How does uniapp solve the problem of out-of-synchronization of the view layer?

With the development of mobile development, UniApp (cross-platform application development framework) is becoming more and more popular among developers. However, when developing applications using UniApp, sometimes the view layer is out of sync. This issue may result in incorrect UI information and users being unable to use the application properly. Today we will discuss how to solve the problem of out-of-synchronization of the view layer.

1. What is the problem of view layer being out of sync?

The problem of out-of-synchronization of the View layer is that when the components in the interface change at a certain point in time, the view layer cannot immediately update the corresponding changes, resulting in incorrect UI information. This issue may affect the user experience using the application.

2. Why does the view layer become out of sync?

In UniApp, we use Vue.js for data binding. When we change the data of Vue.js, UniApp will update the corresponding data to the view layer through the Taro engine. However, when UniApp is processing update tasks, due to the underlying system limitations of Vue.js, the scheduler may hang. This problem will cause the view layer to fail to update correctly, resulting in incorrect UI information.

3. How to solve the problem of out-of-synchronization of the view layer?

To solve the problem of out-of-synchronization of the view layer, you can start from the following three aspects:

(1) Use $nextTick

$nextTick is provided by Vue.js One of the APIs that allows us to execute callback functions after the DOM is updated. Using $nextTick can ensure that some UI-related operations are performed after the view layer is updated. For example, we can put the following code in the component's methods or mounted method:

this.$nextTick(() => {
  // 在DOM更新后执行的代码
})

(2) Using uni.$on and uni.$emit

uni.$on can be An event (name) registers a callback function. When the component triggers the event, the callback function will be called.

uni.$emit can trigger an event to the parent component or ancestor component and pass parameters.

We can use uni.$on and uni.$emit to create a custom event to perform specific operations after the view layer is updated.

For example, we can add the following code in the parent component:

<child @my-custom-event="onCustomEvent"></child>

and add the following method in the parent component:

methods: {
  onCustomEvent() {
    // 在view层更新后执行的代码
  }
}

Add the following code in the child component:

this.$emit('my-custom-event')

(3) Use setTimeout

Using setTimeout can also solve the problem of out-of-synchronization of the view layer. Using setTimeout allows us to defer execution of code until the current execution stack has completed. We can wrap the code in a setTimeout callback function to execute it after the UniApp processing update task is completed.

For example, we can put the following code in the component's methods or mounted method:

setTimeout(() => {
  // 在view层更新后执行的代码
})

4. Conclusion

In UniApp, sometimes There will be problems with the view layer being out of sync. This issue may affect the user experience using the application. In order to solve this problem, we can use methods such as $nextTick, uni.$on and uni.$emit, and setTimeout. I hope this article can help you solve the problem of out-of-synchronization of the view layer.

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