2011斯坦福大学iOS应用开发教程学习笔记(第五课)Protocols,手势识别

第五课内容： 自动旋转、 Protocols、 手势识别、一个自定义UIView的Demo

1、自动旋转

当设备旋转时，你的controller会做什么呢？你可以控制界面是否和设备一起一起旋转。

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)orientation
{
return UIInterfaceOrientationIsPortrait(orientation); // only support portrait
return YES; // support all orientations
return (orientation != UIInterfaceOrientationPortraitUpsideDown); // anything but
}

当旋转的时候，view的bounds会改变，子view的frame,子view的子view也会改变。
改变的规则是：struts和springs。
当view的bound改变时，drawRect不会默认调用



红色的I就是struts，中间的红色箭头就是springs。
右边红白色的显示屏似的就是用动画告诉你view如何改变。白色的是父view，红色的是你选中的view。
这个控制在iPhone上一般使用不到，因为屏幕太小了。
幸运的是，有UIView有这么个属性来控制

三种控制方式：

1、

@property (nonatomic) UIViewContentMode contentMode;

UIViewContentMode{Left,Right,Top,Right,BottomLeft,BottomRight,TopLeft,TopRight}

2、缩放的控制属性：

UIViewContentModeScale{ToFill,AspectFill,AspectFit} // bit stretching/shrinking

分别是填充，内容填充，内容适应。 toFill是默认的模式，它会自动缩放像素点填满新的空间，可能会造成图形扭曲。
3、

@property (nonatomic) CGRect contentStretch;

指定某一个区域拉伸
初始化一个UIView.

2、协议procotol

@protocol Foo <Other, NSObject> // implementors must implement Other and NSObject too
- (void)doSomething; // implementors must implement this (methods are @required by default)
@optional
- (int)getSomething; // implementors do not have to implement this
- (void)doSomethingOptionalWithArgument:(NSString *)argument; // also optional
@required
- (NSArray *)getManySomethings:(int)howMany; // back to being “must implement”
@property (nonatomic, strong) NSString *fooProp; // note that you must specify strength
@end

可以定义在自己的头文件里，也可以定义在其他类的头文件中。
实现协议，并使用的语法：

#import “Foo.h” // importing the header file that declares the Foo @protocol
@interface MyClass : NSObject <Foo> // MyClass is saying it implements the Foo @protocol
...
@en

id <Foo> obj = [[MyClass alloc] init];

@property (nonatomic, weak) id <Foo> myFooProperty; // properties too!

协议的主要作用：
实现委托和数据源。

委托几乎都是weak的，因为被设置为委托的对象通常都是委托对象的所有者或创建者。
比如controller通常把自己设置成view的委托或数据源，你不要它们相互的strong指针指向。
scrollView例子

@protocol UIScrollViewDelegate
@optional
- (UIView *)viewForZoomingInScrollView:(UIScrollView *)sender;
- (void)scrollViewDidEndDragging:(UIScrollView *)sender willDecelerate:(BOOL)decelerate;
@end
@interface UIScrollView : UIView
@property (nonatomic, weak) id <UIScrollViewDelegate> delegate;
@end
@interface MyViewController : UIViewController <UIScrollViewDelegate>
@property (nonatomic, weak) IBOutlet UIScrollView *scrollView;
@end
@implementation MyViewController
- (void)setScrollView:(UIScrollView *)scrollView {
_scrollView = scrollView;
self.scrollView.delegate = self; // compiler won’t complain
}
- (UIView *)viewForZoomingInScrollView:(UIScrollView *)sender { return ... };
@end

3、手势识别

如何获得触摸事件呢？

得到触摸时间的通知
相应预定义好的手势
UIGestureRecognizer类，它是个抽象类，需要实现。

使用手势识别有两步骤:

先创建一个手势，把它附到UIView上，然后当手势被识别时进行处理。
第一步由controller来完成
第二步由UIView自己完成
从controller添加一个手势到UIView：

- (void)setPannableView:(UIView *)pannableView
{
_pannableView = pannableView;
UIPanGestureRecognizer *pangr =
[[UIPanGestureRecognizer alloc] initWithTarget:pannableView action:@selector(pan:)];
[pannableView addGestureRecognizer:pangr];
}

target 是手势识别之后的处理者，这里就是view本身。

UIPangestureRecognizer的三个方法：

- (CGPoint)translationInView:(UIView *)aView;
- (CGPoint)velocityInView:(UIView *)aView;
- (void)setTranslation:(CGPoint)translation inView:(UIView *)aView;

第一个告诉移动的距离
第二个告诉移动的速度
第三个是重新设置

手势识别的状态机

@property (readonly) UIGestureRecognizerState state;

状态从possible 如果手势比较短：recognized 如果持续：Began - Changed ,最后Ended
还有Failed 和 Cancelled状态，取消或其他操作中断时会有这个情况。

pan:是什么样的呢：

- (void)pan:(UIPanGestureRecognizer *)recognizer
{
if ((recognizer.state == UIGestureRecognizerStateChanged) ||
(recognizer.state == UIGestureRecognizerStateEnded)) {
CGPoint translation = [recognizer translationInView:self];
// move something in myself (I’m a UIView) by translation.x and translation.y
// for example, if I were a graph and my origin was set by an @property called origin
self.origin = CGPointMake(self.origin.x+translation.x, self.origin.y+translation.y);
[recognizer setTranslation:CGPointZero inView:self];
}
}

其他实例的手势：

UIPinchGestureRecognizer 缩放
UIRotationGestureRecognizer 旋转手势，两个手指按下，然后旋转，是个弧度，不是角度。
UISwipeGestureRecognizer 滑动手势， 一个或多个手指滑动，
UITapGestureRecognizer 点击手势

4、一个幸福笑脸的Demo:

内容介绍：

Model是： int happiness
View是：自定义的view叫做FaceView
Controller是：HappinessViewController
观察内容有：
drawRect 包括绘制子程序， pop push context(环境)
Faceview委托的数据如何属于Controller的协议。
Controller处理手势，或者view处理手势
通过手势来改变幸福度。

用整数表示幸福度， 0表示悲伤， 100表示非常幸福。

有两个手势，一个被view处理，因为它只修改显示，另外一个被controller处理，它要修改model,修改幸福度。

主要源码：
happinessViewController.h

#import <UIKit/UIKit.h>

@interface HappinessViewController : UIViewController

@property (nonatomic) int happiness;  // 0 is sad; 100 is very happy

@end

happinessViewController.m

#import "HappinessViewController.h"
#import "FaceView.h"

@interface HappinessViewController() <FaceViewDataSource>
@property (nonatomic, weak) IBOutlet FaceView *faceView;
@end

@implementation HappinessViewController

@synthesize happiness = _happiness;
@synthesize faceView = _faceView;

- (void)setHappiness:(int)happiness
{
_happiness = happiness;
[self.faceView setNeedsDisplay]; // any time our Model changes, redraw our View
}

- (void)setFaceView:(FaceView *)faceView
{
_faceView = faceView;
// enable pinch gestures in the FaceView using its pinch: handler
[self.faceView addGestureRecognizer:[[UIPinchGestureRecognizer alloc] initWithTarget:self.faceView action:@selector(pinch:)]];
[self.faceView addGestureRecognizer:[[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handleHappinessGesture:)]];  // gesture to modify our Model
self.faceView.dataSource = self;
}

- (void)handleHappinessGesture:(UIPanGestureRecognizer *)gesture
{
if ((gesture.state == UIGestureRecognizerStateChanged) ||
(gesture.state == UIGestureRecognizerStateEnded)) {
CGPoint translation = [gesture translationInView:self.faceView];
self.happiness -= translation.y / 2;
[gesture setTranslation:CGPointZero inView:self.faceView];
}
}

- (float)smileForFaceView:(FaceView *)sender
{
return (self.happiness - 50) / 50.0; // translate Model for View
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation
{
return YES; // support all orientations
}

@end

FaceView.h

#import <UIKit/UIKit.h>

@class FaceView;  // forward declaration for use in @protocol

@protocol FaceViewDataSource
- (float)smileForFaceView:(FaceView *)sender;
@end

@interface FaceView : UIView

@property (nonatomic) CGFloat scale;

- (void)pinch:(UIPinchGestureRecognizer *)gesture;  // resizes the face

// set this property to whatever object will provide this View's data
// usually a Controller using a FaceView in its View
@property (nonatomic, weak) IBOutlet id <FaceViewDataSource> dataSource;

@end

FaceView.m

#import "FaceView.h"

@implementation FaceView

@synthesize dataSource = _dataSource;
@synthesize scale = _scale;

#define DEFAULT_SCALE 0.90

- (CGFloat)scale
{
if (!_scale) {
return DEFAULT_SCALE; // don't allow zero scale
} else {
return _scale;
}
}

- (void)setScale:(CGFloat)scale
{
if (scale != _scale) {
_scale = scale;
[self setNeedsDisplay]; // any time our scale changes, call for redraw
}
}

- (void)pinch:(UIPinchGestureRecognizer *)gesture
{
if ((gesture.state == UIGestureRecognizerStateChanged) ||
(gesture.state == UIGestureRecognizerStateEnded)) {
self.scale *= gesture.scale; // adjust our scale
gesture.scale = 1;           // reset gestures scale to 1 (so future changes are incremental, not cumulative)
}
}

- (void)setup
{
self.contentMode = UIViewContentModeRedraw; // if our bounds changes, redraw ourselves
}

- (void)awakeFromNib
{
[self setup]; // get initialized when we come out of a storyboard
}

- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
[self setup]; // get initialized if someone uses alloc/initWithFrame: to create us
}
return self;
}

- (void)drawCircleAtPoint:(CGPoint)p withRadius:(CGFloat)radius inContext:(CGContextRef)context
{
UIGraphicsPushContext(context);
CGContextBeginPath(context);
CGContextAddArc(context, p.x, p.y, radius, 0, 2*M_PI, YES); // 360 degree (0 to 2pi) arc
CGContextStrokePath(context);
UIGraphicsPopContext();
}

- (void)drawRect:(CGRect)rect
{
CGContextRef context = UIGraphicsGetCurrentContext();

CGPoint midPoint; // center of our bounds in our coordinate system
midPoint.x = self.bounds.origin.x + self.bounds.size.width/2;
midPoint.y = self.bounds.origin.y + self.bounds.size.height/2;

CGFloat size = self.bounds.size.width / 2;
if (self.bounds.size.height < self.bounds.size.width) size = self.bounds.size.height / 2;
size *= self.scale; // scale is percentage of full view size

CGContextSetLineWidth(context, 5.0);
[[UIColor blueColor] setStroke];

[self drawCircleAtPoint:midPoint withRadius:size inContext:context]; // head

#define EYE_H 0.35
#define EYE_V 0.35
#define EYE_RADIUS 0.10

CGPoint eyePoint;
eyePoint.x = midPoint.x - size * EYE_H;
eyePoint.y = midPoint.y - size * EYE_V;

[self drawCircleAtPoint:eyePoint withRadius:size * EYE_RADIUS inContext:context]; // left eye
eyePoint.x += size * EYE_H * 2;
[self drawCircleAtPoint:eyePoint withRadius:size * EYE_RADIUS inContext:context]; // right eye

#define MOUTH_H 0.45
#define MOUTH_V 0.40
#define MOUTH_SMILE 0.25

CGPoint mouthStart;
mouthStart.x = midPoint.x - MOUTH_H * size;
mouthStart.y = midPoint.y + MOUTH_V * size;
CGPoint mouthEnd = mouthStart;
mouthEnd.x += MOUTH_H * size * 2;
CGPoint mouthCP1 = mouthStart;
mouthCP1.x += MOUTH_H * size * 2/3;
CGPoint mouthCP2 = mouthEnd;
mouthCP2.x -= MOUTH_H * size * 2/3;

float smile = [self.dataSource smileForFaceView:self];
if (smile < -1) smile = -1;
if (smile > 1) smile = 1;

CGFloat smileOffset = MOUTH_SMILE * size * smile;
mouthCP1.y += smileOffset;
mouthCP2.y += smileOffset;

CGContextBeginPath(context);
CGContextMoveToPoint(context, mouthStart.x, mouthStart.y);
CGContextAddCurveToPoint(context, mouthCP1.x, mouthCP2.y, mouthCP2.x, mouthCP2.y, mouthEnd.x, mouthEnd.y); // bezier curve
CGContextStrokePath(context);
}

@end

容芳志 (http://blog.csdn.net/totogo2010)