VFL演示样例

上篇文章向大家介绍了VFL的基本的语法点，假设对下面演示样例不熟的童鞋，能够前去參考。废话不多说。我们直接来看演示样例。

演示样例一

将五个大小同样、颜色不同的view排成一行，view间的间隔为15px,第一个view的间隔与屏幕的左边间隔10px,最后一个view的间隔与屏幕的右边间隔也为10px。

//依据屏幕的宽度。计算view的宽度和高度
    CGFloat width = ([[UIScreen mainScreen] bounds].size.width-2*10-4*15)/5;
    CGFloat height = width;

    //固定第一个view
    UIView *firstView = [UIView new];
    firstView.backgroundColor = [UIColor blackColor];
    // 将次属性设置为NO,表示将使用AutoLayout的方式来布局
    firstView.translatesAutoresizingMaskIntoConstraints = NO;
    [self.view addSubview:firstView];

    //------使用VFL为第一个view加入约束------
    //在水平方向上，让firstview的左边与父视图的左边间隔10px,且自身宽度为width
    NSArray *constraints1 = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-10-[firstView(==width)]" options:0 metrics:@{@"width":@(width)} views:NSDictionaryOfVariableBindings(firstView)];
    //在垂直方向上，让firstView的上边与父视图的上边间隔100px,且自身的高度为height
    NSArray *constraints2 = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-100-[firstView(==height)]" options:0 metrics:@{@"height":@(height)} views:NSDictionaryOfVariableBindings(firstView)];
    [self.view addConstraints:constraints1];
    [self.view addConstraints:constraints2];

    //定义一个颜色数组
    NSArray *colors = @[[UIColor redColor],[UIColor orangeColor],[UIColor yellowColor],[UIColor blueColor]];
    //定义一个views数组
    NSMutableArray *views = [NSMutableArray array];
    [views addObject:firstView];
    for (int i = 0; i < 4; i++) {
        UIView *view = [UIView new];
        view.backgroundColor = colors[i];
         view.translatesAutoresizingMaskIntoConstraints = NO;
        [self.view addSubview:view];
        [views addObject:view];
    }

    //依次给views数组中的view使用vfl加入约束
    for (int i = 1; i < views.count; i++) {
        UIView *view1 = views[i-1];
        UIView *view2 = views[i];
        NSDictionary *bindings = NSDictionaryOfVariableBindings(view1,view2);
        NSArray *constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"H:[view1]-15-[view2(==width)]" options:0 metrics:@{@"width":[NSNumber numberWithFloat:width]} views:bindings];
        [self.view addConstraints:constraints];

    }
    UIView *view1 = views[0];
    for (int i = 0; i < views.count; i++) {
        UIView *view2 = views[i];
        NSDictionary *bindings = NSDictionaryOfVariableBindings(view1,view2);
        NSArray *constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-100-[view2(==view1)]" options:0 metrics:nil views:bindings];
        [self.view addConstraints:constraints];

    }

效果截图: