iOS app进入后台显示模糊效果

AppDelegate.m文件

//懒加载一个毛玻璃效果 UIVisualEffectView
- (UIVisualEffectView *)effectView {
    if (!_effectView) {
        // 初始毛玻璃view
        _effectView = [[UIVisualEffectView alloc] initWithEffect:[UIBlurEffect effectWithStyle:UIBlurEffectStyleLight]];
        // 模糊透明度
        _effectView.alpha = 0.9;
        _effectView.frame = [UIScreen mainScreen].bounds;
    }
    return _effectView;
}

//添加 UIVisualEffectView
-(void)addEffectView {
    [[[UIApplication sharedApplication] keyWindow] addSubview:self.effectView];
}

//移除 UIVisualEffectView
-(void) removeEffectView {
    [UIView animateWithDuration:0.5 animations:^{
        [self.effectView removeFromSuperview];
    }];
}

//执行 添加方法
- (void)applicationWillResignActive:(UIApplication *)application {
     self.addEffectView();
}

//执行 移除方法
- (void)applicationDidBecomeActive:(UIApplication *)application{
     self.removeEffectView();
}