DevFright

Learning Programming

How to Use the CMMotionActivityManager

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Using the various sensors on your device, Apple is able to predict if you are walking, running, in a vehicle, or stationary. This is all done quietly in the background by way of the motion coprocessor that is found in all iPhones since the 5s.

In this tutorial we will look at how your app can read that information, either live, or historically from the last 7 days. The CMMotionActivityManager has both the live updates using the startActivityUpdates: method, or the historical data with queryActivityStarting: both of which we will use. [Read more…]

How to use the CMPedometer for Counting Steps

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The Core Motion framework allows your app access to the sensors on the device. The sensors include the accelerometer, gyroscope, and magnetometer. The CMMotionManager class allows access to each of these to get raw data from them so that your app can detect when the device moves. There are a number of applications for this such as sleep tracking, step counting, to name a few. By using a combination of these sensors, your app can calculate information such as your step count.

Creating a step counter could be quite difficult if you were processing raw data and trying to work out the difference between a step and someone just picking up the phone. Thankfully, Apple does the hard work for you by providing you with the CMPedometer class. This class takes this data and provides you with a step count as well as other information such as cadence etc… To make things even better, Apple also provides 7 days worth of history, thanks to the motion coprocessor (introduced in the iPhone 5s). Even if your app isn’t actively running and tracking step counts, the phone is quietly keeping a log of all step counts and statuses and the CMPedometer is the way we retrieve this data. [Read more…]

CMMotionManager Tutorial – Part 3 – The Magnetometer

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In this tutorial we will have a look at how to set up the magnetometer using the Core Motion framework. Just like enabling the accelerometer or gyroscope, enabling the magnetometer is also extremely simple to do.

The magnetometer is used to provide measurements of the earths magnetic field relative to the device. You can use the magnetometer to derive the heading, but to do so you would need input from other sensors to help with the calculations. If you are more interested in using the compass, then Apple does cater for that with the CLHeading class which we will look at in another tutorial.

We will begin with a single view application, and work in ViewController.swift. [Read more…]

CMMotionManager Tutorial – Part 2 – The Gyroscope

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Yesterday we created a very simple tutorial that let you enable the accelerometer on your device. Today, we’ll look at how to access the gyroscope through the CMMotionManager. These early tutorials are only a very small part of what Core Motion offers, but act as a starting point to show you the very basics of how to get access to the various sensors that Apple has placed in the iPhone.

In later tutorials we’ll look at other aspects of Core Motion and provide some examples of how you might use Core Motion within your own app. [Read more…]

CMMotionManager Tutorial – Part 1 – Accelerometer Data

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Over the coming weeks we are going to delve in to Core Motion and look at what is available and what can be done with the data that your device provides.

Core Motion was introduced in iOS 4 and provided a way for your app to get data from the sensors on your phone. When Apple introduced the iPhone 5s, they changed the game a little by adding a motion coprocessor. This smaller processor has a single job of handling sensor data recorded by the various sensors on the device even while the device is asleep. It quietly stores this information until the phone wakes up and an app requests the data. The processor requires a lot less power to run, and thus it keeps going 24 hours a day silently keeping this data.

The sensors that Core Motion handles include the accelerometer, gyroscope, pedometer, as well as the magnetometer, and barometer. [Read more…]

A Quick Look at HKHealthStore

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HKHealthStore is the way you interact with HealthKit on a users device. It provides the necessary tools to gather permission from the user as well as provides ways to fetch characteristic data, save data, and delete data.

Today’s tutorial will be fairly brief. We will look at a few of the abilities that this class gives to you. Some of them we have already covered. If you want to know how to save an object to Apple Health, check out this tutorial, or this tutorial. If you want to read characteristic data from the health store, that post is for you. [Read more…]

Saving Category Samples with HealthKit

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In our last tutorial we looked at how to save quantity samples with HealthKit. Today we will look at how to save category samples. Just so you are aware of the difference, quantity samples contain a numeric value such as your weight, number of steps taken between 2 points of time, amongst many other things. A category sample is a type where information can be represented from a short list of options such as tracking your sleep. You are either asleep or you are not.

If we look at the sleep analysis category we can see in the documentation that there are 3 options. You are in bed, you are asleep, or you are awake. It is up to you, the developer, to decide how frequent the samples are recorded. An explanation of how to record category samples for sleep is found in the documentation.

In short, out of the 3 states you would record the time that the user was in bed, and then create a second sample with its own timings to show when they were asleep or not. The drawing below shows that the user was in bed for a few hours, slept for some of that, then got out of bed, and then got back in to bed, and then fell asleep, woke up, stayed in bed, fell back asleep, woke up, and then got out of bed. In bed shouldn’t be recorded as the opposite of sleep (ie, in bed is in bed, and not awake).

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Creating and Saving Data in HealthKit

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In earlier tutorials we have focussed on reading information with HealthKit. There are a number of queries that can be used to request information in a variety of ways. In this tutorial we will work on saving information with HealthKit.

Saving data to the health store with HealthKit follows a general procedure which has just 4 steps.

The first step is to find the identifier for the type of data you want to store. For this tutorial we will save body mass. In a later tutorial we will look at saving workouts, and other more complex data types such as step counts where there are more than just 1 reading per day. [Read more…]

HKActivitySummaryQuery Long-Running Query

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Yesterdays tutorial was about the HKActivitySummaryQuery which allows your app to seek permission from the user to access the exercise ring, and all history and details associated with it. The query is one of the simplest available in HealthKit. The only parameter you can pass in is a predicate to specify a range of dates, or a single date. If you set it to nil, it will read all activity of the user.

In todays tutorial we will look at the long-running query that is available for HKActivitySummaryQuery. This particular version of the query keeps running in the background and monitors for changes. Each time the health store is updated with new data; either stand, exercise, or active calories; the update handler will be called which will allow you to refresh your views, should you need to.

As well as looking at the query, we will also add a UIView to the storyboard and set this up as a HKActivityRingView to display the rings on the view. [Read more…]

The HealthKit HKActivitySummaryQuery

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The HKActivitySummaryQuery is useful for apps that are interested in what the user has done each day, in regards to exercise, stand hours, active calories, etc… The query can be used to query a single day, or a range of days.

The easiest way to think about this query is to look at the activity ring, or a collection of activity rings as pictured here. Apple Watch owners will be very aware of what each ring represents. This class allows you to fetch the data that builds up this ring, but also pass it to the HKActivityRingView to represent those numbers in a familiar format to Apple Watch users. For those wanting to use the Apple Watch version of the ring, Apple also has made available WKInterfaceActivityRing.

This tutorial will focus on the query and fetching the data. We might touch upon the activity ring view in a future tutorial, but for now we will focus on executing the query to fetch the available data. [Read more…]