#pragma mark - 尺寸相关
#define HWScreenW [UIScreen mainScreen].bounds.size.width
#define HWScreenH [UIScreen mainScreen].bounds.size.height

@interface ViewController ()<UITableViewDelegate, UITableViewDataSource>
@property (weak, nonatomic) IBOutlet UITableView *tableVIew;
@property(strong,nonatomic)UIWindow *window;
@property(strong,nonatomic)UIButton *button;
/** <#注释#> */
@property (nonatomic, assign) BOOL isShow;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    [self.tableVIew registerClass:[UITableViewCell class] forCellReuseIdentifier:@"cellID"];
    [self loadData];
}
#pragma mark - 模拟数据请求
- (void)loadData {
    NSLog(@"数据请求成功");
    self.isShow = YES;
    if (self.isShow) {
        [self createSuspendButton];
    }
}
#pragma mark - 创建悬浮的按钮
- (void)createSuspendButton {
    CGFloat btnHW = 40; // 按钮宽高
    CGFloat btnTop = 20; // 上间距
    CGFloat btnRight = 20; // 右间距
    CGFloat borderWidth = 2; // 边框宽度
    _button = [UIButton buttonWithType:UIButtonTypeCustom];
    [_button setTitle:@"戴" forState:UIControlStateNormal];
    _button.frame = CGRectMake(0, 0, btnHW, btnHW);
    [_button setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
    [_button addTarget:self action:@selector(tryButtonClick) forControlEvents:UIControlEventTouchUpInside];
    _button.backgroundColor = [UIColor clearColor];
    [_button addRoundedCornersWithRadius:btnHW/2];
    [_button addBorderWithWidth:borderWidth];
    _window = [[UIWindow alloc]initWithFrame:CGRectMake(HWScreenW - btnHW -btnRight, 64+btnTop, btnHW, btnHW)];
    _window.windowLevel = UIWindowLevelAlert + 1;
    _window.backgroundColor = [UIColor clearColor];
    [_window addRoundedCornersWithRadius:btnHW/2];
    [_window addSubview:_button];
    [_window makeKeyAndVisible];//关键语句,显示window
}
#pragma mark - 按钮点击事件
- (void)tryButtonClick {
    twoViewController *ctr = [[twoViewController alloc]init];
    [self.navigationController pushViewController:ctr animated:YES];
}
#pragma mark - 关闭悬浮的window
- (void)closeWindow {
    [_window resignKeyWindow];
    _window = nil;
}
#pragma mark - 即将消失
- (void)viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated];
    [self closeWindow];
}
#pragma mark - 即将显示
- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    if (self.isShow) {
        [self createSuspendButton];
    }
}

用到的分类

.h文件

#import <UIKit/UIKit.h>

@interface UIView (Tools)
/** 
 快速给View添加4边阴影
 参数:阴影透明度，默认0
 */
- (void)addProjectionWithShadowOpacity:(CGFloat)shadowOpacity;
/** 
 快速给View添加4边框
 参数:边框宽度
 */
- (void)addBorderWithWidth:(CGFloat)width;
/**
 快速给View添加4边框
 width:边框宽度
 borderColor:边框颜色
 */
- (void)addBorderWithWidth:(CGFloat)width borderColor:(UIColor *)borderColor;
/**
 快速给View添加圆角
 参数:圆角半径
 */
- (void)addRoundedCornersWithRadius:(CGFloat)radius;
/**
 快速给View添加圆角
 radius:圆角半径
 corners:且那几个角
 类型共有以下几种:
 typedef NS_OPTIONS(NSUInteger, UIRectCorner) {
 UIRectCornerTopLeft,
 UIRectCornerTopRight ,
 UIRectCornerBottomLeft,
 UIRectCornerBottomRight,
 UIRectCornerAllCorners
 };
 使用案例:[self.mainView addRoundedCornersWithRadius:10 byRoundingCorners:UIRectCornerBottomLeft | UIRectCornerBottomRight]; // 切除了左下 右下
 */
- (void)addRoundedCornersWithRadius:(CGFloat)radius byRoundingCorners:(UIRectCorner)corners;

@end

.m文件

#import "UIView+Tools.h"

@implementation UIView (Tools)
#pragma mark - 快速添加阴影
- (void)addProjectionWithShadowOpacity:(CGFloat)shadowOpacity {
    self.layer.shadowColor = [UIColor blackColor].CGColor;//shadowColor阴影颜色
    self.layer.shadowOffset = CGSizeMake(0,0);//shadowOffset阴影偏移,x向右偏移2，y向下偏移6，默认(0, -3),这个跟shadowRadius配合使用
    self.layer.shadowOpacity = shadowOpacity;//阴影透明度，默认0
    self.layer.shadowRadius = 2;//阴影半径，默认3
}
- (void)addBorderWithWidth:(CGFloat)width {
    self.layer.borderWidth = width;
    self.layer.borderColor = [UIColor blackColor].CGColor;
}
- (void)addBorderWithWidth:(CGFloat)width borderColor:(UIColor *)borderColor {
    self.layer.borderWidth = width;
    self.layer.borderColor = borderColor.CGColor;
}
- (void)addRoundedCornersWithRadius:(CGFloat)radius {
    self.layer.cornerRadius = radius;
    self.layer.masksToBounds = YES;
}
- (void)addRoundedCornersWithRadius:(CGFloat)radius byRoundingCorners:(UIRectCorner)corners{
    UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:self.bounds byRoundingCorners:corners cornerRadii:CGSizeMake(radius, radius)];
    CAShapeLayer *maskLayer = [[CAShapeLayer alloc] init];
    maskLayer.frame = self.bounds;
    maskLayer.path = maskPath.CGPath;
    self.layer.mask = maskLayer;
}
@end