code iphone image drawing lines - iphone

Question

Hi everyone I'm french so scuse me for my english.So I want to make a game like flight control. When I draw line from an image like a plane I want that the plane follow that line .How can I do this please?

Answer 1

To draw the line, implement touchesBegan:, touchedMove:, touchedEnded, touchesCancelled: in your view or view controller and build a path (CGPathRef) using the touch points.
To make an an object move along the line, create a CAKeyframeAnimation, set the path and assign it to the object's layer.
Edit: sample code
When you have a CGPathRef path, creating the animation is as easy as:
CAKeyframeAnimation* animation = [CAKeyframeAnimation animation];
animation.path = thePath;
animation.duration = 2;
animation.rotationMode = kCAAnimationRotateAuto; // object auto rotates to follow the path
animation.removedOnCompletion = NO;
animation.fillMode = kCAFillModeForwards;
Finally, assign the animation to a layer:
[layer1 addAnimation:animation forKey:#"position"];
Edit 2: sample application:
I built an entire project called PathAnimation for you.
Edit 3: this is the code I used in the PathAnimation project:
//
// CustomView.m
// PathAnimation
//
// Created by Dominique d'Argent on 19.04.11.
// Copyright 2011 Nicky Nubbel. All rights reserved.
//
#import "CustomView.h"
#implementation CustomView
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
object = [[UIImageView alloc] initWithImage:[UIImage imageNamed:#"arrow"]];
object.frame = CGRectMake(10.0, 30.0, 20.0, 20.0);
[self addSubview:object];
[self createPath];
}
return self;
}
- (void)dealloc
{
[object release];
[super dealloc];
}
#pragma mark - Custom drawing
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
CGContextRef g = UIGraphicsGetCurrentContext();
CGFloat bgColor[4] = {1.0f, 1.0f, 1.0f, 1.0f};
CGContextSetFillColor(g, bgColor);
CGContextFillRect(g, self.frame);
CGFloat color[4] = {1.0f, 0.0f, 0.0f, 1.0f};
CGContextAddPath(g,path);
CGContextSetStrokeColor(g, color);
CGContextDrawPath(g, kCGPathStroke);
CGPoint position = CGPathGetCurrentPoint(path);
CGContextAddArc(g, position.x, position.y, 5.0f, 0.0f, 2 * M_PI, 0);
CGContextSetFillColor(g, color);
CGContextDrawPath(g, kCGPathFill);
}
#pragma mark - Path creation
- (void)createPath {
path = CGPathCreateMutable();
CGPathMoveToPoint(path, NULL, object.center.x, object.center.y);
}
#pragma mark - Touch handling
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
CGPoint position = [touch locationInView:self];
if (CGRectContainsPoint(object.frame, position)) {
// start animation
[self go];
}
else {
CGPoint lastPosition = CGPathGetCurrentPoint(path);
if (CGPointEqualToPoint(lastPosition, object.center)) {
CGFloat angle = -atan2f(position.x - lastPosition.x, position.y - lastPosition.y);
angle += M_PI_2;
object.layer.transform = CATransform3DMakeRotation(angle, 0.0, 0.0, 1.0);
}
CGPathAddLineToPoint(path, NULL, position.x, position.y);
[self setNeedsDisplay];
}
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
}
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
}
#pragma mark - Animations
- (void) go {
NSLog(#"go");
object.layer.transform = CATransform3DIdentity;
CAKeyframeAnimation* animation = [CAKeyframeAnimation animation];
animation.path = path;
animation.duration = 5.0;
animation.rotationMode = kCAAnimationRotateAuto; // object auto rotates to follow the path
animation.removedOnCompletion = NO;
animation.fillMode = kCAFillModeForwards;
[object.layer addAnimation:animation forKey:#"position"];
object.center = CGPathGetCurrentPoint(path);
[self createPath];
}
#end