如何解决动态数据未显示在本机反应中?
我尝试使用以下逻辑在我的 React Native 中显示动态数据。但它只显示一次数据,如果我刷新我的应用程序,它会一次又一次地出错: 错误就像 undefined is not an object('data.map') ....如果逻辑错误,谁能帮助我,我的逻辑中遗漏了什么?
const [chartData,setChartData] = useState({});
const chart = () => {
let status = [];
let dates = [];
let count = 0;
let count1 = 0;
let count2 = 0;
let count3 = 0;
let count4 = 0;
fetch("<API CALL>")
.then(res => res.json())
.then(results => {
for (const stats of results) {
if (stats.status == "Open") {
count = count + 1;
}
else if (stats.status == "Closed") {
count1 = count1 + 1;
}
else if (stats.status == "Resolved") {
count2 = count2 + 1;
}
else if (stats.status == "In Process") {
count3 = count3 + 1;
}
}
count4 = count3 + count2 + count1 + count;
setChartData({
labels: ["Open","Closed","Resolved","In Process"],datasets: [
{
data: [count,count1,count2,count3]
}
]
})
})
console.log(chartData);
}
useEffect(() => {
chart();
},[]);
<BarChart
style={{ borderRadius: 16 }}
data={chartData}
width={screenWidth}
height={400}
chartConfig={chartConfig}
verticalLabelRotation={30}
/>
存储在monogdb图集中的数据
_id:<RANDOM_ID>
name:"Jade Labs access"
request:"Dhanjay"
subject:"PI RPA"
category:"IT"
priority:"High"
desc:"RPA project"
location:"Pune"
status:"Resolved"
date:"2/23/2021"
__v:0
assign:"Dhanjay Bhardwaj"
解决方法
试试看是否有效
{chartData.datasets != undefined ? (<BarChart
style={{ borderRadius: 16 }}
data={chartData}
width={screenWidth}
height={400}
chartConfig={chartConfig}
verticalLabelRotation={30}
/>):null}
它应该在有数据时加载barchat
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