渐变显示渐变消失的BackgroundView

效果如下：

源码：

BackgroundView.h 与 BackgroundView.m

//
//  BackgroundView.h
//  TestHUD
//
//  Created by YouXianMing on 14-9-30.
//  Copyright (c) 2014年 YouXianMing. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface BackgroundView : UIView

@property (nonatomic, assign) NSTimeInterval  startDuration; // 动画开始时持续时间
@property (nonatomic, assign) NSTimeInterval  endDuration;   // 动画结束时持续时间

- (instancetype)initInView:(UIView *)view;

// 开始附加到view中
- (void)addToView;

// 将自己从view中移除掉
- (void)removeSelf;

@end

//
//  BackgroundView.m
//  TestHUD
//
//  Created by YouXianMing on 14-9-30.
//  Copyright (c) 2014年 YouXianMing. All rights reserved.
//

#import "BackgroundView.h"

#ifdef DEBUG
#define BackgroundView_DLog(fmt, ...) NSLog((@"BackgroundView.m:%s:%d" fmt), __PRETTY_FUNCTION__, __LINE__, ##__VA_ARGS__);
#else
#define BackgroundView_DLog(...)
#endif

@interface BackgroundView ()

@property (nonatomic, weak) UIView   *inView;

@end

@implementation BackgroundView

- (instancetype)initInView:(UIView *)view
{
    self = [super initWithFrame:view.bounds];
    if (self) {
        _inView              = view;
        self.backgroundColor = [[UIColor blackColor] colorWithAlphaComponent:0.5f];
        self.alpha           = 0;
    }
    return self;
}

- (void)addToView
{
    // 添加到view中
    [_inView addSubview:self];

    // 开始执行动画
    NSTimeInterval duration = 0.2;
    if (_startDuration > 0) {
        duration = _startDuration;
    }
    [UIView animateWithDuration:duration animations:^{
        self.alpha = 1.f;
    }];
}

- (void)removeSelf
{
    // 开始执行动画
    NSTimeInterval duration = 0.2;
    if (_endDuration > 0) {
        duration = _endDuration;
    }
    [UIView animateWithDuration:duration animations:^{
        self.alpha = 0.f;
    } completion:^(BOOL finished) {
        [self removeFromSuperview];
    }];
}

- (void)dealloc
{
    BackgroundView_DLog(@" 安全释放");
}

@end

category文件：

//
//  UIView+BackgroundView.h
//  BackgroundView
//
//  Created by YouXianMing on 14-10-3.
//  Copyright (c) 2014年 YouXianMing. All rights reserved.
//

#import <UIKit/UIKit.h>
#import "BackgroundView.h"

typedef void (^ConfigBackgroundViewBlock)(BackgroundView *configView);

@interface UIView (BackgroundView)

- (void)showBackgroundViewAndConfig:(ConfigBackgroundViewBlock)block;
- (void)removeBackgroundView;

@end

//
//  UIView+BackgroundView.m
//  BackgroundView
//
//  Created by YouXianMing on 14-10-3.
//  Copyright (c) 2014年 YouXianMing. All rights reserved.
//

#import "UIView+BackgroundView.h"

#define TAG_DATA  0x3d2894

@implementation UIView (BackgroundView)

- (void)showBackgroundViewAndConfig:(ConfigBackgroundViewBlock)block
{
    if (self == nil) {
        return;
    }

    BackgroundView *backView = [[BackgroundView alloc] initInView:self];
    backView.tag = TAG_DATA;
    block(backView);

    [backView addToView];
}

- (void)removeBackgroundView
{
    BackgroundView *backView = (BackgroundView *)[self viewWithTag:TAG_DATA];
    if (backView) {
        [backView removeSelf];
    }
}

@end

使用的源码：

//
//  ViewController.m
//  BackgroundView
//
//  Created by YouXianMing on 14-10-3.
//  Copyright (c) 2014年 YouXianMing. All rights reserved.
//

#import "ViewController.h"
#import "UIView+BackgroundView.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    // 添加手势
    UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self
                                                                          action:@selector(tapEvent:)];
    [self.view addGestureRecognizer:tap];

    UILabel *label      = [[UILabel alloc] initWithFrame:self.view.bounds];
    label.text          = @"YouXianMing";
    label.textAlignment = NSTextAlignmentCenter;
    label.font          = [UIFont fontWithName:@"HelveticaNeue-Thin" size:40.f];
    label.textColor     = [UIColor redColor];
    [self.view addSubview:label];
}

- (void)tapEvent:(UITapGestureRecognizer *)tap
{
    // 显示
    [self.view showBackgroundViewAndConfig:^(BackgroundView *configView) {
        configView.backgroundColor = [[UIColor blackColor] colorWithAlphaComponent:0.6];
        configView.startDuration = 0.4f;
        configView.endDuration   = 0.4f;
    }];

    // 延迟3s执行
    [self performSelector:@selector(affterDelay)
               withObject:nil
               afterDelay:3.f];
}

- (void)affterDelay
{
    // 隐藏
    [self.view removeBackgroundView];
}

@end

以下是需要注意的地方：