使用按鈕單擊在滾動視圖中移動前一圖像

Question

當我按前一個按鈕時，它不會產生任何效果。下一個按鈕工作正常，但上一個按鈕不顯示以前的圖像。我使用scroll view加載圖片：

- (IBAction)next{ 
    int arraycount = [appDelegate.articles count]; 
    for (int nextIndex = [pageControl currentPage]; nextIndex < arraycount; nextIndex++) { 
     if (self.scrollView.contentOffset.x <= self.scrollView.frame.size.width) { 
      CGRect frame; 
      frame.origin.x = self.scrollView.contentOffset.x +  self.scrollView.frame.size.width; 
      frame.origin.y = 0; 
      frame.size = self.scrollView.frame.size; 
      [self.scrollView scrollRectToVisible:frame animated:YES]; 
      pageControlBeingUsed = YES; 
     } 
    } 
} 

-(IBAction)previousButtonAction 
{ 
    int arraycount = [appDelegate.articles count]; 
    NSLog(@" arraycount : %d", arraycount); 
    NSLog(@" [pageControl currentPage] : %d", [pageControl currentPage]); 
    for (int nextIndex = [pageControl currentPage]; nextIndex>arraycount; nextIndex--) { 
     if (self.scrollView.contentOffset.x >= self.scrollView.frame.size.width) { 
      CGRect frame; 
      frame.origin.x = self.scrollView.contentOffset.x + self.scrollView.frame.size.width; 
      frame.origin.y = 0; 
      frame.size = self.scrollView.frame.size; 
      [self.scrollView scrollRectToVisible:frame animated:YES]; 
      pageControlBeingUsed = YES; 
     } 
    } 
} 

Answer 1

好了，現在我想我會不同的方法處理這個。我會在重新分配前檢查當前的偏移量。

未經測試的代碼：

- (IBAction)next{ 
    if (self.scrollView.contentOffset.x <= self.scrollView.frame.size.width) { 
     CGRect frame; 
     frame.origin.x = self.scrollView.contentOffset.x + self.scrollView.frame.size.width; 
     frame.origin.y = 0; 
     frame.size = self.scrollView.frame.size; 
     [self.scrollView scrollRectToVisible:frame animated:YES]; 
     pageControlBeingUsed = YES; 
    } 
} 

Answer 2

我會當用戶到達第三圖像禁用「下一步」按鈕。如果你喜歡返回到第一圖像時，用戶按下第三圖像中的「下一步」，則必須在後面加一個額外否則，如果指示的話：

- (IBAction)next{ 
int arraycount = [appDelegate.articles count]; 
for (int nextIndex = [pageControl currentPage]; nextIndex < arraycount; nextIndex++) {  
    if (nextIndex < arraycount) { 
     CGRect frame; 
     frame.origin.x = self.scrollView.frame.size.width * nextIndex; 
     frame.origin.y = 0; 
     frame.size = self.scrollView.frame.size; 
     [self.scrollView scrollRectToVisible:frame animated:YES]; 
      pageControlBeingUsed = YES; 
     } 
     // If the user clicks on next in the last item, return to the first 
     else { 
     CGRect frame; 
     frame.origin.x = 0; 
     frame.origin.y = 0; 
     frame.size = self.scrollView.frame.size; 
     [self.scrollView scrollRectToVisible:frame animated:YES]; 
      pageControlBeingUsed = YES; 
     } 
    } 

}

Answer 3

arraycount = 3

[的PageControl當前頁]是零索引，所以當你在第3頁上等於2

所以你的for循環nextIndex等於2，小於arrayCount所以它進入您的循環開始。

將其更改爲：

for (int nextIndex = [pageControl currentPage]; nextIndex < (arraycount-1); nextIndex++) { 

好請問這個輸出：

- (IBAction)next{ 
    int arraycount = [appDelegate.articles count]; 
NSLog(@" arraycount : %d", arraycount); 
NSLog(@" [pageControl currentPage] : %d", [pageControl currentPage]); 
    for (int nextIndex = [pageControl currentPage]; nextIndex < (arraycount-1); nextIndex++) { 
NSLog(@" nextIndex : %d", nextIndex); 
     CGRect frame; 
     frame.origin.x = self.scrollView.frame.size.width * nextIndex; 
     frame.origin.y = 0; 
     frame.size = self.scrollView.frame.size; 
     [self.scrollView scrollRectToVisible:frame animated:YES]; 
      pageControlBeingUsed = YES; 

     } 
} 

Answer 4

佛我它迅速3.

func prevAction (sender:UIButton) 
{ 
    print("self.scView.contentOffset.x ..\(self.scView.contentOffset.x)") 
    if (self.scView.contentOffset.x <= self.scView.contentSize.width) 
    { 
     var frame = CGRect() 

     frame.origin.x = self.scView.contentOffset.x - 80; 
     frame.origin.y = 0; 
     frame.size = self.scView.frame.size; 

     self.scView .scrollRectToVisible(frame, animated: true) 

    } 


} 

感謝正努力@ader。