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跟随着黄色砖块前进
现在我们已经找到了我们的路径,我们只需要让猫咪跟随它.
我们接下来要做的是记住整个路径,并且使得猫咪根据路径一步一步的移动.
在CatSprite.h中建立一个存储路径的数组,在CatSprite的@interface的私有段内添加:
NSMutableArray *shortestPath;
然后完成CatSprite.m中的如下修改:
// Add inside the CatSprite private properties and methods section@property (nonatomic, retain) NSMutableArray *shortestPath;// After the CatSprite @implementation@synthesize shortestPath;// Inside initWithLayerself.shortestPath = nil;// Inside dealloc [shortestPath release]; shortestPath = nil;
现在我们将创建一个存储整个路径并且管理开始动画的方法,在CatSprite.m中完成如下修改:
// Add inside the CatSprite private properties and methods section- (void)constructPathAndStartAnimationFromStep:(ShortestPathStep *)step;// Inside moveToward, comment out the pathFound BOOL//BOOL pathFound = NO;// Inside moveToward, replace pathFound = YES with this:[self constructPathAndStartAnimationFromStep:currentStep];// Also comment all of the debugging statements below that.// Inside moveToward, replace if (!pathFound) with this:if (self.shortestPath == nil) { // No path found// Add this new method:// Go backward from a step (the final one) to reconstruct the shortest computed path- (void)constructPathAndStartAnimationFromStep:(ShortestPathStep *)step{self.shortestPath = [NSMutableArray array];do {if (step.parent != nil) { // Don't add the last step which is the start position (remember we go backward, so the last one is the origin position ;-)[self.shortestPath insertObject:step atIndex:0]; // Always insert at index 0 to reverse the path}step = step.parent; // Go backward} while (step != nil); // Until there is no more parentsfor (ShortestPathStep *s in self.shortestPath) {NSLog(@"%@", s);}}
注意在moveToward方法中,我们调用了一个新的方法替换了原来的在控制台中打印结果的代码,并且我们删除了pathFound变量.像往常一样,constructPathAndStartAnimationFromStep方法中的注释详细解释了实际发生了什么.
现在编译运行,如果你触摸和我们之前说过的相同的瓦块,你应该看到如下日志:
<ShortestPathStep: 0x6b37160> pos=[24;1] g=1 h=4 f=5<ShortestPathStep: 0x6b37340> pos=[23;1] g=2 h=3 f=5<ShortestPathStep: 0x6b37590> pos=[22;1] g=3 h=2 f=5<ShortestPathStep: 0x6b395c0> pos=[21;1] g=4 h=3 f=7<ShortestPathStep: 0x6b37ae0> pos=[20;1] g=5 h=4 f=9<ShortestPathStep: 0x6b38c60> pos=[20;2] g=6 h=3 f=9<ShortestPathStep: 0x6b36510> pos=[20;3] g=7 h=2 f=9<ShortestPathStep: 0x6b3b850> pos=[21;3] g=8 h=1 f=9<ShortestPathStep: 0x6b3cf30> pos=[22;3] g=9 h=0 f=9
注意它和以前是相似的,除了现在它是从开始到结束(反转以前的结果)并且存放在数组中的数据更便于我们去使用.
最后要做的事情是通过遍历shortestPath数组并且动画显示猫咪跟随的路径.为了实现这个目的,我们将创建一个方法从数组中弹出每一步的数据,使得猫咪可以移动到该位置,并且添加一个回调方法去重复调用这个方法直到路径完成.
在CatSprite.m中完成以下修改:
// Add inside the CatSprite private properties and methods section- (void)popStepAndAnimate;// Add to bottom of constructPathAndStartAnimationFromStep[self popStepAndAnimate];// Add new method- (void)popStepAndAnimate{ // Check if there remains path steps to go throughif ([self.shortestPath count] == 0) {self.shortestPath = nil;return;}// Get the next step to move toShortestPathStep *s = [self.shortestPath objectAtIndex:0];// Prepare the action and the callbackid moveAction = [CCMoveTo actionWithDuration:0.4 position:[_layer positionForTileCoord:s.position]];id moveCallback = [CCCallFunc actionWithTarget:self selector:@selector(popStepAndAnimate)]; // set the method itself as the callback// Remove the step[self.shortestPath removeObjectAtIndex:0];// Play actions[self runAction:[CCSequence actions:moveAction, moveCallback, nil]];}
编译然后运行…
我们的猫咪自动移动到你点击的位置上了 :-)
