uni showLoading 还有注意关闭 闭包， .finally

    uni.showLoading({  
        title:'正在提交...'  
    });  
    let data = JSON.parse(JSON.stringify($this.sendData));  
    const r = instance.post({  
        url : url,  
        data: data  
    })  
    .then(res => {  
        console.log(res)  
        uni.showToast({ title: '提交成功', icon: "none", position:'bottom'});  
    })  
    .catch(err => {  
        uni.showToast({ title: '提交失败', icon: "none", position:'bottom'});  
    })  
    .finally(() => {  
        uni.hideLoading();  
        console.log('finally')  
    });