1 //
  2 //  TouchDrawView.m
  3 //  CaplessCoderPaint
  4 //
  5 //  Created by backslash112 on 14/10/29.
  6 //  Copyright (c) 2014年 backslash112. All rights reserved.
  7 //
  8
  9 #import "TouchDrawView.h"
 10 #import "Common.h"
 11
 12 @implementation TouchDrawView
 13 {
 14 }
 15 @synthesize currentLine;
 16 @synthesize linesCompleted;
 17 @synthesize drawColor;
 18
 19 - (id)initWithCoder:(NSCoder *)c
 20 {
 21     self = [super initWithCoder:c];
 22     if (self) {
 23         linesCompleted = [[NSMutableArray alloc] init];
 24         [self setMultipleTouchEnabled:YES];
 25
 26         drawColor = [UIColor blackColor];
 27         [self becomeFirstResponder];
 28     }
 29     return self;
 30 }
 31
 32 //  It is a method of UIView called every time the screen needs a redisplay or refresh.
 33 - (void)drawRect:(CGRect)rect
 34 {
 35     CGContextRef context = UIGraphicsGetCurrentContext();
 36     CGContextSetLineWidth(context, 5.0);
 37     CGContextSetLineCap(context, kCGLineCapRound);
 38     [drawColor set];
 39     for (Line *line in linesCompleted) {
 40         [[line color] set];
 41         CGContextMoveToPoint(context, [line begin].x, [line begin].y);
 42         CGContextAddLineToPoint(context, [line end].x, [line end].y);
 43         CGContextStrokePath(context);
 44     }
 45 }
 46
 47 - (void)undo
 48 {
 49     if ([self.undoManager canUndo]) {
 50         [self.undoManager undo];
 51         [self setNeedsDisplay];
 52     }
 53 }
 54
 55 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
 56 {
 57     [self.undoManager beginUndoGrouping];
 58     for (UITouch *t in touches) {
 59         // Create a line for the value
 60         CGPoint loc = [t locationInView:self];
 61         Line *newLine = [[Line alloc] init];
 62         [newLine setBegin:loc];
 63         [newLine setEnd:loc];
 64         [newLine setColor:drawColor];
 65         currentLine = newLine;
 66     }
 67 }
 68
 69 - (void)addLine:(Line*)line
 70 {
 71     [[self.undoManager prepareWithInvocationTarget:self] removeLine:line];
 72     [linesCompleted addObject:line];
 73 }
 74
 75 - (void)removeLine:(Line*)line
 76 {
 77     if ([linesCompleted containsObject:line])
 78         [linesCompleted removeObject:line];
 79 }
 80
 81 - (void)removeLineByEndPoint:(CGPoint)point
 82 {
 83     NSPredicate *predicate = [NSPredicate predicateWithBlock:^BOOL(id evaluatedObject, NSDictionary *bindings) {
 84         Line *evaluatedLine = (Line*)evaluatedObject;
 85         return evaluatedLine.end.x == point.x &&
 86         evaluatedLine.end.y == point.y;
 87     }];
 88     NSArray *result = [linesCompleted filteredArrayUsingPredicate:predicate];
 89     if (result && result.count > 0) {
 90         [linesCompleted removeObject:result[0]];
 91     }
 92 }
 93
 94 - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
 95 {
 96     for (UITouch *t in touches) {
 97         [currentLine setColor:drawColor];
 98         CGPoint loc = [t locationInView:self];
 99         [currentLine setEnd:loc];
100
101         if (currentLine) {
102             [self addLine:currentLine];
103         }
104         Line *newLine = [[Line alloc] init];
105         [newLine setBegin:loc];
106         [newLine setEnd:loc];
107         [newLine setColor:drawColor];
108         currentLine = newLine;
109     }
110     [self setNeedsDisplay];
111 }
112
113 - (void)endTouches:(NSSet *)touches
114 {
115     [self setNeedsDisplay];
116 }
117
118 - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
119 {
120     [self endTouches:touches];
121     [self.undoManager endUndoGrouping];
122 }
123
124 - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
125 {
126     [self endTouches:touches];
127 }
128
129 - (BOOL)canBecomeFirstResponder
130 {
131     return YES;
132 }
133
134 - (void)didMoveToWindow
135 {
136     [self becomeFirstResponder];
137 }
138
139 - (id)initWithFrame:(CGRect)frame
140 {
141     self = [super initWithFrame:frame];
142     if (self) {
143         // Initialization code
144     }
145     return self;
146 }
147
148 @end

还需要讲解下的是，当每次touchMove方法中，往array中添加入了新的Line，要想在画布中显示出来，需要刷新下页面，调用[self setNeedsDisplay]方法即可。

基本的主要逻辑就是这样，我们还差什么？当然是UI！

第六步，创建一个 .xib文件，叫做TouchDrawViewController.xib。在右边的工具箱中添加一个View，再往View中加入多个子View，加多少个你随意，因为这几个子View是用来作为颜色选择器的，多几个少几个无所谓。然后设置这几个子View的Class为 ColorPiker，接着设置他们的背景颜色，颜色值你随意，因为会把被选中的颜色选择器的背景颜色直接作为参数传出来。