15.1 動畫介紹

在iOS中動畫實現技術主要是：Core Animation。 Core Animation負責所有的滾動、旋轉、縮小和放大以及所有的iOS動畫效果。其中UIKit類通常都有animated：引數部分，它可以允許是否使用動畫。 

Core Animation還與Quartz緊密結合在一起，每個UIView都關聯到一個CALayer物件，CALayer是Core Animation中的圖層。 

15.2 Core Animation基礎

Core Animation建立動畫時候會修改CALayer屬性，然後讓這些屬性流暢地變化。Core Animation相關知識點： 

圖層，圖層是動畫發生的地方，CALayer總是與UIView關聯，通過layer屬性訪問。 

隱式動畫，這是一種最簡單的動畫，不用設定定時器，不用考慮執行緒或者重畫。 

顯式動畫，是一種使用CABasicAnimation建立的動畫，通過CABasicAnimation，可以更明確地定義屬性如何改變動 畫。 

關鍵幀動畫，這是一種更復雜的顯式動畫型別，這裡可以定義動畫的起點和終點，還可以定義某些幀之間的動畫。 

15.3 隱式動畫

例項ianimate：

#import <UIKit/UIKit.h>
#import <QuartzCore/QuartzCore.h>

@interface
 
 ianimateViewController : UIViewController {

    IBOutlet UIImageView *plane;
}

-(IBAction)movePlane:(id)sender;

@end

//--m
-(IBAction)movePlane:(id)sender {
    
    [UIView beginAnimations:nil context:NULL];
    CGAffineTransform moveTransform = CGAffineTransformMakeTranslation(180, 200);
    plane.layer.affineTransform
 
=moveTransform;
    plane.layer.opacity = 1;
    [UIView commitAnimations];

}

飛機圖片的不透明度（opacity）初始為0.25，然後在動畫過程中不透明度設定為1.0。這個過程是設定飛機圖片物件的層屬性的，plane.layer.opacity = 1; 

[plane.layer setAffineTransform:moveTransform];設定飛機圖片層物件的仿射移動變換。 

15.4 顯式動畫

eanimate關鍵程式碼：

#import <UIKit/UIKit.h>
#import <QuartzCore/QuartzCore.h>

@interface eanimateViewController : UIViewController {
    IBOutlet UIImageView *plane;
}
-(IBAction)movePlane:(id)sender;
@end

//--m



-(IBAction)movePlane:(id)sender {
    
    CABasicAnimation *opAnim = [CABasicAnimation animationWithKeyPath:@"opacity"];
    opAnim.duration = 3.0;
    opAnim.fromValue = [NSNumber numberWithFloat:.25];
    opAnim.toValue= [NSNumber numberWithFloat:1.0];
    opAnim.cumulative = YES;
    opAnim.repeatCount = 2;
    [plane.layer addAnimation:opAnim forKey:@"animateOpacity"];
    
    CGAffineTransform moveTransform = CGAffineTransformMakeTranslation(180, 200);
    CABasicAnimation *moveAnim = [CABasicAnimation animationWithKeyPath:@"transform"];
    moveAnim.duration = 6.0;
    moveAnim.toValue= [NSValue valueWithCATransform3D:
        CATransform3DMakeAffineTransform(moveTransform)];
    [plane.layer addAnimation:moveAnim forKey:@"animateTransform"];

}

顯式動畫時候，不必定義CALayer的變化，也不必執行它們，而是通過CABasicAnimation逐個定義動畫。其中每個動畫都含有各自的duration、repeatCount等屬性。然後，使用addAnimation:forKey:方法分別將每個動畫應用到層中。 

[CABasicAnimation animationWithKeyPath:@“opacity”]獲得透明度動畫物件，@“transform”是指定轉換動畫。 

opAnim.cumulative 屬性是指定累計 

opAnim.repeatCount 重複執行次數 

CATransform3DMakeAffineTransform函式是將仿射變換矩陣變成Core Animation使用的Transform3D型別的矩陣。 

15.5 關鍵幀顯式動畫

eanimate_keyFrame關鍵程式碼：

#import <UIKit/UIKit.h>
#import <QuartzCore/QuartzCore.h>
@interface eanimateViewController : UIViewController {
    IBOutlet UIImageView *plane;
}
-(IBAction)movePlane:(id)sender;

@end


//-m
-(IBAction)movePlane:(id)sender {
    
    CAKeyframeAnimation *opAnim = [CAKeyframeAnimation animationWithKeyPath:@"opacity"];
    opAnim.duration = 6.0;
    opAnim.values =[NSArray arrayWithObjects: 
                    [NSNumber numberWithFloat:0.25],  
                    [NSNumber numberWithFloat:0.75], 
                    [NSNumber numberWithFloat:1.0],
                    nil]; 
    opAnim.keyTimes = [NSArray arrayWithObjects:
                       [NSNumber numberWithFloat:0.0], 
                       [NSNumber numberWithFloat:0.5], 
                       [NSNumber numberWithFloat:1.0], nil];
    
    [plane.layer addAnimation:opAnim forKey:@"animateOpacity"];
    
    CGAffineTransform moveTransform = CGAffineTransformMakeTranslation(180, 200);
    CABasicAnimation *moveAnim = [CABasicAnimation animationWithKeyPath:@"transform"];
    moveAnim.duration = 6.0;
    moveAnim.toValue= [NSValue valueWithCATransform3D:
                       CATransform3DMakeAffineTransform(moveTransform)];
    [plane.layer addAnimation:moveAnim forKey:@"animateTransform"];
    
}

animation.values是一個值的陣列。 

animation.keyTimes是一個每個幀片段持續的時間比例，取值範圍0.0-1.0之間。 

關鍵幀之路徑例項BallSteps

#import <UIKit/UIKit.h>
#import <QuartzCore/CoreAnimation.h>

@interface BallStepsViewController : UIViewController {
    UIButton *drawButton;
    UIImageView *imageView;
}

@property (nonatomic, retain) IBOutlet UIButton *drawButton;
@property (nonatomic, retain) IBOutlet UIImageView *imageView;

- (IBAction)drawStar:(id)sender;

@end

//--m

#import "BallStepsViewController.h"

@implementation BallStepsViewController

@synthesize drawButton;
@synthesize imageView;

- (IBAction)drawStar:(id)sender {
    [drawButton setEnabled:NO];
    CGMutablePathRef starPath = CGPathCreateMutable();
    CGPathMoveToPoint(starPath,NULL,160.0f, 100.0f);
    CGPathAddLineToPoint(starPath, NULL, 100.0f, 280.0f);
    CGPathAddLineToPoint(starPath, NULL, 260.0, 170.0);
    CGPathAddLineToPoint(starPath, NULL, 60.0, 170.0);
    CGPathAddLineToPoint(starPath, NULL, 220.0, 280.0);
    CGPathCloseSubpath(starPath);
    
    CAKeyframeAnimation *animation = nil;
    animation = [CAKeyframeAnimation animationWithKeyPath:@"position"];
    [animation setDuration:10.0f];
    [animation setDelegate:self];
    [animation setPath:starPath];
    CFRelease(starPath);
    starPath = nil;
    [[imageView layer] addAnimation:animation forKey:@"position"];
}

- (void)animationDidStop:(CAAnimation *)theAnimation finished:(BOOL)flag {
    [drawButton setEnabled:YES];
}

- (void)dealloc {
    [drawButton release];
    [imageView release];
    [super dealloc];
}

@end

[CAKeyframeAnimation animationWithKeyPath:@“position”];建立一個position型別的關鍵幀動畫。 

關鍵幀動畫中可以定義路徑，把這些路徑放入到CGMutablePathRef 中與CG中的很相似。   

CGPathCloseSubpath(starPath);結束路徑。 

[animation setPath:starPath];設定路徑。 

[animation setDelegate:self];設定委託物件為本身，即回撥方法 animationDidStop:finished:。 

最後CFRelease(starPath);釋放路徑。 

15.6 UIView級別動畫

除了直接使用Core Animation 層實現動畫，我們還有UIView直接實現隱式動畫。 

例項ViewAnimation：

@interface MainViewController : UIViewController 
{
  UIImageView *animImageView;
  UIButton *button;
}

@property (assign) IBOutlet UIImageView *animImageView;
@property (assign) IBOutlet UIButton *button;

- (IBAction)action:(id)sender;

@end

//--m
#import "MainViewController.h"

@implementation MainViewController

@synthesize animImageView;
@synthesize button;

- (IBAction)action:(id)sender {
  [UIView beginAnimations:@"Hide Button" context:nil];
  [[self button] setAlpha:0.0];
  [UIView commitAnimations];
  
  [UIView beginAnimations:@"Slide Around" context:nil];
  
  [UIView setAnimationDuration:1.0];
  [UIView setAnimationDelegate:self];
  [UIView setAnimationDidStopSelector:@selector(viewAnimationDone:)];
  [UIView setAnimationRepeatCount:3];
  [UIView setAnimationRepeatAutoreverses:YES];
  
  CGPoint center = [[self animImageView] center];
  center.y += 100;
  
  [[self animImageView] setCenter:center];
  
  [UIView commitAnimations];
}

- (void)viewAnimationDone:(NSString*)name {
  [UIView beginAnimations:@"Show Button" context:nil];
  [[self button] setAlpha:1.0];
  [UIView commitAnimations];
}

@end

UIView中的動畫是在動畫塊中定義的，動畫塊是UIView beginAnimations:context:開始， 在UIView commitAnimations結束。 

首先開始將按鈕設定透明度為0的，結果是開始動畫時候隱藏了。 

然後，又開始新的動畫中設定委託事件： 

[UIView setAnimationDelegate:self] 

[UIView setAnimationDidStopSelector:@selector(viewAnimationDone:)]; 

當動畫結束的時候呼叫viewAnimationDone:方法。 

內建UIView動畫

UIView具有一個UIViewAnimationTransition屬性可以設定動畫，這些動畫是iOS提供幾個常用動畫有： 

UIViewAnimationTransitionNone 

UIViewAnimationTransitionFlipFromLeft 

UIViewAnimationTransitionFlipFromRight 

UIViewAnimationTransitionCurlUp 

UIViewAnimationTransitionCurlDown 

例項UIViewAnimation

#import <UIKit/UIKit.h>

@interface UIViewAnimationViewController : UIViewController {

}

- (IBAction)doUIViewAnimation:(id)sender;

@end

//-m
#import "UIViewAnimationViewController.h"

@implementation UIViewAnimationViewController


- (IBAction)doUIViewAnimation:(id)sender{
    [UIView beginAnimations:@"animationID" context:nil];
    [UIView setAnimationDuration:1.5f];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
    [UIView setAnimationRepeatAutoreverses:NO];
    UIButton *theButton = (UIButton *)sender;
    switch (theButton.tag) {
        case 1:
            [UIView setAnimationTransition:UIViewAnimationTransitionFlipFromLeft forView:self.view cache:YES];//oglFlip, fromLeft 
            break;
        case 2:
            [UIView setAnimationTransition:UIViewAnimationTransitionFlipFromRight forView:self.view cache:YES];//oglFlip, fromRight      
            break;
        case 3:
            [UIView setAnimationTransition:UIViewAnimationTransitionCurlUp forView:self.view cache:YES];
            break;
        case 4:
            [UIView setAnimationTransition:UIViewAnimationTransitionCurlDown forView:self.view cache:YES];
            break;
        default:
            break;
    }
    //[self.view exchangeSubviewAtIndex:1 withSubviewAtIndex:0];
    [UIView commitAnimations];
}

- (void)viewDidUnload {
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

- (void)dealloc {
    [super dealloc];
}

@end

[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut]設定動畫曲線，動畫曲線指定的是動畫進入和退出的方式，它也有幾個常量： 

UIViewAnimationCurveEaseInOut 

UIViewAnimationCurveEaseIn 

UIViewAnimationCurveEaseOut 

UIViewAnimationCurveLinear 

setAnimationTransition: forView: cache:方法第一個引數定義動畫型別，第二個引數是當前檢視物件，第三個引數上使用緩衝區。