//渐入，渐出实现

show: function (that, param, opacity) {

var animation = wx.createAnimation({

//持续时间1000ms

duration: 1000,

timingFunction: 'ease',

});

//var animation = this.animation

animation.opacity(opacity).step();

//将param转换为key

var json = '{"' + param + '":""}'

json = JSON.parse(json);

json[param] = animation.export();

//设置动画

that.setData(json);

},