Detailed explanation of Android life cycle LiveData framework

Detailed explanation of Android life cycle LiveData framework LiveData is a life cycle component for managing data and observing data changes in Android applications.When developing an Android application, it is often necessary to update the data or update the interface according to the changes in the life cycle of the interface, and LiveData provides a lightweight and convenient method to achieve this function. 1. The basic concepts and characteristics of LiveData LiveData is a class that can observe data, which can perceive the life cycle and notify the observer in an active state.It has the following characteristics: -The life cycle perception: Livedata can perceive the life cycle of components related to it (such as Activity, Fragment), and automatically update or notify data at the appropriate time point. -On avoid memory leak: Because LiveData has the ability to perceive life cycle, it will automatically cancel observation after the life cycle of the relevant component is over, thereby avoiding the problem of potential memory leakage. -Orior update: LiveData will automatically notify the observer when the data changes, so that the UI can be updated in real time or performing other corresponding operations. -Data update will only be observed in active state: LiveData will ensure that the data will be observed only when the observer is in an active state, which can save resources and improve performance. 2. Use steps of livedata Below is the basic step of using LiveData: Step 1: Create LiveData object Create a LiveData object in the data type that needs to be managed and observed.For example, the LiveData object can be defined as a global variable or a static variable of a certain class. private LiveData<String> usernameLiveData = new MutableLiveData<>(); Step 2: Update LiveData data Update the data by calling the setValue () or postValue () method of the LiveData object. ((MutableLiveData<String>) usernameLiveData).setValue("John"); Step 3: Observe LiveData data In a component (such as Activity or Fragment) that needs to observe the data, create an observer and bind it to the LiveData object.When the data changes, the onChanged () method of the observer will be called. usernameLiveData.observe(this, new Observer<String>() { @Override public void onChanged(String username) { // Update UI or perform other operations textView.setText(username); } }); Step 4: Cancel observation When you no longer need to observe the LiveData data, in order to avoid potential memory leakage, observation should be canceled at the end of the life cycle of the relevant component. @Override protected void onDestroy() { super.onDestroy(); usernameLiveData.removeObserver(observer); } 3. Livedata life cycle perception LiveData can perceive the life cycle of the following components: Activity, Fragment, Service, and ViewModel.When LiveData is associated with these components, it automatically tracks their life cycle status and trigger data updates or notifications at appropriate time in time. For example, if LiveData is associated with an activity, when the Activity is inStart (), LiveData will notify the observer to update the data.Similarly, when Activity is instop (), LiveData will automatically cancel observation to avoid potential memory leakage. 4. Other functions of livedata LiveData also provides other functions, such as multiple observers support, data conversion and mergers.This makes LiveData a very powerful and flexible tool. In this article, the basic concepts, characteristics, and use steps of the LiveData framework are introduced.By using LiveData, developers can manage and observe changes in data more easily, and provide a better user experience in Android applications. Reference materials: - Android Developers: LiveData Overview. https://developer.android.com/topic/libraries/architecture/livedata#java