UIButton setBackgroundColor:ForState

在使用UIButton时，很多时候我们需要一个类似于- (void)setBackgroundColor:(UIColor *)color forState:(UIControlState)state这样的方法，来实现在不同的状态下使用不同的backgroundColor。遗憾的是，iOS默认并没有实现这个方法，那我们就自己来实现它。

让我们先来看看对于设置BackgroundImage，UIButton提供了如下方法：

- (void)setBackgroundImage:(UIImage *)image forState:(UIControlState)state UI_APPEARANCE_SELECTOR; // default is nil - (UIImage *)backgroundImageForState:(UIControlState)state;

类似的，我们的函数实现声明如下：

- (void)setBackgroundColor:(UIColor *)color forState:(UIControlState)state; - (UIColor *)backgroundColorForState:(UIControlState)state;

具体实现如下所示，代码很简单，不再赘述。

@interface WMButton : UIButton @property (nonatomic, copy) NSString *name; - (void)setBackgroundColor:(UIColor *)backgroundColor forState:(UIControlState)state; - (UIColor *)backgroundColorForState:(UIControlState)state; @end

@implementation WMButton {  NSMutableDictionary *_colors; } - (instancetype)initWithFrame:(CGRect)frame {  if (self = [super initWithFrame:frame]) {   _colors = [NSMutableDictionary dictionary];  }  return self; } - (void)setBackgroundColor:(UIColor *)backgroundColor forState:(UIControlState)state {  // If it is normal then set the standard background here  if(state == UIControlStateNormal)  {   [super setBackgroundColor:backgroundColor];  }  // Store the background colour for that state  [_colors setValue:backgroundColor forKey:[self keyForState:state]]; } - (UIColor *)backgroundColorForState:(UIControlState)state {  return [_colors valueForKey:[self keyForState:state]]; } - (void)setHighlighted:(BOOL)highlighted {  // Do original Highlight  [super setHighlighted:highlighted];  // Highlight with new colour OR replace with orignial  NSString *highlightedKey = [self keyForState:UIControlStateHighlighted];  UIColor *highlightedColor = [_colors valueForKey:highlightedKey];  if (highlighted && highlightedColor) {   [super setBackgroundColor:highlightedColor];  } else {   // 由于系统在调用setSelected后，会再触发一次setHighlighted，故做如下处理，否则，背景色会被最后一次的覆盖掉。   if ([self isSelected]) {    NSString *selectedKey = [self keyForState:UIControlStateSelected];    UIColor *selectedColor = [_colors valueForKey:selectedKey];    [super setBackgroundColor:selectedColor];   } else {    NSString *normalKey = [self keyForState:UIControlStateNormal];    [super setBackgroundColor:[_colors valueForKey:normalKey]];   }  } } - (void)setSelected:(BOOL)selected {  // Do original Selected  [super setSelected:selected];  // Select with new colour OR replace with orignial  NSString *selectedKey = [self keyForState:UIControlStateSelected];  UIColor *selectedColor = [_colors valueForKey:selectedKey];  if (selected && selectedColor) {   [super setBackgroundColor:selectedColor];  } else {   NSString *normalKey = [self keyForState:UIControlStateNormal];   [super setBackgroundColor:[_colors valueForKey:normalKey]];  } } - (NSString *)keyForState:(UIControlState)state {  return [NSString stringWithFormat:@"state_%d", state]; } @end 

使用时，如下调用即可：

[button setBackgroundColor:[UIColor clearColor] forState:UIControlStateNormal]; [button setBackgroundColor:[UIColor clearColor] forState:UIControlStateHighlighted]; [button setBackgroundColor:HotPinkColor forState:UIControlStateSelected];

需要注意的一点是，有些人可能会这样使用

[button setBackgroundColor:HotPinkColor forState:UIControlStateHighlighted | UIControlStateSelected];

这种用法是不被支持的，虽然可以实现，但是，其实对于iOS默认提供方法- (void)setBackgroundImage:(UIImage *)image forState:(UIControlState)state UI_APPEARANCE_SELECTOR; // default is nil这种位于的用法也是不被完全支持的，大家可以试试看。

下面我们再来详细讨论下UIButton切换state的顺序问题。

当UIButton被按下时，会启动一个计时器，每隔一段时间，都会去检测按钮是否还处在被按下的状态。如果系统检测到它还处于被按下的状态，则就会切换到UIControlStateHighlighted，否则，恢复到UIControlStateNormal。当你长按后，在当前按钮的区域抬起手时，会切换到UIControlStateSelected，但是，需要注意的是，这次切换不仅会触发setSelected:被调用，也会触发setHighlighted:的一次调用。大家可以看看下面打印出来的Log。

2015-01-08 19:43:58.782  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:00.227  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:00.277  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:00.294  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:00.327  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:00.344  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:00.377  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:00.494  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:00.528  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:00.577  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:00.660  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:00.777  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:00.894  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:00.927  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:00.944  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:01.127  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:01.661  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:01.696  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:01.762  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:01.795  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:01.862  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:01.895  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:01.930  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:03.961  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]  2015-01-08 19:44:05.162  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]

2015-01-08 19:44:05.328  V |: highlighted = 1 @ WMButton(#38).-[WMButton setHighlighted:]

2015-01-08 19:44:05.346  V |: selected = 1 @ WMButton(#56).-[WMButton setSelected:]

2015-01-08 19:44:05.347  V |: highlighted = 0 @ WMButton(#38).-[WMButton setHighlighted:]