How to solve uniapp echarts distortion

In recent years, with the rapid development of the mobile Internet, the development of mobile applications has become more and more important, which has led to the development of multiple application frameworks and attracted more and more developers to participate. Among them, Uni-App has become a high-profile cross-platform application framework that can quickly build a variety of applications, such as: iOS, Android, WeChat applets, etc.

In the Uni-App framework, ECharts is a powerful, flexible and diverse chart library. It simplifies complex data visualization and interaction design, and is seamlessly integrated with Uni-App. It is the best interface design for Uni-App. an integral part of. This article mainly focuses on possible ECharts chart distortion problems in Uni-App and provides solutions.

1. Causes of ECharts distortion failure

1.1 Screen pixel ratio

Mobile terminals have richer screens than desktop terminals, such as iOS and Android devices, but their screens The resolution and pixel density are very high. When drawing charts when the screen pixel ratio is not 1, we need higher resolution pictures to ensure that the display effect is not distorted.

1.2 Device pixel ratio

The device pixel ratio determines the number of pixels that need to be rendered on the screen. This will directly affect the display of the chart. If the device pixel ratio of the mobile device is not 1, it will cause distortion of the chart.

2. Solution to ECharts distortion problem

In Uni-App, we can use the official configuration file of ECharts to solve the above problems, and we can also use the following methods:

2.1 Set the canvas size

You can set the size of the canvas through style syntax in the div tag. For example, we can set styles in the component div to specify the width and height of the Echarts rendered view.

/*设置可视区域宽度和高度*/
#chart {width: 375px; height: 200px;}

2.2 Set Viewport scaling ratio

This method sets the Viewport size to the actual physical size of the device, thereby improving the resolution. At this point, element objects on the page adapt to the scaling. Set the Viewport right at the head of the viewport, so we can add a meta tag to achieve this.

// HTML代码
<meta name="viewport" content="width=device-width,initial-scale=1.0,maximum-scale=1,user-scalable=no">

2.3 Adjust the ECharts configuration appropriately

We can adjust the Echarts configuration through the following operations:

• Include devicePixelRatio in the Echarts configuration item, which is the current The pixel density of the device, we can adjust the size of ECharts on Retina screens according to it;
• Use type=category in XAxis and YAxis, this will force the axis to align the points to the pixel grid, thus ensuring the axis Clearer;
• Using solid style in Series can make the chart clearer;
• If you need to make a line chart or curve chart, you should also set the smooth control parameter to make the chart smoother.

3. Conclusion

ECharts is an important component used in the Uni-App framework. However, when using ECharts on mobile devices, we need to pay special attention to the distortion problem of ECharts charts due to the high screen pixel density and the device pixel ratio is not 1. In this article, we cover the causes and solutions to ECharts distortion issues. As long as we set the resolution, Viewport and chart configuration correctly, we can enjoy clear ECharts charts on different mobile devices.

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