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1、内容回顾内容回顾代码示例： 这样的代码会不会产生内存泄露？-(void)viewDidUnload self.statusText = nil; 将self.statusTextz的引用计数减一(发送releas)， - 将Nil的引用计数加一！- (void)dealloc statusText release; super dealloc;内容回顾内容回顾看一下属性声明：#import interface Button_FunViewController : UIViewController UILabel *statusText;property (nonatomic, retain)
2、IBOutlet UILabel *statusText;-(IBAction)buttonPressed :(id)sender;end内容回顾内容回顾代码示例：void setStatusText:(UILabel*) aLabel aLabel retain; statusText release; statusText = aLabel;本章授课内容本章授课内容vTarget-Actionv课堂堂实验Target-ActionvTarget-Action:Target-Action是一种设计模式，在这个设计模式中，一个对象保留了一些必要信息，当某种事件发生时将消息发送给另外一个对象。这
3、些必要的信息包含两部分的内容：一部分是一个Selector,用来标识要调用的Action；另一部分是Target，也就是接受消息的对象。Target-ActionTarget-Action按钮包含了target和actionNSButtonaction = seed:Foo-(void)seed:(id)sendertargetTarget-Action当用户和控件交互时，控件就会给它们的target发送action消息。例如：点击一个按钮，将会给它的target发送action消息：Action方法接受一个参数：发送者。该参数可以让接收者知道是哪一个控件发送了这个action消息。NSBut
4、tonaction = seed:Foo-(void)seed:(id)sendertargetseed:-(IBAction)toggleFoo:(id)sender BOOL isOn = sender state;Target-ActionTarget-Action是UIControl类中定义的一种机制，凡是UIControl子类的对象都可以通过设置target和action来通过消息触发某个操作。Target-ActionUIControl类的声明interface UIControl : UIView NSMutableArray* _targetActions; CGPoint _
5、previousPoint; CFAbsoluteTime _downTime;-(void)addTarget:(id)target action:(SEL)action forControlEvents:(UIControlEvents)controlEvents;-(void)removeTarget:(id)target action:(SEL)action forControlEvents:(UIControlEvents)controlEvents;-(NSArray *)actionsForTarget:(id)target forControlEvent:(UIControlE
6、vents)controlEvent; - (void)sendAction:(SEL)action to:(id)target forEvent:(UIEvent *)event;- (void)sendActionsForControlEvents:(UIControlEvents)controlEvents; endTarget-ActionNSButtonNSMutableArray* _targetActions;targetactionidmethodidmethodidmethodidmethodobjobjobjobjTarget-ActionUIControlEventsen
7、um UIControlEventTouchDown = 1 0, UIControlEventTouchDownRepeat = 1 1, UIControlEventTouchDragInside = 1 2, UIControlEventTouchDragOutside = 1 3, UIControlEventTouchDragEnter = 1 4, UIControlEventTouchDragExit = 1 5, UIControlEventTouchUpInside = 1 6, UIControlEventTouchUpOutside = 1 7, UIControlEve
8、ntTouchCancel = 1 8,;Target-ActionNSButtonaction=buttonPressed:Button_FunViewController-(void)seed:(id)sendertargetNSButtonaction=buttonPressed:targetNSLabeltextTarget-Action通过代码设置Target和Action可以通过UIControl的方法触发操作以响应事件：SEL sel;sel = selector(buttonPressed:);btn addTarget:someObjectWithbuttonPressedM
9、ethod Action:sel forEvent:UIControlEventTouchUpInside;(void)sendAction:(SEL)action to:(id)target forEvent:(UIEvent *)event; target PerformSelector:action withObject:self; 本章授课内容本章授课内容vTarget-Actionv课堂堂实验课堂实验课堂实验v实验目的：目的：了解通过代码创建对象的流程理解Target-Action模式课堂实验课堂实验v创建工程：建工程：创建基于视图的工程将工程名命名为DyButton课堂实验课堂实验
10、v修改代修改代码： ：打开DyButtonViewController.cpp修改修改viewDidLoad方法:viewDidLoad方法会在viewController将与之关联的视图加载到内存种后调用，负责进一步的初始化工作。- (void)viewDidLoad super viewDidLoad; UIButton *btn = UIButton buttonWithType:UIButtonTypeRoundedRect; btn.frame = CGRectMake(110,225,100,30); btn setTitle:Click forState:UIControlSta
11、teNormal; self.view addSubview:btn;课堂实验课堂实验课堂实验课堂实验当button被手动创建出来后，无法执行任何自定义操作。所以，我们必须设定button的target和action.对于应用程序来说，控件的target一般都是与控件所在视图的viewController的子类的对象，但也可以是其他的自定义类型的对象。课堂实验课堂实验添加操作方法：打开文件DyButtonViewController.h文件,添加操作方法的声明#import interface DyButtonViewController : UIViewController -(IBActi
12、on)buttonPressed:(id)sender;end课堂实验课堂实验打开DyButtonViewController.cpp实现操作函数:-(IBAction)buttonPressed:(id)sender int x = arc4random()%220; int y = arc4random()%450; UIButton *btn = UIButton buttonWithType:UIButtonTypeRoundedRect; btn.frame = CGRectMake(x,y,100,25); btn setTitle:Click forState:UIControl
13、StateNormal; self.view addSubview:btn; btn addTarget:self action:selector(buttonPressed:) forControlEvents:UIControlEventTouchUpInside;课堂实验课堂实验课堂实验课堂实验v继续修改当前的应用程序使控件能够响应拖动事件。事件就是一个对象用来保存硬件监测到的用户输入。当系统监测到用户输入后就将用户输入的信息封装成UIEvent的对象，发送给当前处于活动状态的应用程序。课堂实验课堂实验课堂实验课堂实验UIEvent种又包含了好多UITouch对象，用来存储触摸事件的详细
14、内容课堂实验课堂实验继续修改DyButtonViewController.h文件，添加新的操作函数的声明：#import interface DyButtonViewController : UIViewController -(IBAction)buttonPressed:(id)sender;-(IBAction)buttonMoved:(id)sender forEvent:(UIEvent *)event;end课堂实验课堂实验修改DyButtonViewController.cpp文件实现新的操作函数：-(IBAction)buttonMoved:(id)sender forEven
15、t:(UIEvent *)event NSSet *set = event allTouches; UITouch *touch = set allObjects objectAtIndex:0; CGPoint currentPoint = touch locationInView:self.view; CGPoint lastPoint = touch previousLocationInView:self.view; UIButton *btn = (UIButton*)sender; CGRect frame = btn.frame; btn.frame = CGRectOffset(
16、frame, currentPoint.x - lastPoint.x, currentPoint.y - lastPoint.y); 课堂实验课堂实验修改viewDidLoad函数：- (void)viewDidLoad super viewDidLoad; UIButton *btn = UIButton buttonWithType:UIButtonTypeRoundedRect; btn.frame = CGRectMake(110,225,100,30); btn setTitle:Click forState:UIControlStateNormal; self.view addS
17、ubview:btn; btn addTarget:self action:selector(buttonPressed:) forControlEvents:UIControlEventTouchDownRepeat; btn addTarget:self action:selector(buttonMoved:forEvent:) forControlEvents:UIControlEventTouchDragInside;课堂实验课堂实验修改buttonPressed函数：-(IBAction)buttonPressed:(id)sender int x = arc4random()%2
18、20; int y = arc4random()%450; UIButton *btn = UIButton buttonWithType:UIButtonTypeRoundedRect; btn.frame = CGRectMake(x,y,100,30); btn setTitle:Click forState:UIControlStateNormal; self.view addSubview:btn; btn addTarget:self action:selector(buttonPressed:) forControlEvents:UIControlEventTouchDownRepeat; btn addTarget:self action:selector(buttonMoved:forEvent:) forControlEvents:UIControlEventTouchDragInside;Thanks
