iOS：練習題中如何用技術去實現一個連線題

一、介紹

本人做的app涉及的是教育行業，所以關于練習題的開發肯定是家常便飯。例如，選擇題、填空題、連線題、判斷題等，每一種題型都需要技術去實現，沒啥多大難度，這里呢，就給出實現連線題的核心代碼吧。過了年后，好久沒寫筆記了，今天就簡單開始吧~~~

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二、思想

采用上下文在畫圖的方法，首先確定起點和終點的坐標，然后通過兩點畫一條直線。

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三、代碼

(1)常量定義

lianXianHeader.h

//
//  LianXianHeader.h
//  LianxianDemo
//
//  Created by 夏遠全 on 2018/2/9.
//  Copyright ? 2018年 beijing. All rights reserved.
//

#ifndef LianXianHeader_h
#define LianXianHeader_hstatic CGFloat const BWidth   = 60;  //按鈕的寬度
static CGFloat const BHeight  = 40;  //按鈕的高度
static CGFloat const margin   = 40;  //按鈕與屏幕的左邊距、右邊距
static CGFloat const Lpadding = 20;  //左邊按鈕上下間距
static CGFloat const Rpadding = 40;  //右邊按鈕上下間距static NSString* const kBeginPositionNotification = @"kBeginPositionNotification";
static NSString* const kEndPositionNotification   = @"kEndPositionNotification";
static NSString* const kClearAllLineNotification  = @"kClearAllLineNotification";
static NSString* const kFreshDrawLineNotification = @"kFreshDrawLineNotification";#endif /* LianXianHeader_h */
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(2)連線模型

lianXianModel.h

//
//  LianXianModel.h
//  LianxianDemo
//
//  Created by 夏遠全 on 2018/2/8.
//  Copyright ? 2018年 beijing. All rights reserved.
//

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>@interface LianXianModel : NSObject
@property (nonatomic, strong) NSArray  *questions;
@property (nonatomic, strong) NSArray  *options;
@property (nonatomic, strong) NSArray  *relationships;
@end
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lianXianModel.m

//
//  LianXianModel.m
//  LianxianDemo
//
//  Created by 夏遠全 on 2018/2/8.
//  Copyright ? 2018年 beijing. All rights reserved.
//

#import "LianXianModel.h"@implementation LianXianModel@end
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(3)繪制連線

lianXianDrawView.h

//
//  LianxianDrawView.h
//  Ubbsz
//
//  Created by 夏遠全 on 2018/2/9.
//  Copyright ? 2018年 beijing. All rights reserved.
//
//

#import <UIKit/UIKit.h>@interface LianxianDrawView : UIView@end
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lianXianDrawView.m

//
//  LianxianDrawView.m
//  Ubbsz
//
//  Created by 夏遠全 on 2018/2/9.
//  Copyright ? 2018年 beijing. All rights reserved.
//
#import "LianxianDrawView.h"
#import "LianXianHeader.h"@interface LianxianDrawView()
{NSMutableArray *pointArray; //存儲當前的一對坐標，起始點和終止點NSMutableArray *lineArray;  //存儲全部的連線，每一條連線就是一對坐標NSString       *startPointString; //當前起點NSString       *endPointString;   //當前起點
    CGFloat        lineWidth;
}@end@implementation LianxianDrawView//對進行重寫，以便在視圖初始化的時候創建并設置自定義的Context
- (id)initWithFrame:(CGRect)frame
{if (self = [super initWithFrame:frame]) {[self setupDefaultValue];[self regesterNotification];}return self;
}//初始值
- (void)setupDefaultValue{pointArray=[[NSMutableArray alloc]init];lineArray=[[NSMutableArray alloc]init];lineWidth = 2.0f;self.backgroundColor = [UIColor colorWithRed:238/255.0 green:243/255.0  blue:248/255.0  alpha:1];
}//注冊通知
- (void)regesterNotification{[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(toucheBegin:) name:kBeginPositionNotification object:nil];[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(toucheEnd:) name:kEndPositionNotification object:nil];[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(clearLine:) name:kClearAllLineNotification object:nil];[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(freshNeedsDisplay:) name:kFreshDrawLineNotification object:nil];
}//對drawRect進行重寫
- (void)drawRect:(CGRect)rect
{//獲取當前上下文，CGContextRef context=UIGraphicsGetCurrentContext();CGContextBeginPath(context);CGContextSetLineWidth(context, lineWidth);//線條拐角樣式，設置為平滑
    CGContextSetLineJoin(context,kCGLineJoinRound);//線條開始樣式，設置為平滑
    CGContextSetLineCap(context, kCGLineCapRound);//查看lineArray數組里是否有線條，有就將之前畫的重繪，沒有只畫當前線條if ([lineArray count] > 0) {for (int i=0; i < [lineArray count]; i++) {NSArray * array=[NSArray arrayWithArray:[lineArray objectAtIndex:i]];if ([array count] > 0 && [array count]%2 == 0) {CGContextBeginPath(context);CGPoint myStartPoint = CGPointFromString(array.firstObject);CGContextMoveToPoint(context, myStartPoint.x, myStartPoint.y);CGPoint myEndPoint = CGPointFromString(array.lastObject);CGContextAddLineToPoint(context, myEndPoint.x,myEndPoint.y);CGContextSetStrokeColorWithColor(context,[[UIColor grayColor] CGColor]);CGContextSetLineWidth(context, lineWidth);CGContextStrokePath(context);}}}
}//接收起點按鈕點擊通知事件
- (void)toucheBegin:(NSNotification *)notification{CGRect beginFrame = [notification.object CGRectValue];CGPoint startPoint = CGPointMake(CGRectGetMaxX(beginFrame), CGRectGetMidY(beginFrame));startPointString = NSStringFromCGPoint(startPoint);if (pointArray.count==0) {[pointArray addObject:startPointString];}else{[pointArray replaceObjectAtIndex:0 withObject:startPointString];}
}//接收終點按鈕點擊通知事件
- (void)toucheEnd:(NSNotification *)notification{CGRect endFrame = [notification.object CGRectValue];CGPoint endPoint = CGPointMake(CGRectGetMinX(endFrame), CGRectGetMidY(endFrame));endPointString = NSStringFromCGPoint(endPoint);if (pointArray.count==2) {[pointArray replaceObjectAtIndex:1 withObject:endPointString];}else{[pointArray addObject:endPointString];}[self clearSomeHistoryLineView];[self addLA];[self setNeedsDisplay];
}//接收清除按鈕點擊通知事件
- (void)clearLine:(NSNotification *)notification{[self clearAllLineView];
}//接收重新繪制通知事件
- (void)freshNeedsDisplay:(NSNotification *)notification{NSArray *relationslineArray = notification.object;lineArray = [NSMutableArray arrayWithArray:relationslineArray];[self setNeedsDisplay];
}//添加連線
-(void)addLA{NSArray *array = [NSArray arrayWithArray:pointArray];[lineArray addObject:array];[pointArray removeAllObjects];
}//清除所有的連線
- (void)clearAllLineView
{[pointArray removeAllObjects];[lineArray removeAllObjects];[self setNeedsDisplay];
}//移除歷史交叉重復的連線
- (void)clearSomeHistoryLineView{NSMutableArray *arrayM = [NSMutableArray array];for (int i=0; i < [lineArray count]; i++) {NSArray *array = [NSArray arrayWithArray:[lineArray objectAtIndex:i]];if ([array count] > 0) {NSString *hisBePointString = array.firstObject;NSString *hisEnPointString = array.lastObject;if ([startPointString isEqualToString:hisBePointString] || [endPointString isEqualToString:hisEnPointString]) {[arrayM addObject:array];}}}[lineArray removeObjectsInArray:arrayM];
}//移除通知
-(void)dealloc{[[NSNotificationCenter defaultCenter] removeObserver:self];
}@end
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(4)計算尺寸

LianXianFrameUitity.h

//
//  LianXianSizeUitity.h
//  LianxianDemo
//
//  Created by 夏遠全 on 2018/2/9.
//  Copyright ? 2018年 beijing. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "LianXianModel.h"@interface LianXianFrameUitity : NSObject+ (CGRect)calculateSizeWithModel:(LianXianModel *)lianxianModel;@end
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LianXianFrameUitity.m?

//
//  LianXianSizeUitity.m
//  LianxianDemo
//
//  Created by 夏遠全 on 2018/2/9.
//  Copyright ? 2018年 beijing. All rights reserved.
//

#import "LianXianFrameUitity.h"
#import "LianXianHeader.h"@implementation LianXianFrameUitity+ (CGRect)calculateSizeWithModel:(LianXianModel *)lianxianModel{NSUInteger questionsCount = lianxianModel.questions.count;NSUInteger optionsCount = lianxianModel.options.count;CGFloat LHeight = questionsCount * (BHeight+Lpadding) + Lpadding;CGFloat RHeight = optionsCount * (BHeight+Rpadding) + Rpadding;CGFloat kWidth  = [UIScreen mainScreen].bounds.size.width; //默認寬度為屏幕的寬return CGRectMake(0, 0, kWidth, MAX(LHeight, RHeight));
}@end
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(5)創建組件

LianXianComponentsView.h

//
//  LianXianComponentsView.h
//  LianxianDemo
//
//  Created by 夏遠全 on 2018/2/6.
//  Copyright ? 2018年 beijing. All rights reserved.
//

#import <UIKit/UIKit.h>
#import "LianXianModel.h"@interface LianXianComponentsView : UIView
@property (nonatomic, strong) LianXianModel *lianxianModel;
@end
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LianXianComponentsView.m

//
//  LianXianComponentsView.m
//  LianxianDemo
//
//  Created by 夏遠全 on 2018/2/6.
//  Copyright ? 2018年 beijing. All rights reserved.
//

#import "LianXianComponentsView.h"
#import "LianxianDrawView.h"
#import "LianXianHeader.h"@interface LianXianComponentsView() {NSMutableArray *_leftBtns;NSMutableArray *_rightBtns;UIButton       *currentLeftBtn;CGFloat        borderWith;
}@end@implementation LianXianComponentsView//對進行重寫，以便在視圖初始化的時候創建并設置自定義的Context
- (id)initWithFrame:(CGRect)frame
{if (self = [super initWithFrame:frame]) {[self setupDefalutValue];}return self;
}//設置默認值
- (void)setupDefalutValue{self.backgroundColor = [UIColor clearColor];borderWith = 2.5;[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(restStatus:) name:kClearAllLineNotification object:nil];
}//接收模型
-(void)setLianxianModel:(LianXianModel *)lianxianModel{_lianxianModel = lianxianModel;[self setupLianXianUnit];if (lianxianModel && lianxianModel.relationships.count>0) {[self showLianXianResult];}else{[self listClickLeftButton];}
}//繪制連線選項
- (void)setupLianXianUnit{_leftBtns  = [[NSMutableArray array] init];_rightBtns = [[NSMutableArray array] init];CGFloat kWidth   = self.frame.size.width;CGFloat kHeight  = self.frame.size.height;CGFloat LY = (kHeight-(BHeight+Lpadding)*(self.lianxianModel.questions.count-1) - BHeight)/2;CGFloat RY = (kHeight-(BHeight+Rpadding)*(self.lianxianModel.options.count-1) - BHeight)/2;for (NSInteger i =0; i < self.lianxianModel.questions.count; i++) {UIButton *btn = [self createButtonWithFrame:CGRectMake(margin, LY+(BHeight+Lpadding)*i, BWidth, BHeight) title:[NSString stringWithFormat:@"%@",self.lianxianModel.questions[i]] tag:i];[self addSubview:btn];[_leftBtns addObject:btn];}for (NSInteger i =0; i< self.lianxianModel.options.count; i++) {UIButton *btn = [self createButtonWithFrame:CGRectMake(kWidth-margin-BWidth, RY+(BHeight+Rpadding)*i, BWidth, BHeight) title:[NSString stringWithFormat:@"%@",self.lianxianModel.options[i]] tag:i];[self addSubview:btn];[_rightBtns addObject:btn];}
}-(UIButton *)createButtonWithFrame:(CGRect)frame title:(NSString *)title tag:(NSInteger)tag{UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];btn.frame = frame;btn.layer.cornerRadius = 5.0;btn.layer.borderColor = [UIColor lightGrayColor].CGColor;btn.layer.borderWidth = borderWith;btn.layer.masksToBounds = YES;btn.tag = tag;[btn setBackgroundImage:[self imageWithColor:[UIColor whiteColor]] forState:UIControlStateNormal];[btn setBackgroundImage:[self imageWithColor:[UIColor colorWithRed:138/255.0 green:193/255.0 blue:211/255.0 alpha:1]] forState:UIControlStateHighlighted];[btn setBackgroundImage:[self imageWithColor:[UIColor colorWithRed:138/255.0 green:193/255.0 blue:211/255.0 alpha:1]] forState:UIControlStateSelected];[btn addTarget:self action:@selector(tapBtn:) forControlEvents:UIControlEventTouchUpInside];[btn setTitle:title forState:UIControlStateNormal];[btn setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];return btn;
}- (UIImage *)imageWithColor:(UIColor *)color
{CGFloat imageW = 20;CGFloat imageH = 20;UIGraphicsBeginImageContextWithOptions(CGSizeMake(imageW, imageH), NO, 0.0);[color set];UIRectFill(CGRectMake(0, 0, imageW, imageH));UIImage *image = UIGraphicsGetImageFromCurrentImageContext();UIGraphicsEndImageContext();return image;
}-(void)tapBtn:(UIButton *)btn{//判斷左邊按鈕是否處于選擇狀態，只有首先左邊處于此狀態下，右邊的按鈕點擊才能進行連線操作（當前僅支持單向連線）if ([_rightBtns containsObject:btn]) {BOOL isLeftBtnSelected = NO;for (UIButton *leftBtn in _leftBtns) {if (leftBtn.selected) {isLeftBtnSelected = YES;break;}}if (!isLeftBtnSelected) {return;}}if ([_leftBtns containsObject:btn]) {//設置連線起點currentLeftBtn.selected = NO;currentLeftBtn.layer.borderColor = [UIColor lightGrayColor].CGColor;btn.selected = YES;currentLeftBtn = btn;currentLeftBtn.layer.borderColor = [UIColor colorWithRed:32/255.0 green:199/255.0 blue:251/255.0 alpha:1].CGColor;//設置終點按鈕可以選中狀態for (UIButton *rightBtn in _rightBtns) {rightBtn.layer.borderColor = [UIColor colorWithRed:32/255.0 green:199/255.0 blue:251/255.0 alpha:1].CGColor;}//發送起點通知[[NSNotificationCenter defaultCenter] postNotificationName:kBeginPositionNotification object:[NSValue valueWithCGRect:btn.frame]];}if ([_rightBtns containsObject:btn]) {for (UIButton *leftBtn in _leftBtns) {if (leftBtn.selected) {//發送終點通知[[NSNotificationCenter defaultCenter] postNotificationName:kEndPositionNotification object:[NSValue valueWithCGRect:btn.frame]];//自動設置起始選擇按鈕
                [self listClickLeftButton];break;}}}
}//自動設置起始選擇按鈕
- (void)listClickLeftButton{if (!currentLeftBtn) {[self tapBtn:_leftBtns[0]];return;}NSUInteger tag = currentLeftBtn.tag;if (tag < _leftBtns.count-1) {  //自動下移[self tapBtn:_leftBtns[tag+1]];}else{[self tapBtn:_leftBtns[0]]; //重新開始
    }
}//繪制默認已經連線的選項，此處僅僅做成績預覽使用，不能再編輯
- (void)showLianXianResult{for (UIButton *leftBtn in _leftBtns) {leftBtn.layer.borderColor = [UIColor lightGrayColor].CGColor;leftBtn.selected = leftBtn.userInteractionEnabled = NO;}for (UIButton *rightBtn in _rightBtns) {rightBtn.layer.borderColor = [UIColor lightGrayColor].CGColor;rightBtn.selected = rightBtn.userInteractionEnabled = NO;}if (self.lianxianModel.relationships.count == 0) {return;}NSMutableArray *relationslineArray = [NSMutableArray array];for (NSString *result in self.lianxianModel.relationships) {NSString *question = [[result componentsSeparatedByString:@"-"] firstObject];NSString *option   = [[result componentsSeparatedByString:@"-"] lastObject];NSMutableArray *pointArray = [NSMutableArray array];for (UIButton *leftBtn in _leftBtns) {if ([leftBtn.currentTitle isEqualToString:question]) {CGPoint startPoint = CGPointMake(CGRectGetMaxX(leftBtn.frame), CGRectGetMidY(leftBtn.frame));NSString *startPointString = NSStringFromCGPoint(startPoint);[pointArray addObject:startPointString];break;}}for (UIButton *rightBtn in _rightBtns) {if ([rightBtn.currentTitle isEqualToString:option]) {CGPoint endPoint = CGPointMake(CGRectGetMinX(rightBtn.frame), CGRectGetMidY(rightBtn.frame));NSString *endPointString = NSStringFromCGPoint(endPoint);[pointArray addObject:endPointString];break;}}[relationslineArray addObject:pointArray];}if (relationslineArray.count > 0) {[[NSNotificationCenter defaultCenter] postNotificationName:kFreshDrawLineNotification object:relationslineArray];}
}//重置初始狀態
- (void)restStatus:(NSNotification *)notification{for (UIButton *leftBtn in _leftBtns) {leftBtn.selected = NO;leftBtn.layer.borderColor = [UIColor lightGrayColor].CGColor;[self tapBtn:_leftBtns[0]]; //重新開始
    }
}@end
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(6)連線容器

LianXianContainerView.h

//
//  LianXianContainerView.h
//  LianxianDemo
//
//  Created by 夏遠全 on 2018/2/8.
//  Copyright ? 2018年 beijing. All rights reserved.
//

#import <UIKit/UIKit.h>
#import "LianXianComponentsView.h"
#import "LianxianDrawView.h"@interface LianXianContainerView : UIView
@property (nonatomic, strong) LianXianComponentsView *componentsView;
@property (nonatomic, strong) LianxianDrawView *lianXianView;
@end
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LianXianContainerView.m

//
//  LianXianContainerView.m
//  LianxianDemo
//
//  Created by 夏遠全 on 2018/2/8.
//  Copyright ? 2018年 beijing. All rights reserved.
//

#import "LianXianContainerView.h"
#import "LianXianComponentsView.h"
#import "LianxianDrawView.h"
#import "LianXianModel.h"@implementation LianXianContainerView- (id)initWithFrame:(CGRect)frame
{if (self = [super initWithFrame:frame]) {[self setup];}return self;
}- (void)setup{self.lianXianView = [[LianxianDrawView alloc]initWithFrame:self.bounds];self.componentsView = [[LianXianComponentsView alloc] initWithFrame:self.bounds];[self addSubview:self.lianXianView];[self addSubview:self.componentsView];
}@end
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(7)顯示連線

//
//  ViewController.m
//  LianxianDemo
//
//  Created by tianjing on 15/3/31.
//  Copyright ? 2015年 tianjing. All rights reserved.
//

#import "ViewController.h"#import "LianXianContainerView.h"
#import "LianXianFrameUitity.h"
#import "LianXianModel.h"
#import "LianXianHeader.h"@interface ViewController ()@end@implementation ViewController- (void)viewDidLoad {[super viewDidLoad];UIButton *clearBtn = [[UIButton alloc] initWithFrame:CGRectMake(50, 50, 100, 40)];clearBtn.backgroundColor = [UIColor greenColor];[clearBtn setTitle:@"重置" forState:UIControlStateNormal];[clearBtn setTitleColor:[UIColor redColor] forState:UIControlStateNormal];[clearBtn addTarget:self action:@selector(clear:) forControlEvents:UIControlEventTouchUpInside];//創建模型LianXianModel *lianxianModel = [[LianXianModel alloc] init];lianxianModel.questions = @[@"天",@"好",@"人"]; /// 左邊選項lianxianModel.options = @[@"夏",@"世",@"鋒"];   /// 右邊選項//lianxianModel.relationships = @[@"天-世",@"好-夏",@"人-鋒"]; /// 連線關系，如果不為空，就只顯示，不能編輯//clearBtn.hidden = (lianxianModel.relationships.count>0);//連線視圖CGRect frame = [LianXianFrameUitity calculateSizeWithModel:lianxianModel];LianXianContainerView *containerView = [[LianXianContainerView alloc] initWithFrame:frame];containerView.center = self.view.center;containerView.componentsView.lianxianModel = lianxianModel;[self.view addSubview:containerView];[self.view addSubview:clearBtn];
}- (void)clear:(UIButton *)sender{[[NSNotificationCenter defaultCenter] postNotificationName:kClearAllLineNotification object:nil];
}@end
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四、效果

提示：

左邊按鈕每次只有一個處于可連狀態，而且每一次連接完會循環自動下移。

右邊所有按鈕始終處于可連狀態。

同一個按鈕再一次連接新的連線后，之前舊的跟其相關的連線都會被取消。?

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五、采坑

如果練習題的界面是放在cell中的，因為復用的問題，在發送起點和終點的通知時，要對通知做唯一標識處理。

如果不這么做，可能會出現的bug是：上一道做過的連線題的連線會出現在下一道還沒有做過的連線題上。

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轉載于:https://www.cnblogs.com/XYQ-208910/p/8532379.html

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