Recently, I had need to provide a back button similar to the one used in Mobile Safari for a consulting project.
Many of the buttons used in the built-in iPhone applications are made available via the SDK with built in button types and graphics. Unfortunately, the back button is not one of these.
Because I needed to display the toolbar button from inside a static library which can not include images, I had to render the back arrow directly in code.
Since this was a bit time consuming, I thought I would share in hopes that it saves someone else a little bit of time.
- (CGContextRef)createContext
{
// create the bitmap context
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(nil,27,27,8,0,
colorSpace,kCGImageAlphaPremultipliedLast);
CFRelease(colorSpace);
return context;
}
- (CGImageRef)createBackArrowImageRef
{
CGContextRef context = [self createContext];
// set the fill color
CGColorRef fillColor = [[UIColor blackColor] CGColor];
CGContextSetFillColor(context, CGColorGetComponents(fillColor));
CGContextBeginPath(context);
CGContextMoveToPoint(context, 8.0f, 13.0f);
CGContextAddLineToPoint(context, 24.0f, 4.0f);
CGContextAddLineToPoint(context, 24.0f, 22.0f);
CGContextClosePath(context);
CGContextFillPath(context);
// convert the context into a CGImageRef
CGImageRef image = CGBitmapContextCreateImage(context);
CGContextRelease(context);
return image;
}
- (UIBarButtonItem *)backButton
{
CGImageRef theCGImage = [self createBackArrowImageRef];
UIImage *backImage = [[UIImage alloc] initWithCGImage:theCGImage];
CGImageRelease(theCGImage);
UIBarButtonItem *backButton = [[UIBarButtonItem alloc] initWithImage:backImage
style:UIBarButtonItemStylePlain
target:self.webView
action:@selector(goBack)];
[backImage release], backImage = nil;
return [backButton autorelease];
}
