Realize the loose coupling architecture: analysis of the advantages and principles of Android dependence on the library

The loose coupling architecture is a design pattern, which aims to decide the dependency relationship of each component in the application, making the system easier to maintain, test and expand.Android dependency injection (DI) library is a tool that realizes the loose coupling architecture, which allows developers to manage the dependencies between objects in a statement. Android dependence on the advantages of injection library: 1. Reduce the hard coding of traditional dependencies: Traditionally, the dependency relationship between objects is hard -coded in the code.Using dependencies into the library, we can abstract the definition of these dependencies and dynamically inject the dependencies of the object during runtime, so that the code is more flexible. 2. Improve code testability: By dependent injection, we can easily replace the dependencies of the object so that they can simulate different situations in the unit test.In this way, we can write more reliable and maintained test cases. 3. Reduce the complexity of the code: The dependency injection library eliminates a large number of manual dependency management code and reduces the redundancy and complexity of the code.It makes the code easier to understand and maintain and improve development efficiency. 4. Support modular development: Relying on the injecting library to manage the dependency relationship between objects through modularity, so that we can better organize and reuse code. Android dependence on the working principle of the injection library: Android dependency injection libraries usually use the reflection mechanism to achieve the dependent injection of the object.They automatically find and inject the dependent objects by analyzing the dependency relationship between objects. Below is a simple example, demonstrating how to use the famous dependency injection library using Dagger 2 in Android: 1. First, we need to add Dagger 2 to the project's Build.gradle file: implementation 'com.google.dagger:dagger:2.x' annotationProcessor 'com.google.dagger:dagger-compiler:2.x' 2. Next, we define an injecting class: public class DatabaseHelper { // Database Connectivity private SQLiteDatabase database; // Constructor public DatabaseHelper(Context context) { // Initialize database connection database = new SQLiteDatabase(); } // ... } 3. Then, we use the @Inject annotation mark to be injected with dependencies: public class MainActivity extends AppCompatActivity { @Inject DatabaseHelper databaseHelper; // ... } 4. Finally, at the entrance point of the application, we need to create a Dagger component (Component) to organize the dependent relationship between objects and injects: public class MyApplication extends Application { private AppComponent appComponent; @Override public void onCreate() { super.onCreate(); appComponent = DaggerAppComponent.builder() .appModule(new AppModule(this)) .build(); appComponent.inject(this); } public AppComponent getAppComponent() { return appComponent; } } In the above code, AppComponent is a Dagger component that provides an instance of the DataBasehelper object through AppModule.In the inlet point of the application, we injected the DataBasehelper object in the mainactivity by calling the AppComponent.inject (this). Through the above steps, we successfully achieved the dependency injection in Android.By using DAGGER 2 or other similar DI libraries, we can easily manage the dependent relationship between objects, so as to achieve the loose coupling architecture and improve the maintenance of applications and testability.