UniApp tips and practices for implementing incremental updates and hot updates

UniApp is a cross-platform development framework that can quickly deploy applications to multiple platforms, such as iOS, Android, H5 and applets. During development, we often need to update applications, and the traditional update method often requires re-downloading the entire application package. For users, this is undoubtedly a waste of bandwidth and time. In order to solve this problem, UniApp has introduced incremental update and hot update technology, which can only download the changed part of the code to achieve efficient updates.

In UniApp, incremental updates refer to downloading only the changed part of the code, rather than the entire application package. The advantage of this is that it can greatly reduce download volume and update time, and improve user experience. So, how to implement incremental updates? Here are some tips and practices for your reference.

First, we need a server to store and manage incremental update files. You can use cloud storage services or build your own server. The server needs to provide an interface to check and obtain incremental update files.

Next, in the application, we need to perform the following steps.

1. Get the version number of the current application. You can use the uni.getSystemInfo() method to obtain the version information of the application.
2. Initiate a network request to query the server for available incremental updates. Incremental updates are available in the form of patch packages, which contain changed code files. The data returned by the server needs to include the current application version number and the available patch package version number.
3. Compare the patch package version returned by the server with the current application version to determine whether incremental updates are needed. If the patch package version is higher than the current application version, then an incremental update is available, otherwise no update is required.
4. If incremental updates are required, the patch package needs to be downloaded and merged. UniApp provides the uni.downloadFile() method to download files, while merging patch packages requires using JavaScript's eval() function to dynamically execute the code. For specific implementation methods, please refer to the official documentation of UniApp.
5. After completing the merging of the patch package, we need to restart the application for the update to take effect. The application can be restarted through the uni.reLaunch() method.

The above are the general steps to implement incremental updates. Let’s look at a sample code below. Assume that the server provides an interface "/api/checkUpdate" for querying and returning available incremental update information. We can write the following code in the application's entry file main.js:

uni.getSystemInfo({
  success: res => {
    // 获取当前应用程序版本号
    const currentVersion = res.version;

    // 发起网络请求，查询可用的增量更新
    uni.request({
      url: '/api/checkUpdate',
      success: res => {
        const { updateAvailable, patchVersion } = res.data;
        if (updateAvailable) {
          // 判断是否需要增量更新
          if (patchVersion > currentVersion) {
            // 下载并合并补丁包
            uni.downloadFile({
              url: '/api/downloadPatch',
              success: res => {
                // 合并补丁包
                eval(res.data);

                // 重启应用程序
                uni.reLaunch();
              }
            });
          }
        }
      }
    });
  }
});

The above code is only an example, and the specific implementation method will vary depending on the project. At the same time, you also need to pay attention to the error handling and rollback mechanism during the incremental update process to ensure the stability and reliability of the update.

To sum up, UniApp provides an efficient incremental update and hot update technology that can greatly reduce update time and bandwidth consumption. By rationally utilizing incremental updates and hot updates, we can provide users with a better user experience. I hope the above tips and practices will be helpful to everyone.

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