iOS不规则按钮实现

UIButton 在使用 png 作為按鈕時

即使點到透明的部份依然會觸發 touch 事件

為了達到更準確的點擊效果

需建立繼承 UIButton 的類別 (NonRectButton.h)

覆寫 -(BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event 的觸發條件

和擴展 UIImage 類別的功能 (UIImage+GetPixelRGBA.h)

以配合 UIButton 圖片縮放取得點擊位置 pixel 資料

首先擴展 UIImage 功能 (add new category file)
UIImage+GetPixelRGBA.h

@interface UIImage (GetPixelRGBA)
-(UIColor *)colorAtPoint:(CGPoint)point WithImageSize:(CGSize)size;
-(UIImage *)reSizeImage:(UIImage *)image toSize:(CGSize)reSize;
@end

UIImage+GetPixelRGBA.m

@implementation UIImage (GetPixelRGBA)

//取得 point pixel color
-(UIColor*)colorAtPoint:(CGPoint)point WithImageSize:(CGSize)size{
UIImage *resizeimage = [self reSizeImage:self toSize:size];

CGRect rect = CGRectMake(0.0f, 0.0f, resizeimage.size.width, resizeimage.size.height);
if (CGRectContainsPoint(rect, point) == NO)  {return nil;}

CGImageRef image = resizeimage.CGImage;
size_t width = CGImageGetWidth(image);
size_t height = CGImageGetHeight(image);
int bytesPerPixel = 4;
int bytesPerRow = (bytesPerPixel*1);        // 8bpp
unsigned char pixelData[4] = {0, 0, 0, 0};
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(pixelData, 1, 1, 8, bytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast|kCGBitmapByteOrder32Big);
CGColorSpaceRelease(colorSpace);

if (context == NULL)  {
NSLog(@"[colorAtPixel] Unable to create context!");
return nil;
}

CGContextSetBlendMode(context, kCGBlendModeCopy);
CGFloat pointX = point.x;
CGFloat pointY = height-point.y;
CGContextTranslateCTM(context, -pointX, -pointY);
CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, (CGFloat)width, (CGFloat)height), image);
CGContextRelease(context);

//Convert color values [0..255] to floats [0.0..1.0]
CGFloat red = (CGFloat)pixelData[0]/255.0f;
CGFloat green = (CGFloat)pixelData[1]/255.0f;
CGFloat blue = (CGFloat)pixelData[2]/255.0f;
CGFloat alpha = (CGFloat)pixelData[3]/255.0f;
return [UIColor colorWithRed:red green:green blue:blue alpha:alpha];
}

//更改 UIImage 大小
-(UIImage *)reSizeImage:(UIImage *)image toSize:(CGSize)reSize
{
UIGraphicsBeginImageContext(CGSizeMake(reSize.width, reSize.height));
[image drawInRect:CGRectMake(0, 0, reSize.width, reSize.height)];
UIImage *reSizeImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return reSizeImage;
}

再來建立 NonRectButton 類別並繼承 UIButton

並覆寫 -(BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event 方法
NonRectButton.h

#import <UIKit/UIKit.h>
@interface NonRectButton : UIButton

@end

NonRectButton.m

#import "NonRectButton.h"
#import "UIImage+GetPixelRGBA.h"

@implementation NonRectButton

-(BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event  {
UIImage *image = [self backgroundImageForState:UIControlStateNormal];
if (image == nil)  {return YES;}

CGColorRef color = [[image colorAtPoint:point WithImageSize:self.frame.size] CGColor];
CGFloat alphaValue = CGColorGetAlpha(color);
return (alphaValue >= 0.1f);
}

@end

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