cse4443 – mobile user interfaces€¦ · android touch “gestures” • question: – is it...

Scott MacKenzieYork University

CSE4443 – Mobile User Interfaces

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(Part 2)

Demo_Multitouch

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EscLet’s have a look.

What is Where!


DemoTouchActivity.java

PaintPanel

Activity

View

onTouch

DemoInkActivity.java

PaintPanel.java

Activity

View

onTouch

Demo Touch Demo InkDemoMultitouchActivity.java

PaintPanel.java

Activity

View

onTouch

Demo Multitouch

DemoScaleActivity.java

Activity

PaintPanel.java

View

onTouchEvent

Demo Scale

Coming Up…

Map

• Android’s “Touch Mode”• Single touch• Multitouch• Touch gestures


Android Touch “Gestures”

• Question:– Is it possible to detect high-level finger actions, such

as double tap, flick, drag, pinch, etc.?

• Answer: – Yes (of course) … but how?

• Two approaches:– Roll your own (use a touch listener in combination

with MotionEvent, state variables, timers, etc.) – Use Android’s gesture detector classes


1-Finger ( ) Gestures

Touch Longpress

Swipe ordrag

Double touchdrag

Doubletouch

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Long pressdrag

Android’s GestureDetector Class(single touch)

• From the API:– Detects various gestures and events using the

supplied MotionEvents

• Programming approach:– Extend the “convenience” class…

… and implement methods of interest


GestureDetector.SimpleOnGestureListener

GestureDetector.SimpleOnGestureListenera “convenience” class

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Minimum Implementation

Note: We are handing touch events in the view, not in the activity.

2-finger ( ) Gestures

Pinchopen

Pinchclosed

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Android’s ScaleGestureDetector Class(multitouch)

• From the API:– Detects scaling transformation gestures using the

supplied MotionEvents

• Programming approach:– Extend the “convenience” class…

… and implement methods of interest


ScaleGestureDetector.SimpleOnScaleGestureListener

ScaleGestureDetector.SimpleOnScaleGestureListener

a “convenience” class


Notes:• The listener methods above receive a ScaleGestureDetector

object. • This is different from the listener methods in GestureDetector.SimpleOnGestureListener, which receive a MotionEvent object.

• What methods are available with ScaleGestureDetector? (next slide)

ScaleGestureDetector



Minimum Implementation

Focus-point Zooming(see DemoScale for details)


Zooming PhilosophyDo not:

• Zoom about the centre of the imageDo:

• Zoom about the focus point

Focus-point zooming is desirable because the focus point is• The point of interest to the user• Where the user is looking

Homework

• The usual…

• I.e.,– Download all the “demo” programs from earlier slides– Import into Android Studio projects– Connect your device and click “Run”– Observe UI behaviour– Ready the APIs (and links within)– Study source code


Thank You


cse4443 – mobile user interfaces€¦ · android touch “gestures” • question: – is it...

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