Ios 我如何在视野中保持下降的Spritodes？

我正在尝试制作一款类似于raywenderlich的iphone游戏：精灵工具包初学者教程。我试图在portait模式下实现这一点，而不是教程中使用的横向模式。我使用了这段代码，并对其进行了调整，使精灵从屏幕的顶部下降到底部，但有时精灵一半在视图之外，甚至更多

这就是我得到的：

SKSpriteNode * monster = [SKSpriteNode spriteNodeWithImageNamed:@"AcornFinal.png"];

// Determine where to spawn the monster along the X axis
int minX = self.frame.size.width;
int maxX = self.frame.size.width - monster.size.width;
int rangeX = maxX + minX;
int actualX = (arc4random() % + rangeX);

// Random position along the X axis as calculated above
// This describe from which way the acorns move
// - means moving from top to the right and + means moving from the top to the left
monster.position = CGPointMake(actualX,self.frame.size.height);
[self addChild:monster];

// Determine speed of the monster
int minDuration = 2.0;
int maxDuration = 4.0;
int rangeDuration = maxDuration - minDuration;
int actualDuration = (arc4random() % rangeDuration) + minDuration;



// Create the actions
SKAction * actionMove = [SKAction moveTo:CGPointMake(actualX,-monster.size.height) duration:actualDuration];
SKAction * actionMoveDone = [SKAction removeFromParent];
[monster runAction:[SKAction sequence:@[actionMove, actionMoveDone]]];

所以我相信问题可能在于这四行代码：

// Determine where to spawn the monster along the X axis
int minX = self.frame.size.width;
int maxX = self.frame.size.width - monster.size.width;
int rangeX = maxX + minX;
int actualX = (arc4random() % + rangeX);

如何修复此错误>

编辑

解决方案是将前四行更改为

int minX = monster.size.width;
int maxX = self.frame.size.width - monster.size.width;
int rangeX = maxX - minX;
int actualX = (arc4random() % rangeX)+minX;

---

如果你的想法是让怪物保持在屏幕的水平范围内，那么你的数学似乎有点不对劲。如果精灵的定位点为0.5、0.5，并且场景大小等于屏幕大小，我认为应该是：

int minX = monster.size.width / 2; 
int maxX = self.frame.size.width - monster.size.width;
int x = (arc4random() % + maxX) +  minX;

---

在视图的水平边界之外？多亏了您，我发现了错误，我不得不将您的int x行更改为：int actualX=arc4random%rangeX+minX；但是现在它很好用，谢谢！！我不知道我的计算中哪一部分没有凝结，但如果你弄明白了，我想一切都好-