iOS开发 -UIScrollView详解
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UIScrollView
移动设备的屏幕大小是极其有限的,因此直接展示在用户眼前的内容也相当有限
当展示的内容较多,超出一个屏幕时,用户可通过滚动手势来查看屏幕以外的内容
普通的UIView不具备滚动功能,不能显示过多的内容
UIScrollView是一个能够滚动的视图控件,可以用来展示大量的内容,并且可以通过滚动查看所有的内容
举例:手机上的“设置”、其他示例程序
UIScrollView的用法
将需要展示的内容添加到UIScrollView中
设置UIScrollView的contentSize属性,告诉UIScrollView所有内容的尺寸,也就是告诉它滚动的范围(能滚多远,滚到哪里是尽头)
UIScrollView无法滚动的解决办法
<code class="hljs objectivec has-numbering">如果<span class="hljs-built_in">UIScrollView</span>无法滚动,可能是以下原因:<span class="hljs-number">1.</span>没有设置contentSize<span class="hljs-number">2.</span>scrollEnabled = <span class="hljs-literal">NO</span><span class="hljs-number">3.</span>没有接收到触摸事件:userInteractionEnabled = <span class="hljs-literal">NO</span><span class="hljs-number">4.</span>没有取消autolayout功能(要想scrollView滚动,必须取消autolayout)</code><ul style="display: block;" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li></ul>
UIScrollView的代理(delegate)
<code class="hljs objectivec has-numbering">很多时候,我们想在<span class="hljs-built_in">UIScrollView</span>正在滚动 或 滚动到某个位置 或者 停止滚动 时做一些特定的操作要想完成上述功能,前提条件就是能够监听到<span class="hljs-built_in">UIScrollView</span>的整个滚动过程当<span class="hljs-built_in">UIScrollView</span>发生一系列的滚动操作时, 会自动通知它的代理(delegate)对象,给它的代理发送相应的消息,让代理得知它的滚动情况也就是说,要想监听<span class="hljs-built_in">UIScrollView</span>的滚动过程,就必须先给<span class="hljs-built_in">UIScrollView</span>将delegate需要实现的方法都定义在了<span class="hljs-built_in">UIScrollViewDelegate</span>协议中,因此要想成为<span class="hljs-built_in">UIScrollView</span>的delegate,必须遵守<span class="hljs-built_in">UIScrollViewDelegate</span>协议,然后实现协议中相应的方法,就可以监听<span class="hljs-built_in">UIScrollView</span>的滚动过程了</code><ul style="display: block;" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li></ul>
UIScrollView和控制器
<code class="hljs objectivec has-numbering">一般情况下,就设置<span class="hljs-built_in">UIScrollView</span>所在的控制器 为 <span class="hljs-built_in">UIScrollView</span>的delegate设置控制器为<span class="hljs-built_in">UIScrollView</span>的delegate有<span class="hljs-number">2</span>种方法:通过代码(<span class="hljs-keyword">self</span>就是控制器)<span class="hljs-keyword">self</span><span class="hljs-variable">.scrollView</span><span class="hljs-variable">.delegate</span> = <span class="hljs-keyword">self</span>;</code><ul style="display: block;" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li></ul>
通过storyboard拖线(右击UIScrollView)
UIScrollView的常见属性
<code class="hljs objectivec has-numbering"><span class="hljs-keyword">@property</span>(<span class="hljs-keyword">nonatomic</span>) <span class="hljs-built_in">CGPoint</span> contentOffset; <span class="hljs-comment">//这个属性用来表示UIScrollView滚动的位置</span><span class="hljs-keyword">@property</span>(<span class="hljs-keyword">nonatomic</span>) <span class="hljs-built_in">CGSize</span> contentSize; <span class="hljs-comment">//这个属性用来表示UIScrollView内容的尺寸,滚动范围(能滚多远)</span><span class="hljs-keyword">@property</span>(<span class="hljs-keyword">nonatomic</span>) <span class="hljs-built_in">UIEdgeInsets</span> contentInset; <span class="hljs-comment">//这个属性能够在UIScrollView的4周增加额外的滚动区域</span><span class="hljs-keyword">@property</span>(<span class="hljs-keyword">nonatomic</span>) <span class="hljs-built_in">BOOL</span> bounces;<span class="hljs-comment">//设置UIScrollView是否需要弹簧效果</span><span class="hljs-keyword">@property</span>(<span class="hljs-keyword">nonatomic</span>,getter=isScrollEnabled) <span class="hljs-built_in">BOOL</span> scrollEnabled; <span class="hljs-comment">//设置UIScrollView是否能滚动</span><span class="hljs-keyword">@property</span>(<span class="hljs-keyword">nonatomic</span>) <span class="hljs-built_in">BOOL</span> showsHorizontalScrollIndicator;<span class="hljs-comment">//是否显示水平滚动条</span><span class="hljs-keyword">@property</span>(<span class="hljs-keyword">nonatomic</span>) <span class="hljs-built_in">BOOL</span> showsVerticalScrollIndicator;<span class="hljs-comment">//是否显示垂直滚动条</span></code><ul style="display: block;" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li><li>10</li><li>11</li><li>12</li><li>13</li><li>14</li><li>15</li><li>16</li><li>17</li><li>18</li><li>19</li><li>20</li><li>21</li></ul>
UIScrollView的常用代理方法
<code class="hljs objectivec has-numbering"><span class="hljs-comment">// 用户开始拖拽时调用</span>- (<span class="hljs-keyword">void</span>)scrollViewWillBeginDragging:(<span class="hljs-built_in">UIScrollView</span> *)scrollView;<span class="hljs-comment">// 滚动到某个位置时调用</span>- (<span class="hljs-keyword">void</span>)scrollViewDidScroll:(<span class="hljs-built_in">UIScrollView</span> *)scrollView;<span class="hljs-comment">// 用户结束拖拽时调用</span>- (<span class="hljs-keyword">void</span>)scrollViewDidEndDragging:(<span class="hljs-built_in">UIScrollView</span> *)scrollView willDecelerate:(<span class="hljs-built_in">BOOL</span>)decelerate;</code><ul style="display: block;" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li></ul>
UIScrollView的缩放
当用户在UIScrollView身上使用捏合手势时,UIScrollView会给代理发送一条消息,询问代理究竟要缩放自己内部的哪一个子控件(哪一块内容)
1.实现UIScrollViewDelegate协议
<code class="hljs objectivec has-numbering"><span class="hljs-comment">// 用户使用捏合手势时调用</span>- (<span class="hljs-built_in">UIView</span> *)viewForZoomingInScrollView:(<span class="hljs-built_in">UIScrollView</span> *)scrollView;</code><ul style="display: block;" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li></ul>
遵守协议,实现相应的方法
<code class="hljs objectivec has-numbering"><span class="hljs-keyword">id</span><<span class="hljs-built_in">UIScrollViewDelegate</span>> delegate</code><ul style="display: block;" class="pre-numbering"><li>1</li><li>2</li></ul>
当用户在UIScrollView身上使用捏合手势时,UIScrollView会调用代理的viewForZoomingInScrollView:方法,这个方法返回的控件就是需要进行缩放的控件
缩放实现步骤
<code class="hljs objectivec has-numbering">设置<span class="hljs-built_in">UIScrollView</span>的<span class="hljs-keyword">id</span><UISCrollViewDelegate> delegate代理对象设置minimumZoomScale :缩小的最小比例设置maximumZoomScale :放大的最大比例让代理对象实现下面的方法,返回需要缩放的视图控件- (<span class="hljs-built_in">UIView</span> *)viewForZoomingInScrollView:(<span class="hljs-built_in">UIScrollView</span> *)scrollView;跟缩放相关的其他代理方法缩放完毕的时候调用 - (<span class="hljs-keyword">void</span>)scrollViewWillBeginZooming:(<span class="hljs-built_in">UIScrollView</span> *)scrollView withView:(<span class="hljs-built_in">UIView</span> *)view正在缩放的时候调用- (<span class="hljs-keyword">void</span>)scrollViewDidZoom:(<span class="hljs-built_in">UIScrollView</span> *)scrollView</code><ul style="display: block;" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li><li>10</li><li>11</li><li>12</li><li>13</li></ul>
UIScrollView和UIPageControl的分页
<code class="hljs objectivec has-numbering">只要将<span class="hljs-built_in">UIScrollView</span>的pageEnabled属性设置为<span class="hljs-literal">YES</span>,<span class="hljs-built_in">UIScrollView</span>会被分割成多个独立页面,里面的内容就能进行分页展示一般会配合UIPageControl增强分页效果,UIPageControl常用属性如下 <span class="hljs-comment">//一共有多少页</span><span class="hljs-keyword">@property</span>(<span class="hljs-keyword">nonatomic</span>) <span class="hljs-built_in">NSInteger</span> numberOfPages;<span class="hljs-comment">//当前显示的页码</span><span class="hljs-keyword">@property</span>(<span class="hljs-keyword">nonatomic</span>) <span class="hljs-built_in">NSInteger</span> currentPage; <span class="hljs-comment">//只有一页时,是否需要隐藏页码指示器</span><span class="hljs-keyword">@property</span>(<span class="hljs-keyword">nonatomic</span>) <span class="hljs-built_in">BOOL</span> hidesForSinglePage; <span class="hljs-comment">//其他页码指示器的颜色</span><span class="hljs-keyword">@property</span>(<span class="hljs-keyword">nonatomic</span>,retain) <span class="hljs-built_in">UIColor</span> *pageIndicatorTintColor;<span class="hljs-comment">//当前页码指示器的颜色</span><span class="hljs-keyword">@property</span>(<span class="hljs-keyword">nonatomic</span>,retain) <span class="hljs-built_in">UIColor</span> *currentPageIndicatorTintColor;</code><ul style="display: block;" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li><li>6</li><li>7</li><li>8</li><li>9</li><li>10</li><li>11</li><li>12</li><li>13</li><li>14</li><li>15</li><li>16</li><li>17</li><li>18</li></ul>
NSTimer的使用
NSTimer叫做“定时器”,它的作用如下
在指定的时间执行指定的任务
每隔一段时间执行指定的任务
<code class="hljs css has-numbering">调用下面的方法就会开启一个定时任务+ (<span class="hljs-tag">NSTimer</span> *)<span class="hljs-tag">scheduledTimerWithTimeInterval</span><span class="hljs-pseudo">:(NSTimeInterval)ti</span> <span class="hljs-tag">target</span><span class="hljs-pseudo">:(id)aTarget</span> <span class="hljs-tag">selector</span><span class="hljs-pseudo">:(SEL)aSelector</span> <span class="hljs-tag">userInfo</span><span class="hljs-pseudo">:(id)userInfo</span> <span class="hljs-tag">repeats</span><span class="hljs-pseudo">:(BOOL)yesOrNo</span>;</code><ul style="display: block;" class="pre-numbering"><li>1</li><li>2</li><li>3</li><li>4</li><li>5</li></ul>
每隔ti秒,调用一次aTarget的aSelector方法,yesOrNo决定了是否重复执行这个任务
通过invalidate方法可以停止定时器的工作,一旦定时器被停止了,就不能再次执行任务。只能再创建一个新的定时器才能执行新的任务
<code class="hljs erlang has-numbering"><span class="hljs-pp">- <span class="hljs-params">(void)</span>invalidate;</span></code><ul style="display: block;" class="pre-numbering"><li>1</li></ul>
UIScrollView实例
<code class="hljs java has-numbering"><span class="hljs-javadoc">/** * 1.成为代理的条件: UIScrollView将delegate需要实现的方法都定义在了UIScrollViewDelegate协议中, 因此要想成为UIScrollView的delegate,必须遵守UIScrollViewDelegate协议, 然后实现协议中相应的方法,就可以监听UIScrollView的滚动过程了 2.设置UIScrollView的id<UISCrollViewDelegate> delegate代理对象 设置minimumZoomScale :缩小的最小比例 设置maximumZoomScale :放大的最大比例 让代理对象实现下面的方法,返回需要缩放的视图控件 - (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView; */</span>#<span class="hljs-keyword">import</span> <span class="hljs-string">"ViewController.h"</span><span class="hljs-annotation">@interface</span> ViewController () <UIScrollViewDelegate><span class="hljs-annotation">@property</span> (weak, nonatomic) IBOutlet UIScrollView *scrollView;<span class="hljs-annotation">@property</span> (weak, nonatomic) IBOutlet UIImageView *minionView;<span class="hljs-annotation">@end</span><span class="hljs-comment">//委托 代理模式</span><span class="hljs-annotation">@implementation</span> ViewController- (<span class="hljs-keyword">void</span>)viewDidLoad { [<span class="hljs-keyword">super</span> viewDidLoad]; <span class="hljs-comment">//设置内容尺寸</span> self.scrollView.contentSize=self.minionView.frame.size; <span class="hljs-comment">//设置</span> self.scrollView.delegate=self; <span class="hljs-comment">//设置最大和最小的缩放比例</span> self.scrollView.maximumZoomScale=<span class="hljs-number">2.0</span>; self.scrollView.minimumZoomScale=<span class="hljs-number">0.2</span>;}<span class="hljs-javadoc">/** * 当用户开始拖拽scrollView时就会调用 */</span>- (<span class="hljs-keyword">void</span>)scrollViewWillBeginDragging:(UIScrollView *)scrollView{ NSLog(@<span class="hljs-string">"开始拖拽...."</span>);}<span class="hljs-javadoc">/** * 只要scrollView正在滚动,就会调用 */</span>- (<span class="hljs-keyword">void</span>)scrollViewDidScroll:(UIScrollView *)scrollView{ NSLog(@<span class="hljs-string">"正在滚动------%@"</span>,NSStringFromCGPoint(scrollView.contentOffset));}<span class="hljs-javadoc">/** * 当用户使用捏合手势时就会调用 * <span class="hljs-javadoctag"> @return</span> 返回的控件就是需要进行缩放的控件 */</span>- (UIView*)viewForZoomingInScrollView:(UIScrollView *)scrollView{ NSLog(@<span class="hljs-string">"开始缩放-----"</span>); <span class="hljs-keyword">return</span> self.minionView;}- (<span class="hljs-keyword">void</span>) scrollViewDidZoom:(UIScrollView *)scrollView{ NSLog(@<span class="hljs-string">"正在缩放----"</span>);}</code>
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