我实现的解决方案确实使用了队列。这是一个非常完整的描述：
这一切都在一个名为 PlayerView 的视图类中完成。在标题中，我包括以下内容：
#import "NSMutableArray+QueueAdditions.h"
@interface PlayerView : UIImageView {
Player* representedPlayer; // The model object represented by the view
NSMutableArray* actionQueue; // An array used as a queue for the actions
bool animatingPlayer; // Notes if the player is in the middle of an animation
bool stoppingAnimation; // Notes if all animations should be stopped (e.g., for re-setting the game)
CGFloat actionDuration; // A convenient way for me to change the duration of all animations
// ... Removed other variables in the class (sound effects, etc) not needed for this example
}
// Notifications
+ (NSString*) AnimationsDidStopNotification;
@property (nonatomic, retain) Player* representedPlayer;
@property (nonatomic, retain, readonly) NSMutableArray* actionQueue;
@property (nonatomic, assign) CGFloat actionDuration;
@property (nonatomic, assign) bool animatingPlayer;
@property (nonatomic, assign) bool stoppingAnimation;
// ... Removed other properties in the class not need for this example
- (void)placePlayer; // puts view where needed (according to the model) without animation
- (void)moveEventHandler:(NSNotification *) notification; // handles events when the player moves
- (void)rotateEventHandler:(NSNotification *) notification; // handles events when the player rotates
// ... Removed other action-related event handles not needed for this example
// These methods actually perform the proper animations
- (void) doMoveAnimation:(CGRect) nextFrame;
- (void) doRotateAnimation:(CGRect)nextFrame inDirection:(enum RotateDirection)rotateDirection;
// ... Removed other action-related methods not needed for this example
// Handles things when each animation stops
- (void) animationDidStop:(NSString*)animationID
finished:(BOOL)finished
context:(void*)context;
// Forces all animations to stop
- (void) stopAnimation;
@end
顺便说一句，NSMutableArray+QueueAdditions.h/m 中的 QueueAdditions 类别如下所示：
@interface NSMutableArray (QueueAdditions)
- (id)popObject;
- (void)pushObject:(id)obj;
@end
@implementation NSMutableArray (QueueAdditions)
- (id)popObject
{
// nil if [self count] == 0
id headObject = [self objectAtIndex:0];
if (headObject != nil) {
[[headObject retain] autorelease]; // so it isn't dealloc'ed on remove
[self removeObjectAtIndex:0];
}
return headObject;
}
- (void)pushObject:(id)obj
{
[self addObject: obj];
}
@end
接下来，在 PlayerView 的实现中，我有以下内容：
#import "PlayerView.h"
#import <QuartzCore/QuartzCore.h>
@implementation PlayerView
@synthesize actionQueue;
@synthesize actionDuration;
@synthesize animatingPlayer;
@synthesize stoppingAnimation;
// ... Removed code not needed for this example (init to set up the view's image, sound effects, actionDuration, etc)
// Name the notification to send when animations stop
+ (NSString*) AnimationsDidStopNotification
{
return @"PlayerViewAnimationsDidStop";
}
// Getter for the representedPlayer property
- (Player*) representedPlayer
{
return representedPlayer;
}
// Setter for the representedPlayer property
- (void)setRepresentedPlayer:(Player *)repPlayer
{
if (representedPlayer != nil)
{
[[NSNotificationCenter defaultCenter] removeObserver:self];
[representedPlayer release];
}
if (repPlayer == nil)
{
representedPlayer = nil;
// ... Removed other code not needed in this example
}
else
{
representedPlayer = [repPlayer retain];
if (self.actionQueue == nil)
{
actionQueue = [[NSMutableArray alloc] init];
}
[actionQueue removeAllObjects];
animatingPlayer = NO;
stoppingAnimation = NO;
[[NSNotificationCenter defaultCenter]
addObserver:self
selector:@selector(moveEventHandler:)
name:[Player DidMoveNotification]
object:repPlayer ];
[[NSNotificationCenter defaultCenter]
addObserver:self
selector:@selector(rotateEventHandler:)
name:[Player DidRotateNotification]
object:repPlayer ];
// ... Removed other addObserver actions and code not needed in this example
}
}
// ... Removed code not needed for this example
- (void) placePlayer
{
// Example not helped by specific code... just places the player where the model says it should go without animation
}
// Handle the event noting that the player moved
- (void) moveEventHandler: (NSNotification *) notification
{
// Did not provide the getRectForPlayer:onMazeView code--not needed for the example. But this
// determines where the player should be in the model when this notification is captured
CGRect nextFrame = [PlayerView getRectForPlayer:self.representedPlayer onMazeView:self.mazeView];
// If we are in the middle of an animation, put information for the next animation in a dictionary
// and add that dictionary to the action queue.
// If we're not in the middle of an animation, just do the animation
if (animatingPlayer)
{
NSDictionary* actionInfo = [NSDictionary dictionaryWithObjectsAndKeys:
[NSValue valueWithCGRect:nextFrame], @"nextFrame",
@"move", @"actionType",
@"player", @"actionTarget",
nil];
[actionQueue pushObject:actionInfo];
}
else
{
animatingPlayer = YES; // note that we are now doing an animation
[self doMoveAnimation:nextFrame];
}
}
// Handle the event noting that the player rotated
- (void) rotateEventHandler: (NSNotification *) notification
{
// User info in the notification notes the direction of the rotation in a RotateDirection enum
NSDictionary* userInfo = [notification userInfo];
NSNumber* rotateNumber = [userInfo valueForKey:@"rotateDirection"];
// Did not provide the getRectForPlayer:onMazeView code--not needed for the example. But this
// determines where the player should be in the model when this notification is captured
CGRect nextFrame = [PlayerView getRectForPlayer:self.representedPlayer onMazeView:self.mazeView];
if (animatingPlayer)
{
NSDictionary* actionInfo = [NSDictionary dictionaryWithObjectsAndKeys:
[NSValue valueWithCGRect:nextFrame], @"nextFrame",
@"rotate", @"actionType",
rotateNumber, @"rotateDirectionNumber",
@"player", @"actionTarget",
nil];
[actionQueue pushObject:actionInfo];
}
else
{
enum RotateDirection direction = (enum RotateDirection) [rotateNumber intValue];
animatingPlayer = YES;
[self doRotateAnimation:nextFrame inDirection:direction];
}
}
// ... Removed other action event handlers not needed for this example
// Perform the actual animation for the move action
- (void) doMoveAnimation:(CGRect) nextFrame
{
[UIView beginAnimations:@"Move" context:NULL];
[UIView setAnimationDuration:actionDuration];
[UIView setAnimationDelegate:self];
[UIView setAnimationDidStopSelector:@selector(animationDidStop:finished:context:)];
self.frame = nextFrame;
[UIView commitAnimations];
}
// Perform the actual animation for the rotate action
- (void) doRotateAnimation:(CGRect)nextFrame inDirection:(enum RotateDirection)rotateDirection
{
int iRot = +1;
if (rotateDirection == CounterClockwise)
{
iRot = -1;
}
[UIView beginAnimations:@"Rotate" context:NULL];
[UIView setAnimationDuration:(3*actionDuration)];
[UIView setAnimationDelegate:self];
[UIView setAnimationDidStopSelector:@selector(animationDidStop:finished:context:)];
CGAffineTransform oldTransform = self.transform;
CGAffineTransform transform = CGAffineTransformRotate(oldTransform,(iRot*M_PI/2.0));
self.transform = transform;
self.frame = nextFrame;
[UIView commitAnimations];
}
- (void) animationDidStop:(NSString*)animationID
finished:(BOOL)finished
context:(void *)context
{
// If we're stopping animations, clear the queue, put the player where it needs to go
// and reset stoppingAnimations to NO and note that the player is not animating
if (self.stoppingAnimation)
{
[actionQueue removeAllObjects];
[self placePlayer];
self.stoppingAnimation = NO;
self.animatingPlayer = NO;
}
else if ([actionQueue count] > 0) // there is an action in the queue, execute it
{
NSDictionary* actionInfo = (NSDictionary*)[actionQueue popObject];
NSString* actionTarget = (NSString*)[actionInfo valueForKey:@"actionTarget"];
NSString* actionType = (NSString*)[actionInfo valueForKey:@"actionType"];
// For actions to the player...
if ([actionTarget isEqualToString:@"player"])
{
NSValue* rectValue = (NSValue*)[actionInfo valueForKey:@"nextFrame"];
CGRect nextFrame = [rectValue CGRectValue];
if ([actionType isEqualToString:@"move"])
{
[self doMoveAnimation:nextFrame];
}
else if ([actionType isEqualToString:@"rotate"])
{
NSNumber* rotateNumber = (NSNumber*)[actionInfo valueForKey:@"rotateDirectionNumber"];
enum RotateDirection direction = (enum RotateDirection) [rotateNumber intValue];
[self doRotateAnimation:nextFrame inDirection:direction];
}
// ... Removed code not needed for this example
}
else if ([actionTarget isEqualToString:@"cell"])
{
// ... Removed code not needed for this example
}
}
else // no more actions in the queue, mark the animation as done
{
animatingPlayer = NO;
[[NSNotificationCenter defaultCenter]
postNotificationName:[PlayerView AnimationsDidStopNotification]
object:self
userInfo:[NSDictionary dictionaryWithObjectsAndKeys: nil]];
}
}
// Make animations stop after current animation by setting stopAnimation = YES
- (void) stopAnimation
{
if (self.animatingPlayer)
{
self.stoppingAnimation = YES;
}
}
- (void)dealloc {
if (representedPlayer != nil)
{
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
[representedPlayer release];
[actionQueue release];
// …Removed other code not needed for example
[super dealloc];
}
@end
解释：
视图订阅来自模型对象（播放器）的适当通知。当它捕获一个通知时，它会检查它是否已经在做动画（使用 animatingPlayer 属性）。如果是这样，它会从通知中获取信息（注意玩家应该如何被动画化），将该信息放入字典中，然后将该字典添加到动画队列中。如果当前没有动画，该方法会将 animatingPlayer 设置为 true 并调用适当的 do[Whatever]Animation 例程。
每个 do[Whatever]Animation 例程都会执行正确的动画，将 setAnimationDidStopSelector 设置为 animationDidStop:finished:context:。当每个动画结束时，animationDidStop:finished:context: 方法（在检查是否所有动画都应该立即停止之后）将通过从队列中拉出下一个字典并解释其数据来执行队列中的下一个动画，以便调用适当的 do[Whatever] 动画方法。如果队列中没有动画，则该例程将 animatingPlayer 设置为 NO 并发布通知，以便其他对象可以知道播放器何时适当地停止了其当前的动画运行。
就是这样。可能有一个更简单的方法（？），但这对我来说效果很好。如果您有兴趣查看实际结果，请查看我在 App Store 中的 Mazin 应用程序。
谢谢。