问题：
如何用 Spritekit 实现这个动画？
我做了什么：
问题：
1）我可以画出所有四个花瓣，但是一旦我抬起手指来画圆，它仍然会从我抬起手指的前一个点到新的触摸开始点创建一条线。参考下面的gif：
2）如何逐步从视图中删除橙色实线（我的太突然了）？
3) 需要调整 .sks 文件属性。
4) https://stackoverflow.com/questions/29792443/set-the-initial-state-of-skemitternode
这是我的代码：
#import "GameScene.h"
@interface GameScene()
@property (nonatomic) SKEmitterNode* fireEmmitter;
@property (nonatomic) SKEmitterNode* fireEmmitter2;
@end
@implementation GameScene
NSMutableArray *_wayPoints;
NSTimer* myTimer;
-(void)didMoveToView:(SKView *)view {
_wayPoints = [NSMutableArray array];
//Setup a background
self.backgroundColor = [UIColor blackColor];
//setup a fire emitter
NSString *fireEmmitterPath = [[NSBundle mainBundle] pathForResource:@"magic" ofType:@"sks"];
_fireEmmitter = [NSKeyedUnarchiver unarchiveObjectWithFile:fireEmmitterPath];
_fireEmmitter.position = CGPointMake(self.frame.size.width/2, self.frame.size.height/2 - 200);
_fireEmmitter.name = @"fireEmmitter";
_fireEmmitter.zPosition = 1;
_fireEmmitter.targetNode = self;
_fireEmmitter.particleBirthRate = 0;
[self addChild: _fireEmmitter];
//setup another fire emitter
NSString *fireEmmitterPath2 = [[NSBundle mainBundle] pathForResource:@"fireflies" ofType:@"sks"];
_fireEmmitter2 = [NSKeyedUnarchiver unarchiveObjectWithFile:fireEmmitterPath2];
_fireEmmitter2.position = CGPointMake(self.frame.size.width/2, self.frame.size.height/2);
_fireEmmitter2.name = @"fireEmmitter";
_fireEmmitter2.zPosition = 1;
_fireEmmitter2.targetNode = self;
_fireEmmitter2.particleBirthRate = 0;
[self addChild: _fireEmmitter2];
//Setup a LightNode
SKLightNode* light = [[SKLightNode alloc] init];
light.categoryBitMask = 1;
light.falloff = 1;
light.ambientColor = [UIColor whiteColor];
light.lightColor = [[UIColor alloc] initWithRed:1.0 green:1.0 blue:0.0 alpha:0.5];
light.shadowColor = [[UIColor alloc] initWithRed:0.0 green:0.0 blue:0.0 alpha:0.3];
[_fireEmmitter addChild:light];
}
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
CGPoint touchPoint = [[touches anyObject] locationInNode:self.scene];
CGMutablePathRef ref = CGPathCreateMutable();
CGPoint p = touchPoint;
p = [self.scene convertPointToView:p];
CGPathMoveToPoint(ref, NULL, p.x, p.y);
_fireEmmitter.position = CGPointMake(touchPoint.x, touchPoint.y);
_fireEmmitter.particleBirthRate = 2000;
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
CGPoint touchPoint = [[touches anyObject] locationInNode:self.scene];
//On Dragging make the emitter with the attached light follow the position
for (UITouch *touch in touches) {
[self addPointToMove:touchPoint];
CGPoint location = [touch locationInNode:self];
[self childNodeWithName:@"fireEmmitter"].position = CGPointMake(location.x, location.y);
}
}
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{
_fireEmmitter.particleBirthRate = 0;
[self performSelector:@selector(userHasCompletedTheDrawing) withObject:nil afterDelay:3];
}
- (void)userHasCompletedTheDrawing{
CGMutablePathRef path = CGPathCreateMutable();
if (_wayPoints && _wayPoints.count > 0) {
CGPoint p = [(NSValue *)[_wayPoints objectAtIndex:0] CGPointValue];
//p = [self.scene convertPointToView:p];
CGPathMoveToPoint(path, nil, p.x, p.y);
_fireEmmitter2.position = CGPointMake(p.x,p.y);
_fireEmmitter2.particleBirthRate = 1000;
for (int i = 0; i < _wayPoints.count; ++i) {
p = [(NSValue *)[_wayPoints objectAtIndex:i] CGPointValue];
CGPathAddLineToPoint(path, nil, p.x, p.y);
}
SKAction *followTrack = [SKAction followPath:path asOffset:NO orientToPath:YES duration:1];
[_fireEmmitter2 runAction:followTrack completion:^{
_fireEmmitter2.particleBirthRate = 0;
[_fireEmmitter2 runAction:[SKAction waitForDuration:1] completion:^{
//_fireEmmitter2.particleBirthRate = 0;
}];
}];
}
//myTimer = [NSTimer scheduledTimerWithTimeInterval: 0.01 target: self selector: @selector(removePointToMove) userInfo: nil repeats: YES];
[self performSelector:@selector(removeAllPointToMove) withObject:nil afterDelay:1];
}
- (void)addPointToMove:(CGPoint)point {
[_wayPoints addObject:[NSValue valueWithCGPoint:point]];
}
- (void)removeAllPointToMove{
[_wayPoints removeAllObjects];
}
- (void)removePointToMove{
if ([_wayPoints count]>0) {
[_wayPoints removeObjectAtIndex:0];
}
}
- (void)drawLines {
//1
NSMutableArray *temp = [NSMutableArray array];
for(CALayer *layer in self.view.layer.sublayers) {
if([layer.name isEqualToString:@"line"]) {
[temp addObject:layer];
}
}
[temp makeObjectsPerformSelector:@selector(removeFromSuperlayer)];
//3
CAShapeLayer *lineLayer = [CAShapeLayer layer];
lineLayer.name = @"line";
lineLayer.strokeColor = [UIColor orangeColor].CGColor;
lineLayer.fillColor = nil;
lineLayer.lineWidth = 3;
lineLayer.lineJoin = kCALineJoinRound; /* The join style used when stroking the path. Options are `miter', `round'
* and `bevel'. Defaults to `miter'. */
lineLayer.zPosition = -1;
//4
CGPathRef path = [self createPathToMove];
lineLayer.path = path;
CGPathRelease(path);
[self.view.layer addSublayer:lineLayer];
}
- (CGPathRef)createPathToMove {
//1
CGMutablePathRef ref = CGPathCreateMutable();
//2
for(int i = 0; i < [_wayPoints count]; ++i) {
CGPoint p = [_wayPoints[i] CGPointValue];
p = [self.scene convertPointToView:p];
//3
if(i == 0 ) {
CGPathMoveToPoint(ref, NULL, p.x, p.y);
} else {
CGPathAddLineToPoint(ref, NULL, p.x, p.y);
}
}
return ref;
}
-(void)update:(CFTimeInterval)currentTime {
/* Called before each frame is rendered */
[self drawLines];
if ([_wayPoints count]==0) {
[myTimer invalidate];
}
}
@end
这是我的 .sks 文件属性：
