179在屏幕中绘制一个三角形

1 #import <UIKit/UIKit.h>
2 
3 @interface ViewController : UIViewController
4 @end

 1 #import "ViewController.h"
 2 #import "KMTriangleView.h"
 3 
 4 @interface ViewController ()
 5 - (void)layoutUI;
 6 @end
 7 
 8 @implementation ViewController
 9 
10 - (void)viewDidLoad {
11     [super viewDidLoad];
12     
13     [self layoutUI];
14 }
15 
16 - (void)didReceiveMemoryWarning {
17     [super didReceiveMemoryWarning];
18     // Dispose of any resources that can be recreated.
19 }
20 
21 - (void)layoutUI {
22     KMTriangleView *triangleView = [[KMTriangleView alloc] initWithFrame:self.view.frame];
23     self.view = triangleView;
24 }
25 
26 @end

1 #import <UIKit/UIKit.h>
2 
3 @interface KMTriangleView : UIView
4 @property CGPoint firstPoint;
5 @property CGPoint secondPoint;
6 @property CGPoint thirdPoint;
7 @property NSMutableArray *mArrPoint;
8 
9 @end

 1 #import "KMTriangleView.h"
 2 
 3 @implementation KMTriangleView
 4 #define kPointCount 3
 5 
 6 - (id)initWithFrame:(CGRect)frame {
 7     if (self = [super initWithFrame:frame]) {
 8         self.backgroundColor = [UIColor whiteColor];
 9         UILabel *lblMsg = [[UILabel alloc] initWithFrame:CGRectMake(20, 20, self.frame.size.width, 40)];
10         lblMsg.text = @"任意点击屏幕内的3点以确定一个三角形";
11         [self addSubview:lblMsg];
12         
13         _mArrPoint = [[NSMutableArray alloc] initWithCapacity:kPointCount];
14     }
15     return self;
16 }
17 
18 - (void)drawRect:(CGRect)rect {
19     CGContextRef contextRef = UIGraphicsGetCurrentContext(); //获取绘制上下文对象实例
20     CGContextSetRGBStrokeColor(contextRef, 0.5, 0.5, 0.5, 1.0); //设置笔画颜色
21     CGContextSetLineWidth(contextRef, 2.0); //设置线条粗细大小
22     CGPoint points[] = { _firstPoint, _secondPoint, _thirdPoint, _firstPoint };
23     CGContextAddLines(contextRef, points, kPointCount+1); //设置线条的连接端点
24     CGContextStrokePath(contextRef); //沿着要求的路径，开始绘制
25 }
26 - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
27     UITouch *touch = [touches anyObject];
28     CGPoint touchPoint = [touch locationInView:self];
29     [_mArrPoint addObject:[NSValue valueWithCGPoint:touchPoint]];
30     
31     if (_mArrPoint.count > 3) {
32         [_mArrPoint removeObjectAtIndex:0];
33     }
34     if (_mArrPoint.count == 3) {
35         _firstPoint = [_mArrPoint[0] CGPointValue];
36         _secondPoint = [_mArrPoint[1] CGPointValue];
37         _thirdPoint = [_mArrPoint[2] CGPointValue];
38     }
39     [self setNeedsDisplay]; //设置触发drawRect方法重新绘制内容；这句很关键，如不使用就不会触发drawRect方法
40 }
41 
42 @end