Slide from one button to another without lifting your finger

Question

I have two buttons (Button 1 and button 2) and if I press button 1, note1 starts and if i press button 2, note 2 starts.

So what I try to do is: press button one (note1 starts) and SLIDE to button2 and than should note2 start. As in, you slide without lifting your finger over a piano keyboard and all notes from c to h sound.

I did this with UIImageViews and I did it also with UIButtons.

If i press the c1pianoview it sounds a "c". If I press the d1pianoview it sounds a "d".

But if I slide without lifting my finger from c1pianoview to d1pianoview it only sounds a "c". What did I wrong? Can I also do this with UIButtons?

Touch down works but sliding doesn't work.

Can somebody help me, please? Here my code:

-(void)touchesBeganNSSet *)touches withEventUIEvent *)event
{
    UITouch *touch = [[event allTouches] anyObject];
    CGPoint location = [touch locationInView:touch.view];

    if(CGRectContainsPoint(c1pianoview.frame, location))
    { 
      NSString *path = [[NSBundle mainBundle]
      pathForResource: @"c1piano" ofType:@"mp3"];
      AVAudioPlayer* theAudio = [[AVAudioPlayer alloc] 
          initWithContentsOfURL:[NSURL fileURLWithPathath] error:NULL];
      [theAudio play];
    }

    if(CGRectContainsPoint(d1pianoview.frame, location))
    { 
      NSString *path = [[NSBundle mainBundle]
      pathForResource: @"d1piano" ofType:@"mp3"];
      AVAudioPlayer* theAudio=[[AVAudioPlayer alloc] 
          initWithContentsOfURL: [NSURL fileURLWithPathath] error:NULL];
      [theAudio play];
    }
}

Update:

I have a further question. Now I have two UIImageVIews on each other. A black piano key over two white piano keys. If I press on the black key it also sound the note from the white key under it.

How do I prevent this?

Answer 1

I think a simpler solution is to create a superview that intercepts all the touches and decides what to do. Then in IB, you make your view an instance of PianoView, and make all the keys subviews. Each key would have a tag that identifies which key it is, so PianoView knows what note to play. PianoView has a currentView property which keeps track of the last view in touchesMoved so it doesn't keep trying to play the same key. I have a keyboard with similar but different requirements, and this approach works well.

The sample code below intercepts touches in hitTest:withEvent:. Then, in the touches* methods, it uses UIView's default implementation of hitTest:withEvent: to determine which key is being played. You'll have to modify it a bit if you want to support playing keys simultaneously with multi-touch.

@implementation PianoView

-(UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event {
    // intercept touches
    if ([self pointInside:point withEvent:event]) {
        return self;        
    }
    return nil;
}

-(void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    UIView* view = [super hitTest: [[touches anyObject] locationInView: self] withEvent: nil];
    // highlight subview under touch
    if (view != nil && view != self) {
        if ([view isKindOfClass:[UIButton class]]) {
            [(UIControl *)view setHighlighted:YES];
        }
        [self setCurrentView:view];
        [self playKey:view];
    }
}

-(void) touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
    // un-highlight everything
    for (UIView *subview in [self subviews]) {
        if ([subview isKindOfClass:[UIButton class]]) {
            [(UIControl *)subview setHighlighted:NO];
        }
    }
    [self stopPlaying];
    [self setCurrentView:nil];
}

-(void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    UIView* view = [super hitTest: [[touches anyObject] locationInView: self] withEvent: nil];
    if (view != [self currentView]) {
        UIView *oldKey = [self currentView];
        // un-highlight
        if ([oldKey isKindOfClass:[UIButton class]]) {
            [(UIControl *)oldKey setHighlighted:NO];
        }    
        if ([view isKindOfClass:[UIButton class]]) {
            [(UIControl *)view setHighlighted:YES];
        }    
        [self stopPlaying];
        [self playKey:view];
        [self setCurrentView:view];
    }
}

-(void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    UIView* view = [super hitTest: [[touches anyObject] locationInView: self] withEvent: nil];
    for (UIView *subview in [self subviews]) {
        if ([subview isKindOfClass:[UIButton class]]) {
            [(UIControl *)subview setHighlighted:NO];
        }
    }
    [self stopPlaying];
    [self setCurrentView:nil];
}

@end

Answer 2

[Merged further question into original post]

Answer 3

Don't you need the:

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

Answer 4

You can probably achieve this easily by using the "Touch Down" and "Touch Drag Inside" events of the UIButton.

If you want to use the -touchesMoved: approach, you can use a variable to keep track of the last button that triggered a sound and only play a sound if the current button is not the one that last played a sound.

In more detail:

Declare a UIView *lastButton; in your header and then:

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [[event allTouches] anyObject];
CGPoint location = [touch locationInView:touch.view];

if(CGRectContainsPoint(c1pianoview.frame, location) && lastButton != c1pianoview) {
    //play c1
    lastButton = c1pianoview;
}
else if(CGRectContainsPoint(d1pianoview.frame, location) && lastButton != d1pianoview) {
    //play d1
    lastButton = d1pianoview;
}
}

- (void)touchedEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    lastButton = nil;
}

- (void)touchedCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
    [self touchesEnded:touches withEvent:event];
}