iPhone 開發筆記15: 單點觸控與多點觸控

// 單點觸控
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
   
    UITouch *touch = [[event allTouches] anyObject];
    CGPoint location = [touch locationInView:touch.view];

    // location.x

    // location.y
}

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// 多點觸控
A. 新增一個 Window-based Application Project: multiTouch

B. 新增繼承 UIView 的 Class: TouchView
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C. multiTouchAppDelegate.h
#import <UIKit/UIKit.h>
//@add
#import "TouchView.h"

@interface multiTouchAppDelegate : NSObject <UIApplicationDelegate> {
    UIWindow *window;
}

@property (nonatomic, retain) IBOutlet UIWindow *window;

@end

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D. multiTouchAppDelegate.m

#import "multiTouchAppDelegate.h"

@implementation multiTouchAppDelegate

@synthesize window;

#pragma mark -
#pragma mark Application lifecycle

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {   
   
    // Override point for customization after application launch.
    //@add
    [application setStatusBarStyle:UIStatusBarStyleBlackOpaque]; // 改變狀態列背景

    TouchView *touchView = [[[TouchView alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];

    [window addSubview:touchView];   
   
    [window makeKeyAndVisible];
   
    return YES;
}

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E. TouchView.h

#import <UIKit/UIKit.h>

@interface TouchView : UIView {
    //@add
    CGPoint touch1;
    CGPoint touch2;
    double unitDistance;
    double initialDistance;
}

//@add
- (double)getDistance:(CGPoint)fromPoint toPoint:(CGPoint)otherPoint;

@end

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F. TouchView.m

#import "TouchView.h"

@implementation TouchView

- (id)initWithFrame:(CGRect)frame {
    if ((self = [super initWithFrame:frame])) {
        // Initialization code
        //@add
        [self setMultipleTouchEnabled:YES];
    }
    return self;
}

- (void) touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event {
    NSArray *allTouches = [touches allObjects];
    int count = [allTouches count];
    if (count > 0)
        touch1 = [[allTouches objectAtIndex:0] locationInView:self];
    if (count > 1)
    {
        touch2 = [[allTouches objectAtIndex:1] locationInView:self];
        initialDistance = [self getDistance:touch1 toPoint:touch2];
        NSLog(@"initialDistance:%f",initialDistance);
    }
    [self setNeedsDisplay]; // 強制更新畫面: invoke -> drawRect
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
   
    NSArray *allTouches = [touches allObjects];
    int count = [allTouches count];
    if (count > 0)
        touch1 = [[allTouches objectAtIndex:0] locationInView:self];
    if (count > 1)
    {
        touch2 = [[allTouches objectAtIndex:1] locationInView:self];
        unitDistance = [self getDistance:touch1 toPoint:touch2];
        NSLog(@"unitDistance:%f",unitDistance);
    }
    [self setNeedsDisplay]; // 強制更新畫面: invoke -> drawRect
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {

    if (initialDistance > unitDistance) {
        // 縮小
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"multiTouch" message:@"Your touch is close to eachother" delegate:nil cancelButtonTitle:@"Yep, I did." otherButtonTitles:nil];
 
        [alert show];
        [alert release];   
    }
    else if (initialDistance < unitDistance){
        // 放大
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"multiTouch" message:@"Your touch is distant from eachother" delegate:nil cancelButtonTitle:@"Yep, I did." otherButtonTitles:nil];
 
        [alert show];
        [alert release];
    }
}

// 二點距離: 平方相加, 開根號
- (double)getDistance:(CGPoint)fromPoint toPoint:(CGPoint)otherPoint
{
    double deltaX = otherPoint.x - fromPoint.x;
    double deltaY = otherPoint.y - fromPoint.y;
    return sqrt(pow(deltaX, 2) + pow(deltaY, 2));
}

// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
    // Drawing code
    //@add Line
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetLineWidth(context, 2);
    CGContextSetStrokeColorWithColor(context, [UIColor blueColor].CGColor);
    CGContextMoveToPoint(context,touch1.x,touch1.y);
    CGContextAddLineToPoint(context,touch2.x,touch2.y);
    CGContextStrokePath(context);
}

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

@end