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詳解iOS中UIButton的三大UIEdgeInsets屬性用法

編輯:IOS開發綜合

UIEdgeInsets是什麼

UIEdgeInsets是什麼?我們點進去看一下:

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;

UIEdgeInsets是個結構體類型。裡面有四個參數,分別是:top, left, bottom, right。這四個參數表示距離上邊界、左邊界、下邊界、右邊界的距離。

哪三個UIEdgeInsets屬性

不知道大家發現沒有,UIButton裡面有三個UIEdgeInsets屬性,分別是:

@property(nonatomic)     UIEdgeInsets contentEdgeInsets UI_APPEARANCE_SELECTOR; // default is UIEdgeInsetsZero

@property(nonatomic)     UIEdgeInsets titleEdgeInsets;        // default is UIEdgeInsetsZero

@property(nonatomic)     UIEdgeInsets imageEdgeInsets;        // default is UIEdgeInsetsZero

contentEdgeInsets後面有個UI_APPEARANCE_SELECTOR是什麼意思呢?

提示:UI_APPEARANCE_SELECTOR標記的屬性都支持通過外觀代理來定制。
舉例,設置UIButton的contentEdgeInsets屬性,可以直接調用:

[[UIButton appearance] setTitleEdgeInsets:UIEdgeInsetsMake(0, 0, 0, 0)];

創建UIButton:

UIButton *button = [[UIButton alloc] init];
button.frame = CGRectMake(50, 200, 200, 50);
[button setTitle:@"我是UIButton" forState:UIControlStateNormal];
[button setTitleColor:[UIColor blueColor] forState:UIControlStateNormal];
[button setBackgroundColor:[UIColor orangeColor]];
button.titleLabel.textAlignment = NSTextAlignmentLeft;
button.contentHorizontalAlignment = UIControlContentHorizontalAlignmentLeft;
[self.view addSubview:button];

創建一個button,讓button的title居左,以便觀察:

2016425143210943.png (146×97)

UIButton的contentEdgeInsets屬性

@property(nonatomic)     UIEdgeInsets contentEdgeInsets UI_APPEARANCE_SELECTOR; 

// default is UIEdgeInsetsZero

contentEdgeInsets裡有一個content應該指的就是UIButton的title。

參數含義:

上面我們講了UIEdgeInsets是個結構體類型。裡面有四個參數,分別是:top, left, bottom, right。這四個參數表示距離上邊界、左邊界、下邊界、右邊界的距離。

這四個參數的值可以為正值,也可以為負值。拿left舉例:

left = 10; //代表以當前位置為基准,向右移動10個像素
left = -10; //代表以當前位置為基准,向左移動10個像素

向右移動20個像素

button.contentEdgeInsets = UIEdgeInsetsMake(0, 20, 0, 0);

向右移動20個像素,left = 20,就可以了。

2016425143256442.png (154×80)

向左移動20個像素

button.contentEdgeInsets = UIEdgeInsetsMake(0, -20, 0, 0);

2016425143338999.png (146×80)

UIButton的titleEdgeInsets屬性

titleEdgeInsets和contentEdgeInsets的作用差不多。我們及設置contentEdgeInsets,又設置titleEdgeInsets,會怎樣呢?

button.titleEdgeInsets = UIEdgeInsetsMake(0, 20, 0, 0);
button.contentEdgeInsets = UIEdgeInsetsMake(0, 20 , 0, 0);

看一下效果:

2016425143400935.png (152×97)

UIButton的imageEdgeInsets屬性

創建一個帶照片的button:

UIButton *button = [[UIButton alloc] init];
button.frame = CGRectMake(50, 200, 200, 200);
[button setTitleColor:[UIColor blueColor] forState:UIControlStateNormal];
[button setBackgroundColor:[UIColor orangeColor]];
[button setImage:[UIImage imageNamed:@"test"] forState:UIControlStateNormal];
[self.view addSubview:button];

運行一下:

2016425143505909.png (169×161)

向右移動50個像素

button.imageEdgeInsets = UIEdgeInsetsMake(0, 50, 0, 0);

看看效果:

2016425143526865.png (170×190)

向左移動50個像素

button.imageEdgeInsets = UIEdgeInsetsMake(0, -50, 0, 0);

看看效果:

2016425143547866.png (181×178)

大家可以自行設置其他三個參數看看效果是怎樣的,自己動手便於理解。

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