使用nsbezierpath使可可中的球/圆移动(目标-c))

Question

我正在尝试在应用程序运行时在图像上创建一个点，然后尝试将点缓慢移动到其他位置。这是我的代码。此代码有效，但存在两个问题。

首先，处理在窗口加载之前已经发生，所以我只看到完成的结果。（我想显示图像中的一个点移动到另一个点）

其次，当我创建新点时，不会删除前面的点。所以看起来重点不是在移动，而是看起来像是被复制。如何删除点。

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    // Insert code here to initialize your application
    NSGraphicsContext* gc = [NSGraphicsContext currentContext];
    // Save the current graphics context settings
    [gc saveGraphicsState];
    // Set the color in the current graphics context for future draw operations
    [[NSColor blackColor] setStroke];
    [[NSColor redColor] setFill];

    for(int i=1;i<100;i++){
        NSRect rect = NSMakeRect(130+i, 130, 10, 10);
        NSBezierPath* circlePath = [NSBezierPath bezierPath];
        [circlePath appendBezierPathWithOvalInRect: rect];
        // Outline and fill the path
        [circlePath stroke];
        [circlePath fill];

        //    // Restore the context to what it was before we messed with it
        //    [gc restoreGraphicsState];
    }
}

Answer 1

编辑：

这是一个有效的实现：

@interface AppDelegate ()
@property ( nonatomic, readonly ) CALayer * ballLayer ;
@end
@implementation AppDelegate
@synthesize ballLayer = _ballLayer ;
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    [ ((NSView*)self.window.contentView) setWantsLayer:YES ] ;
    [ self performSelectorOnMainThread:@selector( doAnimation ) withObject:nil waitUntilDone:NO ] ;
}
-(void)doAnimation
{
    [ self.ballLayer addAnimation:[ self createBallLayerAnimation ] forKey:nil ] ;
}
-(CALayer*)ballLayer
{
    if ( !_ballLayer )
    {
        CALayer * layer = [ CALayer layer ] ;
        NSImage * image = [[ NSImage alloc ] initWithContentsOfURL:[ NSURL URLWithString:@"http://etc-mysitemyway.s3.amazonaws.com/icons/legacy-previews/icons/glossy-black-icons-sports-hobbies/044450-glossy-black-icon-sports-hobbies-ball-beach.png" ] ] ;
        layer.contents = image ;
        layer.bounds = (CGRect){ .size = { 100, 100 } } ;
        [((NSView*)self.window.contentView).layer addSublayer:layer ] ;
        _ballLayer = layer ;
    }
    return _ballLayer ;
}
-(CAAnimation*)createBallLayerAnimation
{
    CAKeyframeAnimation * anim = [ CAKeyframeAnimation animationWithKeyPath:@"position" ] ;
    {
        CGPathRef p = [ self createBallAnimationPath ] ;
        anim.path = p ;
        CGPathRelease( p ) ;
    }
    anim.duration = 3.0 ;
    anim.repeatCount = FLT_MAX ;
    return anim ;
}
-(CGPathRef)createBallAnimationPath
{
    CGRect bounds = ((NSView*)self.window.contentView).bounds ;
    CGPathRef p = CGPathCreateWithEllipseInRect( CGRectInset( bounds, bounds.size.width * 0.25, bounds.size.width * 0.25 ), NULL ) ;
    return p ;
}
@end

---

你会想阅读CGPath和CALayer...

正如其他人所说，不要在你的applicationDidFinishLaunching方法中这样做 - 你应该在你的窗口/视图出现后这样做。如果您从笔尖加载了自己的 NSView 子类，一个选项可能是覆盖-awakeFromNib：

-(void)awakeFromNib
{
    [ super awakeFromNib ] ;
    [ self performSelectorOnMainThread:@selector( doAnimation ) withObject:nil waitUntilDone:NO ] ; // when the main thread runs again, call `-doAnimation`
}

那么在你的视图中子类也有一个-doAnimation方法（从上面的-awakeFromNib调用）

-(void)doAnimation:
{
    CAAnimation * animation = [ CAKeyframeAnimation animationForKeyPath:@"position" ] ;
    CGPathRef path = [ self createBallAnimationPath ] ; // method -createBallAnimationPath is defined below...
    animation.path = path ;
    CGPathRelease( path ) ;
    [ self.ballLayer addAnimation:animation forKey:nil ] ; // ballLayer is the property that contains a reference to layer that contains the image you want to animate along the path
}

有一个创建路径的方法：

-(CGPathRef)createBallAnimationPath
{
    CGMutablePathRef result = CGPathCreateMutable() ;
    CGPathMoveToPoint( result, 100, 100 ) ;
    CGPathAddLineToPoint( result, 1000, 1000 ) ;
    return result ;
}