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[操作系统](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 UIDynamicAnimatorUIDynamicAnimator *animator = [[UIDynamicAnimator alloc] initWithReferenceView:aView];//Create and add UIDynamicBehaviorsUIGravityBehavior *gravity = [[UIGravityBehavior alloc] init]; [animator addBehavior:gravity];UICollisionBehavior *collider = [[UICollisionBehavior alloc] init]; [animator addBehavior:collider];//Add UIDynamicItems to a UIDynamicBehaviorid <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