Publishers of technology books, eBooks, and videos for creative people

Home > Articles > Apple > iPhone

  • Print
  • + Share This
This chapter is from the book


Almost all the drawing functionality you've learned about so far also applies to controls. Most controls inherit their class from UIControl, and as you can see in Figure 4.36, UIControl is a subclass of UIView; this is how controls know how to draw themselves.

Figure 4.36

Figure 4.36 The UIControl class hierarchy.

You'll never actually create instances of UIControl directly the way you do with UIView. UIControl is simply used to define a common set of functionality and behavior for its subclasses.

As mentioned at the beginning of this chapter, controls use the target-action mechanism to respond to touch events. Since the iPhone is a Multi-Touch device, many different events can occur, such as tapping, multitapping, dragging, and releasing. Luckily, each control has been designed to respond to only those events appropriate for its usage, and each does so in an intuitive and consistent manner.

You'll now take a closer look at the controls available to iPhone developers.


When adding buttons to your application, you'll use the UIButton class. The default initializer for buttons is the buttonWithType: method:

UIButton *myButton = [[UIButton buttonWithType:UIButtonTypeRoundedRect];

Figure 4.37 shows the default buttons types available.

Figure 4.37

Figure 4.37 The default button types for UIButton.

To be notified when a button changes state, add a target and action:

[myButton addTarget:self action:@selector(buttonClick:) forControlEvents:UIControlEventTouchUpInside];

The UIControlEventTouchUpInside event is most commonly used for handling regular button presses.

The UIButtonTypeCustom type lets you create buttons with images or even draw them yourself using your own custom drawing code (as discussed earlier in the "Views" section).

To create a button with an image:

  1. Specify an image for the button's default state using NSControlStateNormal:
    UIImage *buttonImage = [UIImage imageNamed:@"myButtonImage.png"];
    [myButton setImage:buttonImage forState:UIControlStateNormal];

    UIButton will automatically apply highlight effects to indicate that the button is pressed or disabled.

  2. You can also set multiple appearance properties for each of these states, including the title text, font, and color.

    You can use different images for the four different states: the default (as shown in step 1), highlighted, selected, and disabled. This enables you to create buttons to represent other controls.

To create a checkbox button:

  1. Assign images for both of the buttons' states:
    [checkbox setImage:[UIImage imageNamed:@"checkbox_off.png"] forState:UIControlStateNormal];
    [checkbox setImage:[UIImage imageNamed:@"checkbox_on.png"] forState:UIControlStateSelected];
  2. Set the target method to call when the button is tapped:
    [checkbox addTarget:self action:@selector(checkboxClick:)
  3. In the checkboxClick: method, simply flip the button's selected property:

    btn.selected = !btn.selected;

    Since you've previously defined images for the two different states, the button automatically updates to display the correct image. Code Listing 4.29 shows the updated code.


    Code Listing 4.29 Creating a check box.


Switches, represented by the UISwitch class, let you create an on/off control (Figure 4.38).

Figure 4.38

Figure 4.38 Switches are used extensively in the Settings application of the iPhone.

To create a switch:

  1. Use the initWithFrame: method:
    CGRect switchRect = CGRectMake(120,50,0,0);
    UISwitch *mySwitch = [[UISwitch alloc] initWithFrame:switchRect];
    Since switches are always the same size, the width and height properties are ignored.
  2. When you change a switch's value, it generates a UIControlEventValueChanged event:
    [mySwitch addTarget:self action:@selector(switchAction:) forControlEvents:UIControlEventValueChanged];
  3. To turn a switch on/off, call the setOn:Animated: method:
    [mySwitch setOn:YES animated:YES];

Switches don't have any properties for modifying the default visual appearance, but with a little digging, you can control a couple of elements.

Figure 4.39 shows the control hierarchy of a UISwitch. The "on" and "off" elements are both UILabels. You can manipulate the text, font, color, and more.

Figure 4.39

Figure 4.39 The control hierarchy that makes up a UISwitch.

To alter the appearance of a switch:

  1. To retrieve the two UILabels within the switch that hold the switch's text, you can use this:
    UIView *mainView = [[[[mySwitch subviews] objectAtIndex:0] subviews] objectAtIndex:2];
    UILabel *onLabel = [[mainView subviews] objectAtIndex:0];
    UILabel *offLabel = [[mainView subviews] objectAtIndex:1];
  2. Now you can change the text and color of these labels. The choice of text values is quite limited since the labels are small in size and are clipped by their containing view:
    onLabel.text = @"YES";
    offLabel.text = @"NO";
    onLabel.textColor = [UIColor yellowColor];
    offLabel.textColor = [UIColor greenColor];
  3. When setting the text values you should localize your replacement text wherever possible. Code Listing 4.30 shows the updated code.

    Code Listing 4.30 Customizing the switch control.


Although switches have only two possible states, sliders let you select from a range of values on a horizontal bar, or track, with a thumb indicator that can be moved from side to side to select values (Figure 4.40).

Figure 4.40

Figure 4.40 The brightness slider control indicates the change in value with graphics at both ends of the control.

Unlike the UISwitch, there's quite a lot you can do to customize the visual appearance of sliders, such as putting images to represent the values at either end of the track. You can also customize the thumb image and the graphics that appear on the track on both sides of the thumb as the values change (Figure 4.41).

Figure 4.41

Figure 4.41 A custom slider control.

Just as with the UISwitch, sliders create a UIControlEventValueChanged event when their value is changed. By setting the continuous property, you can choose to have these events fired either as the slider is changed or at the end of a change. Code Listing 4.31 demonstrates this with a custom UISlider, with minimum, maximum, and thumb images. In the sliderAction: method, you are forcing a "step" behavior, making the slider jump to the next value in increments of ten. A label added to the view displays the current slider value.


Code Listing 4.31 Implementing a custom slider.

Segmented controls

The UISegmentedControl consists of a horizontal control divided into segments (Figure 4.42). Segmented controls are useful for allowing users to pick from a group or set of values.

Figure 4.42

Figure 4.42 A segment control.

Each segment functions as its own button. By default, selecting a segment will deselect the others in the control (much as a radio button does in HTML). You can alter this behavior by setting the momentary property.

To create a segmented control:

  1. Create an array of UIImages or NSStrings, and then call the default initializer initWithItems: (Code Listing 4.32).

    Code Listing 4.32 Creating a segment control.

  2. Set the frame, and the control will automatically resize to accommodate its segments. Each segment will initially be the same size.
  3. Set the width of individual segments using the setWidth:forSegmentIndex: method.

    This will automatically resize any other segments that have not had their widths explicitly set to fit within the control.

  4. Select segments using the setSelectedSegmentIndex: method.
  5. Disable individual segments using the setEnabled:forSegementAtIndex: method.
  6. Add more segments using insertSegmentsWithImage:atIndex:animated:



  7. Set the animated property to YES so your segments will "slide in" as they are added.
  8. To remove segments, use the removeSegmentsAtIndex:animated: method.
  9. Use removeAllSegments to clear the entire control.
  • + Share This
  • 🔖 Save To Your Account

Peachpit Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from Peachpit and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about Peachpit products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites; develop new products and services; conduct educational research; and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by Adobe Press. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive:

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020