擦除功能上UITouch

Question

我有兩個UIView一個在另一個之上，其中，所述第一個具有紅色作爲backgroundColor，並且上一個具有白色如backgroundColor，當用戶觸摸和色調上UIVIEW下UIView具有是可見的..有可能在這裏...？

Answer 1

是的，這是可能的，我也在我的項目中做到了這一點。看看這個link

希望這有助於你和你想要做的;-)

Answer 2

我有類代碼爲你的這個要求是什麼..只是試着去了解流動

創建一個UIView類像波紋管......

看到TouchView.h文件波紋管..

// 
// TouchView.h 
// 
// Created by Paras Joshi on 23/08/12.. 
// 

#import <UIKit/UIKit.h> 

@interface TouchView : UIView { 

    // array of all the touch locations 
    NSMutableArray *points; 

    // image to mask on user gesture 
    UIImage *maskImage; 

} 
@property (nonatomic, retain) UIImage *maskImage; 
@property (nonatomic, retain) NSMutableArray *points; 
-(void)drawPic:(UIImage *)thisPic; 
@end 

，也TouchView.m FIL Ë像波紋管..

// TouchView.m 
// 
// Created by Paras Joshi on 23/08/12.. 

#import "TouchView.h" 

// Define method POINT to return the CGPoint value of the object at self.points[index] 

#define POINT(index) [[self.points objectAtIndex:index] CGPointValue]; 




@interface TouchView (PrivateMethods) 

    -(void)clipImage; 

    @end 


    @implementation TouchView 
    @synthesize points,maskImage; 

    // mask will be a sphere of maskWidth X maskHeight 
    float maskWidth = 30.0f; 
    float maskHeight = 30.0f; 


    - (id)initWithFrame:(CGRect)frame { 

     self = [super initWithFrame:frame]; 
     if (self) { 
      // Initialization code. 
      self.backgroundColor = [UIColor clearColor]; 
      self.points = [NSMutableArray array]; 

      // set the 'maskImage' 
      maskImage = [[UIImage alloc]init]; 
    //  maskImage = [UIImage imageNamed:@"house1.jpeg"]; 

      // listen for 'reset' notification event 
    //  [[NSNotificationCenter defaultCenter] addObserver:self 
    //            selector:@selector(reset:) 
    //             name:ResetNotification 
    //             object:nil]; 

     } 
     return self; 
    } 

    -(void)drawPic:(UIImage *)thisPic { 

     maskImage = thisPic; 

     [maskImage retain]; 
     [self setNeedsDisplay]; 
    } 

    -(void)reset:(NSNotification *)notification{ 

     [self.points removeAllObjects]; 
     [self setNeedsDisplay]; 

    } 
    -(void)drawRect:(CGRect)rect{ 

     // break if there are no points to mask 
     if (!self.points || self.points.count < 2) return; 

     // mask the image 
     [self clipImage]; 
    } 

    // clipImage handles creating and adding a path of masks (ellipses), to our drawing context (display) based on gesture input 
    - (void) clipImage{ 

     // grab a reference to the image we're going to mask 
     UIImage *image = maskImage; 

     // determine the extents of the image so that we do not 
     // do unnecessary drawing ouside the image bounds 
    // CGRect bounds = CGRectMake(0.0f, 0.0f, maskImage.size.width, maskImage.size.height); 
     CGRect bounds = CGRectMake(0.0f, 0.0f, 1024, 694); 
     // get the graphics context and init a path to draw our mask to 
     CGContextRef context = UIGraphicsGetCurrentContext(); 
     CGMutablePathRef path = CGPathCreateMutable(); 

     // add ellipses to every CGPoint in self.points 
     for(int i = 0; i < self.points.count - 1; i++){ 

      // get the CGPoint value stored in self.points[i] 
      CGPoint pt = POINT(i); 

      // add the ellipse at that point 
      CGPathAddEllipseInRect(path, NULL, CGRectMake(pt.x - (maskWidth/2), pt.y - (maskHeight/2), maskWidth, maskHeight)); 
     } 

     // add the path of ellipses to our drawing context 
     CGContextAddPath(context, path); 

     // clip the Core Graphics drawing context to our display 
     CGContextClip(context); 

     // now add the image to our display (it will only appear wherever the CGPoints of self.points are located) 
     [image drawInRect:bounds]; 

     // finalize drawing 
     CGContextClosePath(context); 

    } 


    - (void)dealloc { 
     points = nil; 

     // remove event listener 
     [[NSNotificationCenter defaultCenter] removeObserver:self]; 
     [super dealloc]; 
    } 


    #pragma mark - 
    #pragma mark Gesture Methods 

    -(BOOL) isMultipleTouchEnabled{ return NO; };  

    -(void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{ 

     // get the location of the touch 
     CGPoint pt = [[touches anyObject] locationInView:self]; 

     // puch the touch location (pt) onto our array of points 
     [self.points addObject:[NSValue valueWithCGPoint:pt]]; 

     // update display by calling it's 'drawRect' method 
     [self setNeedsDisplay]; 

    } 

    -(void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{ 

     // get the location of the touch 
     CGPoint pt = [[touches anyObject] locationInView:self]; 

     // puch the touch location (pt) onto our array of points 
     [self.points addObject:[NSValue valueWithCGPoint:pt]]; 

     // update display by calling it's 'drawRect' method 
     [self setNeedsDisplay]; 


    } 
    @end 

只需添加這種觀點爲您MAINVIEW像波紋管的子視圖...

先在.h文件中添加類..

@class TouchView; 

，然後創建對象像.h文件波紋管..

TouchView *viewScratch; 

和.m文件中添加以下代碼

- (void)viewDidLoad 
    { 
    viewScratch = [[TouchView alloc]initWithFrame:CGRectMake(0, 0, 1024, 694)];// set frame which you want... 
    [viewScratch clipsToBounds]; 
    [viewScratch drawPic:[UIImage imageNamed:@"yourImageName"]]; 
    [self.view addSubview:viewScratch]; 
    }