如何创建一个渐变背景色的按钮

//
//  NVUIGradientButton.m
//
//  Created by Nicolas Verinaud on 20/06/12.
//  Copyright (c) 2012 nverinaud.com. All rights reserved.
//

#import "NVUIGradientButton.h"

@interface NVUIGradientButton ()
- (void)performDefaultInit;
- (void)updateAccordingToStyle;
- (BOOL)isHighlightedOrSelected;
- (UIColor *)tintColorAccordingToCurrentState;
- (UIColor *)borderColorAccordingToCurrentState;
- (UIColor *)textColorAccordingToCurrentState;
- (UIColor *)textShadowColorAccordingToCurrentState;
- (NSString *)textAccordingToCurrentState;
- (UIImage *)rightAccessoryImageAccordingToCurrentState;
- (CGGradientRef)newGradientAccordingToCurrentState;
@property (strong, nonatomic, readwrite) UILabel *titleLabel;
@end

@implementation NVUIGradientButton

#pragma mark - Creation

#define NVUIGradientButtonDefaultCorderRadius    10.0
#define NVUIGradientButtonDefaultBorderWidth    2.0

- (void)performDefaultInit
{
// Defaults
_highlightedText = _text;
_disabledText = _text;

// Label
_titleLabel = [[UILabel alloc] init];
_titleLabel.textAlignment = UITextAlignmentCenter;
_titleLabel.lineBreakMode = UILineBreakModeMiddleTruncation;
_titleLabel.numberOfLines = 0;
_titleLabel.font = [UIFont boldSystemFontOfSize:15.0];
_titleLabel.minimumFontSize = 12.0;
_titleLabel.shadowOffset = CGSizeMake(0, -1);

_gradientEnabled = YES;

self.opaque = NO;
self.backgroundColor = [UIColor clearColor];
}

- (void)updateAccordingToStyle
{
switch (_style)
{
case NVUIGradientButtonStyleBlackOpaque:
{
self.tintColor = [UIColor colorWithRed:0 green:0 blue:0 alpha:1];
self.highlightedTintColor = [UIColor colorWithRed:(CGFloat)3/255 green:(CGFloat)112/255 blue:(CGFloat)236/255 alpha:1];
self.borderColor = [UIColor whiteColor];
self.highlightedBorderColor = [UIColor whiteColor];
self.textColor = [UIColor whiteColor];
self.highlightedTextColor = [UIColor whiteColor];
self.textShadowColor = [UIColor clearColor];
self.highlightedTextShadowColor = [UIColor clearColor];
break;
}

case NVUIGradientButtonStyleBlackTranslucent:
{
self.tintColor = [UIColor colorWithRed:0 green:0 blue:0 alpha:0.7];
self.highlightedTintColor = [UIColor colorWithRed:(CGFloat)3/255 green:(CGFloat)112/255 blue:(CGFloat)236/255 alpha:0.7];
self.borderColor = [UIColor whiteColor];
self.highlightedBorderColor = [UIColor whiteColor];
self.textColor = [UIColor whiteColor];
self.highlightedTextColor = [UIColor whiteColor];
self.textShadowColor = [UIColor clearColor];
self.highlightedTextShadowColor = [UIColor clearColor];
break;
}

case NVUIGradientButtonStyleDefault:
{
CGFloat gray = 220.0/255.0;
self.tintColor = [UIColor colorWithRed:gray green:gray blue:gray alpha:1];
self.highlightedTintColor = [UIColor colorWithRed:0 green:(CGFloat)157/255 blue:1 alpha:1];
self.borderColor = [UIColor darkGrayColor];
self.highlightedBorderColor = [UIColor whiteColor];
self.textColor = [UIColor blackColor];
self.highlightedTextColor = [UIColor whiteColor];
self.textShadowColor = [UIColor clearColor];
self.highlightedTextShadowColor = [UIColor darkGrayColor];
break;
}
}
}

#pragma mark Designated initializer

- (id)initWithFrame:(CGRect)frame style:(NVUIGradientButtonStyle)style cornerRadius:(CGFloat)cornerRadius borderWidth:(CGFloat)borderWidth andText:(NSString *)text
{
self = [super initWithFrame:frame];
if (self)
{
_cornerRadius = cornerRadius;
_borderWidth = borderWidth;
_text = text;

[self performDefaultInit];

self.style = style;
}
return self;
}

#pragma mark Convenient initializers

- (id)initWithFrame:(CGRect)frame cornerRadius:(CGFloat)cornerRadius borderWidth:(CGFloat)borderWidth andText:(NSString *)text
{
return [self initWithFrame:frame style:NVUIGradientButtonStyleDefault cornerRadius:cornerRadius borderWidth:borderWidth andText:text];
}

- (id)initWithFrame:(CGRect)frame style:(NVUIGradientButtonStyle)style
{
return [self initWithFrame:frame style:style cornerRadius:NVUIGradientButtonDefaultCorderRadius borderWidth:NVUIGradientButtonDefaultBorderWidth andText:nil];
}

#pragma mark Overriden initializers

- (id)initWithFrame:(CGRect)frame
{
return [self initWithFrame:frame style:NVUIGradientButtonStyleDefault cornerRadius:NVUIGradientButtonDefaultCorderRadius borderWidth:NVUIGradientButtonDefaultBorderWidth andText:nil];
}

- (id)initWithCoder:(NSCoder *)aDecoder
{
self = [super initWithCoder:aDecoder];
if (self)
{
_cornerRadius = NVUIGradientButtonDefaultCorderRadius;
_borderWidth = NVUIGradientButtonDefaultBorderWidth;

[self performDefaultInit];

self.style = NVUIGradientButtonStyleDefault;
}
return self;
}

#pragma mark - Setters

- (void)setStyle:(NVUIGradientButtonStyle)style
{
if (style != _style)
{
_style = style;
[self updateAccordingToStyle];
}
}

- (void)setTintColor:(UIColor *)tintColor
{
if (tintColor != _tintColor)
{
_tintColor = tintColor;

if (self.state == UIControlStateNormal)
[self setNeedsDisplay];
}
}

- (void)setHighlightedTintColor:(UIColor *)highlightedTintColor
{
if (highlightedTintColor != _highlightedTintColor)
{
_highlightedTintColor = highlightedTintColor;

if ([self isHighlightedOrSelected])
[self setNeedsDisplay];
}
}

- (void)setBorderColor:(UIColor *)borderColor
{
if (borderColor != _borderColor)
{
_borderColor = borderColor;

if (self.state == UIControlStateNormal)
[self setNeedsDisplay];
}
}

- (void)setHighlightedBorderColor:(UIColor *)highlightedBorderColor
{
if (highlightedBorderColor != _highlightedBorderColor)
{
_highlightedBorderColor = highlightedBorderColor;

if ([self isHighlightedOrSelected])
[self setNeedsDisplay];
}
}

- (void)setTextColor:(UIColor *)textColor
{
if (textColor != _textColor)
{
_textColor = textColor;

if (self.state == UIControlStateNormal)
[self setNeedsDisplay];
}
}

- (void)setHighlightedTextColor:(UIColor *)highlightedTextColor
{
if (highlightedTextColor != _highlightedTextColor)
{
_highlightedTextColor = highlightedTextColor;

if ([self isHighlightedOrSelected])
[self setNeedsDisplay];
}
}

- (void)setTextShadowColor:(UIColor *)textShadowColor
{
if (textShadowColor != _textShadowColor)
{
_textShadowColor = textShadowColor;

if (self.state == UIControlStateNormal)
[self setNeedsDisplay];
}
}

- (void)setHighlightedTextShadowColor:(UIColor *)highlightedTextShadowColor
{
if (highlightedTextShadowColor != _highlightedTextShadowColor)
{
_highlightedTextShadowColor = highlightedTextShadowColor;

if ([self isHighlightedOrSelected])
[self setNeedsDisplay];
}
}

- (void)setText:(NSString *)text
{
if (![text isEqualToString:_text])
{
_text = text;

if (self.state == UIControlStateNormal)
[self setNeedsDisplay];
}
}

- (void)setHighlightedText:(NSString *)highlightedText
{
if (![highlightedText isEqualToString:_highlightedText])
{
_highlightedText = highlightedText;

if ([self isHighlightedOrSelected])
[self setNeedsDisplay];
}
}

- (void)setDisabledText:(NSString *)disabledText
{
if (![disabledText isEqualToString:_disabledText])
{
_disabledText = disabledText;

if (self.state & UIControlStateDisabled)
[self setNeedsDisplay];
}
}

- (void)setRightAccessoryImage:(UIImage *)rightAccessoryImage
{
if (rightAccessoryImage != _rightAccessoryImage)
{
_rightAccessoryImage = rightAccessoryImage;

if (self.state == UIControlStateNormal)
[self setNeedsDisplay];
}
}

- (void)setRightHighlightedAccessoryImage:(UIImage *)rightHighlightedAccessoryImage
{
if (rightHighlightedAccessoryImage != _rightHighlightedAccessoryImage)
{
_rightHighlightedAccessoryImage = rightHighlightedAccessoryImage;

if ([self isHighlightedOrSelected])
[self setNeedsDisplay];
}
}

#pragma mark - Convenience configuration for states

- (BOOL)isHighlightedOrSelected
{
return (self.state & UIControlStateHighlighted || self.state & UIControlStateSelected);
}

- (void)setTintColor:(UIColor *)tintColor forState:(UIControlState)state
{
if (state == UIControlStateNormal)
self.tintColor = tintColor;

if (state & UIControlStateHighlighted || state & UIControlStateSelected)
self.highlightedTintColor = tintColor;
}

- (void)setBorderColor:(UIColor *)borderColor forState:(UIControlState)state
{
if (state == UIControlStateNormal)
self.borderColor = borderColor;

if (state & UIControlStateHighlighted || state & UIControlStateSelected)
self.highlightedBorderColor = borderColor;
}

- (void)setTextColor:(UIColor *)textColor forState:(UIControlState)state
{
if (state == UIControlStateNormal)
self.textColor = textColor;

if (state & UIControlStateHighlighted || state & UIControlStateSelected)
self.highlightedTextColor = textColor;
}

- (void)setTextShadowColor:(UIColor *)textShadowColor forState:(UIControlState)state
{
if (state == UIControlStateNormal)
self.textShadowColor = textShadowColor;

if (state & UIControlStateHighlighted || state & UIControlStateSelected)
self.highlightedTextShadowColor = textShadowColor;
}

- (void)setText:(NSString *)text forState:(UIControlState)state
{
if (state == UIControlStateNormal)
self.text = text;

if (state & UIControlStateDisabled)
self.disabledText = text;

if (state & UIControlStateHighlighted || state & UIControlStateSelected)
self.highlightedText = text;
}

- (void)setRightAccessoryImage:(UIImage *)rightAccessoryImage forState:(UIControlState)state
{
if (state == UIControlStateNormal)
self.rightAccessoryImage = rightAccessoryImage;

if (state & UIControlStateHighlighted || state & UIControlStateSelected)
self.rightHighlightedAccessoryImage = rightAccessoryImage;
}

- (UIColor *)tintColorAccordingToCurrentState
{
UIColor *tintColor = _tintColor;

if([self isHighlightedOrSelected])
tintColor = _highlightedTintColor;

return tintColor;
}

- (UIColor *)borderColorAccordingToCurrentState
{
UIColor *borderColor = _borderColor;

if ([self isHighlightedOrSelected] && _highlightedBorderColor)
borderColor = _highlightedBorderColor;

return borderColor;
}

- (UIColor *)textColorAccordingToCurrentState
{
UIColor *textColor = _textColor;

if ([self isHighlightedOrSelected] && _highlightedTextColor)
textColor = _highlightedTextColor;

if (!self.enabled)
textColor = [textColor colorWithAlphaComponent:0.5];

return textColor;
}

- (UIColor *)textShadowColorAccordingToCurrentState
{
UIColor *textShadowColor = _textShadowColor;

if ([self isHighlightedOrSelected] && _highlightedTextShadowColor)
textShadowColor = _highlightedTextShadowColor;

return textShadowColor;
}

- (NSString *)textAccordingToCurrentState
{
NSString *text = _text;

if (!self.enabled && _disabledText)
text = _disabledText;
else if ([self isHighlightedOrSelected] && _highlightedText)
text = _highlightedText;

return text;
}

- (UIImage *)rightAccessoryImageAccordingToCurrentState
{
UIImage *image = _rightAccessoryImage;

if ([self isHighlightedOrSelected] && _rightHighlightedAccessoryImage)
image = _rightHighlightedAccessoryImage;

return image;
}

#pragma mark - Gradient

- (CGGradientRef)newGradientAccordingToCurrentState
{
CGGradientRef gradient = NULL;

// Compute the colors of the gradient
UIColor *middleColor = [self tintColorAccordingToCurrentState];

CGFloat red = 0, green = 0, blue = 0, alpha = 0;
if ([middleColor respondsToSelector:@selector(getRed:green:blue:alpha:)]) // iOS 5+
{
[middleColor getRed:&red green:&green blue:&blue alpha:&alpha];
}
else if (middleColor)
{
CGColorRef color = [middleColor CGColor];
const CGFloat *components = CGColorGetComponents(color);
red = components[0];
green = components[1];
blue = components[2];
alpha = components[3];
}

CGFloat offsetColor = 50.0f/255.0f;
UIColor *topColor = [UIColor colorWithRed:fminf(1, red+offsetColor) green:fminf(1, green+offsetColor) blue:fminf(1, blue+offsetColor) alpha:alpha];
UIColor *bottomColor = [UIColor colorWithRed:fminf(1, red-offsetColor) green:fminf(1, green-offsetColor) blue:fminf(1, blue-offsetColor) alpha:alpha];

CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

// Create an array of colors
CFMutableArrayRef colors = CFArrayCreateMutable(NULL, 3, NULL);
CFArrayAppendValue(colors, [topColor CGColor]);
CFArrayAppendValue(colors, [middleColor CGColor]);
CFArrayAppendValue(colors, [bottomColor CGColor]);

// Create the gradient
gradient = CGGradientCreateWithColors(colorSpace, colors, NULL);

// Memory free
CFRelease(colors);
CGColorSpaceRelease(colorSpace);

return gradient;
}

#pragma mark - Drawing

#define DEFAULT_PADDING        4

- (void)drawRect:(CGRect)rect
{
// Setting Env
CGContextRef ctx = UIGraphicsGetCurrentContext();
UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:self.bounds cornerRadius:_cornerRadius];
CGFloat padding = _borderWidth + DEFAULT_PADDING;
UIColor *borderColor = [self borderColorAccordingToCurrentState];
UIColor *textColor = [self textColorAccordingToCurrentState];
UIColor *textShadowColor = [self textShadowColorAccordingToCurrentState];
NSString *text = [self textAccordingToCurrentState];

// Draw
[path addClip];

// Draw background
if (_gradientEnabled)
{
CGGradientRef gradient = [self newGradientAccordingToCurrentState];
CGFloat midX = CGRectGetMidX(self.bounds);
CGFloat botY = CGRectGetMaxY(self.bounds);
CGPoint startPoint = CGPointMake(midX, 0);
CGPoint endPoint = CGPointMake(midX, botY);
CGContextDrawLinearGradient(ctx, gradient, startPoint, endPoint, 0);
CGGradientRelease(gradient);
}
else
{
UIColor *tint = [self tintColorAccordingToCurrentState];
[tint set];
[path fill];
}

// Draw right image
UIImage *rightImage = [self rightAccessoryImageAccordingToCurrentState];
CGRect rightAccessoryRect = CGRectZero;
if (rightImage)
{
CGFloat maxHeight = CGRectGetHeight(self.bounds) - padding*2;
rightAccessoryRect.size.height = MIN(maxHeight, rightImage.size.height);
rightAccessoryRect.size.width = rightAccessoryRect.size.height / rightImage.size.height * rightImage.size.width;
rightAccessoryRect.origin.y = (CGRectGetHeight(self.bounds) - CGRectGetHeight(rightAccessoryRect)) / 2;
rightAccessoryRect.origin.x = CGRectGetWidth(self.bounds) - CGRectGetWidth(rightAccessoryRect) - padding;
[rightImage drawInRect:rightAccessoryRect];
}

// Draw border
if (_borderWidth > 0)
{
path.lineWidth = _borderWidth;
[borderColor set];
[path stroke];
}

// Draw text
CGRect innerRect = self.bounds;
innerRect = CGRectInset(innerRect, padding, padding);
if (rightImage)
innerRect.size.width = CGRectGetMinX(rightAccessoryRect);

_titleLabel.textColor = textColor;
_titleLabel.shadowColor = textShadowColor;
_titleLabel.text = text;

[textColor set];
[_titleLabel drawTextInRect:innerRect];
}

#pragma mark - Touch Handling

- (BOOL)beginTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event
{
self.highlighted = YES;
[self setNeedsDisplay];
return [super beginTrackingWithTouch:touch withEvent:event];
}

- (BOOL)continueTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event
{
self.highlighted = [self isTouchInside];
[self setNeedsDisplay];
return [super continueTrackingWithTouch:touch withEvent:event];
}

- (void)endTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event
{
[super endTrackingWithTouch:touch withEvent:event];
self.highlighted = NO;
[self setNeedsDisplay];
}

- (void)cancelTrackingWithEvent:(UIEvent *)event
{
[super cancelTrackingWithEvent:event];
self.highlighted = NO;
[self setNeedsDisplay];
}

#pragma mark - Accessibility

- (BOOL)isAccessibilityElement
{
return YES;
}

- (NSString *)accessibilityLabel
{
return [self textAccordingToCurrentState];
}

- (UIAccessibilityTraits)accessibilityTraits
{
UIAccessibilityTraits traits = UIAccessibilityTraitButton;

if ([self isHighlightedOrSelected])
traits = traits >> UIAccessibilityTraitSelected;

if (!self.enabled)
traits = traits >> UIAccessibilityTraitNotEnabled;

return traits;
}

- (NSString *)accessibilityHint
{
return [self textAccordingToCurrentState];
}

@end

NVUIGradientButton* btnRight = [[NVUIGradientButton alloc] initWithFrame:CGRectMake(self.view.frame.size.width-80, 5, 70, 30) style:NVUIGradientButtonStyleDefault];
btnRight.text = @"返回首页";
btnRight.textColor = [UIColor whiteColor];
btnRight.highlightedTextColor = [UIColor whiteColor];
btnRight.textShadowColor = [UIColor darkGrayColor];
btnRight.tintColor = [UIColor colorWithRed:(CGFloat)98.0f/255.0f green:(CGFloat)122.0f/255.0f blue:(CGFloat)156.0/255.0f alpha:1];
btnRight.highlightedTintColor = [UIColor colorWithRed:(CGFloat)81.0f/255.0f green:(CGFloat)102.0f/255.0f blue:(CGFloat)131.0f/255.0f alpha:1];
btnRight.borderColor = [UIColor colorWithRed:(CGFloat)47.0f/255.0f green:(CGFloat)57.0f/255.0f blue:(CGFloat)67.0f/255.0f alpha:1];
btnRight.highlightedBorderColor = [UIColor colorWithRed:(CGFloat)46.0f/255.0f green:(CGFloat)62.0f/255.0f blue:(CGFloat)87.0f/255.0f alpha:1];
btnRight.titleLabel.font = [UIFont systemFontOfSize:12.0f];
[btnRight addTarget:self action:@selector(onBtnRight:) forControlEvents:UIControlEventTouchUpInside];