iphone 开发周记2 触摸事件处理与简单绘图。

iphone中由touchesBegan，touchesMoved，touchesEnded三个函数处理触摸事件。

分别代表开始触摸，移动，离开屏幕三个事件。

iphone中一般绘图在drawrect中进行。

下面是一段实现移动手指，当向不同方向移动时显示不同方向的箭头的代码。

#import "draw.h"

@implementation draw

- (id)initWithFrame:(CGRect)frame {

    if (self = [super initWithFrame:frame]) {

        // Initialization code

    }

    return self;

}

- (void)drawRect:(CGRect)rect {

    // Drawing code

    UIImage *image =[UIImage imageNamed:@"aa.gif"];

    [image drawAtPoint:CGPointMake(p.x-30, p.y-30)];

    if (move==LEFT) {

       

        UIImage *imagemove =[UIImage imageNamed:@"left.png"];

        [imagemove drawAtPoint:CGPointMake(50, 120) blendMode:kCGBlendModeNormal alpha:0.5f];

    }

   

    if (move==RIGHT) {

       

        UIImage *imagemove =[UIImage imageNamed:@"right.png"];

        [imagemove drawAtPoint:CGPointMake(50, 120) blendMode:kCGBlendModeNormal alpha:0.5f];   

    }

   

    if (move==UP) {

       

        UIImage *imagemove =[UIImage imageNamed:@"upp.png"];

        [imagemove drawAtPoint:CGPointMake(50, 120) blendMode:kCGBlendModeNormal alpha:0.5f];   

    }

   

    if (move==DOWN) {

       

        UIImage *imagemove =[UIImage imageNamed:@"down.png"];

        [imagemove drawAtPoint:CGPointMake(50, 120) blendMode:kCGBlendModeNormal alpha:0.5f];   

    }

}

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

    UITouch *touch = [touches anyObject];

    CGPoint location = [touch locationInView:self];

    p.x=location.x;   

    p.y=location.y;

    touchstart.x=p.x;

    touchstart.y=p.y;

    [self setNeedsDisplay];

   

}

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

    UITouch *touch = [touches anyObject];

    CGPoint location = [touch locationInView:self];

    p.x=location.x;

    p.y=location.y;

    [self setNeedsDisplay];

   

}

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

    CGPoint end;

    UITouch *touch = [touches anyObject];

    CGPoint location = [touch locationInView:self];

    end.x=location.x;   

    end.y=location.y;

    if (end.x-touchstart.x>10.0f&&end.y-touchstart.y<50.0f&&end.y-touchstart.y>-50.0f) {

        move=RIGHT;

    }

    if (end.x-touchstart.x<-10.0f&&end.y-touchstart.y<50.0f&&end.y-touchstart.y>-50.0f) {

        move=LEFT;

    }

    if (end.y-touchstart.y>10.0f&&end.x-touchstart.x<50.0f&&end.x-touchstart.x>-50.0f) {

        move=DOWN;

    }

    if (end.y-touchstart.y<-10.0f&&end.x-touchstart.x<50.0f&&end.x-touchstart.x>-50.0f) {

        move=UP;

    }

    [self setNeedsDisplay];

   

}

- (void)dealloc {

    [super dealloc];

}

@end

首先要建立一个基于uiview的名叫draw的类。

其中draw.h

 

#import <UIKit/UIKit.h>

#define LEFT 1

#define RIGHT 2

#define UP 3

#define DOWN 4

@interface draw : UIView {

    CGPoint p;

    CGPoint touchstart;

    int move;

}

@end

然后打开IB，将viewcontoller中的主视图命名为draw。

再加载自定义的图片（箭头）。

点击运行：

当我拖动小狗向右时出现了向右的箭头。