我正在关注本教程[self determineInvaderMovementDirection];，在添加到 GameScene.m 文件的部分之后（特别是我的moveInvadersForUpdate方法），我遇到了一个问题
该教程指出，在添加这段代码后，太空入侵者应该会相应地移动，但是当我运行它们时，它们会向左移动并且不会回来。我不确定自己做错了什么，因为我非常仔细地遵循了本教程。任何帮助或澄清将不胜感激。提前致谢 ！
这是完整的 GameScene.m
#import "GameScene.h"
#import <CoreMotion/CoreMotion.h>
#pragma mark - Custom Type Definitions
/*
The type definition and constant definitions 1,2,3 take care of
the following tasks:
1.Define the possible types of invader enemies. This can be used in switch
statements later when things like displaying different sprites images for each enemy type. The typedef makes InvaderType a formal Obj-C type that is type checked for method arguments and variables.This is so that the wrong
method argument is not used or assigned to the wrong variable.
2. Define the size of the invaders and that they'll be laid out in
a grid of rows and columns on the screen.
3. Define a name that will be used to identify invaders when searching for them.
*/
//1
typedef enum InvaderType {
InvaderTypeA,
InvaderTypeB,
InvaderTypeC
} InvaderType;
/*
Invaders move in a fixed pattern: right, right, down, left, down, right
right. InvaderMovementDirection tracks the invaders' progress through this pattern
*/
typedef enum InvaderMovementDirection {
InvaderMovementDirectionRight,
InvaderMovementDirectionLeft,
InvaderMovementDirectionDownThenRight,
InvaderMovementDirectionDownThenLeft,
InvaderMovementDirectionNone
} InvaderMovementDirection;
//2
#define kInvaderSize CGSizeMake(24,16)
#define kInvaderGridSpacing CGSizeMake(12,12)
#define kInvaderRowCount 6
#define kInvaderColCount 6
//3
#define kInvaderName @"invader"
#define kShipSize CGSizeMake(30, 16) //stores the size of the ship
#define kShipName @"ship" // stores the name of the ship stored on the sprite node
#define kScoreHudName @"scoreHud"
#define kHealthHudName @"healthHud"
/*
this class extension allows you to
add “private” properties to GameScene class, without revealing the properties to other classes or code. You still get the benefit of using Objective-C properties, but your GameScene state is stored internally and can’t be modified by other external classes.
As well, it doesn’t clutter the namespace of datatypes that your other classes see. This class extension is used in the method didMoveToView
*/
#pragma mark - Private GameScene Properties
@interface GameScene ()
@property BOOL contentCreated;
@property InvaderMovementDirection invaderMovementDirection;
@property NSTimeInterval timeOfLastMove;
@property NSTimeInterval timePerMove;
@end
@implementation GameScene
#pragma mark Object Lifecycle Management
#pragma mark - Scene Setup and Content Creation
/*This method simply invokes createContent using the
BOOL property contentCreated to make sure you
don’t create your scene’s content more than once.
This property is defined in an Objective-C Class Extension found near the top of the file()*/
- (void)didMoveToView:(SKView *)view
{
if (!self.contentCreated) {
[self createContent];
self.contentCreated = YES;
}
}
- (void)createContent {
//1 - Invaders begin by moving to the right
self.invaderMovementDirection = InvaderMovementDirectionRight;
//2 - Invaders take 1 sec for each move. Each step left, right or down
// takes 1 second.
self.timePerMove = 1.0;
//3 - Invaders haven't moved yet, so set the time to zero
self.timeOfLastMove = 0.0;
[self setupInvaders];
[self setupShip];
[self setupHud];
}
/*
Creates an invade sprite of a given type
1. Use the invadeType parameterr to determine color of the invader
2. Call spriteNodeWithColor:size: of SKSpriteNode to alloc and init a sprite
that renders as a rect of the given color invaderColor with size kInvaderSize
*/
-(SKNode*)makeInvaderOfType:(InvaderType)invaderType {
//1
SKColor* invaderColor;
switch (invaderType) {
case InvaderTypeA:
invaderColor = [SKColor redColor];
break;
case InvaderTypeB:
invaderColor = [SKColor greenColor];
break;
case InvaderTypeC:
invaderColor = [SKColor blueColor];
break;
}
//2
SKSpriteNode* invader = [SKSpriteNode spriteNodeWithColor:invaderColor size:kInvaderSize];
invader.name = kInvaderName;
return invader;
}
-(void)setupInvaders {
//1 - loop over the rows
CGPoint baseOrigin = CGPointMake(kInvaderSize.width / 2, 180);
for (NSUInteger row = 0; row < kInvaderRowCount; ++row) {
//2 - Choose a single InvaderType for all invaders
// in this row based on the row number
InvaderType invaderType;
if (row % 3 == 0) invaderType = InvaderTypeA;
else if (row % 3 == 1) invaderType = InvaderTypeB;
else invaderType = InvaderTypeC;
//3 - Does some math to figure out where the first invader
// in the row should be positioned
CGPoint invaderPosition = CGPointMake(baseOrigin.x, row * (kInvaderGridSpacing.height + kInvaderSize.height) + baseOrigin.y);
//4 - Loop over the columns
for (NSUInteger col = 0; col < kInvaderColCount; ++col) {
//5 - Create an invader for the current row and column and add it
// to the scene
SKNode* invader = [self makeInvaderOfType:invaderType];
invader.position = invaderPosition;
[self addChild:invader];
//6 - update the invaderPosition so that it's correct for the
//next invader
invaderPosition.x += kInvaderSize.width + kInvaderGridSpacing.width;
}
}
}
-(void)setupShip {
//1 - creates ship using makeShip. makeShip can easily be used later
// to create another ship (ex. to set up more lives)
SKNode* ship = [self makeShip];
//2 - Places the ship on the screen. In SpriteKit the origin is at the lower
//left corner of the screen. The anchorPoint is based on a unit square with (0, 0) at the lower left of the sprite's area and (1, 1) at its top right. Since SKSpriteNode has a default anchorPoint of (0.5, 0.5), i.e., its center, the ship's position is the position of its center. Positioning the ship at kShipSize.height/2.0f means that half of the ship's height will protrude below its position and half above. If you check the math, you'll see that the ship's bottom aligns exactly with the bottom of the scene.
ship.position = CGPointMake(self.size.width / 2.0f, kShipSize.height/2.0f);
[self addChild:ship];
}
-(SKNode*)makeShip {
SKNode* ship = [SKSpriteNode spriteNodeWithColor:[SKColor greenColor] size:kShipSize];
ship.name = kShipName;
return ship;
}
-(void)setupHud {
//Sets the score label font to Courier
SKLabelNode* scoreLabel = [SKLabelNode labelNodeWithFontNamed:@"Courier"];
//1 - Give the score label a name so it becomes easy to find later when
// the score needs to be updated.
scoreLabel.name = kScoreHudName;
scoreLabel.fontSize = 15;
//2 - Color the score label green
scoreLabel.fontColor = [SKColor greenColor];
scoreLabel.text = [NSString stringWithFormat:@"Score: %04u", 0];
//3 - Positions the score label near the top left corner of the screen
scoreLabel.position = CGPointMake(20 + scoreLabel.frame.size.width/2, self.size.height - (20 + scoreLabel.frame.size.height/2));
[self addChild:scoreLabel];
//Applies the font of the health label
SKLabelNode* healthLabel = [SKLabelNode labelNodeWithFontNamed:@"Courier"];
//4 - Give the health label a name so it can be referenced later when it needs
// to be updated to display the health
healthLabel.name = kHealthHudName;
healthLabel.fontSize = 15;
//5 - Colors the health label red
healthLabel.fontColor = [SKColor redColor];
healthLabel.text = [NSString stringWithFormat:@"Health: %.1f%%", 100.0f];
//6 - Positions the health Label on the upper right hand side of the screen
healthLabel.position = CGPointMake(self.size.width - healthLabel.frame.size.width/2 - 20, self.size.height - (20 + healthLabel.frame.size.height/2));
[self addChild:healthLabel];
}
#pragma mark - Scene Update
- (void)update:(NSTimeInterval)currentTime {
//Makes the invaders move
[self moveInvadersForUpdate:currentTime];
}
#pragma mark - Scene Update Helpers
//This method will get invoked by update
-(void)moveInvadersForUpdate:(NSTimeInterval)currentTime {
//1 - if it's not yet time to move, exit the method. moveInvadersForUpdate:
// is invoked 60 times per second, but you don't want the invaders to move
// that often since the movement would be too fast to see
if (currentTime - self.timeOfLastMove < self.timePerMove) return;
//2 - Recall that the scene holds all the invaders as child nodes; which were
// added to the scene using addChild: in setupInvaders identifying each invader
// by its name property. Invoking enumerateChildNodesWithName:usingBlock only loops over the invaders because they're named kInvaderType; which makes the loop skip the ship and the HUD. The guts og the block moves the invaders 10 pixels either right, left or down depending on the value of invaderMovementDirection
[self enumerateChildNodesWithName:kInvaderName usingBlock:^(SKNode *node, BOOL *stop) {
switch (self.invaderMovementDirection) {
case InvaderMovementDirectionRight:
node.position = CGPointMake(node.position.x - 10, node.position.y);
break;
case InvaderMovementDirectionLeft:
node.position = CGPointMake(node.position.x - 10, node.position.y);
break;
case InvaderMovementDirectionDownThenLeft:
case InvaderMovementDirectionDownThenRight:
node.position = CGPointMake(node.position.x, node.position.y - 10);
break;
InvaderMovementDirectionNone:
default:
break;
}
}];
//3 - Record that you just moved the invaders, so that the next time this method is invoked (1/60th of a second from when it starts), the invaders won't move again until the set time period of one second has elapsed.
self.timeOfLastMove = currentTime;
//Makes it so that the invader movement direction changes only when the invaders are actually moving. Invaders only move when the check on self.timeOfLastMove passes (when conditional expression is true)
[self determineInvaderMovementDirection];
}
#pragma mark - Invader Movement Helpers
-(void)determineInvaderMovementDirection {
//1 - Since local vars accessed by block are default const(means they cannot be changed), this snippet of code qualifies proposedMovementDirection with __block so that you can modify it in //2
__block InvaderMovementDirection proposedMovementDirection = self.invaderMovementDirection;
//2 - Loops over the invaders in the scene and refers to the block with the invader as an argument
[self enumerateChildNodesWithName:kInvaderName usingBlock:^(SKNode *node, BOOL *stop) {
switch (self.invaderMovementDirection) {
case InvaderMovementDirectionRight:
//3 - If the invader's right edge is within 1pt of the right edge of the scene, it's about to move offscreen. Sets proposedMovementDirection so that the invaders move down then left. You compare the invader's frame(the frame that contains its content in the scene's coordinate system) with the scene width. Since the scene has an anchorPoint of (0,0) by default and is scaled to fill it's parent view, this comparison ensures you're testing against the view's edges.
if (CGRectGetMaxX(node.frame) >= node.scene.size.width - 1.0f) {
proposedMovementDirection = InvaderMovementDirectionDownThenLeft;
*stop = YES;
}
break;
case InvaderMovementDirectionLeft:
//4 - If the invader's left edge is within 1 pt of the left edge of the scene, it's about to move offscreen. Sets the proposedMovementDirection so invaders move down then right
if (CGRectGetMinX(node.frame) <= 1.0f) {
proposedMovementDirection = InvaderMovementDirectionDownThenRight;
*stop = YES;
}
break;
case InvaderMovementDirectionDownThenLeft:
//5 - If invaders are moving down then left, they already moved down at this point, so they should now move left.
proposedMovementDirection = InvaderMovementDirectionLeft;
*stop = YES;
break;
case InvaderMovementDirectionDownThenRight:
//6 - if the invaders are moving down then right, they already moved down so they should now move right.
proposedMovementDirection = InvaderMovementDirectionRight;
*stop = YES;
break;
default:
break;
}
}];
//7 - if the proposed invader movement direction is different than the current invader movement direction, update the current direction to the proposed direction
if (proposedMovementDirection != self.invaderMovementDirection) {
self.invaderMovementDirection = proposedMovementDirection;
}
}
#pragma mark - Bullet Helpers
#pragma mark - User Tap Helpers
#pragma mark - HUD Helpers
#pragma mark - Physics Contact Helpers
#pragma mark - Game End Helpers
@end