objective-c - 使用 nsbezierpath(objective -c)) 在 cocoa 中移动球/圆？

Question

我试图在应用程序运行时在图像上创建一个点，然后尝试将该点缓慢移动到不同的位置。这是我的代码。该代码可以工作，但有两个问题。

首先，处理已经在窗口加载之前发生，因此我只能看到最终的结果。(我想显示一个点移动到图像中的另一个点)

第二，当我创建一个新点时，前一个点并没有被删除。所以它看起来不像是在移动，而是看起来像是在重复。如何删除一个点。

- (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

<小时/>

您需要阅读 CGPath 和 CALayer...

正如其他人所说，不要在您的 applicationDidFinishLaunching 方法中执行此操作 - 您应该在窗口/ View 出现后执行此操作。如果您有自己的从 Nib 加载的 NSView 子类，一种选择可能是覆盖 -awakeFromNib:

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

然后在您的 View 子类中还有一个 -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
}

有一个方法来创建你的路径:

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