Lecture 12 Working with Location Sensors and Review

Transcription

1 Lecture 12 Working with Location Sensors and Review Lecture Overview Working with Location Sensors Review of Unit HIT3328 / HIT8328 Software Development for Mobile Devices Dr. Rajesh Vasa, 2011 Blog: Location Sensors Smart phones can detect location via different methods: IP Geo location over WiFi (~few Km error) Cell Tower Triangulation* (~500m error) GPS (~10m error) Cell tower based location must be supported by Telephone network provider Constraints when working with Location We need to design apps to cope with, Different types of location providers (GPS, Network, Cell tower) User that is mobile -- continuous data change Varying accuracy + intermittent loss of data GPS / WiFi drain battery 3 4 Use Location Sensors Sparingly Use location sensors sparingly, cache location if possible Accuracy and Response Times Vary GPS can take many minutes to provide location WiFi is near instantaneous (if internet is available) Cell Triangulation is quick, if provided by Tel. provider 5 6

2 Be Prepared to Continuously Improve Cache & Work with Last Known Location Last known location / Cached location are better than no location (depends on context) Design to use the best location information continuously 7 8 Key Android API for Location Location Provider Location Manager Location Listener lm = (LocationManager) this.getsystemservice(context.location_service); lm.requestlocationupdates(locationmanager.gps_provider,0,0,listener); Location l = lm.getlastknownlocation(locationmanager.gps_provider); Location Sensors & Android Emulator The emulator does not have a location sensor GPS/Network/ Passive providers do not work You can send Mock locations to emulator Handy for testing -- but you will need a device to properly test this Hardware is needed to work with any sensor Other Location Providers LocationManager.PASSIVE_PROVIDER, LocationManager.NETWORK_PROVIDER 9 10 Lecture Overview Working with Location Sensors Review of Unit Mobile Ecosystem Content Providers (Music/Video/Books) Ad Networks Platform App. Distribution Billing Telephone Networks Handset OEMs Cloud Infrastructure 11 12

3 Mobile phones are a fashion statement Culture Fashion Time-Bound User View: Ugly apps. ruin the look of a pretty (expensive) gadget Convention Over Configuration Software design paradigm Aims to reduce decisions developers make Why is this needed? When we build software, there is a lot of routine and repetitive decision making By following a certain development style, we reduce the decisions we need to make What do we lose? -- Some flexibility, and developers have to accept the convention Android Project Structure (convention) Source code (src) Generated code (gen) Resources (res) Images (drawable) Layout of app (layout) Constants/Strings (values) Android Programming languages: Java, C/C++ Image Source: Android is a bi-lingual platform C/C++ Java Android Device User Interaction Android has a three key buttons Menu Apart from these buttons, vendors can add more buttons (if they wish) Image Source: Back Home 17 18

4 Drawable at Different Resolutions Separation of Concerns in Android High Presentation Functionality Low Medium Layout Definition (main.xml) Activity Class Event Handling, I/O Wiring up the Buttons (Another Way) Bundle stores simple state information putdouble(key, value) putstring(key, value) putint(key, value) putstringarray (key, value[]) Bundle Buttons support onclick in the layout XML Code Snippet: It is a Key, Value store system (like a Hash Table or a Hash Map) state.putstring("inputtemperature", inputtemp); Working with Resources Layout XML File Via Java Code on.png 23 off.png Android Activities are Managed by O/S 24 Application Activity-C Activity-A Activity-B Activities have a parent application Activity has Life Cycle Application is NOT managed directly by the O/S Life Cycle => Managed by Operating System

5 Using Read-Tap Asymmetry Heuristics to Check for Usability Labels set to 24sp Labels set to 14sp Usability/Design Check List Sketch Paper Prototype Interactive Prototype Reflect on Answers Early Release Beta Release In Forms, we can reduce label text size, while keeping input field size at unchanged Make Changes 26 Final Release 25 Occlusion on Mobile Devices Occlusion -- The human hand can get in the way of interaction Which layout offers less occlusion issues? Impact of the Style <TextView android:text="first Name:" android:layout_width="wrap_content" android:layout_height="wrap_content"> </TextView> Customising IME Parcel Protocol (more details)... <EditText android:layout_width="match_parent" android:imeoptions="actionnext" Next Button android:text="" android:layout_height="wrap_content"> </EditText> This constant has to be created and named CREATOR Many IME options are available Useful Factoid: ios also offers similar customisation 29 30

6 Custom List Row Mobile App. Design Approach Motivation Features Scenarios Constraints Sketching Prototyping Navigation Flow Design We can specify a custom layout for rows in a list Styles & Layouts Strings & Resources Screen (Activity) Definition/Design Domain/Data Model Mobile App. Design Approach Navigation Flow - Example Motivation Features Scenarios Constraints Styles & Layouts Strings & Resources Screen (Activity) Definition/Design Sketching Prototyping Navigation Flow Design Complete as much as possible on paper Domain/Data Model Messaging List Menu [Settings] Settings List [New Message] Compose Message [Compose] Menu Select Ringtone Vibrate Resources Stored in Compressed Form Key DB Classes/Interfaces (in Android) Applications are deployed as APK files (compressed archives) Resources are also compressed as part of the package creation process If you have to access any resources, they need to be uncompressed first SQLiteOpenHelper SQLiteDatabase SQLiteStatement Open/Create DB Interact with DB Encapsulates SQL Statement 35 36

7 UI is Single Threaded - Beware! User taps button User taps 4 button (again) Button 1 touch event Update View State (touched) Execute Custom Code Invalidate View (redraw) Event Queue 5 This event causes a lock up 2 dequeue UI Thread (dequeue, notify & redraw) Rendering of Components (Android) Tree of UI Components Two Pass Process Measure and Determine Position of Components Draw (visible) Components/Bitmaps Assume this is a long task! (over 5 seconds) 3 inform widget Parents are responsible for layout of child components Each View is responsible for drawing itself to screen See: General Design Solution for Networking All network access has to be done on a separate thread UI Thread cannot block We have to assume it will block Options: Custom threading Use a message based solution Async Task 39