Android Programming: Lecture 14

Android Programming Lecture 14 Vladimir Kulyukin Department of Computer Science Utah State Universitywww.youtube.com/vkedco www.vkedco.blogspot.com

Resources Source code and presentation materials for this lecture are available at http://vkedco.blogspot.com/2011/12/android-programming-lecture-14.htmlwww.youtube.com/vkedco www.vkedco.blogspot.com

Outline ● Touchscreens ● NDK – Native Development Kit ● Notable Future Trendswww.youtube.com/vkedco www.vkedco.blogspot.com

Touchscreenswww.youtube.com/vkedco www.vkedco.blogspot.com

Motivation ● Touchscreen is a viable input alternative, especially on the go ● Touchscreen is a viable input alternative for visually impaired individuals ● Touch gestures are generally better recognized than speech gestures ● Unlike speech, touch gestures preserve privacywww.youtube.com/vkedco www.vkedco.blogspot.com

Touchscreens ● A Touchscreen is made up of special materials that capture pressure inputs and translate them into digital data ● Digital data are passed to software that process them ● On Android, digital data come in the form of MotionEvent objectswww.youtube.com/vkedco www.vkedco.blogspot.com

MotionEvent ● MotionEvent objects are created when the user touches the devices touchscreen ● At the most basic level, MotionEvent objects contains the x and y coordinates of the touch ● MotionEvent objects are typically passed to the onTouchEvent() method of a View objectwww.youtube.com/vkedco www.vkedco.blogspot.com

MotionEvent ● MotionEvent object sequence is created when the user touches the touchscreen, moves the finger on the screen, and then lifts it up ● Each MotionEvent object contains information on – Type of action captured – Pressure value – X and Y coordinates – Time of the eventwww.youtube.com/vkedco www.vkedco.blogspot.com

MotionEvent.getAction() ● MotionEvent.getAction() returns ACTION_DOWN, when the user touches the touchscreen ● MotionEvent.getAction() returns ACTION_MOVE, when the user moves sideways ● MotionEvent.getAction() returns ACTION_UP, when the user lifts up his/her fingerwww.youtube.com/vkedco www.vkedco.blogspot.com

View.OnTouchListener ● The class that receives touchscreen events must implement View.OnTouchListener ● There are two methods to handle MotionEvent objects: onTouch(View, MotionEvent) and onTouchEvent(MotionEvent) ● onTouch(View, MotionEvent) is used if one OnTouchListener is set to process touchscreen events from multiple viewswww.youtube.com/vkedco www.vkedco.blogspot.com

View.OnTouchListener ● If onTouch() or onTouchEvent() consumes the MotionEvent and no other component needs to know about it, it should return true ● If onTouch() or onTouchEvent() does not consume a received MotionEvent, it should return falsewww.youtube.com/vkedco www.vkedco.blogspot.com

DragDropTouchDemo Projectwww.youtube.com/vkedco www.vkedco.blogspot.com

The Problem Draw a 3x3 TicTacToe board, five red circles, and five crosses. Capture touchscreen events allow the user to move circles and crosses on the touchscreen (e.g., play TicTacToe)www.youtube.com/vkedco www.vkedco.blogspot.com

DragDropTouchDemo Project Demo and Source Codewww.youtube.com/vkedco www.vkedco.blogspot.com

Development and Consumption of Touch Gestureswww.youtube.com/vkedco www.vkedco.blogspot.com

Development of Touchscreen Gestures ● If you have a set of gestures that you want to define and process, you may want to use Android GestureBuilder application to develop a library of gestures ● On the emulator, the built gestures are saved in mnt/sdcard/gestures ● Each gesture receives a name and can be subsequently deleted and redefinedwww.youtube.com/vkedco www.vkedco.blogspot.com

Consumption of Touchscreen Gestures ● Eclipse project that implements a consumer of built gestures must create a directory /res/raw ● The file mnt/sdcard/gestures must be saved in /res/raw ● The main layout of the gesture consumer must be android.gesture.GestureOverlayView ● The class that consumes gestures must implement OnGesturePerformedListenerwww.youtube.com/vkedco www.vkedco.blogspot.com

BuiltGestureConsumer Projectwww.youtube.com/vkedco www.vkedco.blogspot.com

The Problem Develop a library of three touchscreen gestures for written letters a, b, and c with Android GestureBuilder. Consume the developed gestures in an application that toasts each recognized gesture.www.youtube.com/vkedco www.vkedco.blogspot.com

BuiltGestureConsumer Project Demo and Source Codewww.youtube.com/vkedco www.vkedco.blogspot.com

Android NDK - Native Development Toolkitwww.youtube.com/vkedco www.vkedco.blogspot.com

Android NDK Development ● If you need efficiency in your code, you may want to integrate C/C++ into your projects ● On Windows, install cygwin for C/C++ compilation ● Develop your C/C++ code in your favorite editor ● Create jni folder in your Eclipse project and place there your C/C++ source code in there, plus the two files: Android.mk and Application.mkwww.youtube.com/vkedco www.vkedco.blogspot.com

Android NDK Development ● Leave Application.mk alone ● Edit the value of LOCAL_SRC_FILES in Android.mk by listing all your .cpp files ● On command line (cygwin command line on Windows), cd into your project directory ● In your project directory, call <NDK-path>/ndk-build ● Debug errors and run the applicationwww.youtube.com/vkedco www.vkedco.blogspot.com

NDKDemo Projectwww.youtube.com/vkedco www.vkedco.blogspot.com

The Problem Write an application that fills an array of five random integers (created on the Java side), passes it to a C++ program that increments each integer by 1.www.youtube.com/vkedco www.vkedco.blogspot.com

NDKDemo Project Demo and Source Codewww.youtube.com/vkedco www.vkedco.blogspot.com

NDKImageBinarization Projectwww.youtube.com/vkedco www.vkedco.blogspot.com

The Problem Write an application that uses C++ to binarize grayscale images.www.youtube.com/vkedco www.vkedco.blogspot.com

NDKImageBinarization Project Demo and Source Codewww.youtube.com/vkedco www.vkedco.blogspot.com

NDKImageBinarization Project Source Codewww.youtube.com/vkedco www.vkedco.blogspot.com

Notable Future Trends ● Cloud-Based Integrated Development Environments ● Crowd Sourcing ● Speech UIswww.youtube.com/vkedco www.vkedco.blogspot.com

References & Reading Suggestions ● http://developer.android.com/sdk/ndk/overview.html ● http://developer.android.com/sdk/ndk/index.html ● Meier, “Professional Android 2 Application Development” ● Hashimi, Komatineni, MacLean, “Pro Android 2”www.youtube.com/vkedco www.vkedco.blogspot.com

Feedback Bugs, errors to vladimir dot kulyukin at gmail dot comwww.youtube.com/vkedco www.vkedco.blogspot.com

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Android Programming: Lecture 14

by Vladimir Kulyukin on Dec 07, 2011

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