分享一个iOS下实现基本绘画板功能的简单方法

代码部分
touchview.h

#import <uikit/uikit.h> 
 
@interface touchview : uiview 
{ 
    nsmutablearray *points; 
    nsarray *points_all; 
    cgcontextref context; 
    uicolor *paint_clr; 
} 
@property (strong,nonatomic) nsmutablearray *points; 
@property (strong,nonatomic) nsarray *points_all; 
@property (strong,nonatomic) uicolor *paint_clr; 
 
@end 

touchview.m

#import "touchview.h" 
 
@implementation touchview 
@synthesize points, points_all, paint_clr; 
 
- (id)initwithframe:(cgrect)frame 
{ 
    self = [super initwithframe:frame]; 
    if (self) { 
        // initialization code 
        paint_clr = [uicolor greencolor]; 
    } 
    return self; 
} 
 
// only override drawrect: if you perform custom drawing. 
// an empty implementation adversely affects performance during animation. 
- (void)drawrect:(cgrect)rect 
{ 
    // drawing code 
    if ((!self.points) || (self.points.count < 2)) { 
        return; 
    } 
       
    context = uigraphicsgetcurrentcontext(); 
    //设置画笔粗细  
    cgcontextsetlinewidth(context, 5.0f); 
    //设置画笔颜色 
    //[[uicolor bluecolor]set ]; 
    // [paint_clr set]; 
    //cgcontextsetstrokecolorwithcolor(context, [[uicolor bluecolor]cgcolor]); 
    cgcontextsetstrokecolorwithcolor(context, [paint_clr cgcolor]); 
     
    //画以前的轨迹 
    for (int j = 0 ; j < [self.points_all count]; j++) { 
        nsmutablearray *points_tmp = [points_all objectatindex:j]; 
             
            for (int i = 0;i < [points_tmp count]-1;i++) 
            { 
                cgpoint point1 = [[points_tmp objectatindex:i] cgpointvalue]; 
                cgpoint point2 = [[points_tmp objectatindex:(i+1)] cgpointvalue]; 
                cgcontextmovetopoint(context, point1.x, point1.y); 
                cgcontextaddlinetopoint(context, point2.x, point2.y); 
                cgcontextstrokepath(context); 
            } 
        } 
     
    //画这次 
    for (int i=0; i < [self.points count]-1; i++) { 
        cgpoint point1 = [[self.points objectatindex:i] cgpointvalue]; 
        cgpoint point2 = [[self.points objectatindex:(i+1)] cgpointvalue]; 
        cgcontextmovetopoint(context, point1.x, point1.y); 
        cgcontextaddlinetopoint(context, point2.x, point2.y); 
        cgcontextstrokepath(context); 
    }     
} 
 
//不支持多点触摸 
- (bool) ismultipletouchenabled 
{ 
    return no; 
} 
 
//创建一个array，并且记录初始ponit 
- (void) touchesbegan:(nsset *) touches withevent:(uievent *) event 
{ 
    self.points = [nsmutablearray array]; 
    cgpoint pt = [[touches anyobject] locationinview:self]; 
    [self.points addobject:[nsvalue valuewithcgpoint:pt]]; 
} 
 
//移动过程中记录这些points 
//调用setneedsdisplay，会触发drawrect方法的调用 
- (void) touchesmoved:(nsset *)touches withevent:(uievent *)event 
{ 
    cgpoint pt = [[touches anyobject] locationinview:self]; 
    [self.points addobject:[nsvalue valuewithcgpoint:pt]]; 
    [self setneedsdisplay]; 
} 
 
- (void) touchesended:(nsset *)touches withevent:(uievent *)event 
{ 
    nsmutablearray *points_tmp = [[nsmutablearray alloc] initwitharray:self.points]; 
    if (self.points_all == nil) { 
        self.points_all = [[nsarray alloc] initwithobjects:points_tmp, nil]; 
    }else { 
        self.points_all = [self.points_all arraybyaddingobject:points_tmp]; 
    } 
} 
@end 

viewcontroller.h

#import <uikit/uikit.h> 
 
@class touchview; 
@interface viewcontroller : uiviewcontroller 
{ 
    touchview *tv; 
} 
@end 

viewcontroller.m

#import "viewcontroller.h" 
#import "touchview.h" 
 
@interface viewcontroller () 
 
@end 
 
@implementation viewcontroller 
 
- (void)viewdidload 
{ 
    [super viewdidload]; 
    // do any additional setup after loading the view, typically from a nib. 
    self.view.userinteractionenabled = yes; 
     
  // touchview *tv = [[touchview alloc]initwithframe:cgrectmake(0.0f, 0.0f, 260.0f, 260.0f)]; 
    tv = [[touchview alloc]initwithframe:self.view.frame]; 
    tv.backgroundcolor = [uicolor blackcolor]; 
     
    [self.view addsubview:tv]; 
     
    uisegmentedcontrol *seg = [[uisegmentedcontrol alloc] initwithitems:[@"white red blue green yellow" componentsseparatedbystring:@" "]]; 
    seg.segmentedcontrolstyle = uisegmentedcontrolsegmentcenter; 
    seg.tintcolor = [uicolor blackcolor];  
    seg.center = cgpointmake(self.view.center.x, (self.view.bounds.size.height - seg.bounds.size.height));  
    [self.view addsubview:seg]; 
     
    [seg addtarget:self action:@selector(colorchange:) forcontrolevents:uicontroleventvaluechanged]; 
} 
 
- (void)viewdidunload 
{ 
    [super viewdidunload]; 
    // release any retained subviews of the main view. 
} 
 
- (bool)shouldautorotatetointerfaceorientation:(uiinterfaceorientation)interfaceorientation 
{ 
    return (interfaceorientation != uiinterfaceorientationportraitupsidedown); 
} 
 
- (void) colorchange: (uisegmentedcontrol *) seg 
{ 
    switch ([seg selectedsegmentindex]) 
    { 
        case 0:  
            tv.paint_clr = [uicolor whitecolor]; 
            break; 
        case 1: 
            tv.paint_clr = [uicolor redcolor]; 
            break; 
        case 2: 
            tv.paint_clr = [uicolor bluecolor]; 
            break; 
        case 3: 
            tv.paint_clr = [uicolor greencolor]; 
            break; 
        case 4: 
            tv.paint_clr = [uicolor yellowcolor]; 
            break; 
        default: 
             
            break; 
    } 
} 
 
@end 

效果图