Question

大家好，我是法国人，所以请原谅我的英语。所以我想做一个像飞行控制这样的游戏。当我从像平面的图像中画线时，我希望飞机跟随那条线。我怎么能这样做呢？

Answer 1

要绘制线条，请在视图中实施touchesBegan:，touchedMove:，touchedEnded，touchesCancelled:或查看控制器，并使用触摸点构建路径（CGPathRef）。
要使对象沿着线移动，请创建CAKeyframeAnimation，设置路径并将其指定给对象的图层。

修改示例代码

当您拥有CGPathRef path时，创建动画就像以下一样简单：

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;

最后，将动画分配给图层：

[layer1 addAnimation:animation forKey:@"position"];

编辑2：示例应用程序：

我为你建立了一个名为PathAnimation的整个项目。

编辑3：这是我在PathAnimation项目中使用的代码：

//
//  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

代码iphone图像绘制线

1 个答案: