NSLayoutConstraint

- (void)createThreeViews{
    
    //1 创建3个view的对象
    
    UIView *leftView = [[UIView alloc]init];
    
    UIView *rightView = [[UIView alloc]init];
    
    UIView *bottomView = [[UIView alloc]init];
    
    //2 设置背景颜色
    
    leftView.backgroundColor = [UIColor greenColor];
    
    rightView.backgroundColor = [UIColor purpleColor];
    
    bottomView.backgroundColor = [UIColor orangeColor];
    
    //3 添加视图上显示
    
    [self.view addSubview:leftView];
    
    [self.view addSubview:rightView];
    
    [self.view addSubview:bottomView];
    
    //4 关闭系统的自定义布局
    
    leftView.translatesAutoresizingMaskIntoConstraints = NO;
    
    rightView.translatesAutoresizingMaskIntoConstraints = NO;
    
    bottomView.translatesAutoresizingMaskIntoConstraints = NO;
    
    //leftView的上 = self.view的上+20
    
    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:leftView
                              
                                                          attribute:NSLayoutAttributeTop
                              
                                                          relatedBy:NSLayoutRelationEqual
                              
                                                             toItem:self.view
                              
                                                          attribute:NSLayoutAttributeTop
                              
                                                         multiplier:1.
                              
                                                           constant:20]];
    
    // leftView的左 = self.view的左 + 20
    
    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:leftView
                              
                                                          attribute:NSLayoutAttributeLeft
                              
                                                          relatedBy:NSLayoutRelationEqual
                              
                                                             toItem:self.view
                              
                                                          attribute:NSLayoutAttributeLeft
                              
                                                         multiplier:1.
                              
                                                           constant:20]];
    
    // rightView的上 = leftView的上
    
    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:rightView
                              
                                                          attribute:NSLayoutAttributeTop
                              
                                                          relatedBy:NSLayoutRelationEqual
                              
                                                             toItem:leftView
                              
                                                          attribute:NSLayoutAttributeTop
                              
                                                         multiplier:1.
                              
                                                           constant:0]];
    
    // rightView的左 = leftView的右 + 20
    
    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:rightView
                              
                                                          attribute:NSLayoutAttributeLeft
                              
                                                          relatedBy:NSLayoutRelationEqual
                              
                                                             toItem:leftView
                              
                                                          attribute:NSLayoutAttributeRight
                              
                                                         multiplier:1.
                              
                                                           constant:20]];
    
    // rightView的右 = self.view的右 - 20
    
    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:rightView
                              
                                                          attribute:NSLayoutAttributeRight
                              
                                                          relatedBy:NSLayoutRelationEqual
                              
                                                             toItem:self.view
                              
                                                          attribute:NSLayoutAttributeRight
                              
                                                         multiplier:1.
                              
                                                           constant:-20]];
    
    // rightView的高 = leftView的高
    
    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:rightView
                              
                                                          attribute:NSLayoutAttributeHeight
                              
                                                          relatedBy:NSLayoutRelationEqual
                              
                                                             toItem:leftView
                              
                                                          attribute:NSLayoutAttributeHeight
                              
                                                         multiplier:1.
                              
                                                           constant:0]];
    
    // rightView的宽 = leftView的宽
    
    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:rightView
                              
                                                          attribute:NSLayoutAttributeWidth
                              
                                                          relatedBy:NSLayoutRelationEqual
                              
                                                             toItem:leftView
                              
                                                          attribute:NSLayoutAttributeWidth
                              
                                                         multiplier:1.0
                              
                                                           constant:0]];
    
    //bottomView的左 = self.view的左 + 20
    
    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:bottomView
                              
                                                          attribute:NSLayoutAttributeLeft
                              
                                                          relatedBy:NSLayoutRelationEqual
                              
                                                             toItem:self.view
                              
                                                          attribute:NSLayoutAttributeLeft
                              
                                                         multiplier:1
                              
                                                           constant:20]];
    
    //bottomView的右 = self.view的右 - 20
    
    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:bottomView
                              
                                                          attribute:NSLayoutAttributeRight
                              
                                                          relatedBy:NSLayoutRelationEqual
                              
                                                             toItem:self.view
                              
                                                          attribute:NSLayoutAttributeRight
                              
                                                         multiplier:1
                              
                                                           constant:-20]];
    
    //bottomView的上 = leftView的下 + 20
    
    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:bottomView
                              
                                                          attribute:NSLayoutAttributeTop
                              
                                                          relatedBy:NSLayoutRelationEqual
                              
                                                             toItem:leftView
                              
                                                          attribute:NSLayoutAttributeBottom
                              
                                                         multiplier:1
                              
                                                           constant:20]];
    
    //bottomView的高 = leftView的高
    
    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:bottomView
                              
                                                          attribute:NSLayoutAttributeHeight
                              
                                                          relatedBy:NSLayoutRelationEqual
                              
                                                             toItem:leftView
                              
                                                          attribute:NSLayoutAttributeHeight
                              
                                                         multiplier:1
                              
                                                           constant:0]];
    
    //bottomView的下 = self.view的下 + 20
    
    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:bottomView
                              
                                                          attribute:NSLayoutAttributeBottom
                              
                                                          relatedBy:NSLayoutRelationEqual
                              
                                                             toItem:self.view
                              
                                                          attribute:NSLayoutAttributeBottom
                              
                                                         multiplier:1
                              
                                                           constant:-20]];
    

    
}

Simulator Screen Shot - iPhone X - 2018-04-17 at 10.07.37.png