景象形容：

快利用中通过setinterval周期函数来循环触发canvas绘制代码，在华为手机上绘制的动画会很卡顿，不晦涩。

问题代码如下：

click0() {

this.speed = 0.3

let ctx = this.$element('canvas').getContext('2d')

setInterval(() => {

this.num0 += 2

this.noise = Math.min(0.5, 1) * this.MAX

this._draw(ctx)

this.MAX <= 200 && (this.MAX += 4)

}, 20)

},

_draw(ctx) {

this.phase = (this.phase + this.speed) % (Math.PI * 64)

ctx.clearRect(0, 0, this.width, this.height)

this._drawLine(ctx, -2, 'rgba(0, 194, 255, 0.2)')

this._drawLine(ctx, -6, 'rgba(0, 194, 255, 0.4)')

this._drawLine(ctx, 4, 'rgba(0, 194, 255, 0.6)')

this._drawLine(ctx, 2, 'rgba(0, 194, 255, 0.8)')

this._drawLine(ctx, 1, 'rgba(0, 194, 255, 1)', 4)

},

问题剖析：

this._draw()办法中的canvas绘制操作工夫长，最低须要100ms的绘制工夫，而代码中周期时间只有20ms，华为快利用引擎会执行这个周期内的操作，而后能力执行下一个周期。所以设置为20ms时的成果会看起来比较慢。

解决办法：

开发者能够先依据设施信息接口获取下设施信息中的引擎的提供商判断是否是华为的快利用引擎，如果是华为快利用引擎则设置间隔时间大于100ms，不是则能够设置小于100ms，可解决华为快利用引擎和快利用联盟引擎差别问题。代码如下(红色局部)：

onShow: function () {

var that = this

device.getInfo({

success: function (ret) {

console.log("handling success:", JSON.stringify(ret));

that.engineProvider = ret.engineProvider;

},

fail: function (erromsg, errocode) {

console.log("message:", erromsg, errocode);

}

})

},

click0() {

var that = this

this.speed = 0.3

console.log(that.engineProvider)

let ctx = this.$element('canvas').getContext('2d')

if (that.engineProvider === "huawei") {

setInterval(() => {

this.num0 += 2

this.noise = Math.min(0.5, 1) * this.MAX

this._draw(ctx)

this.MAX <= 200 && (this.MAX += 4)

}, 120)

} else {

setInterval(() => {

this.num0 += 2

this.noise = Math.min(0.5, 1) * this.MAX

this._draw(ctx)

this.MAX <= 200 && (this.MAX += 4)

}, 20)

}

},

_draw(ctx) {

this.phase = (this.phase + this.speed) % (Math.PI * 64)

ctx.clearRect(0, 0, this.width, this.height)

this._drawLine(ctx, -2, 'rgba(0, 194, 255, 0.2)')

this._drawLine(ctx, -6, 'rgba(0, 194, 255, 0.4)')

this._drawLine(ctx, 4, 'rgba(0, 194, 255, 0.6)')

this._drawLine(ctx, 2, 'rgba(0, 194, 255, 0.8)')

this._drawLine(ctx, 1, 'rgba(0, 194, 255, 1)', 4)

},

_drawLine(ctx, attenuation, color, width) {

ctx.save()

ctx.moveTo(0, 0);

ctx.beginPath();

ctx.strokeStyle = color;

ctx.lineWidth = width || 1;

var x, y;

for (var i = -this.K; i <= this.K; i += 0.01) {

x = this.width * ((i + this.K) / (this.K * 2))

y = this.height / 2 + this.noise * this._globalAttenuationFn(i) * (1 / attenuation) * Math.sin(this.F * i - this.phase)

ctx.lineTo(x, y)

}

ctx.stroke()

ctx.restore()

},

欲了解更多详情，请参阅：

canvas接口介绍：

https://developer.huawei.com/consumer/cn/doc/development/quickApp-References/quickapp-api-canvas

快利用开发领导文档：https://developer.huawei.com/consumer/cn/doc/development/quickApp-Guides/quickapp-whitepaper

原文链接：https://developer.huawei.com/consumer/cn/forum/topic/0204404988672310224?fid=18

原作者：Mayism