重写UIPageControl实现自定义按钮

有时候UIPageControl需要用到白色的背景, 那么会导致上面的点按钮看不见或不清楚,
我们可以通过继承该类重写函数来更换点按钮的图片现实.
实现思路如下.
新建类继承UIPageControl :
   @interface MyPageControl : UIPageControl
   {
       UIImage *imagePageStateNormal;
       UIImage *imagePageStateHighlighted;
   }
   - (id)initWithFrame:(CGRect)frame;
   @property (nonatomic, retain) UIImage *imagePageStateNormal;
   @property (nonatomic, retain) UIImage *imagePageStateHighlighted;
   @end
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声明了初始化该类的函数
用了两个UIIma
 
接下来实现该类以及重写父类方法:
   @interface MyPageControl(private)  // 声明一个私有方法, 该方法不允许对象直接使用
   - (void)updateDots;
   @end
 
   @implementation MyPageControl  // 实现部分
 
   @synthesize imagePageStateNormal;
   @synthesize imagePageStateHighlighted;
 
  - (id)initWithFrame:(CGRect)frame { // 初始化
      self = [super initWithFrame:frame];
      return self;
  }
 
  - (void)setImagePageStateNormal:(UIImage *)image {  // 设置正常状态点按钮的图片
      [imagePageStateHighlighted release];
      imagePageStateHighlighted = [image retain];
      [self updateDots];
  }
 
  - (void)setImagePageStateHighlighted:(UIImage *)image { // 设置高亮状态点按钮图片
      [imagePageStateNormal release];
      imagePageStateNormal = [image retain];
      [self updateDots];
  }
 
  - (void)endTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event { // 点击事件
      [super endTrackingWithTouch:touch withEvent:event];
      [self updateDots];
  }
 
  - (void)updateDots { // 更新显示所有的点按钮
 
      if (imagePageStateNormal || imagePageStateHighlighted)
      {
          NSArray *subview = self.subviews;  // 获取所有子视图
          for (NSInteger i = 0; i < [subview count]; i++)
          {
              UIImageView *dot = [subview objectAtIndex:i];  // 以下不解释, 看了基本明白
              dot.image = self.currentPage == i ? imagePageStateNormal : imagePageStateHighlighted;
          }
      }
  }
 
  - (void)dealloc { // 释放内存
      [imagePageStateNormal release], imagePageStateNormal = nil;
      [imagePageStateHighlighted release], imagePageStateHighlighted = nil;
      [super dealloc];
  }
 
  @end
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OK, 在添加处加入以下来实例化该对象代码:
   MyPageControl *pageControl = [[MyPageControl alloc] initWithFrame:CGRectMake(0,0, 200, 30)];
   pageControl.backgroundColor = [UIColor clearColor];
   pageControl.numberOfPages = 5;
   pageControl.currentPage = 0;
   [pageControl setImagePageStateNormal:[UIImage imageNamed:@"pageControlStateNormal.png"]];
   [pageControl setImagePageStateHighlighted:[UIImage imageNamed:@"pageControlStateHighlighted.png"]];
   [self.view addSubview:pageControl];
   [pageControl release];这里有点问题在休整一下：如果直接做setCurrentPage的話，圖片就會失效了，所以覆寫setCurrentPage// 覆寫setCurrentPage
- (void)setCurrentPage:(NSInteger)currentPage
{
    [super setCurrentPage:currentPage];
    [self updateDots];

}