详解iPhone SDK开发基础之自定义仪表控件

iPhone SDK开发基础之自定义仪表控件是本文要介绍的内容，主要是来学习仪表控件。在iOS开发中，因为程序的需要，有时要自行绘制iPhone SDK没有提供的界面控件，通常使用QuartzCore.framework即可画出你所需要的各种图形，在这里我们实现一个圆形的“仪表盘”控件，控件的外观如图3-48所示，用户可以通过旋转仪表控件的指针来设置程序需要的各种系统参数,如图所示：

控件使用两个UIView来实现仪表控件，并通过CGAffineTransform类来实现仪表指针的旋转，控件在UIDialView类中实现，UIDialView类的定义如下。

    // UIDialView.h    #import <UIKit/UIKit.h>    @protocol UIDialViewDelegate    @optional    - (void)dialValue:(int)tag Value:(float)value;    @end    @interface UIDialView : UIView {    id<UIDialViewDelegate> delegate;    NSTimer *timer;    UIImageView *iv;    float maxValue,minValue;    CGAffineTransform initialTransform ;    float currentValue;    }    @property(nonatomic,assign)id<UIDialViewDelegate>delegate;    @property CGAffineTransform initialTransform;    @property float currentValue;    @end 

在UIDialView类的实现文件中，通过init()方法读取图片文件初始化控件背景和指针，代码如下。

    // UIDialView.m    #import "UIDialView.h"    @interface    UIDialView()    -(void)spin:(NSTimer *)timer;    -(float) goodDegrees:(float)degrees;    @end    #define degreesToRadians(degrees) (M_PI * degrees / 180.0)    #define radiansToDegrees(radians) (radians * 180 / M_PI)    static CGPoint delta;    static float deltaAngle;    static float currentAngle;    @implementation UIDialView    @synthesize initialTransform,currentValue;    - (void)dealloc {    [iv release];    [super dealloc];    }    @synthesize    delegate;    - (id)init{    if ((self = [super init])) {    self.userInteractionEnabled = YES;    iv =[[UIImageView alloc] initWithImage:[UIImage imageNamed:@"knob. png"]];    UIImage *backgroundTile = [UIImage imageNamed: @"clock.png"];    UIColor *backgroundPattern = [[UIColor alloc] initWithPatternImage: backgroundTile];    self.contentMode = UIViewContentModeCenter;    [self setBackgroundColor:backgroundPattern];    [backgroundPattern release];    iv.backgroundColor = [UIColor clearColor];    iv.autoresizesSubviews= YES;    self.frame = CGRectMake(0, 0, iv.frame.size.width, iv.frame.size. height);    [self addSubview:iv];    [self bringSubviewToFront:iv];    [iv release];    currentValue = 0;    currentAngle = 0;    deltaAngle = 0.0;    }    return self;    } 

在UIView的touchesBegan()方法中捕获用户Touch点的位置，并根据此位置使用atan2()函数计算出控件的初始化角度，代码如下。

    - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{    UITouch *thisTouch = [touches anyObject];    delta = [thisTouch locationInView:self];    float dx = delta.x - iv.center.x;    float dy = delta.y - iv.center.y;    deltaAngle = atan2(dy,dx);    initialTransform = iv.transform;    } 

在用户的旋转过程中通过设置指针UIView对象的transform属性实现仪表控件指针伴随用户手指的旋转而旋转，代码如下。

    - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{    UITouch *touch = [touches anyObject];    CGPoint pt = [touch locationInView:self];    float dx = pt.x - iv.center.x;    float dy = pt.y - iv.center.y;    float ang = atan2(dy,dx);    if (deltaAngle == 0.0) {    deltaAngle = ang;    initialTransform = iv.transform;    }else{    float angleDif = deltaAngle - ang;    CGAffineTransform newTrans = CGAffineTransformRotate(initialTransform, -angleDif);    iv.transform = newTrans;    float diffValue = [self goodDegrees:radiansToDegrees(angleDif)];    currentValue = maxValue - ((maxValue - minValue)/300)*diffValue;    if(currentValue > 100) currentValue = 100;    }    if (delegate != nil) {    [delegate dialValue:self.tag Value:currentValue];    }    } 

客户通过实现UIDialViewDelegate接口协议的dialValue()方法而得到控件的通知消息，代码如下。

    // DialViewController.h    #import <UIKit/UIKit.h>    #import "UIDialView.h"    @interface    DialViewController : UIViewController< UIDialViewDelegate> {    UIDialView *dialView;    UILabel *myLabel;    }    - (void)dialValue:(int)tag Value:(float)value{    NSString *str = [NSString stringWithFormat:@"%.1f",v*100];    [myLabel performSelector:@selector(setText:) withObject:str];    } 

小结：详解iPhone SDK开发基础之自定义仪表控件的内容介绍完了，希望通过本文的的学习能对你有所帮助