What is the implementation principle of MVVM?

The implementation principle of MVVM is to separate the business logic and data of the application, and bind the view with the data model through data binding to achieve automatic updating of the view.

The specific implementation principle is as follows:

1. Model: responsible for managing the data logic of the application, including operations such as data retrieval, storage, and processing.
2. View: Responsible for displaying the user interface, usually described by using XML or code to determine the layout and appearance.
3. ViewModel acts as a bridge between the view and the model, handling the display logic and user interactions, while converting user actions into data that the model can process.
4. Data binding: By establishing a data binding relationship between the view and the view model, the display of the view is automatically updated when the data in the view model changes.

The implementation principle mainly includes the following steps:

1. Create a view and define the layout and appearance of the view.
2. Create a view model, and define data and business logic within it.
3. Use data binding in the view to bind the data of the view model with the view.
4. Automatically update the display of the view when the data in the view model changes.
5. When the user interacts with the view, the view model receives the user input and processes the corresponding business logic.
6. View models interact with models to retrieve, store, and manipulate data.

By implementing MVVM, the decoupling of the view and data model is achieved, which enhances code readability and maintainability, while also making the code easier to test and reuse.