Quickies for UIView

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General

• Adding gesture recognizers [permalink]
  Gesture recognizers are cool. Here is how you can add them to a UIView, say at init or view loading time:

      UITapGestureRecognizer *tap =
          [[UITapGestureRecognizer alloc] initWithTarget: self
                                          action: @selector(twoByThreeTap:)];
      tap.numberOfTapsRequired = 2;
      tap.numberOfTouchesRequired = 3;
      [self addGestureRecognizer: tap];
      [tap release];

  If you're not getting taps, perhaps you're using a default UIImageView, you'll probably need to turn on interaction and multitouch, either in IB or in code:

      // So we can get the taps.
      self.userInteractionEnabled = YES;
      self.multipleTouchEnabled = YES;

• Converting touch coordinate to the view [permalink]
  

  - (void) touchesEnded: (NSSet *) touches  withEvent: (UIEvent *) event {
      UITouch *touch = [touches anyObject];
      CGPoint point = [touch locationInView: self];
      if (CGRectContainsPoint(self.bounds, point)) {
          NSLog (@"YAY!");
      }
  
  } // touchesEnded
  

• Discriminating single and double tap gesture [permalink]
  You want a single tap to do something, and a double tap to do something else. You don't want the single tap to fire unless it's fer sher not a double-tap. (assuming you can live for the timeout before your single tap gesture happens). You can make the single-tap recognizer wait until the double-tap one fails:

      UITapGestureRecognizer *singleTap =
          [[UITapGestureRecognizer alloc] initWithTarget: self
                                          action: @selector(startStop:)];
      singleTap.numberOfTapsRequired = 1;
      singleTap.numberOfTouchesRequired = 1;
      [self addGestureRecognizer: singleTap];
  
      UITapGestureRecognizer *doubleTap =
          [[UITapGestureRecognizer alloc] initWithTarget: self
                                          action: @selector(resetTimer:)];
      doubleTap.numberOfTapsRequired = 2;
      doubleTap.numberOfTouchesRequired = 1;
      [self addGestureRecognizer: doubleTap];
  
      [singleTap requireGestureRecognizerToFail: doubleTap];
  
      [singleTap release];
      [doubleTap release];
  
  

• Displaying stuff on a monitor hooked up to the phone [permalink]
  

  BOOL haveSecondScreen = [UIScreen screens].count > 1;
  
  if (haveSecondScreen) {
      UIScreen *screen = [[UIScreen screens] objectAtIndex: 1];
  
      // Figure out the largest screen mode we can use.
      CGSize max = CGSizeMake (0.0, 0.0);
      UIScreenMode *maxScreenMode = nil;
      for (UIScreenMode *mode in [screen availableModes]) {
          if (mode.size.width * mode.size.height > max.width * max.height) {
              max = mode.size;
              maxScreenMode = mode;
          }
      }
      screen.currentMode = maxScreenMode;
  
      UIView *view = [[UIView alloc] initWithFrame: screen.bounds];
      view.backgroundColor = [UIColor greenColor];
  
      UIWindow *window = [[UIWindow alloc] init];
      window.screen = screen;
      [window addSubview: view];
      window.hidden = NO;
  
      [view release];
      // Stash |window| into an ivar or something.
  }

  This doesn't deal with stuff like aspect ratios, etc.

• Make a UIView round-cornered with a border [permalink]
  

      self.groovyView.layer.cornerRadius = 5;
      self.groovyView.layer.borderColor = [[UIColor purpleColor] CGColor];
      self.groovyView.layer.borderWidth = 1;
      self.groovyView.layer.masksToBounds = YES;
  

• Put a border around a UITextView [permalink]
  (or around any UIView for that matter)

  #import <QuartzCore/QuartzCore.h>  // For layer styles
  
  ...
  
  textview.layer.borderWidth = 1.0f;
  textview.layer.borderColor = [UIColor blackColor].CGColor;
  

• The UIResponder touch methods [permalink]
  

  - (void) touchesBegan: (NSSet *) touches  withEvent: (UIEvent *) event;
  - (void) touchesMoved: (NSSet *) touches  withEvent: (UIEvent *) event;
  - (void) touchesEnded: (NSSet *) touches  withEvent: (UIEvent *) event;
  - (void) touchesCancelled: (NSSet *) touches  withEvent: (UIEvent *) event;
  

Hacks

• Unique looking custom placeholder views [permalink]
  Every now and then I want a placeholder view that just draws itself. In this particular case, I wasn't sure where the contents of various view controllers were being set up, and whether it was re-using views or making them new each time. I added one of these to the view hierarchy. If I saw it, I know where it was created. Because the color is based on the view's address, each view will get a different color, making it easy to see if distinct views are being used or if one is being recycled.

  @interface BlahView : UIView
  @end
  
  @implementation BlahView
  
  - (void) drawRect: (CGRect) rect {
      CGRect bounds = self.bounds;
  
      UIColor *color = [UIColor colorWithRed: (((int)self >> 0) & 0xFF) / 255.0
                                green: (((int)self >> 8) & 0xFF) / 255.0
                                blue: (((int)self >> 16) & 0xFF) / 255.0
                                alpha: 1.0];
  
      [color set];
      UIRectFill(bounds);
  
      [[UIColor blackColor] set];
      UIRectFrame(bounds);
  } // drawRect
  
  @end // BlahView
  
  ...
  
         CGRect frame = CGRectMake(200, 5, 300, 30);
          BlahView *view = [[BlahView alloc] initWithFrame: frame];
          [viewController.view addSubview:view];
  

  And here is the version for Cocoa-non-touch:

  @interface BlahView : NSView
  @end
  
  @implementation BlahView
  
  - (void) drawRect: (CGRect) rect {
      CGRect bounds = self.bounds;
  
      NSColor *color = [NSColor colorWithDeviceRed: (((int)self >> 0) & 0xFF) / 255.0
                                green: (((int)self >> 8) & 0xFF) / 255.0
                                blue: (((int)self >> 16) & 0xFF) / 255.0
                                alpha: 1.0];
  
      [color set];
      NSRectFill(bounds);
  
      [[NSColor blackColor] set];
      NSFrameRect (bounds);
  } // drawRect
  
  @end // BlahView
  

  And for Swift/Cocoa-touch:

  func prettyColor(instance: T) -> UIColor {
         var address = unsafeBitCast(instance, Int.self)
         let red =   CGFloat(address >> 0 & 0xFF) / 255.0
         let green = CGFloat(address >> 8 & 0xFF) / 255.0
         let blue =  CGFloat(address >> 16 & 0xFF) / 255.0
  
         let derivedColor = UIColor(red: red, green: green, blue: blue, alpha: 1.0)
         return derivedColor
     }
  

  (thanks to Step Christopher for the translation)

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