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Near Field Communication with Android Cookbook
Near Field Communication with Android Cookbook

Near Field Communication with Android Cookbook: Discover the endless possibilities of using Android NFC capabilities to enhance your apps through over 60 practical recipes

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Near Field Communication with Android Cookbook

Chapter 2. Detecting a Tag

In this chapter, we will cover the following topics:

  • Understanding the foreground dispatch system
  • Understanding the tag dispatch system
  • Verifying if your app started because of an NFC intent
  • Filtering tags by their content type
  • Filtering tags by their content type using programs
  • Filtering tags by their technology
  • Filtering tags by their technology using programs
  • Filtering URI tags

Introduction

As a software developer, I have learned that one should never jump steps regarding any new subject. We should always understand how the machine works and what can we do with it. Practicing with some basic examples and some trial and error always helps setting our minds on the right path.

In this chapter, we will perform some basic examples that will allow us to start writing NFC applications and interacting with those awesome stickers called NFC tags.

NFC tags are small electronic stickers without their own power source that can be placed anywhere and contain small blocks of data—typically, URL, contacts, and text. This data can then be read by any NFC-enabled device when there is a communication between the device and the tag; this is typically done by bringing the device very close to the tag. Since the tag has no power source, we can say it is the passive element in the communication and, therefore, the active element is the NFC-enabled device such as a smartphone...

Understanding the foreground dispatch system

In Android, we can have multiple applications to complete the same task. For example, we can have multiple web browsers installed, and when we want to open a web page, the Android system prompts us to choose which application to open; NFC applications are no different. The foreground dispatch system allows an activity to intercept an NFC intent (tag detected or P2P events) and claim priority over other activities that are registered to handle the same intent. This way, when our application is in the foreground, users won't be prompted to choose which application to open, and the intent is sent to our application.

An Intent is a messaging object that describes an operation to be performed and is generally used to start activities, services, and facilitate data exchange among different applications.

How to do it...

We are going to create an application that demonstrates how the foreground dispatch system works and how it is useful to us. To do...

Understanding the tag dispatch system

The Android system has a structured way to deal with the different tag types, technologies, and content. In this recipe, we will create a simple app that will allow us to visualize the implemented structure.

How to do it...

By performing the following steps, we are going to create an application that will allow us to see the triggered action when we tag different tags in our device:

  1. Open the MainActivity.java file from the previously created NfcBookCh2Example1 project.
  2. On the onNewIntent method, add the following lines of code:
    String action = intent.getAction();
    Toast.makeText(this, action, Toast.LENGTH_SHORT).show();
    
  3. Open the NFC Simulator tool and simulate a few taps for different tag types and then see the results.

    In the NFC Simulator tool, when tag names end with _LOCKED, it means that the tags are formatted and have content on them; probably, an NDEF record. Therefore, the NDEF_DISCOVERED action will be triggered. Unformatted tags will trigger the...

Verifying if your app started because of an NFC intent

Because the onNewIntent method is triggered by any intent, we need to perform some additional tests just to make sure it is an NFC intent.

How to do it...

  1. Open the MainActivity.java file from the previously created NfcBookCh2Example1 project.
  2. In the onNewIntent method, add the following lines of code:
    if (!intent.hasExtra(NfcAdapter.EXTRA_TAG)) {
      return;
    }

How it works...

On the onNewIntent method, we test the incoming intent for its action. The intent action must match ACTION_NDEF_DISCOVERED, ACTION_TAG_DISCOVERED, or ACTION_TECH_DISCOVERED, to be an NFC intent. In this example, we are only testing for the ACTION_NDEF_DISCOVERED action because this is the simplest format to work with.

When the Intent action is an NDEF, EXTRA_TAG is required so that we can test if the extra is not null. This extra represents the tag object instance.

Tip

For more readable and organized code, we can create a method that verifies if any intent is an NFC intent...

Filtering tags by their content type

NFC tags can hold several types of data such as URIs and simple text. In our applications, we may only want to handle tags in which content is recognized. That way, we avoid unexpected exceptions.

How to do it...

We'll create an application that is executed only when the content type matches what is specified by us. Open the AndroidManifest.xml file from the previously created NfcBookCh2Example1 project and add the following intent-filter to the main activity declaration:

<intent-filter>
    <action android:name="android.nfc.action.NDEF_DISCOVERED"/>
    <category android:name="android.intent.category.DEFAULT"/>
    <data android:mimeType="text/plain" />
</intent-filter>

How it works...

While declaring the activity in the AndroidManifest.xml file, we also specify that the activity only receives intents that match some conditions. In this case, the main activity receives only NFC intents with...

Introduction


As a software developer, I have learned that one should never jump steps regarding any new subject. We should always understand how the machine works and what can we do with it. Practicing with some basic examples and some trial and error always helps setting our minds on the right path.

In this chapter, we will perform some basic examples that will allow us to start writing NFC applications and interacting with those awesome stickers called NFC tags.

NFC tags are small electronic stickers without their own power source that can be placed anywhere and contain small blocks of data—typically, URL, contacts, and text. This data can then be read by any NFC-enabled device when there is a communication between the device and the tag; this is typically done by bringing the device very close to the tag. Since the tag has no power source, we can say it is the passive element in the communication and, therefore, the active element is the NFC-enabled device such as a smartphone or an NFC...

Understanding the foreground dispatch system


In Android, we can have multiple applications to complete the same task. For example, we can have multiple web browsers installed, and when we want to open a web page, the Android system prompts us to choose which application to open; NFC applications are no different. The foreground dispatch system allows an activity to intercept an NFC intent (tag detected or P2P events) and claim priority over other activities that are registered to handle the same intent. This way, when our application is in the foreground, users won't be prompted to choose which application to open, and the intent is sent to our application.

An Intent is a messaging object that describes an operation to be performed and is generally used to start activities, services, and facilitate data exchange among different applications.

How to do it...

We are going to create an application that demonstrates how the foreground dispatch system works and how it is useful to us. To do so,...

Understanding the tag dispatch system


The Android system has a structured way to deal with the different tag types, technologies, and content. In this recipe, we will create a simple app that will allow us to visualize the implemented structure.

How to do it...

By performing the following steps, we are going to create an application that will allow us to see the triggered action when we tag different tags in our device:

  1. Open the MainActivity.java file from the previously created NfcBookCh2Example1 project.

  2. On the onNewIntent method, add the following lines of code:

    String action = intent.getAction();
    Toast.makeText(this, action, Toast.LENGTH_SHORT).show();
    
  3. Open the NFC Simulator tool and simulate a few taps for different tag types and then see the results.

    In the NFC Simulator tool, when tag names end with _LOCKED, it means that the tags are formatted and have content on them; probably, an NDEF record. Therefore, the NDEF_DISCOVERED action will be triggered. Unformatted tags will trigger the...

Verifying if your app started because of an NFC intent


Because the onNewIntent method is triggered by any intent, we need to perform some additional tests just to make sure it is an NFC intent.

How to do it...

  1. Open the MainActivity.java file from the previously created NfcBookCh2Example1 project.

  2. In the onNewIntent method, add the following lines of code:

    if (!intent.hasExtra(NfcAdapter.EXTRA_TAG)) {
      return;
    }

How it works...

On the onNewIntent method, we test the incoming intent for its action. The intent action must match ACTION_NDEF_DISCOVERED, ACTION_TAG_DISCOVERED, or ACTION_TECH_DISCOVERED, to be an NFC intent. In this example, we are only testing for the ACTION_NDEF_DISCOVERED action because this is the simplest format to work with.

When the Intent action is an NDEF, EXTRA_TAG is required so that we can test if the extra is not null. This extra represents the tag object instance.

Tip

For more readable and organized code, we can create a method that verifies if any intent is an NFC intent...

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Description

An easy-to-follow guide, full of hands-on examples of and real-world applications. Each recipe is explained and placed in context. If you want to learn how to create NFC-enabled Android applications, this is the book for you. Perhaps you already know a bit about Android application developments but have never used NFC, or perhaps you know a little about NFC android development but want some more advanced features and examples. In either case, this book will get you up and running quickly. You are expected to have Android programming knowledge.

What you will learn

  • Work with the foreground dispatch system NFC data exchange format
  • Create several applications to consolidate knowledge and see what NFC can be used for
  • Read and write tags with URI, text, mime, and external types
  • Share content across two NFCenabled devices
  • Extend NFC usage using Bluetooth and WiFi
  • Combine NFC with social networks and games
  • Use Open NFC for Android to set up a virtual development and testing environment
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Publication date : Jun 13, 2014
Length: 286 pages
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Language : English
ISBN-13 : 9781783289653
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Table of Contents

11 Chapters
1. Getting Started with NFC Chevron down icon Chevron up icon
2. Detecting a Tag Chevron down icon Chevron up icon
3. Writing Tag Content Chevron down icon Chevron up icon
4. Writing Tag Content – Real-life Examples Chevron down icon Chevron up icon
5. Reading Tag Content Chevron down icon Chevron up icon
6. Reading Tag Content – Real-life Examples Chevron down icon Chevron up icon
7. Sharing Content across Devices Chevron down icon Chevron up icon
8. Error Handling and Content Validation Chevron down icon Chevron up icon
9. Extending NFC Chevron down icon Chevron up icon
10. Real-life Examples – NFC Utilities Chevron down icon Chevron up icon
Index Chevron down icon Chevron up icon

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W Boudville Aug 15, 2014
Full star icon Full star icon Full star icon Full star icon Empty star icon 4
NFC is a limited range technology that has proved successful in a few uses. Mostly to do with financial transactions. The book starts with a good question and answer section. Mostly about objections often raised to NFC. Principally, the concern is power drainage. The response is that NFC is low power, at least compared to Bluetooth or WiFi. So the book argues that you can keep your NFC transceiver continuously on.Some chapters deal with a common NFC use - reading and occasionally writing tags. The reading is far more common. While the writing of a tag means it must have more complex and hence more expensive circuitry. Hopefully you know that an URL is a special case of an URI. The book has a list of the standard prefixes for all the possible URIs. Because the limited capacity of an NFC tag means it is ideal to hold an URI. Granted in practice the most common URI put into the tags will probably be an URL anyway. But it helps to be aware of the broader possibilities inherent in what can be put into a tag.Naturally, the reading and subsequent parsing of a tag then specialises to parsing an URI. One section of the text explains the parsing. Easy for experienced programmers.The book also goes beyond tag access. Another key recent functionality is Android Beam. Which is Android's take on the Simple NDEF Exchange Protocol [SNEP]. It lets 2 Android phones exchange data in a peer to peer mode. Perhaps here is where it can interesting for some readers. You have a chance via the code snippets to garner inspiration for novel interactions. Of necessity, the snippets just display trivial functionality. Your job is to improve on these.
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