DevTut

# UIButton

UIButton (opens new window) : UIControl (opens new window) intercepts touch events and sends an action message to a target object when it's tapped. You can set the title, image, and other appearance properties of a button. In addition, you can specify a different appearance for each button state.

# Attaching a Method to a Button

To add a method to a button, first create an action method:

Objective-C

-(void) someButtonAction{
    NSLog(@"Button is tapped");

}

Swift

func someButtonAction() {
        print("Button is tapped")
    }

Now to add this action method to your button, you have to write following line of code:

Objective C

[yourButtonInstance addTarget:self action:@selector(someButtonAction) forControlEvents:UIControlEventTouchUpInside];

Swift

yourButtonInstance.addTarget(self, action: #selector(someButtonAction), forControlEvents: .touchUpInside)

For ControlEvents, all members of ENUM UIControlEvents (opens new window) are valid.

# Creating a UIButton

UIButtons can be initialized in a frame:

Swift

let button = UIButton(frame: CGRect(x: x, y: y, width: width, height: height)

Objective C

UIButton *button = [[UIButton alloc] initWithFrame:CGRectMake(x, y, width, height)];

A specific type of UIButton can be created like this:

Swift

let button = UIButton(type: .Custom)

Objective C

UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];

where type is a UIButtonType:

enum UIButtonType : Int {
    case Custom
    case System
    case DetailDisclosure
    case InfoLight
    case InfoDark
    case ContactAdd
    static var RoundedRect: UIButtonType { get }
}

# Set title

Swift

button.setTitle(titleString, forState: controlState)

Objective C

[button setTitle:(NSString *) forState:(UIControlState)];

To set the default title to "Hello, World!"

Swift

button.setTitle("Hello, World!", forState: .normal)

Objective C

[button setTitle:@"Hello, World!" forControlState:UIControlStateNormal];

# Set title color

//Swift
button.setTitleColor(color, forControlState: controlState)

//Objective-C
[button setTitleColor:(nullable UIColor *) forState:(UIControlState)];

To set the title color to blue

//Swift
button.setTitleColor(.blue, for: .normal)

//Objective-C
[button setTitleColor:[UIColor blueColor] forState:UIControlStateNormal]

# Horizontally aligning contents

Swift

//Align contents to the left of the frame
button.contentHorizontalAlignment = .left

//Align contents to the right of the frame
button.contentHorizontalAlignment = .right

//Align contents to the center of the frame
button.contentHorizontalAlignment = .center

//Make contents fill the frame
button.contentHorizontalAlignment = .fill

Objective C

//Align contents to the left
button.contentHorizontalAlignment = UIControlContentHorizontalAlignmentLeft;

//Align contents to the right
button.contentHorizontalAlignment = UIControlContentHorizontalAlignmentRight;

//Align contents to the center
button.contentHorizontalAlignment = UIControlContentHorizontalAlignmentCenter;

//Align contents to fill the frame
button.contentHorizontalAlignment = UIControlContentHorizontalAlignmentFill;

# Getting the title label

The underlying title label, if one exists, can be fetched using

Swift

var label: UILabel? = button.titleLabel

Objective C

UILabel *label = button.titleLabel;

This can be used to set the font of the title label, for example

Swift

button.titleLabel?.font = UIFont.boldSystemFontOfSize(12)

Objective C

button.titleLabel.font = [UIFont boldSystemFontOfSize:12];

# Disabling a UIButton

A button can be disabled by

Swift

myButton.isEnabled = false

Objective-C:

myButton.enabled = NO;

The button will become gray:

enter image description here (opens new window)

If you don't want the button appearance to change when disabled set adjustsImageWhenDisabled to false / NO

# Adding an action to an UIButton via Code (programmatically)

To add a method to a button, first create an action method:

Objective-C

-(void)someButtonAction:(id)sender {
  // sender is the object that was tapped, in this case its the button.
    NSLog(@"Button is tapped"); 
}

Swift

func someButtonAction() {
    print("Button is tapped")
}

Now to add this action method to your button, you have to write following line of code:

Objective C

[yourButtonInstance addTarget:self action:@selector(someButtonAction) forControlEvents:UIControlEventTouchUpInside];

Swift

yourButtonInstance.addTarget(self, action: #selector(someButtonAction), forControlEvents: .TouchUpInside)

For ControlEvents parameter, all members of ENUM UIControlEvents (opens new window) are valid.

# Setting Font

Swift

myButton.titleLabel?.font =  UIFont(name: "YourFontName", size: 20)

Objective C

myButton.titleLabel.font = [UIFont fontWithName:@"YourFontName" size:20];

# Get UIButton's size strictly based on its text and font

To get the the exact size of a UIButton's text based on its font, use the function intrinsicContentSize.

Swift

button.intrinsicContentSize.width

Objective-C

button.intrinsicContentSize.width;

# Set Image

# Swift

button.setImage(UIImage(named:"test-image"), forState: .normal)

# Objective C

[self.button setImage:[UIImage imageNamed:@"test-image"] forState:UIControlStateNormal];

# Multiple Control States

You can also set an image for multiple UIControlStates, for example to set the same image for the Selected and Highlighted state:

# Swift

button.setImage(UIImage(named:"test-image"), forState:[.selected, .highlighted])

# Objective C

[self.button setImage:[UIImage imageNamed:@"test-image"] forState:UIControlStateSelected|UIControlStateHighlighted];

# Remarks

# Button Types

A button’s type defines its basic appearance and behavior. After creating a button, you cannot change its type. The most commonly used button types are the Custom and System types, but use the other types when appropriate

  • UIButtonTypeCustom 
    No button style.
  • UIButtonTypeSystem 
    A system style button, such as those shown in navigation bars and toolbars.
  • UIButtonTypeDetailDisclosure 
    A detail disclosure button.
  • UIButtonTypeInfoLight 
    An information button that has a light background.
  • UIButtonTypeInfoDark 
    An information button that has a dark background.
  • UIButtonTypeContactAdd 
    A contact add button.

    • When creating a custom button—that is a button with the type custom—the frame of the button is set to (0, 0, 0, 0) initially. Before adding the button to your interface, you should update the frame to a more appropriate value.

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