空状态之间的转换

    @Component({
        ...
        animations: [
            trigger('appear', [
                transition(':enter', [
                    style({
                      //style applied at the start of animation
                    }),
                animate('300ms ease-in', style({
                    //style applied at the end of animation
                }))
                ])
            ])
        ]
    })
    class AnimComponent {

    }
]