iPad SDK : New Graphics Functionality - We Are All Tool Users (part 1)

In addition, DudelViewController will maintain state information about other potential user-selected values, such as the current fill color (used to fill the inside of the shape that's being drawn) and the current stroke color (used to draw the edge of the shape). That information will be available for the active tool to access when it's doing its temporary drawing and when it's creating a completed drawing operation to give to the view. For now, we're not going to provide any mechanism for setting the fill and stroke colors. We'll just give them predefined values.

The final piece of functionality that DudelView will include is responding to presses of the UIBarButtonItems in the toolbar, which will result in a new tool being set as the active tool. To get started, add a few lines to DudelViewController.h:

//  DudelViewController.h
#import <UIKit/UIKit.h>
#import "Tool.h"
#import "DudelView.h"

@interface DudelViewController : UIViewController <ToolDelegate, DudelViewDelegate> {
  id <Tool> currentTool;
  IBOutlet DudelView *dudelView;

					  

IBOutlet UIBarButtonItem *freehandButton;
  IBOutlet UIBarButtonItem *ellipseButton;
  IBOutlet UIBarButtonItem *rectangleButton;
  IBOutlet UIBarButtonItem *lineButton;
  IBOutlet UIBarButtonItem *pencilButton;
  UIColor *strokeColor;
  UIColor *fillColor;
  CGFloat strokeWidth;
}

@property (retain, nonatomic) id <Tool> currentTool;
@property (retain, nonatomic) UIColor *strokeColor;
@property (retain, nonatomic) UIColor *fillColor;
@property (assign, nonatomic) CGFloat strokeWidth;
- (IBAction)touchFreehandItem:(id)sender;
- (IBAction)touchEllipseItem:(id)sender;
- (IBAction)touchRectangleItem:(id)sender;
- (IBAction)touchLineItem:(id)sender;
- (IBAction)touchPencilItem:(id)sender;
@end

Next, move to DudelViewController.m. This is where the real changes take place. Among other things, this file contains implementations for all the action methods we defined in the header file. These are all empty for now, but will be filled in later as we cover each new tool. It also defines a few utility methods for internal use, for taking care of some repetitive tasks that we'll need to do for each of those action methods.

//  DudelViewController.m
#import "DudelViewController.h"

#import "DudelView.h"

@implementation DudelViewController

@synthesize currentTool, fillColor, strokeColor, strokeWidth;

- (void)deselectAllToolButtons {
  [textButton setImage:[UIImage imageNamed:@"button_text.png"]];
  [freehandButton setImage:[UIImage imageNamed:@"button_bezier.png"]];
  [ellipseButton setImage:[UIImage imageNamed:@"button_ellipse.png"]];
  [rectangleButton setImage:[UIImage imageNamed:@"button_rectangle.png"]];
  [lineButton setImage:[UIImage imageNamed:@"button_line.png"]];
  [pencilButton setImage:[UIImage imageNamed:@"button_cdots.png"]];
}
- (void)setCurrentTool:(id <Tool>)t {
  [currentTool deactivate];
  if (t != currentTool) {
    [currentTool release];
    currentTool = [t retain];
    currentTool.delegate = self;
    [self deselectAllToolButtons];
  }
  [currentTool activate];
  [dudelView setNeedsDisplay];
}

					  

- (IBAction)touchFreehandItem:(id)sender {
}
- (IBAction)touchEllipseItem:(id)sender {
}
- (IBAction)touchRectangleItem:(id)sender {
}
- (IBAction)touchLineItem:(id)sender {
}
- (IBAction)touchPencilItem:(id)sender {
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
  [currentTool touchesBegan:touches withEvent:event];
  [dudelView setNeedsDisplay];
}
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
  [currentTool touchesCancelled:touches withEvent:event];
  [dudelView setNeedsDisplay];
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
  [currentTool touchesEnded:touches withEvent:event];
  [dudelView setNeedsDisplay];
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
  [currentTool touchesMoved:touches withEvent:event];
  [dudelView setNeedsDisplay];
}
- (void)addDrawable:(id <Drawable>)d {
  [dudelView.drawables addObject:d];
  [dudelView setNeedsDisplay];
}
- (UIView *)viewForUseWithTool:(id <Tool>)t {
  return self.view;
}
- (void)drawTemporary {
  [self.currentTool drawTemporary];
}
- (void)viewDidLoad {
  [super viewDidLoad];
  self.fillColor = [UIColor lightGrayColor];
  self.strokeColor = [UIColor blackColor];
  self.strokeWidth = 2.0;
}
// Override to allow orientations other than the default portrait orientation.
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)orientation {
    return YES;
}
- (void)dealloc {
  self.currentTool = nil;
  self.fillColor = nil;
  self.strokeColor = nil;
  [super dealloc];
}
@end

					  

That code also refers to a file called Tool.h, and the Tool protocol it defines. That's the protocol with which the controller communicates with the selected tool. Create a new protocol header file in your project, name it Tool.h, and fill it with this:

// Tool.h
#import <UIKit/UIKit.h>

@protocol ToolDelegate;
@protocol Drawable;

@protocol Tool <NSObject>

@property (assign, nonatomic) id <ToolDelegate> delegate;
- (void)activate;
- (void)deactivate;

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

- (void)drawTemporary;
@end

@protocol ToolDelegate

- (void)addDrawable:(id <Drawable>)d;
- (UIView *)viewForUseWithTool:(id <Tool>)t;
- (UIColor *)strokeColor;
- (UIColor *)fillColor;

@end

This also defines the ToolDelegate protocol, with which each tool can communicate back to the controller.

At this point, you should be able to build and run your app. You'll still wind up with a blank slate that doesn't do anything, but doing so will at least verify that you're on track.

Next, let's tackle the tools.