iOS - 滚动视图

使用滚动视图

滚动视图用于显示超出屏幕大小的内容。 它可以包含所有其他 UI 元素，例如图像视图、标签、文本视图，甚至是另一个滚动视图本身。

重要属性

• contentSize
• contentInset
• contentOffset
• delegate

重要方法

- (void)scrollRectToVisible:(CGRect)rect animated:(BOOL)animated
- (void)setContentOffset:(CGPoint)contentOffset animated:(BOOL)animated

重要的委托方法

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView
willDecelerate:(BOOL)decelerate
- (void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView

更新 ViewController.h 如下−

Make your class conform to scroll view delegate protocol by adding < UIScrollViewDelegate> and declaring a scroll view instance as shown below in ViewController.h.

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController<UIScrollViewDelegate> {
   UIScrollView *myScrollView;
}	
@end

添加自定义方法 addScrollView

-(void)addScrollView {
   myScrollView = [[UIScrollView alloc]initWithFrame:
   CGRectMake(20, 20, 280, 420)];
   myScrollView.accessibilityActivationPoint = CGPointMake(100, 100);
   imgView = [[UIImageView alloc]initWithImage:
   [UIImage imageNamed:@"AppleUSA.jpg"]];
   [myScrollView addSubview:imgView];
   myScrollView.minimumZoomScale = 0.5;
   myScrollView.maximumZoomScale = 3;
   myScrollView.contentSize = CGSizeMake(imgView.frame.size.width,
   imgView.frame.size.height);
   myScrollView.delegate = self;
   [self.view addSubview:myScrollView];
}

注意 −

我们必须将名为 "AppleUSA1.jpg" 的图像添加到我们的项目中，这可以通过将图像拖到列出项目文件的导航器区域来完成。 图像的分辨率应高于设备以查看图像的滚动。

在 ViewController.m 中实现 scrollView 委托

-(UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {
   return imgView;
}

-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
   NSLog(@"Did end decelerating");
}	

-(void)scrollViewDidScroll:(UIScrollView *)scrollView {
   // NSLog(@"Did scroll");
}

-(void)scrollViewDidEndDragging:(UIScrollView *)scrollView 
   willDecelerate:(BOOL)decelerate {
   NSLog(@"Did end dragging");
}

-(void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView {
   NSLog(@"Did begin decelerating");
}

-(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
   NSLog(@"Did begin dragging");
}

更新 ViewController.m 中的 viewDidLoad 如下 −

(void)viewDidLoad {
   [super viewDidLoad];
   [self addScrollView];
   //Do any additional setup after loading the view, typically from a nib
}

输出

当我们运行应用程序时，我们将得到以下输出。 滚动视图后，您将能够看到图像的剩余部分。

❮ iOS - UI 元素