屏幕兼容的問題

為了讓我們的應用在不容尺寸的屏幕下都能 “正常”的表示，我們盡量不要把數據寫死。

大多數可視元素都是一個矩形區域，當然這個矩形區域有坐標的，我們有了這個區域坐標就能確定可視元素的現實位置了。

但是iphone5 和以前的屏幕不一樣了，在以前的設備中，我們可以添加一個 xx.@2x.png 來適應retina屏幕，但是iphoen5咋辦呢？

ios 引入了 Auto Layout 的東東，這個要和UIViewAutoresizing 區分下。

看下面代碼

- (void)viewDidLoad
{
??? [super viewDidLoad];
?????? ?
??? UIView *aView = [[UIView alloc] init];
??? aView.backgroundColor = [UIColor redColor];

//為了不和autosizing沖突，我們設置No

??? [aView setTranslatesAutoresizingMaskIntoConstraints:NO];
??? [self.view addSubview:aView];
?? ?
??? UIView *bView = [[UIView alloc] init];
??? bView.backgroundColor = [UIColor blueColor];
??? [bView setTranslatesAutoresizingMaskIntoConstraints:NO];
??? [self.view addSubview:bView];
?? ?
??? NSDictionary *views = NSDictionaryOfVariableBindings(aView, bView);

//NSDictionaryOfVariableBindings? 宏? 其實 NSDictionaryOfVariableBindings(v1, v2, v3) 等效于 [NSDictionary dictionaryWithObjectsAndKeys:v1, @"v1", v2, @"v2", v3, @"v3", nil];????
??? [self.view addConstraints:
??? [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-(>=50)-[aView(100)]"
???????????????????????????????????????????? options:0
???????????????????????????????????????????? metrics:nil
?????????????????????????????????????????????? views:views]];
?? ?
??? [self.view addConstraints:
???? [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-(>=100)-[aView(50)]"
???????????????????????????????????????????? options:0
???????????????????????????????????????????? metrics:nil
?????????????????????????????????????????????? views:views]];
? ?
??? [self.view addConstraints:
???? [NSLayoutConstraint constraintsWithVisualFormat:@"H:[bView(==aView)]"
???????????????????????????????????????????? options:0
???????????????????????????????????????????? metrics:nil
?????????????????????????????????????????????? views:views]];
??? [self.view addConstraints:
???? [NSLayoutConstraint constraintsWithVisualFormat:@"V:[bView(==aView)]"
???????????????????????????????????????????? options:0
???????????????????????????????????????????? metrics:nil
?????????????????????????????????????????????? views:views]];
?? ?
??? [self.view addConstraint:
???? [NSLayoutConstraint constraintWithItem:bView
????????????????????????????????? attribute:NSLayoutAttributeLeft
????????????????????????????????? relatedBy:NSLayoutRelationEqual
???????????????????????????????????? toItem:aView
????????????????????????????????? attribute:NSLayoutAttributeRight
???????????????????????????????? multiplier:1
?????????????????????????????????? constant:10]];
??? //添加一個限制? 等效于 bView.frame.origin.x? = (aView.frame.origin.x +aView.frame.size.width)? * 1? + 10,好像是這樣的！個人覺得！

? 它是一種依賴關系，bView依賴aView，這樣就算aView變了，bView也會跟著變換。
??? [self.view addConstraint:
???? [NSLayoutConstraint constraintWithItem:bView
????????????????????????????????? attribute:NSLayoutAttributeTop
????????????????????????????????? relatedBy:NSLayoutRelationEqual
???????????????????????????????????? toItem:aView
????????????????????????????????? attribute:NSLayoutAttributeTop
???????????????????????????????? multiplier:1
?????????????????????????????????? constant:0]];
?? ?
??? [aView release];
??? [bView release];
}

?

?

?

constraintWithItem:attribute:relatedBy:toItem:attribute:multiplier:constant:

?

Create a constraint of the form "view1.attr1 <relation> view2.attr2 * multiplier + constant".

屬性

typedef NS_ENUM(NSInteger, NSLayoutAttribute) {
??? NSLayoutAttributeLeft = 1,
??? NSLayoutAttributeRight,
??? NSLayoutAttributeTop,
??? NSLayoutAttributeBottom,
??? NSLayoutAttributeLeading,
??? NSLayoutAttributeTrailing,
??? NSLayoutAttributeWidth,
??? NSLayoutAttributeHeight,
??? NSLayoutAttributeCenterX,
??? NSLayoutAttributeCenterY,
??? NSLayoutAttributeBaseline,
?? ?
??? NSLayoutAttributeNotAnAttribute = 0
};

關系

typedef NS_ENUM(NSInteger, NSLayoutRelation) {
??? NSLayoutRelationLessThanOrEqual = -1,
??? NSLayoutRelationEqual = 0,
??? NSLayoutRelationGreaterThanOrEqual = 1,
};

最后的結果就是 “view1.attr1? < ?? ?? >= ?? 或者 == ? 或者 ?? <= ? ? ? >? view2.attr2 * multiplier + constant”

轉載于:https://www.cnblogs.com/DamonTang/p/3570743.html

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