颜色选择器的困惑

Question

我正在尝试实现一个简单的颜色选择器，该颜色选择器由UIImageView 中的图像组成。当用户在其上拖动手指时，我希望相邻视图使用当前像素颜色不断更新。

我在@rdelmar 对this question on SO 的回答中找到了接近理想解决方案的东西，因此我借用了代码并对其进行了修改，以将pickedColor 发送回AddCategoryViewController 上的方法。但是，此方法 (setColorview) 不会更新 colorView。

我的断点和 NSLog 显示颜色信息正在从触摸中收集、发送和接收，但显然没有应用，正如受影响的 UIView colorView 不反映颜色的事实所示。最明显的问题是属性colorView 读取null，我不明白为什么。

作为奖励，我真的希望选择器能够响应滑动手指，而不仅仅是点击。

我已经在下面包含了所有相关代码，重要的行用//************************标记

感谢收看！感谢所有帮助！

代码从这里开始，文件用--------------------------分隔：

//
//  UIView+UIView_ColorOfPoint.m
//  WMDGx
//
//

#import "UIView+UIView_ColorOfPoint.h"
#import <QuartzCore/QuartzCore.h>


@implementation UIView (UIView_ColorOfPoint)

-(UIColor *) colorOfPoint:(CGPoint)point
{
    unsigned char pixel[4] = {0};
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(pixel,
                                                 1, 1, 8, 4, colorSpace, (CGBitmapInfo)kCGImageAlphaPremultipliedLast);

    CGContextTranslateCTM(context, -point.x, -point.y);

    [self.layer renderInContext:context];

    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);
    UIColor *color = [UIColor colorWithRed:pixel[0]/255.0
                                     green:pixel[1]/255.0 blue:pixel[2]/255.0
                                     alpha:pixel[3]/255.0];
    return color;
}

@end




-----------------------------------------


//
//  ColorPickerView.m
//  WMDGx
//
//

#import "ColorPickerView.h"

AddCategoryViewController *addCatVC;

@implementation ColorPickerView


- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
    }
    return self;
}


- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [[event allTouches] anyObject];
    CGPoint loc = [touch locationInView:self];
    self.pickedColor = [self colorOfPoint:loc];
    NSLog(@"Touches began");

    //******************** For sending color info to setColorView in AddCategoryViewController
    addCatVC = [[AddCategoryViewController alloc]init];
    addCatVC.colorForColorView = self.pickedColor;

    NSLog(@"Picked color is %@",self.pickedColor);

    //******************** Call the method in AddCategoryViewController, which should display the color of the current pixel
    [addCatVC setColorview];
}


@end



--------------------------------


//
//  AddCategoryViewController.m
//  WMDGx
//
//

#import "AddCategoryViewController.h"

@interface AddCategoryViewController ()

@end

@implementation AddCategoryViewController

NSMutableArray *array;


- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self)
    {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    // Do any additional setup after loading the view.
    self.catTextField.delegate = self;
    [self.pickerImageView setUserInteractionEnabled:YES];

    self.colorView.layer.cornerRadius = 6;

    // ********************I put this NSLog here to check the status of the property self.colorView

    NSLog(@"Color view is %@",self.colorView);//_colorView  UIView * 0x8a63d30 0x08a63d30 (from Variables View)
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
    [self.catTextField resignFirstResponder];
    return YES;
}


-(void)setColorview // ********************This is where the backgroundColor of self.colorView should be set
{
    NSLog(@"colorForColorView is %@",self.colorForColorView);

    NSLog(@"Color view is %@",self.colorView); //_colorView UIView *    nil 0x00000000 (from Variables View)

    [self.colorView setBackgroundColor:self.colorForColorView]; //colorView should display the color, but doesn't

    NSLog(@"Color view is %@",self.colorView); //_colorView UIView *    nil 0x00000000 (from Variables View)

    NSLog(@"Color view color is %@",self.colorView.backgroundColor);
}

- (IBAction)saveButton:(UIBarButtonItem *)sender
{
    if (self.catTextField.text.length < 1)
    {
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"No category created"
                                                        message:@"Please create a new category"
                                                       delegate:nil
                                              cancelButtonTitle:@"OK"
                                              otherButtonTitles:nil];
        [alert show];
    }

    else if (!self.colorView.backgroundColor)
    {
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"No color selected"
                                                        message:@"Please select a color for your new category"
                                                       delegate:nil
                                              cancelButtonTitle:@"OK"
                                              otherButtonTitles:nil];
        [alert show];
    }
    else
    {
        NSManagedObjectContext *localContext = [NSManagedObjectContext MR_contextForCurrentThread];
        self.thisCategory = [WMDGCategory MR_createInContext:localContext];
        self.thisCategory.name = [self.catTextField.text uppercaseString];
        self.thisCategory.color = self.colorView.backgroundColor;
        [localContext MR_saveToPersistentStoreAndWait];
        [self.thisCell setUserInteractionEnabled:NO];
        [self.delegate addCatControllerDidSave];
    }
}

- (IBAction)cancelButton:(UIBarButtonItem *)sender
{
    [self.delegate addCatControllerDidCancel:self.thisCategory];

}

@end

Answer 1

这是我用于此目的的代码。除了开始触摸之外，我还有相同的触摸移动代码，并且允许您也想要的滑动效果。我的相邻视图有一个标签 200，我根据所选颜色查找并设置它。看起来你的链接代码比我的要干净一些，但也许看到这个会很有用。

首先，当我接触到时：

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    NSSet *allTouches = [event allTouches];

    if ([allTouches count] != 1)
        return;

    UIView *picker = [self.view viewWithTag:100];

    UITouch *touch = [[allTouches allObjects] objectAtIndex:0];
    CGPoint p = [touch locationInView:self.view];
    if (CGRectContainsPoint(picker.frame, p))
    {
        printf("Hit gradient!\n");
        p = [touch locationInView:picker];
        UIColor *c = [self getPixelColor:[UIImage imageNamed:@"gradient.png"]
                                xLoc:p.x
                                yLoc:p.y];

        UIView *display = [self.view viewWithTag:200]; // representative color
        [display setBackgroundColor:c];
    }
}

获取颜色的代码（我相信这段代码是改编自 SO 上的其他代码）：

- (UIColor*)getPixelColor:(UIImage *)image xLoc:(int)x yLoc:(int)y
{
    CFDataRef pixelData = CGDataProviderCopyData(CGImageGetDataProvider(image.CGImage));
    const UInt8* data = CFDataGetBytePtr(pixelData);
    if (x < 0 || x >= image.size.width || y < 0 || y >= image.size.height)
    {
        CFRelease(pixelData);
        return [UIColor whiteColor];
    }
    int pixelInfo = ((image.size.width  * y) + x ) * 4;

    UInt8 red = data[pixelInfo];
    UInt8 green = data[(pixelInfo + 1)];
    UInt8 blue = data[pixelInfo + 2];
    UInt8 alpha = data[pixelInfo + 3];
    CFRelease(pixelData);

    UIColor* color = [UIColor colorWithRed:red/255.0f green:green/255.0f blue:blue/255.0f alpha:alpha/255.0f];

    return color;
}