UIbutton 上设置文字图片垂直居中对齐

     UIEdgeInsets

typedef struct UIEdgeInsets {    CGFloat top, left, bottom, right;  // specify amount to inset (positive) for each of the edges. values can be negative to 'outset'} UIEdgeInsets;
在UIButton中有三个对EdgeInsets的设 置：ContentEdgeInsets、titleEdgeInsets、imageEdgeInsets
@PRoperty(nonatomic)          UIEdgeInsets contentEdgeInsets UI_APPEARANCE_SELECTOR; // default is UIEdgeInsetsZero@property(nonatomic)          UIEdgeInsets titleEdgeInsets;                // default is UIEdgeInsetsZero@property(nonatomic)          BOOL         reversesTitleShadowWhenHighlighted; // default is NO. if YES, shadow reverses to shift between engrave and emboss appearance@property(nonatomic)          UIEdgeInsets imageEdgeInsets;                // default is UIEdgeInsetsZero
UIEdgeInsetsMake
里面的四个参数表示距离上边界、左边界、下边界、右边界的距离，默认都为零，title／image在button的正中央
UIKIT_STATIC_INLINE UIEdgeInsets UIEdgeInsetsMake(CGFloat top, CGFloat left, CGFloat bottom, CGFloat right) {    UIEdgeInsets insets = {top, left, bottom, right};    return insets;}
 self.view.backgroundColor = [UIColor blackColor];        UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];//button的类型    button.frame = CGRectMake(100, 100,90, 90);//button的frame   button.backgroundColor = [UIColor cyanColor];//button的背景颜色    //    [button setBackgroundImage:[UIImage imageNamed:@"man_64.png"] forState:UIControlStateNormal];    //    在UIButton中有三个对EdgeInsets的设置：ContentEdgeInsets、titleEdgeInsets、imageEdgeInsets    [button setImage:[UIImage imageNamed:@"IconHome@2x.png"] forState:UIControlStateNormal];//给button添加image    button.imageEdgeInsets = UIEdgeInsetsMake(5,13,21,button.titleLabel.bounds.size.width);//设置image在button上的位置（上top，左left，下bottom，右right）这里可以写负值，对上写－5，那么image就象上移动5个像素        [button setTitle:@"首页" forState:UIControlStateNormal];//设置button的title    button.titleLabel.font = [UIFont systemFontOfSize:16];//title字体大小    button.titleLabel.textAlignment = NSTextAlignmentCenter;//设置title的字体居中    [button setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];//设置title在一般情况下为白色字体    [button setTitleColor:[UIColor grayColor] forState:UIControlStateHighlighted];//设置title在button被选中情况下为灰色字体     button.titleEdgeInsets = UIEdgeInsetsMake(71, -button.titleLabel.bounds.size.width-50, 0, 0);//设置title在button上的位置（上top，左left，下bottom，右right）    //    [button setContentEdgeInsets:UIEdgeInsetsMake(70, 0, 0, 0)];//    //   button.contentHorizontalAlignment = UIControlContentHorizontalAlignmentCenter;//设置button的内容横向居中。。设置content是title和image一起变化            [button addTarget:self action:@selector(tap) forControlEvents:UIControlEventTouchUpInside];                        [self.view addSubview:button];//button相应的事件-(void)tap {    NSLog(@"tap a button");       UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"hello" message:@"willingseal" delegate:self cancelButtonTitle:@"ok" otherButtonTitles: nil];    [alertView show];}