cocos2d中如何添加画圆的动画效果

Question

我正在开发一款游戏以找出两张图片之间的差异。

我想在你发现它时添加一个效果。画一个圆圈比突然显示圆圈要好得多。但我以前从未做过核心动画或opengl。

我不认为准备 100 个精灵并逐帧更改精灵是一个好主意。 这是我的代码：（只需在左右图像中添加一个圆形图像。）

-(void) show {
    CCSprite* leftCircle = [CCSprite spriteWithFile:@"circle.png"];
    CCSprite* rightCircle = [CCSprite spriteWithFile:@"circle.png"];
    leftCircle.scaleX = size.width / [leftCircle boundingBox].size.width;
    leftCircle.scaleY = size.height / [leftCircle boundingBox].size.height;
    rightCircle.scaleX = size.width / [rightCircle boundingBox].size.width;
    rightCircle.scaleY = size.height / [rightCircle boundingBox].size.height;
    leftCircle.anchorPoint = ccp(0, 1);
    rightCircle.anchorPoint = ccp(0, 1);
    leftCircle.position = leftPosition;
    rightCircle.position = rightPosition;
    [[GameScene sharedScene] addChild:leftCircle z: 3];
    [[GameScene sharedScene] addChild:rightCircle z: 3];
    shown = YES;
}

那么我该如何实现呢？如果您能提供一些源代码，那就太好了。

Answer 1

作为一种简单的方法，我可以建议您创建一个圆圈并将其比例设为零。然后创建一个 CCScale 动作并运行它。它会给你一个成长的圈子。代码如下：

CCSprite *sprite = [CCSprite spriteWithFile:@"mySprite.png"];
[sprite setScale:0.01];
id scale = [CCScale actionWithDuration:0.3 scale:1];
[sprite runAction:scale];

另一个可以使用的动作是CCFadeIn。您可以在创建后使您的精灵不可见并使其淡入：

CCSprite *sprite = [CCSprite spriteWithFile:@"mySprite.png"];
[sprite setOpacity:0];
id fade = [CCFadeIn actionWithDuration:0.3];
[sprite runAction:fade];

您也可以组合这些操作：

[sprite runAction:fade];
[sprite runAction:scale];

您也可以将其放大（例如设置比例 3）和透明。并使其淡入并缩小以突出显示您的图像

要通过绘图效果画一个圆，您可以用小零件（弧线）制作它，然后用它们构建您的圆。我认为如果您在添加时不要使该部分可见，而是使其淡入，那也会很酷。我的意思是这样的：

-(void) init
{
    NSMutableArray *parts = [[NSMutableArray array] retain]; //store it in your class variable
    parts_ = parts;
    localTime_ = 0; //float localTime_ - store the local time in your layer
    //create all the parts here, make them invisible and add to the layer and parts
}

-(void) update: (CCTime) dt //add update method to your layer that will be called every simulation step
{
    localTime_ += dt;

    const float fadeTime = 0.1;
    int currentPart = localTime_ / fadeTime;

    int i = 0;
    for (CCSprite *part in parts)
    {
        //setup the opacity of each part according to localTime
        if (i < currentPart) [part setOpacity:255];
        else if (i == currentPart)
        {
            float localLocalTime = localTime - i*fadeTime;
            float alpha = localLocalTime / fadeTime;
            [part setOpacity:alpha];
        }
        ++i;
    } 
} 

Answer 2

创建您想要的效果相当简单。 可以通过设置 CAShapeLayer 的 strokeEnd 来实现。

以下是详细信息：

1. 创建一个路径，然后分配给 CAShapeLayer

   UIBezierPath* circlePath = [UIBezierPath bezierPathWithArcCenter:CGPointMake(100.0, 100.0) radius:80.0 startAngle:DEGREES_TO_RADIANS(270) endAngle:DEGREES_TO_RADIANS(270.01) clockwise:NO];
   
   circle = [CAShapeLayer layer];
   circle.path = circlePath.CGPath;
   circle.strokeColor = [[UIColor blackColor] CGColor];
   circle.fillColor   = [[UIColor whiteColor] CGColor];
   circle.lineWidth   = 6.0;
   circle.strokeEnd   = 0.0;
   
   [self.view.layer addSublayer:circle];
   

2. 设置 strokeEnd 以隐式动画绘制圆

   circle.strokeEnd = 1.0;

就是这样！圆圈将自动为您绘制；）。这是上面带有 GestureRecognizer 来触发动画的代码。将其复制到“Single View Application”类型的空项目并将其粘贴到 ViewController。

    #define DEGREES_TO_RADIANS(angle) ((angle) / 180.0 * M_PI)

    - (void)viewDidLoad
    {
        [super viewDidLoad];
        // Do any additional setup after loading the view, typically from a nib.

        UIBezierPath* circlePath = [UIBezierPath bezierPathWithArcCenter:CGPointMake(100.0, 100.0) radius:80.0 startAngle:DEGREES_TO_RADIANS(270) endAngle:DEGREES_TO_RADIANS(270.01) clockwise:NO];

        circle = [CAShapeLayer layer];
        circle.path = circlePath.CGPath;
        circle.strokeColor = [[UIColor blackColor] CGColor];
        circle.fillColor   = [[UIColor whiteColor] CGColor];
        circle.lineWidth   = 6.0;
        circle.strokeEnd   = 0.0;

        [self.view.layer addSublayer:circle];

        // add a tag gesture recognizer
        // add a single tap gesture recognizer
        UITapGestureRecognizer* tapGR = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleTapGesture:)];
        [self.view addGestureRecognizer:tapGR];
    }


    #pragma mark - gesture recognizer methods

    //
    // GestureRecognizer to handle the tap on the view
    //
    - (void)handleTapGesture:(UIGestureRecognizer *)gestureRecognizer {

        circle.strokeEnd = 1.0;
    }