Book Image

Android 9 Development Cookbook - Third Edition

By : Rick Boyer
Book Image

Android 9 Development Cookbook - Third Edition

By: Rick Boyer

Overview of this book

The Android OS has the largest installation base of any operating system in the world. There has never been a better time to learn Android development to write your own applications, or to make your own contributions to the open source community! With this extensively updated cookbook, you'll find solutions for working with the user interfaces, multitouch gestures, location awareness, web services, and device features such as the phone, camera, and accelerometer. You also get useful steps on packaging your app for the Android Market. Each recipe provides a clear solution and sample code you can use in your project from the outset. Whether you are writing your first app or your hundredth, this is a book that you will come back to time and time again, with its many tips and tricks on the rich features of Android Pie.
Table of Contents (24 chapters)
Title Page
Copyright and Credits
Dedication
About Packt
Contributors
Preface
Index

Recognizing tap and other common gestures


Unlike the Event Listeners described in the previous recipe, gestures require a two-step process:

  1. Gather movement data
  2. Analyze the data to determine whether it matches a known gesture

Step 1 begins when the user touches the screen, which fires the onTouchEvent() callback with the movement data sent in a MotionEvent object. Fortunately, Android makes step 2, analyzing the data, easier with the GestureDetector class, which detects the following gestures:

  • onTouchEvent()
  • onDown()
  • onFling()
  • onLongPress()
  • onScroll()
  • onShowPress()
  • onDoubleTap()
  • onDoubleTapEvent()
  • onSingleTapConfirmed()

This recipe will demonstrate using GestureDetector.SimpleOnGestureListener to recognize the touch and double tap gestures.

Getting ready

Create a new project in Android Studio and call it CommonGestureDetector. Use the default Phone & Tablet options and select Empty Activity when prompted for the Activity Type.

How to do it...

We will be using the activity itself to detect gestures, so...