UIView : UIResponder
  /**
通過一個frame來初始化一個UI控件
 */
 - (id)initWithFrame:(CGRect)frame;
 // YES:能夠跟用戶進行交互
@property(nonatomic,getter=isUserInteractionEnabled) BOOL userInteractionEnabled;  // default is YES
// 控件的一個標記(父控件可以通過tag找到對應的子控件)
@property(nonatomic)                                 NSInteger tag;                // default is 0
// 圖層(可以用來設置圓角效果\陰影效果)
@property(nonatomic,readonly,retain)                 CALayer  *layer;
@interface UIView(UIViewGeometry)
// 位置和尺寸(以父控件的左上角為坐標原點(0, 0))
@property(nonatomic) CGRect            frame;
// 位置和尺寸(以自己的左上角為坐標原點(0, 0))
@property(nonatomic) CGRect            bounds;
// 中點(以父控件的左上角為坐標原點(0, 0))
@property(nonatomic) CGPoint           center;      
// 形變屬性(平移\縮放\旋轉)
@property(nonatomic) CGAffineTransform transform;   // default is CGAffineTransformIdentity
// YES:支持多點觸摸
@property(nonatomic,getter=isMultipleTouchEnabled) BOOL multipleTouchEnabled;   // default is NO
@end
@interface UIView(UIViewHierarchy)
 // 父控件
@property(nonatomic,readonly) UIView       *superview;
// 子控件(新添加的控件默認都在subviews數組的后面, 新添加的控件默認都顯示在最上面\最頂部)
@property(nonatomic,readonly,copy) NSArray *subviews;
// 獲得當前控件所在的window
@property(nonatomic,readonly) UIWindow     *window;
// 從父控件中移除一個控件
- (void)removeFromSuperview;
// 添加一個子控件(可以將子控件插入到subviews數組中index這個位置)
- (void)insertSubview:(UIView *)view atIndex:(NSInteger)index;
// 交換subviews數組中所存放子控件的位置
-  (void)exchangeSubviewAtIndex:(NSInteger)index1 withSubviewAtIndex:(NSInteger)index2;
// 添加一個子控件(新添加的控件默認都在subviews數組的后面, 新添加的控件默認都顯示在最上面\最頂部)
- (void)addSubview:(UIView *)view;
// 添加一個子控件view(被擋在siblingSubview的下面)
- (void)insertSubview:(UIView *)view belowSubview:(UIView *)siblingSubview;
// 添加一個子控件view(蓋在siblingSubview的上面)
- (void)insertSubview:(UIView *)view aboveSubview:(UIView *)siblingSubview;
// 將某個子控件拉到最上面(最頂部)來顯示
- (void)bringSubviewToFront:(UIView *)view;
// 將某個子控件拉到最下面(最底部)來顯示
- (void)sendSubviewToBack:(UIView *)view;
/**系統自動調用(留給子類去實現)**/
- (void)didAddSubview:(UIView *)subview;
- (void)willRemoveSubview:(UIView *)subview;
- (void)willMoveToSuperview:(UIView *)newSuperview;
- (void)didMoveToSuperview;
- (void)willMoveToWindow:(UIWindow *)newWindow;
- (void)didMoveToWindow;
/**系統自動調用**/
 // 是不是view的子控件或者子控件的子控件(是否為view的后代)
- (BOOL)isDescendantOfView:(UIView *)view;  // returns YES for self.
 // 通過tag獲得對應的子控件(也可以或者子控件的子控件)
- (UIView *)viewWithTag:(NSInteger)tag;     // recursive search. includes self
/**系統自動調用(留給子類去實現)**/
// 控件的frame發生改變的時候就會調用,一般在這里重寫布局子控件的位置和尺寸
// 重寫了這個寫方法后,一定調用[super layoutSubviews];
- (void)layoutSubviews;
@end
@interface UIView(UIViewRendering)
// YES : 超出控件邊框范圍的內容都剪掉
@property(nonatomic)                 BOOL              clipsToBounds;
// 背景色
@property(nonatomic,copy)            UIColor          *backgroundColor; // default is nil
// 透明度(0.0~1.0)
@property(nonatomic)                 CGFloat           alpha;                      // default is 1.0
// YES:不透明  NO:透明
@property(nonatomic,getter=isOpaque) BOOL              opaque;                     // default is YES
 // YES : 隱藏  NO : 顯示
@property(nonatomic,getter=isHidden) BOOL              hidden;
 // 內容模式
 @property(nonatomic)                 UIViewContentMode contentMode;                // default is UIViewContentModeScaleToFill
 @end
 //動畫
@interface UIView(UIViewAnimationWithBlocks)
+ (void)animateWithDuration:(NSTimeInterval)duration delay:(NSTimeInterval)delay options:(UIViewAnimationOptions)options animations:(void (^)(void))animations completion:(void (^)(BOOL finished))completion;
+ (void)animateWithDuration:(NSTimeInterval)duration animations:(void (^)(void))animations completion:(void (^)(BOOL finished))completion;
+ (void)animateWithDuration:(NSTimeInterval)duration animations:(void (^)(void))animations;
+ (void)animateWithDuration:(NSTimeInterval)duration delay:(NSTimeInterval)delay usingSpringWithDamping:(CGFloat)dampingRatio initialSpringVelocity:(CGFloat)velocity options:(UIViewAnimationOptions)options animations:(void (^)(void))animations completion:(void (^)(BOOL finished))completion;
 @end