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NSButton Class Reference

Inherits from
Conforms to
Framework
/System/Library/Frameworks/AppKit.framework
Availability
Available in Mac OS X v10.0 and later.
Companion guide
Declared in
NSButton.h
Related sample code

Overview

The NSButton class is a subclass of NSControl that intercepts mouse-down events and sends an action message to a target object when it’s clicked or pressed.

The NSButton class uses NSButtonCell to implement its user interface.

NSButton and NSMatrix both provide a control view, which is needed to display an NSButtonCell object. However, while NSMatrix requires you to access the NSButtonCell objects directly, most of the NSButton class' methods are “covers” for identically declared methods in NSButtonCell. (In other words, the implementation of the NSButton method invokes the corresponding NSButtonCell method for you, allowing you to be unconcerned with the existence of the NSButtonCell.) The only NSButtonCell methods that don’t have covers relate to the font used to display the key equivalent and to specific methods for highlighting or showing the state of the NSButton (these last are usually set together with the NSButton setButtonType: method).

Tasks

Configuring Buttons

Configuring Button Images

Managing Button State

Accessing Key Equivalents

Handling Keyboard Events

Instance Methods

allowsMixedState

Returns a Boolean value indicating whether the button allows a mixed state.

- (BOOL)allowsMixedState

Return Value

YES if the receiver has three states: on, off, and mixed. NO if the receiver has two states: on and off. The default is NO.

Availability
See Also
Declared In
NSButton.h

alternateImage

Returns the image that appears on the button when it’s in its alternate state.

- (NSImage *)alternateImage

Return Value

The image displayed by the button when it's in its alternate state, or nil if there is no alternate image. Note that some button types don’t display an alternate image. Buttons don’t display images by default.

Availability
See Also
Declared In
NSButton.h

alternateTitle

Returns the title that the button displays when it’s in its alternate state.

- (NSString *)alternateTitle

Return Value

The string that appears on the receiver when it's in its alternate state, or the empty string if the receiver doesn't display an alternate title. By default, a button’s alternate title is “Button.”

Availability
See Also
Declared In
NSButton.h

attributedAlternateTitle

Returns the title that the button displays when it’s in its alternate state as an attributed string.

- (NSAttributedString *)attributedAlternateTitle

Return Value

The string that appears on the receiver when it's in its alternate state, as an NSAttributedString, or the empty string if the receiver doesn't display an alternate title. By default, a button’s alternate title is “Button.”

Availability
See Also
Declared In
NSButton.h

attributedTitle

Returns the title that the button displays in its normal state as an attributed string.

- (NSAttributedString *)attributedTitle

Return Value

The string that appears on the receiver when it’s in its normal state as an NSAttributedString, or an empty attributed string if the receiver doesn’t display a title.

A button’s title is always displayed if the button doesn’t use its alternate contents for highlighting or displaying the alternate state. By default, a button’s title is “Button.”

Availability
See Also
Declared In
NSButton.h

bezelStyle

Returns the appearance of the receiver’s border.

- (NSBezelStyle)bezelStyle

Return Value

The bezel style of the button. See the “Constants” section of NSButtonCell for the list of possible values.

Availability
See Also
Declared In
NSButton.h

getPeriodicDelay:interval:

Returns by reference the delay and interval periods for a continuous button.

- (void)getPeriodicDelay:(float *)delay interval:(float *)interval

Parameters
delay

On return, the amount of time (in seconds) the button will pause before starting to periodically send action messages to the target object. The default delay is taken from a user's default (60 seconds maximum). If the user hasn’t specified a default value, delay defaults to 0.4 seconds,

interval

On return, the amount of time (in seconds) between each action message that is sent. The default interval is taken from a user's default (60 seconds maximum). If the user hasn’t specified a default value, interval defaults to 0.075 seconds.

Availability
See Also
Declared In
NSButton.h

highlight:

Highlights (or unhighlights) the receiver.

- (void)highlight:(BOOL)flag

Parameters
flag

YES to highlight the button; NO to unhighlight the button. If the current state of the button matches flag, no action is taken.

Discussion

Highlighting may involve the button appearing “pushed in” to the screen, displaying its alternate title or image, or causing the button to appear to be “lit.”

Availability
See Also
Declared In
NSButton.h

image

Returns the image that appears on the receiver when it’s in its normal state.

- (NSImage *)image

Return Value

The image displayed by the button when it's in its normal state, or nil if there is no such image. This image is always displayed on a button that doesn’t change its contents when highlighting or showing its alternate state. Buttons don’t display images by default.

Availability
See Also
Declared In
NSButton.h

imagePosition

Returns the position of the receiver’s image relative to its title.

- (NSCellImagePosition)imagePosition

Return Value

The position of the button's image. This is one of the image positions described in the “Constants” section of NSCell.

Discussion

If the title is above, below, or overlapping the image, or if there is no image, the text is horizontally centered within the button.

Availability
See Also
Declared In
NSButton.h

isBordered

Returns a Boolean value indicating whether the button has a border.

- (BOOL)isBordered

Return Value

YES if the receiver has a border, NO otherwise. A button’s border isn’t the single line of most other controls’ borders—instead, it’s a raised bezel. By default, buttons are bordered.

Availability
See Also
Declared In
NSButton.h

isTransparent

Returns a Boolean value indicating whether the button is transparent.

- (BOOL)isTransparent

Return Value

YES if the receiver is transparent, NO otherwise. A transparent button never draws itself, but it receives mouse-down events and tracks the mouse properly.

Availability
See Also
Declared In
NSButton.h

keyEquivalent

Returns the key-equivalent character of the receiver.

- (NSString *)keyEquivalent

Return Value

The button's key equivalent, or the empty string if one hasn’t been defined. Buttons don’t have a default key equivalent.

Availability
See Also
Declared In
NSButton.h

keyEquivalentModifierMask

Returns the mask specifying the modifier keys for the receiver’s key equivalent.

- (NSUInteger)keyEquivalentModifierMask

Return Value

The mask specifying the modifier keys that are applied to the button's key equivalent. Mask bits are defined in NSEvent.h. The only mask bits relevant in button key-equivalent modifier masks are NSControlKeyMask, NSAlternateKeyMask, and NSCommandKeyMask.

Availability
See Also
Declared In
NSButton.h

performKeyEquivalent:

Checks the button's key equivalent against the specified event and, if they match, simulates the button being clicked.

- (BOOL)performKeyEquivalent:(NSEvent *)anEvent

Parameters
anEvent

The event containing the key equivalent.

Return Value

YES if the key equivalent in anEvent matches the button's key equivalent; NO if it does not. This method also returns NO if he receiver is blocked by a modal panel or the button is disabled.

Discussion

If the character in anEvent matches the receiver’s key equivalent, and the modifier flags in anEvent match the key-equivalent modifier mask, performKeyEquivalent: simulates the user clicking the button and returning YES. Otherwise, performKeyEquivalent: does nothing and returns NO.

Availability
See Also
Declared In
NSButton.h

setAllowsMixedState:

Sets whether the button allows a mixed state.

- (void)setAllowsMixedState:(BOOL)flag

Parameters
flag

YES to indicate that the receiver has three states: on, off, and mixed. If flag is NO, the receiver has two states: on and off.

Availability
See Also
Related Sample Code
Declared In
NSButton.h

setAlternateImage:

Sets the image displayed by the button when it’s in its alternate state and, if necessary, redraws the contents of the button.

- (void)setAlternateImage:(NSImage *)image

Parameters
image

The image that appears on the receiver when it’s in its alternate state. Note that some button types don’t display an alternate image.

Availability
See Also
Declared In
NSButton.h

setAlternateTitle:

Sets the title that appears on the button when it’s in its alternate state.

- (void)setAlternateTitle:(NSString *)aString

Parameters
aString

The string to set as the button's alternate title. Note that some button types don't display an alternate title.

Availability
See Also
Declared In
NSButton.h

setAttributedAlternateTitle:

Sets the title that appears on the button when it’s in its alternate state to the given attributed string.

- (void)setAttributedAlternateTitle:(NSAttributedString *)aString

Parameters
aString

The attributed string to set as the button's alternate title. Note that some button types don't display an alternate title.

Availability
See Also
Declared In
NSButton.h

setAttributedTitle:

Sets the string that appears on the button when it’s in its normal state to the given attributed string and redraws the button.

- (void)setAttributedTitle:(NSAttributedString *)aString

Parameters
aString

The attributed string to set as the button's title. The title is always shown on buttons that don’t use their alternate contents when highlighting or displaying their alternate state.

Discussion

Availability
See Also
Declared In
NSButton.h

setBezelStyle:

Sets the appearance of the border, if the receiver has one.

- (void)setBezelStyle:(NSBezelStyle)bezelStyle

Parameters
bezelStyle

The bezel style of the button. This must be one of the bezel styles described in the “Constants” section of NSButtonCell.

If the button is not bordered, the bezel style is ignored.

Discussion

The button uses shading to look like it’s sticking out or pushed in. You can set the shading with the NSButtonCell method setGradientType:.

Availability
See Also
Declared In
NSButton.h

setBordered:

Sets whether the receiver has a bezeled border.

- (void)setBordered:(BOOL)flag

Parameters
flag

YES if the receiver should display a border; NO if it should not. A button’s border is not the single line of most other controls’ borders—instead, it’s a raised bezel.

Discussion

This method redraws the button if setBordered: causes the bordered state to change.

Availability
See Also
Declared In
NSButton.h

setButtonType:

Sets how the receiver button highlights while pressed and how it shows its state.

- (void)setButtonType:(NSButtonType)aType

Parameters
aType

A constant specifying the type of the button—one of the constants described in the Constants section of NSButtonCell.

Discussion

setButtonType: redisplays the button before returning.

The types available are for the most common button types, which are also accessible in Interface Builder. You can configure different behavior with the NSButtonCell methods setHighlightsBy: and setShowsStateBy:.

Note that there is no -buttonType method. The set method sets various button properties that together establish the behavior of the type.

Availability
See Also
Declared In
NSButton.h

setImage:

Sets the receiver’s image and redraws the button.

- (void)setImage:(NSImage *)anImage

Parameters
anImage

The button's image. A button’s image is displayed when the button is in its normal state, or all the time for a button that doesn’t change its contents when highlighting or displaying its alternate state.

Availability
See Also
Declared In
NSButton.h

setImagePosition:

Sets the position of the button's image relative to its title.

- (void)setImagePosition:(NSCellImagePosition)aPosition

Parameters
aPosition

A constant specifying the position of the button's image. See the “Constants” section of NSCell for a listing of possible values.

Availability
See Also
Declared In
NSButton.h

setKeyEquivalent:

Sets the key equivalent character of the receiver to the given character.

- (void)setKeyEquivalent:(NSString *)charCode

Parameters
charCode

The character to set as the button's key equivalent.

Discussion

This method redraws the button’s interior if it displays a key equivalent instead of an image. The key equivalent isn’t displayed if the image position is set to NSNoImage, NSImageOnly, or NSImageOverlaps; that is, the button must display both its title and its “image” (the key equivalent in this case), and they must not overlap.

To display a key equivalent on a button, set the image and alternate image to nil, then set the key equivalent, then set the image position.

Availability
See Also
Related Sample Code
Declared In
NSButton.h

setKeyEquivalentModifierMask:

Sets the mask indicating the modifier keys used by the receiver’s key equivalent.

- (void)setKeyEquivalentModifierMask:(NSUInteger)mask

Parameters
mask

The mask identifying the modifier keys to be applied to the button's key equivalent.

Mask bits are defined in NSEvent.h. The only mask bits relevant in button key-equivalent modifier masks are NSControlKeyMask, NSAlternateKeyMask, and NSCommandKeyMask.

Availability
See Also
Declared In
NSButton.h

setNextState

Sets the receiver to its next state.

- (void)setNextState

Discussion

If the button has three states, it cycles through them in this order: on, off, mixed, on, and so forth. If the button has two states, it toggles between them.

Availability
See Also
Declared In
NSButton.h

setPeriodicDelay:interval:

Sets the message delay and interval periods for a continuous button.

- (void)setPeriodicDelay:(float)delay interval:(float)interval

Parameters
delay

The amount of time (in seconds) that a continuous button will pause before starting to periodically send action messages to the target object. The maximum allowed value is 60.0 seconds; if a larger value is supplied, it is ignored, and 60.0 seconds is used.

interval

The amount of time (in seconds) between each action message. The maximum value is 60.0 seconds; if a larger value is supplied, it is ignored, and 60.0 seconds is used.

Discussion

The delay and interval values are used if the button is configured (by a setContinuous: message) to continuously send the action message to the target object while tracking the mouse.

Availability
See Also
Declared In
NSButton.h

setShowsBorderOnlyWhileMouseInside:

Sets whether the receiver’s border is displayed only when the cursor is over the button.

- (void)setShowsBorderOnlyWhileMouseInside:(BOOL)show

Parameters
show

YES to display the border only when the cursor is within the button’s border and the button is active. NO, to continue to display the button’s border when the cursor is outside the button’s bounds.

Discussion

If isBordered returns NO, the border is never displayed, regardless of what this method returns.

Availability
See Also
Declared In
NSButton.h

setSound:

Sets the sound played when the user presses the button.

- (void)setSound:(NSSound *)aSound

Parameters
aSound

The sound that should be played when the user presses the button. The sound is played during a mouse-down event, such as NSLeftMouseDown.

Availability
See Also
Declared In
NSButton.h

setState:

Sets the cell’s state to the specified value.

- (void)setState:(NSInteger)value

Parameters
value

The state of the button. This can be NSOnState, NSOffState,NSMixedState. See the discussion for a more detailed explanation.

Discussion

If necessary, this method also redraws the receiver.

The cell can have two or three states. If it has two, value can be NSOffState (the normal or unpressed state) and NSOnState (the alternate or pressed state). If it has three, value can be NSOnState (the feature is in effect everywhere), NSOffState (the feature is in effect nowhere), or NSMixedState (the feature is in effect somewhere). Note that if the cell has only two states and value is NSMixedState, this method sets the cell’s state to NSOnState.

Although using the enumerated constants is preferred, value can also be an integer. If the cell has two states, 0 is treated as NSOffState, and a nonzero value is treated as NSOnState. If the cell has three states, 0 is treated as NSOffState; a negative value, as NSMixedState; and a positive value, as NSOnState.

To check whether the button uses the mixed state, use the method allowsMixedState.

Availability
See Also
Related Sample Code
Declared In
NSButton.h

setTitle:

Sets the title displayed by the receiver when in its normal state and, if necessary, redraws the button’s contents.

- (void)setTitle:(NSString *)aString

Parameters
aString

The string to set as the button's title. This title is always shown on buttons that don’t use their alternate contents when highlighting or displaying their alternate state.

Availability
See Also
Related Sample Code
Declared In
NSButton.h

setTitleWithMnemonic:

Sets the title of a button with a character denoting an access key.

- (void)setTitleWithMnemonic:(NSString *)aString

Discussion

Mnemonics are not supported in Mac OS X.

Availability
See Also
Declared In
NSButton.h

setTransparent:

Sets whether the receiver is transparent and redraws the receiver if necessary.

- (void)setTransparent:(BOOL)flag

Parameters
flag

YES if the button is transparent; otherwise NO.

Discussion

A transparent button tracks the mouse and sends its action, but doesn’t draw. A transparent button is useful for sensitizing an area on the screen so that an action gets sent to a target when the area receives a mouse click.

Availability
See Also
Declared In
NSButton.h

showsBorderOnlyWhileMouseInside

Returns a Boolean value indicating whether the button displays its border only when the cursor is over it.

- (BOOL)showsBorderOnlyWhileMouseInside

Return Value

YES if the receiver’s border is displayed only when the cursor is over the button and the button is active; NO if the border is displayed all the time.

By default, this method returns NO.

Discussion

If isBordered returns NO, the border is never displayed, regardless of what this method returns.

Availability
See Also
Declared In
NSButton.h

sound

Returns the sound that’s played when the user presses the button.

- (NSSound *)sound

Return Value

The sound played when the user presses the button.

Availability
See Also
Declared In
NSButton.h

state

Returns the receiver’s state.

- (NSInteger)state

Return Value

The button's state. A button can have two or three states. If it has two, this value is either NSOffState (the normal or unpressed state) or NSOnState (the alternate or pressed state). If it has three, this value can be NSOnState (the feature is in effect everywhere), NSOffState (the feature is in effect nowhere), or NSMixedState (the feature is in effect somewhere).

Discussion

To check whether the button uses the mixed state, use the method allowsMixedState.

Availability
See Also
Related Sample Code
Declared In
NSButton.h

title

Returns the title displayed on the button when it’s in its normal state.

- (NSString *)title

Return Value

The title displayed on the receiver when it’s in its normal state or the empty string if the button doesn’t display a title. This title is always displayed if the button doesn’t use its alternate contents for highlighting or displaying the alternate state. By default, a button’s title is “Button.”

Availability
See Also
Related Sample Code
Declared In
NSButton.h

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© 2007 Apple Inc. All Rights Reserved. (Last updated: 2007-04-01)

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