如何创建一个渐变背景色的按钮

通过 NVUIGradientButton 类来实现，作者： Nicolas Verinaud

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

#import <UIKit/UIKit.h>

typedef enum {
    NVUIGradientButtonStyleDefault = 1,
    NVUIGradientButtonStyleBlackOpaque,
    NVUIGradientButtonStyleBlackTranslucent
} NVUIGradientButtonStyle;


@interface NVUIGradientButton : UIControl

@property (nonatomic, assign) NVUIGradientButtonStyle style;
//角度半径
@property (nonatomic) CGFloat cornerRadius; // Default to 10.0
//边宽
@property (nonatomic) CGFloat borderWidth; // Default to 2.0
//填充颜色
@property (strong, nonatomic) UIColor *tintColor; // Default to gray
//高亮时填充颜色
@property (strong, nonatomic) UIColor *highlightedTintColor; // Default to nice blue
//边框颜色
@property (strong, nonatomic) UIColor *borderColor; // Default to darkGray
//高亮时边框颜色
@property (strong, nonatomic) UIColor *highlightedBorderColor; // Default to white
//字体颜色
@property (strong, nonatomic) UIColor *textColor; // Default to black
//高亮时字体颜色
@property (strong, nonatomic) UIColor *highlightedTextColor; // Default to white
//字体阴影颜色
@property (strong, nonatomic) UIColor *textShadowColor; // Default to clear
//高亮时字体阴影颜色
@property (strong, nonatomic) UIColor *highlightedTextShadowColor; // Default to darkGrey
//内容文字
@property (copy, nonatomic) NSString *text;
//高亮时内容文字
@property (copy, nonatomic) NSString *highlightedText; // Default to text
//设置disabled状态颜色
@property (copy, nonatomic) NSString *disabledText; // Default to text
//字所在的label
@property (strong, nonatomic, readonly) UILabel *titleLabel;
//设置YES渐变色,设置NO单色
@property (nonatomic, getter = isGradientEnabled) BOOL gradientEnabled; // Default to YES, set to NO to draw flat color
//rightAccessory图片
@property (nonatomic, strong) UIImage *rightAccessoryImage;
//高亮时rightAccessory图片
@property (nonatomic, strong) UIImage *rightHighlightedAccessoryImage;

//三种初始化便利方式
// Designated initializer
- (id)initWithFrame:(CGRect)frame style:(NVUIGradientButtonStyle)style cornerRadius:(CGFloat)cornerRadius borderWidth:(CGFloat)borderWidth andText:(NSString *)text;
// Convenient initializers
- (id)initWithFrame:(CGRect)frame cornerRadius:(CGFloat)cornerRadius borderWidth:(CGFloat)borderWidth andText:(NSString *)text;
- (id)initWithFrame:(CGRect)frame style:(NVUIGradientButtonStyle)style;

// Convenience for configuration depending on states
//填充颜色
- (void)setTintColor:(UIColor *)tintColor forState:(UIControlState)state;
//边颜色
- (void)setBorderColor:(UIColor *)borderColor forState:(UIControlState)state;
//字颜色
- (void)setTextColor:(UIColor *)textColor forState:(UIControlState)state;
//字阴影颜色
- (void)setTextShadowColor:(UIColor *)textShadowColor forState:(UIControlState)state;
//文字
- (void)setText:(NSString *)text forState:(UIControlState)state;
//RightAccessory
- (void)setRightAccessoryImage:(UIImage *)rightAccessoryImage forState:(UIControlState)state;

@end

//
//  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

使用范例：

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];