使用autolayout的NSLayoutConstraint类中的constraintWithItem 、constraintsWithVisualFormat这两个类方法来创建视图并可以实现自动布局

#import "ViewController.h"



@interface ViewController ()



@end



@implementation ViewController



- (void)viewDidLoad

{

    [super viewDidLoad];

    

    [self createViewWithConstraintItem];

    [self createViewWithConstraint];

}



- (void)createViewWithConstraintItem

{

    UIView *redView = [[UIView alloc]init];

    redView.backgroundColor=[UIColor redColor];

    redView.translatesAutoresizingMaskIntoConstraints = NO;

    [self.view addSubview:redView];

    

    /**左边距50*/

    NSLayoutConstraint *viewLeftConstraint = [NSLayoutConstraint constraintWithItem:redView

                                                            attribute:NSLayoutAttributeLeading relatedBy:NSLayoutRelationEqual toItem:self.view

                                                            attribute:NSLayoutAttributeLeading multiplier:1 constant:50.f];

    /**上边距50*/

    NSLayoutConstraint *viewTopConstraint = [NSLayoutConstraint constraintWithItem:redView

                                                    attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self.view

                                                            attribute:NSLayoutAttributeTop multiplier:1 constant:100.f];

    

    /*--------------------------------------------------------------------------------

     注意：通常在设置宽度高度的时候最好不要固定死，另外当viw1.attribute不等于view2.attribute*multiplier

     +constant的时候，我们则要constraintWithItem函数中的toItem设置为nil以及attribute参数设置

     为NSLayoutAttributeNotAnAttribute

     ---------------------------------------------------------------------------------*/

    /**宽度150*/

    NSLayoutConstraint *viewWidthConstaint = [NSLayoutConstraint constraintWithItem:redView

                                                            attribute:NSLayoutAttributeWidth

                                                    relatedBy:NSLayoutRelationGreaterThanOrEqual

                                                            toItem:nil

                                                        attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:150];

    /**高度150*/

    NSLayoutConstraint *viewHeightConstaint = [NSLayoutConstraint constraintWithItem:redView

                                                                attribute:NSLayoutAttributeHeight

                                                    relatedBy:NSLayoutRelationGreaterThanOrEqual

                                                                toItem:nil

                                                        attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:150];

    

    [self.view addConstraints:@[viewLeftConstraint,viewTopConstraint,viewWidthConstaint,viewHeightConstaint]];

}



- (void)createViewWithConstraint

{

    /**创建左边view*/

    UIView *leftView = [[UIView alloc]init];

    leftView.backgroundColor = [UIColor redColor];

    leftView.translatesAutoresizingMaskIntoConstraints = NO;

    [self.view addSubview:leftView];

    

    /**创建右边view*/

    UIView *rightView = [[UIView alloc]init];

    rightView.backgroundColor = [UIColor blueColor];

    rightView.translatesAutoresizingMaskIntoConstraints = NO;

    [self.view addSubview:rightView];

    

    

    /**创建右下方view*/

    UIView *rightBottomView = [[UIView alloc]init];

    rightBottomView.backgroundColor = [UIColor yellowColor];

    rightBottomView.translatesAutoresizingMaskIntoConstraints = NO;

    [self.view addSubview:rightBottomView];

    

    NSDictionary *viewDic = NSDictionaryOfVariableBindings(leftView,rightView,rightBottomView);

    

    /*距父视图左边距50以及自身宽度大于等于150*/

    NSArray *leftView_H = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-50-[leftView(>=150)]" options:0 metrics:nil views:viewDic];



    /*距父视图上边距100以及自身高度大于等于150*/

     NSArray *leftView_V = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-100-[leftView(>=150)]" options:0 metrics:nil views:viewDic];



    /*水平方向布局，rightView 在 leftView 右侧标准距离处，并且宽度不小于 50 点。*/

    NSArray *rightView_H = [NSLayoutConstraint constraintsWithVisualFormat:@"H:[leftView]-[rightView(>=50)]" options:0 metrics:nil views:viewDic];

    

    NSArray *rightView_V = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-100-[rightView(>=50)]" options:0 metrics:nil views:viewDic];

    

    

    

    NSArray *rightBottomView_H = [NSLayoutConstraint constraintsWithVisualFormat:@"H:[leftView]-[rightBottomView(>=50)]" options:0 metrics:nil views:viewDic];

    

    /*垂直方向布局距离父视图100，另外rightBottomView 在 rightView下方也就是相当于紧贴*/

    NSArray *rightBottomView_V = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-100-[rightView(>=50)][rightBottomView(>=100)]" options:0 metrics:nil views:viewDic];

    

    

    [self.view addConstraints:leftView_H];

    [self.view addConstraints:leftView_V];

    

    [self.view addConstraints:rightView_H];

    [self.view addConstraints:rightView_V];

    

    [self.view addConstraints:rightBottomView_H];

    [self.view addConstraints:rightBottomView_V];

    

}



@end