(8/18)重学Standford_iOS7开发_协议、block、动画_课程笔记

第八课：

1、协议

另一种安全处理id类型的方式如：id <MyProtocol> obj

a.声明

//协议一般放于.h文件中或者在类的.h文件中  @protocol Foo <Xyzzy, NSObject>//<>中的内容表示还需实现自哪些协议，所有协议的根协议一般都是NSObject - (void)someMethod;//默认为必须实现的方法 @optional//可选方法声明 - (void)methodWithArgument:(BOOL)argument; @required @property (readonly) int readonlyProperty; //只有getter在协议中 @property NSString *readwriteProperty; //getter与setter都在协议中  - (int)methodThatReturnsSomething; @end

b.在类中实现协议

#import “Foo.h”  @interface MyClass : NSObject <Foo>  //(do not have to declare Foo’s methods again here, it’s implicit that you implement it) @end  //或者私有实现 @interface MyClass() <Foo> @end @implementation MyClass //@required methods here!  @end

c.用途

①委托

②数据源

//UI与controller盲通信的方式 @property (nonatomic, weak) id <UISomeObjectDelegate> delegate; @property (nonatomic, weak) id <UISomeObjectDataSource> dataSource;

③动画

2、Block（来源于API文档）

实际上为一段代码块，类似于C语言中的函数指针

a.声明

int multiplier = 7; int (^myBlock)(int) = ^(int num) {  return num * multiplier; }; //int 为block返回值  //^表示为此为代码块 //myBlock为此代码块名 //int 为参数类型 //等号右边为block实现 

block可以使用和他的同一范围内声明的变量，使用block与使用C函数类似

int multiplier = 7; int (^myBlock)(int) = ^(int num) {     return num * multiplier; };   printf("%d", myBlock(3)); // prints "21"

b.直接使用block

block可以省略block声明直接使用

char *myCharacters[3] = { "TomJohn", "George", "Charles Condomine" };  //直接使用block作为参数  qsort_b(myCharacters, 3, sizeof(char *), ^(const void *l, const void *r) {     char *left = *(char **)l;     char *right = *(char **)r;     return strncmp(left, right, 1); });   // myCharacters is now { "Charles Condomine", "George", "TomJohn" } 

c.Cocoa中使用block

NSArray *stringsArray = @[ @"string 1",          @"String 21",          @"string 12",          @"String 11",          @"String 02" ]; static NSStringCompareOptions comparisonOptions = NSCaseInsensitiveSearch | NSNumericSearch |   NSWidthInsensitiveSearch | NSForcedOrderingSearch; NSLocale *currentLocale = [NSLocale currentLocale]; //比较器为代码块 NSComparator finderSortBlock = ^(id string1, id string2) {  NSRange string1Range = NSMakeRange(0, [string1 length]);  return [string1 compare:string2 options:comparisonOptions range:string1Range locale:currentLocale]; }; NSArray *finderSortArray = [stringsArray sortedArrayUsingComparator:finderSortBlock]; NSLog(@"finderSortArray: %@", finderSortArray); /* Output: finderSortArray: (  "string 1",  "String 02",  "String 11",  "string 12",  "String 21" ) */ 

d.__block变量

首先看简单的例子

//直接使用变量 int x = 123;   void (^printXAndY)(int) = ^(int y) {     printf("%d %d/n", x, y); };   printXAndY(456); // prints: 123 456  //不可以直接更改变量，此处变量对block来说为只读 int x = 123; void (^printXAndY)(int) = ^(int y) {     x = x + y; // error     printf("%d %d/n", x, y); };

解决方法，引入__block变量

__block int x = 123; //  x lives in block storage void (^printXAndY)(int) = ^(int y) {  x = x + y;  printf("%d %d/n", x, y); }; printXAndY(456); // prints: 579 456 // x is now 579 

e.各种类型的变量在block中的使用

对于普通局部变量，在block声明时保存其值，之后普通局部变量的改变对block不可见

//注意block的调用时机 extern NSInteger CounterGlobal;//block对全局变量有读写权限 static NSInteger CounterStatic;//静态变量 {  NSInteger localCounter = 42;//普通本地变量  __block char localCharacter;//__block本地变量  void (^aBlock)(void) = ^(void) {   ++CounterGlobal;   ++CounterStatic;   CounterGlobal = localCounter; // localCounter fixed at block creation   localCharacter = 'a'; // sets localCharacter in enclosing scope  };  ++localCounter; // unseen by the block，对block不可见，block的值认为42  localCharacter = 'b';  aBlock(); // execute the block  // localCharacter now 'a' } 

f.对象在block中的使用

dispatch_async(queue, ^{  /*   block中访问实例变量，instanceVariable为block所在类的实例变量，此时直接访问了实例变量，因此需要对包含它的对象（self）保留  */  doSomethingWithObject(_instanceVariable); }); id localVariable = _instanceVariable; dispatch_async(queue, ^{  /*  在本地创建了指向实例变量的引用，因此需要保留localVariable而不是self  */  doSomethingWithObject(localVariable); }); 

g.使用typedef声明block

typedef float (^MyBlockType)(float, float);   MyBlockType myFirstBlock = // ... ; MyBlockType mySecondBlock = // ... ;

h.Memory Cycles

//block中引用self，所以有强指针指向self，而block又在self中定义，所以self又有强指针指向block [self.myBlocks addObject:^ {     [self doSomething]; }];

解决方法

__weak MyClass *weakSelf = self; //重新声明为弱引用 [self.myBlocks addObject:^ {     [weakSelf doSomething]; }];

i.用途

枚举，动画，排序，通知（Notification），Error handlers，Completion handlers （错误与完成事件的处理，可以理解为回调函数）， 多线程 等

3、动画（Animation）

a.动画的种类

Animating views ：视图动画，包括移动、缩放、淡入淡出、旋转等

Animation of View Controller transitions：视图控制器动画，视图的切换等

Core Animation：核心动画框架

本节课只涉及视图动画

b.为视图添加动画的三种方法

①通过设置视图属性

frame

transform (translation, rotation and scale)

alpha (opacity) 

值会立即改变，但动画效果会延时

+ (void)animateWithDuration:(NSTimeInterval)duration                                   delay:(NSTimeInterval)delay                                options:(UIViewAnimationOptions)options                           animations:(void (^)(void))animations                           completion:(void (^)(BOOL finished))completion;//适用于常规动画设置 //example [UIView animateWithDuration:3.0                       delay:0.0                     options:UIViewAnimationOptionBeginFromCurrentState                  animations:^{ myView.alpha = 0.0; }                  completion:^(BOOL fin) { if (fin) [myView removeFromSuperview]; }];//视图在3秒内从父视图淡出，完成动画后并移除自己  + (void)transitionWithView:(UIView *)view                   duration:(NSTimeInterval)duration                    options:(UIViewAnimationOptions)options                 animations:(void (^)(void))animations                 completion:(void (^)(BOOL finished))completion;//适用于转场动画设置,比如卡牌的翻转  + (void)transitionFromView:(UIView *)fromView                     toView:(UIView *)toView                   duration:(NSTimeInterval)duration                    options:(UIViewAnimationOptions)options                 completion:(void (^)(BOOL finished))completion;//适用于切换视图动画

//UIViewAnimationOptions  //常规动画属性设置（可以同时选择多个进行设置） UIViewAnimationOptionLayoutSubviews          //父视图变化时自动更新子视图约束@see:http://segmentfault.com/q/1010000002872390  UIViewAnimationOptionAllowUserInteraction      //动画时响应用户事件，如 touch等    UIViewAnimationOptionBeginFromCurrentState     //从当前状态开始动画，比如此时有动画正在改变属性 UIViewAnimationOptionRepeat                    //无限制重复动画 UIViewAnimationOptionAutoreverse               //执行动画回路(动画运行到结束点后仍然以动画方式回到初始点),前提是设置动画无限重复 UIViewAnimationOptionOverrideInheritedDuration //忽略嵌套动画时间设置 UIViewAnimationOptionOverrideInheritedCurve    //忽略嵌套动画速度设置 UIViewAnimationOptionAllowAnimatedContent      //动画过程中重绘视图（注意仅仅适用于转场动画） UIViewAnimationOptionShowHideTransitionViews   //视图切换时直接隐藏旧视图、显示新视图，而不是将旧视图从父视图移除（仅仅适用于转场动画） UIViewAnimationOptionOverrideInheritedOptions  //不继承父动画设置或动画类型  //动画速度控制（可从其中选择一个设置） UIViewAnimationOptionCurveEaseInOut           //动画先缓慢，然后逐渐加速 UIViewAnimationOptionCurveEaseIn               //动画逐渐变慢 UIViewAnimationOptionCurveEaseOut              //动画逐渐加速 UIViewAnimationOptionCurveLinear              //动画匀速执行，默认值  //转场类型（仅适用于转场动画设置，可以从中选择一个进行设置，基本动画、关键帧动画不需要设置） UIViewAnimationOptionTransitionNone            //没有转场动画效果 UIViewAnimationOptionTransitionFlipFromLeft    //从左侧翻转效果 UIViewAnimationOptionTransitionFlipFromRight   //从右侧翻转效果 UIViewAnimationOptionTransitionCurlUp          //向后翻页的动画过渡效果 UIViewAnimationOptionTransitionCurlDown        //向前翻页的动画过渡效果 UIViewAnimationOptionTransitionCrossDissolve   //旧视图溶解消失显示下一个新视图的效果 UIViewAnimationOptionTransitionFlipFromTop     //从上方翻转效果 UIViewAnimationOptionTransitionFlipFromBottom  //从底部翻转效果

②Dynamic Animator :动力动画

实现步骤：a.创建一个UIDynamicAnimator

b.向UIDynamicAnimator添加UIDynamicBehaviors(gravity, collisions, etc.)

c.向UIDynamicAnimator添加UIDynamicItems(usually UIViews)

d.动画自动运行

//Create a UIDynamicAnimator UIDynamicAnimator *animator = [[UIDynamicAnimator alloc] initWithReferenceView:aView];  //Create and add UIDynamicBehaviors UIGravityBehavior *gravity = [[UIGravityBehavior alloc] init];  [animator addBehavior:gravity]; UICollisionBehavior *collider = [[UICollisionBehavior alloc] init];  [animator addBehavior:collider];  //Add UIDynamicItems to a UIDynamicBehavior id <UIDynamicItem> item1 = ...;  id <UIDynamicItem> item2 = ...;  [gravity addItem:item1];  [collider addItem:item1];  [gravity addItem:item2];

//UIDynamicItem 协议 @protocol UIDynamicItem @property (readonly) CGRect bounds; @property (readwrite) CGPoint center; @property (readwrite) CGAffineTransform transform;  @end  //一般UIView即可作为Item，天生实现了UIDynamic协议  //以上属性一般有动画运行时的animator来改变，若需要主动改变，需要调用 - (void)updateItemUsingCurrentState:(id <UIDynamicItem>)item;

UIDynamicBehaviors

//UIGravityBehavior @property CGFloat angle;//重力方向，默认向下 @property CGFloat magnitude; // 1.0 is 1000 points/s/s  //UICollisionBehavior 碰撞 @property UICollisionBehaviorMode collisionMode; // Items,Boundaries,Everything (default)  - (void)addBoundaryWithIdentifier:(NSString *)identifier forPath:(UIBezierPath *)path; //用UIBezierPath自定义碰撞边界 @property BOOL translatesReferenceBoundsIntoBoundary;//参考视图（动力动画的顶级视图）作为碰撞边界  //UIAttachmentBehavior 吸附行为 - (instancetype)initWithItem:(id <UIDynamicItem>)item attachedToAnchor:(CGPoint)anchor;//以点作为吸附 - (instancetype)initWithItem:(id <UIDynamicItem>)i1 attachedToItem:(id <UIDynamicItem>)i2;//以动力项作为吸附,两个动力项的吸附 - (instancetype)initWithItem:(id <UIDynamicItem>)item offsetFromCenter:(CGPoint)offset ... //偏移中心的吸附 @property (readwrite) CGFloat length; // 吸附的长度 @property (readwrite) CGPoint anchorPoint; // 吸附点 @property (readwrite, nonatomic) CGFloat damping; // 锚点移动时的阻尼 @property (readwrite, nonatomic) CGFloat frequency; // 锚点移动时的频率  //UISnapBehavior 捕捉行为 - (instancetype)initWithItem:(id <UIDynamicItem>)item snapToPoint:(CGPoint)point;  @property CGFloat damping;.//移动到锚点时振动的阻尼  //UIPushBehavior 推动行为 @property UIPushBehaviorMode mode; // Continuous or Instantaneous @property CGVector pushDirection; @property CGFloat magnitude/angle; // magnitude 1.0 moves a 100x100 view at 100 pts/s/s  //UIDynamicItemBehavior 动力项行为，应用于所有Items @property (readwrite, nonatomic) CGFloat elasticity; // 弹力，[0.1] @property (readwrite, nonatomic) CGFloat friction; //摩擦力，0表示无摩擦力 @property (readwrite, nonatomic) CGFloat density; // 密度，默认为1 @property (readwrite, nonatomic) CGFloat resistance; //线性阻力系数0--CGFLOAT_MAX @property (readwrite, nonatomic) CGFloat angularResistance; //角度阻力系数0--CGFLOAT_MAX @property (readwrite, nonatomic) BOOL allowsRotation; //是否允许旋转 - (CGPoint)linearVelocityForItem:(id <UIDynamicItem>)item;//获取Item速度 - (CGFloat)angularVelocityForItem:(id <UIDynamicItem>)item;//获取Item角速度

创建UIDynamicBehavior子类实现自定义行为

- (void)addChildBehavior:(UIDynamicBehavior *)behavior;//将其他行为添加到自定义行为中 @property UIDynamicAnimator *dynamicAnimator;//获取当前行为所在的Animator - (void)willMoveToAnimator:(UIDynamicAnimator *)animator;//行为加入到方法或者移除时（此时参数为nil）会调用 @property (copy) void (^action)(void);//每当行为发生时总会执行此block，注意调用比较频繁的效率问题 

4、demo

Dropit: https://github.com/NSLogMeng/Stanford_iOS7_Study/commit/515b76c7ed6e74a7e30108efe6d4c833f33a6e0c

课程视频地址：网易公开课： http://open.163.com/movie/2014/1/D/L/M9H7S9F1H_M9H80D0DL.html

或者iTunes U搜索standford课程