最近因为需要，做了下哔哩哔哩动画这个应用。从数据、素材的抓取、分类、测试，到应用的基本功能实现，确实用了一段时间。下面是做哔哩哔哩动画的开机动画效果的实现。
![Uploading LuanchImage设置_552569.png . . .]](http://upload-images.jianshu.io/upload_images/2023147-b27b7518b9e7f8c7.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)
动画开机图.png
从图一到图二，中间的人物从小到大，从透明到呈现的过程。
实现这个效果并不难，步骤如下
1.在LuanchImage设置开机图片
LuanchImage设置.png
LuanchImage.png
2.使用CABasicAnimationGroup实现动画效果
这里创建了一个视图控制器类LaunchViewController，用于实现动画效果。
设置两个属性，其中bgImageView是背景图，playImageView是做动画的图片。
@property (nonatomic,strong)UIImageView *bgImageView;
@property (nonatomic,strong)UIImageView *playImageView;
给这两个属性懒加载
- (UIImageView *)bgImageView{
if(!_bgImageView){
_bgImageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, ScreenWidth, ScreenHeight)];
_bgImageView.image = [UIImage imageNamed:@"bilibili_splash_iphone_bg"];
}
return _bgImageView;
}
- (UIImageView *)playImageView{
if(!_playImageView){
_playImageView = [[UIImageView alloc] initWithFrame:CGRectMake(ScreenWidth/2, ScreenHeight/2-100, 1, 1.3)];
_playImageView.image = [UIImage imageNamed:@"bilibili_splash_default"];
}
return _playImageView;
}
在viewDidLoad中把视图添加上去
[self.view addSubview:self.bgImageView];
[self.bgImageView addSubview:self.playImageView];
[self performSelector:@selector(animationLunch) withObject:self afterDelay:0];
animationLunch中实现组合动画效果
- (void)animationLunch{
CGFloat duration = 1.5;
CABasicAnimation *scale = [CABasicAnimation animationWithKeyPath:@"transform.scale"];
scale.fromValue = @1;
scale.toValue = @(ScreenWidth - 40);
scale.duration = duration;
scale.repeatCount = 1;
scale.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
CABasicAnimation *opacity = [CABasicAnimation animationWithKeyPath:@"opacity"];
opacity.fromValue = @0;
opacity.toValue = @1;
opacity.duration = duration;
scale.repeatCount = 1;
CAAnimationGroup *animationGroup = [CAAnimationGroup animation];
animationGroup.animations = @[scale,opacity];
animationGroup.duration = duration;
animationGroup.repeatCount = 1;
//如果是一个动画CAAnimation,则需要将其removedOnCompletion设置为NO,要不然fillMode不起作用
animationGroup.removedOnCompletion = NO;
//决定当前在非active时间段的行为,比如动画开始之前,动画结束之后
animationGroup.fillMode =kCAFillModeForwards;
animationGroup.delegate = self;
[self.playImageView.layer addAnimation:animationGroup forKey:nil];
}
让LaunchViewController遵循代理，并实现CAAnimationDelegate协议
- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag{
[NSThread sleepForTimeInterval:2.0];
//移除开机动画
[self.bgImageView removeFromSuperview];
}
这个类要做的事情完成了，回到AppDelegate中，导入刚创建的类头文件，在application: didFinishLaunchingWithOptions:中加入以下代码,把动画添加到场景中
_launchVC = [[LaunchViewController alloc] init];
//添加到场景
[self.window addSubview:_launchVC.view];
//放到最顶层
[self.window bringSubviewToFront:_launchVC.view];
[self performSelector:@selector(removeLunch) withObject:self afterDelay:2.0];
到此，哔哩哔哩动画的开机动画效果就实现了。
