iPhone trim audio recording - cocoa-touch

Question

I have a voice memo component in my app, and I want to allow the user to trim the audio, similar to QuickTime X on Mac OS Ten point Six handles it, or like the Voice Memos app on the iPhone. Here's an example of both:
Any help is appreciated.

Answer 1

I am not a UI programmer by any means. This was a test I wrote to see how to write custom controls. This code may or may not work. I have not touched it in some time.
header
#interface SUIMaxSlider : UIControl {
#private
float_t minimumValue;
float_t maximumValue;
float_t value;
CGPoint trackPoint;
}
#property (nonatomic, assign) float_t minimumValue, maximumValue;
#property (nonatomic, assign) float_t value;
#end
implementation
#import "SUIMaxSlider.h"
#import <CoreGraphics/CoreGraphics.h>
#import <QuartzCore/QuartzCore.h>
//#import "Common.h"
#define kSliderPadding 5
#implementation SUIMaxSlider
#synthesize minimumValue, maximumValue;
#pragma mark -
#pragma mark Interface Initialization
- (id) initWithCoder:(NSCoder *)aDecoder {
if (self = [super initWithCoder:aDecoder]) {
trackPoint.x = self.bounds.size.width;
self.backgroundColor = [UIColor colorWithRed:135.0/255.0 green:173.0/255.0 blue:255.0/255.0 alpha:0.0];
}
return self;
}
- (id) initWithFrame: (CGRect) aFrame {
if (self = [super initWithFrame:aFrame]) {
self.frame = aFrame;
self.bounds = aFrame;
self.center = CGPointMake(CGRectGetMidX(aFrame), CGRectGetMidY(aFrame));
trackPoint.x = aFrame.size.width;
}
return self;
}
- (id) init {
return [self initWithFrame:CGRectZero];
}
#pragma mark -
#pragma mark Properties.
#pragma mark -
- (float_t) value {
return value;
}
- (void) setValue:(float_t) v {
value = fmin(v, maximumValue);
value = fmax(value, minimumValue);
float_t delta = maximumValue - minimumValue;
float_t scalar = ((self.bounds.size.width - 2 * kSliderPadding) / delta) ;
float_t x = (value - minimumValue) * scalar;
x += 5.0;
trackPoint.x = x;
[self setNeedsDisplay];
}
#pragma mark -
#pragma mark Interface Drawing
#pragma mark -
- (void) drawRect:(CGRect) rect {
CGContextRef context = UIGraphicsGetCurrentContext();
CGColorRef lightBlue = [UIColor colorWithRed:135.0/255.0 green:173.0/255.0 blue:255.0/255.0 alpha:1.0].CGColor;
CGColorRef lightBlueAlpha = [UIColor colorWithRed:135.0/255.0 green:173.0/255.0 blue:255.0/255.0 alpha:0.7].CGColor;
CGColorRef lightGrayColor = [UIColor colorWithRed:130.0/255.0 green:130.0/255.0 blue:130.0/255.0 alpha:1.0].CGColor;
CGColorRef darkGrayColor = [UIColor colorWithRed:70.0/255.0 green:70.0/255.0 blue:70.0/255.0 alpha:1.0].CGColor;
CGColorRef redColor = [UIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:0.6].CGColor;
CGRect boundsRect = self.bounds;
CGRect sliderRect = CGRectMake(0, 0, boundsRect.size.width, boundsRect.size.height / 2);
/*
CGContextSetFillColorWithColor(context, lightGrayColor);
CGContextFillRect(context, sliderRect);
halfHeight.origin.y = sliderRect.size.height;
CGContextSetFillColorWithColor(context, darkGrayColor);
CGContextFillRect(context, sliderRect);
*/
CGFloat tx = fmin(sliderRect.size.width - kSliderPadding, trackPoint.x);
tx = fmax(kSliderPadding, tx);
sliderRect.origin.y = boundsRect.origin.y;
sliderRect.size.width = tx ;
CGContextSetFillColorWithColor(context, lightBlueAlpha);
CGContextFillRect(context, sliderRect);
sliderRect.origin.y = sliderRect.size.height;
CGContextSetFillColorWithColor(context, lightBlue);
CGContextFillRect(context, sliderRect);
CGFloat mid = boundsRect.size.height / 2 ;
CGPoint a = CGPointMake(tx - kSliderPadding, mid);
CGPoint b = CGPointMake(tx, mid - kSliderPadding);
CGPoint c = CGPointMake(tx + kSliderPadding, mid);
CGPoint d = CGPointMake(tx, mid + kSliderPadding);
CGContextSetRGBFillColor(context, 1.0, 1.0, 1.0, 1.0);
CGContextSetLineWidth(context, 2.0);
CGContextBeginPath(context);
CGContextMoveToPoint(context, a.x, a.y);
CGContextAddLineToPoint(context, b.x, b.y);
CGContextAddLineToPoint(context, c.x, c.y);
CGContextAddLineToPoint(context, d.x, d.y);
CGContextAddLineToPoint(context, a.x, a.y);
CGContextFillPath(context);
}
#pragma mark -
#pragma mark Touch Tracking
#pragma mark -
- (void) trackTouch:(UITouch *) touch {
CGPoint p = [touch locationInView:self];
//bound track point
trackPoint.x = fmax(p.x, kSliderPadding) ;
trackPoint.x = fmin(trackPoint.x, self.bounds.size.width - kSliderPadding);
[self setNeedsDisplay];
float_t x = trackPoint.x - kSliderPadding;
float_t delta = maximumValue - minimumValue;
float_t scalar = (x / (self.bounds.size.width - 2 * kSliderPadding)) ;
value = minimumValue + (delta * scalar);
[self sendActionsForControlEvents:UIControlEventValueChanged];
}
- (void)endTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event {
[self trackTouch:touch];
}
- (BOOL)beginTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event {
CGPoint p = [touch locationInView:self];
trackPoint.x = fmax(p.x, kSliderPadding) ;
trackPoint.x = fmin(trackPoint.x, self.bounds.size.width - kSliderPadding);
[self setNeedsDisplay];
return YES;
}
- (BOOL)continueTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event {
[self trackTouch:touch];
return YES;
}
#end