Let's talk about the problem of uniapp not re-rendering after pull-down refresh

With the development of mobile Internet, mobile applications are becoming more and more popular. In order to improve development efficiency and cross-end compatibility, many developers have begun to choose to use uniapp to develop cross-platform mobile applications. However, when developing applications using uniapp, we may encounter some problems. One of them is the problem of not re-rendering after pull-down refresh.

In some applications, we need to use pull-down refresh to update data. Generally speaking, we will re-request data and re-render the page after triggering the pull-down refresh event. However, when using uniapp to develop applications, some developers will find that the page does not re-render after pulling down to refresh, but remains in its original state. In this case, the user will not be able to see the latest data after pulling down to refresh.

There may be many reasons for this. In this article, we will discuss several situations and solutions to why drop-down does not re-render after refresh.

1. Vue’s asynchronous update mechanism

Vue is the default framework in uniapp, and its responsive data mechanism is based on asynchronous updates. In other words, when the data changes, Vue will not render the page immediately, but will put the update request into the queue, and wait until the next tick (that is, the next event loop) to update the entire queue. This is the so-called asynchronous update mechanism.

In many cases, the asynchronous update mechanism is very convenient. However, in a pull-down refresh scenario, since we need to update data and re-render the page as quickly as possible, the asynchronous update mechanism may cause the page to not be updated in time.

Solution:

There are two solutions:

One is to use Vue's $nextTick method to manually trigger asynchronous updates. In the pull-down refresh event, we can first call the $nextTick method to wait for the asynchronous update of the page to be completed, and then perform data request and re-render the page. An example is as follows:

this.$nextTick(() => {
  // 更新数据和渲染页面的操作
})

The second is to use Vue's $forceUpdate method to force the page to update. The $forceUpdate method can force the update of the entire component without waiting for the next event loop. However, using the $forceUpdate method will cause performance losses and is not recommended for frequent use. An example is as follows:

this.$forceUpdate()

2. pages.json configuration of uni-app

In uniapp, each page needs to be configured in the pages.json file. In pages.json, we can set some properties of the page, including the path of the page, default title, whether to enable pull-down refresh, etc. If we set the pull-down refresh attribute of a page to false, then the pull-down refresh will not take effect on this page.

Solution:

Ensure that the pull-down refresh attribute (enablePullDownRefresh) of the page is set to true. If the page does not re-render after a pull-down refresh, you can check whether the configuration in the pages.json file is correct.

3. Problems with third-party component libraries

When using third-party component libraries, some components may conflict with the pull-down refresh of uniapp, resulting in the page not being refreshed after the pull-down refresh Rendering situation. In this case, we need to find the problematic component and try to resolve the conflict.

Solution:

Generally speaking, we need to first check all third-party components used in the page and find out the components that may conflict. We can then try to temporarily disable or replace these components with other components in order to troubleshoot the problem.

For example, if we use the mescroll pull-down refresh component and find the problem of not re-rendering after pull-down refresh, we can first try to switch to uniapp's official pull-down refresh component uni-refresher.

<uni-refresher @refresh="onPullDownRefresh">
  <view slot="content">
    <!-- 下拉刷新的内容 -->
  </view>
</uni-refresher>

If the conflict cannot be resolved, we can contact the developer of the third-party component to see if there is a relevant solution or an updated version that can be used.

Summary

Not re-rendering after pull-down refresh is one of the common problems in uniapp development. Reasons for this problem may include Vue's asynchronous update mechanism, pages.json configuration errors, third-party component conflicts, etc. To solve this problem, you need to first find the cause of the problem and then take corresponding solutions. If you encounter a problem that cannot be solved, you can seek help from uniapp official or third-party component developers.

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