利用UIScrollView实现展示图片的无限滚动及自动滚动

1 //

2 // GXViewController.m

3 // 自动滚动及无线循环

4 //

5 // Created by 郭晓 on 14-3-7.

6 // Copyright (c) 2014年 郭晓. All rights reserved.

7 //

8

9 #import “GXViewController.h”

10

11 #define kCount 6 //图片总张数

12

13 static long step = 0; //记录时钟动画调用次数

14

15 @interface GXViewController ()

16 {

17 UIScrollView *_scrollView;

18 UIImageView *_currentImageView; //当前视图

19 UIImageView *_nextImageView; //下一个视图

20 UIImageView *_previousView; //上一个视图

21 CADisplayLink *_timer; //定时器

22

23 BOOL _isDraging; //当前是否正在拖拽

24 }

25

26 @end

27

28 @implementation GXViewController

29

30 - (void)viewDidLoad

31 {

32 [super viewDidLoad];

33

34 CGFloat width = self.view.bounds.size.width;

35 CGFloat height = self.view.bounds.size.height;

36

37 _scrollView = [[UIScrollView alloc] initWithFrame:self.view.bounds];

38 _scrollView.contentSize = CGSizeMake(3 * width, 0);

39 _scrollView.showsHorizontalScrollIndicator = NO;

40 _scrollView.pagingEnabled = YES;

41 _scrollView.delegate = self;

42 _scrollView.bounces = NO;

43 _scrollView.contentOffset = CGPointMake(width, 0);

44 [self.view addSubview:_scrollView];

45

46 //初始化当前视图

47 _currentImageView = [[UIImageView alloc] init];

48 _currentImageView.image = [UIImage imageNamed:@”01.jpg”];

49 _currentImageView.frame = CGRectMake(width, 0, width, height);

50 _currentImageView.contentMode = UIViewContentModeScaleAspectFill;

51 [_scrollView addSubview:_currentImageView];

52

53 //初始化下一个视图

54 _nextImageView = [[UIImageView alloc] init];

55 _nextImageView.image = [UIImage imageNamed:@”02.jpg”];

56 _nextImageView.frame = CGRectMake(width * 2, 0, width, height);

57 _nextImageView.contentMode = UIViewContentModeScaleAspectFill;

58 [_scrollView addSubview:_nextImageView];

59

60 //初始化上一个视图

61 _previousView = [[UIImageView alloc] init];

62 _previousView.image = [UIImage imageNamed:@”06.jpg”];

63 _previousView.frame = CGRectMake(0, 0, width, height);

64 _previousView.contentMode = UIViewContentModeScaleAspectFill;

65 [_scrollView addSubview:_previousView];

66

67 // 时钟动画

68 _timer = [CADisplayLink displayLinkWithTarget:self selector:@selector(update:)];

69 [_timer addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];

70

71 }

72

73 #pragma mark 时钟动画调用方法

74 - (void)update:(CADisplayLink *)timer

75 {

76 step++;

77

78 if ((step % 120 != 0) || _isDraging) {

79 return;

80 }

81

82 CGPoint offset = _scrollView.contentOffset;

83

84 offset.x += 320;

85 if (offset.x > 640) {

86 offset.x = 320;

87 }

88

89 [_scrollView setContentOffset:offset animated:YES];

90 }

91

92 #pragma mark - 代理方法

93 #pragma mark 准备开始拖动

94 - (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView

95 {

96 _isDraging = YES;

97 }

98

99 #pragma mark 视图停止滚动

100 - (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView

101 {

102 _isDraging = NO;

103 step = 0;

104 }

105

106 #pragma mark 已经拖动

107 - (void)scrollViewDidScroll:(UIScrollView *)scrollView{

108

109 static int i = 1;//当前展示的是第几张图片

110

111 float offset = scrollView.contentOffset.x;

112 if (_nextImageView.image == nil || _previousView.image == nil) {

113

114 //加载下一个视图

115 NSString *imageName1 = [NSString stringWithFormat:@”0%d.jpg”, i == kCount ? 1 : i + 1];

116 _nextImageView.image = [UIImage imageNamed:imageName1];

117

118 //加载上一个视图

119 NSString *imageName2 = [NSString stringWithFormat:@”0%d.jpg”, i == 1 ? kCount : i - 1];

120 _previousView.image = [UIImage imageNamed:imageName2];

121 }

122

123 if (offset == 0) {

124 _currentImageView.image = _previousView.image;

125 scrollView.contentOffset = CGPointMake(scrollView.bounds.size.width, 0);

126 _previousView.image = nil;

127

128 if (i == 1) {

129 i = kCount;

130 }else{

131 i -= 1;

132 }

133

134 }

135

136 if (offset == scrollView.bounds.size.width * 2) {

137 _currentImageView.image = _nextImageView.image;

138 scrollView.contentOffset = CGPointMake(scrollView.bounds.size.width, 0);

139 _nextImageView.image = nil;

140

141 if (i == kCount) {

142 i = 1;

143 }else{

144 i += 1;

145 }

146

147 }

148 }

149

150 @end