources>
  

• To access the string resource in XML use "@string/name"

Multiple String Resources

• The string resources in the res/values directory are the default resources
• To provide a string file based on locale, create strings.xml in the res/values-code directory
  • The code must be a valid 2 or 5 letter ISO code for a locale
    • fr for French
    • es for Spanish
    • de for German
    • es_rUS for American Spanish
• The correct strings will automatically be used.