code iphone image drawing lines

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

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.
2. 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