iOS開發之實現圖片自動切換（相似android畫廊效果）

# import ViewController.h #define ImageViewCount 5   @interface ViewController ()<uiscrollviewdelegate>   @property (weak, nonatomic) IBOutlet UIScrollView *imageScrollView; @property (weak, nonatomic) IBOutlet UIPageControl *imageViewPageControl; @property (strong, nonatomic) NSTimer *timer; @end   @implementation ViewController   - ( void )viewDidLoad {      [ super viewDidLoad];          [self addImageView2ScrollView];      self.imageScrollView.contentSize = CGSizeMake(self.imageScrollView.frame.size.width * ImageViewCount, 0 );        self.imageScrollView.delegate = self;      self.imageScrollView.pagingEnabled = YES; //UIScrollView支持拖動分頁      self.imageViewPageControl.numberOfPages  = ImageViewCount;            [self addScrollTimer]; }   - ( void )rotatePic{      int currentPageIndex = self.imageViewPageControl.currentPage;      if (++currentPageIndex == 5 ){          currentPageIndex = 0 ;      }      CGFloat offsetX = currentPageIndex * self.imageScrollView.frame.size.width;      [UIView animateWithDuration: 1 animations:^{          self.imageScrollView.contentOffset = CGPointMake(offsetX, 0 );      }]; }   /**添加圖片到imageScrollView*/ - ( void )addImageView2ScrollView{      CGFloat imageWidth = self.imageScrollView.frame.size.width;      CGFloat imageHeight = self.imageScrollView.frame.size.height;      for ( int i = 0 ;i <= ImageViewCount;i++){          UIImageView *imageInScroll = [[UIImageView alloc] init];          imageInScroll.frame = CGRectMake(i * imageWidth, 0 , imageWidth, imageHeight);          imageInScroll.image = [UIImage imageNamed:[NSString stringWithFormat: @img_ %02d,i + 1 ]];          [self.imageScrollView addSubview:imageInScroll];      } }   // 正滾動時執行 - ( void )scrollViewDidScroll:(UIScrollView *)scrollView{      CGFloat offX = self.imageScrollView.contentOffset.x; //（0，0）距離content內部左上頂點的x軸長度      NSLog(@~~~~~~~%f ^^^^^^%f, offX, self.imageScrollView.frame.size.width);      int currentPageIndex = (offX + .5f * self.imageScrollView.frame.size.width) / self.imageScrollView.frame.size.width;      self.imageViewPageControl.currentPage = currentPageIndex; }   - ( void )addScrollTimer{      self.timer = [NSTimer timerWithTimeInterval: 2 target:self selector: @selector (rotatePic) userInfo:nil repeats:YES];      [[NSRunLoop mainRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes]; }   - ( void )removeScrollTimer{      [self.timer invalidate]; //釋放定時器      self.timer = nil; }   // 開始準備滾動時執行 移除定時滾動操做 - ( void )scrollViewWillBeginDragging:(UIScrollView *)scrollView{      NSLog(@~~~scrollViewWillBeginDragging);      [self removeScrollTimer]; }www.2cto.com   // 結束滾動後執行 添加定時滾動操做 - ( void )scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{      NSLog(@~~~scrollViewDidEndDragging);      [self addScrollTimer]; } @end </uiscrollviewdelegate>

對UIScrollView的運用，以上代碼中有詳細註釋，需注意2點：

 

1.注意設置contentSize屬性。其中contentSize表示scroll內容尺寸大小

2.注意設置代理UIScrollViewDelegate，纔可調用其中的方法

對於定時器NSTimer的運用需注意

1.在線程的loop中添加定時器

2.注意使用完成回收NSTimer

 

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