詳解iPhone SDK開發基礎之自定義儀表控件

iPhone SDK開發基礎之自定義儀表控件是本文要介紹的內容，主要是來學習儀表控件。在iOS開發中，因爲程序的需要，有時要自行繪製iPhone SDK沒有提供的界面控件，通常使用QuartzCore.framework即可畫出你所需要的各種圖形，在這裏我們實現一個圓形的“儀表盤”控件，控件的外觀如圖3-48所示，用戶可以通過旋轉儀表控件的指針來設置程序需要的各種系統參數,如圖所示：

控件使用兩個UIView來實現儀表控件，並通過CGAffineTransform類來實現儀表指針的旋轉，控件在UIDialView類中實現，UIDialView類的定義如下。

    // 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類的實現文件中，通過init()方法讀取圖片文件初始化控件背景和指針，代碼如下。

    // 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()方法中捕獲用戶Touch點的位置，並根據此位置使用atan2()函數計算出控件的初始化角度，代碼如下。

    - (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;
    } 

在用戶的旋轉過程中通過設置指針UIView對象的transform屬性實現儀表控件指針伴隨用戶手指的旋轉而旋轉，代碼如下。

    - (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];
    }
    } 

客戶通過實現UIDialViewDelegate接口協議的dialValue()方法而得到控件的通知消息，代碼如下。

    // 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];
    } 

小結：詳解iPhone SDK開發基礎之自定義儀表控件的內容介紹完了，希望通過本文的的學習能對你有所幫助