Xamarin.Android - Gesture Detector

Introduction

 The gesture detector means finger movement in the touchscreen interface. The gesture types are Tab, Drag, Flick, Swipe, Double Tab, Pinch, Three Finger Pinch, Three Finger Swipe , Touch, Hold, Rotate and Shake. In this article, we are going to learn how to implement these gestures in our application.

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Let's start the story

Create a Xamarin Android project in Visual Studio 201.Go to the Visual Studio >> Create new project >> select Android App (Xamarin) and click Next. In the Next dialog box, give Project Name, Location Name and Location, then click the Create button. 

After the project creation, open content_main.xml file and add TextView widget in the UI and set width and height as match_parent. The code is given below.

Next, open MainActivity.cs class by double-clicking it. The gesture interfaces are going to implement in this MainActivity.This interface will create following gesture methods:

• OnDown
• OnScroll
• OnSingleTabUp
• OnLongPress
• OnFling
• OnShowPress

Methods with definitions here:

• OnDown(MotionEvent e) - Down MotionEvent will get triggers, once touch or tab the UI.
• OnFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) - Notifies of swipe occurs in the start and end of MotionEvent or threshold of swipe.
• OnLongPress(MotionEvent e) - This event will trigger, once long touch or tab of UI
• OnScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) - while scrolling this event will get trigger.
• OnShowPress(MotionEvent e) - performed a done MotionEvent and not above performed a moment.
• OnSingleTabTabUp(MotionEvent e) - On single tab the widget or layout this event.

Based on the Fling start and end velocity, we can set the following swipe directions:

1. Top to Bottom
2. Bottom to Top
3. Right to Left
4. Left to Right

Velocity has two types 

1. Swipe threshold - the difference between the initial position and final position of touch in the any four directions, we already seen before.
2. Velocity threshold - how quickly swiped gesture.

Finally set this interface to that TextView, we already designed in content_main.xml and this page code is give below.

Run your application and get output like below gif

The full source code is here - GitHub

Conclusion

I hope you all, understand the gestures and how to implement our application, Thank for reading.