效果：

.wxml页面：

<view class="opinion_wrap">
    <view class="wrap">
        <form bindsubmit="formSubmit">
            <view class="contant_wrap">
                <view class="contant">
                    <textarea name="opinion"   value="{{contact}}" auto-height placeholder-class="placeholder" placeholder="为了带给您更好的体验,期待您的任何反馈,我们将会不断改进" />
                </view>
            </view>
            <view class="phone">
                <input name="contant" value="{{contant}}" placeholder-class="placeholder" placeholder="您的手机号或者邮箱,方便我们及时给您回复" />
            </view>
            <button formType="submit" hover-class="none" loading="{{loading}}">提交</button>
        </form>
    </view>
</view>

.wxcss样式：

/* pages/advice/advice.wxss */
page{
    background-color: #efefef;
}

.contant_wrap{
    background-color: #fff;
}
.contant{
    width: 94%;
    margin: 0 auto
}
textarea{
    min-height: 300rpx;
    padding: 10rpx 0;
    width: 100%;
}
input{
    margin-top: 30rpx;
    height: 100rpx;
    padding-left: 20rpx;
    background-color: #fff;
}
button{
    margin-top: 60rpx;
    background-color: #353331;
    color: #fff;
}
.placeholder{
    color: #999999;
    font-size: 12pt;
}