Dagger - 从其他类访问Singleton对象(Dagger - Accessing Singleton object from other class)

 我一直在努力理解并设置Dagger来处理Android项目的依赖注入。 我的单一（没有双关语）目标是创建我可以在我的应用程序中访问的单例对象。 我已经在初始活动中成功设置了对象。 我被困在哪里是从其他类访问这些对象。 这是我到目前为止的设置： 
 
 初始App活动 
 
public class SplashScreenActivity extends AppCompatActivity {

    @Inject SessionKeyExchangerService exchangerService;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_splash_screen);

        AppComponent component = DaggerAppComponent.builder().appModule(new AppModule()).build();

        // establish the session id as a singleton object
        exchangerService = component.provideSessionKeyExchangerService();

        // test whether I can access the singleton from another class
        exchangerService.sendEncryptedKeyToServer();
    } 
 
 组件类 
 
@Singleton
@Component(modules = {AppModule.class})
public interface AppComponent {

    SessionKeyExchangerService provideSessionKeyExchangerService();

    AESCipherService provideCipherService();
}
 
 模块类 
 
@Module
public class AppModule {

    @Provides @Singleton
    AESCipherService provideCipherService() {
        return new AESCipherService();
    }

    @Provides @Singleton
    SessionKeyExchangerService provideSessionKeyExchangerService(AESCipherService service) {
        return new SessionKeyExchangerService(service);
    }
}
 
 AESCipherService 
 
public class AESCipherService {

    private Long sessionId;

    public AESCipherService() {
        sessionId = makeSessionId();
        Log.d(Constants.TAG, "Session ID: " + Long.toString(sessionId));
    }

    private Long makeSessionId() {
        // this generates a random unsigned integer in the space {0, 2^32-1)
        Random random = new Random();
        return random.nextLong() & 0xffffffffL;
    }

    public Long getSessionId() {
        return sessionId;
    }
}
 
 SessionKeyExchanger类 
 
public class SessionKeyExchangerService {

    private static SessionKeyExchangerService exchanger;
    private AESCipherService cipherService;

    @Inject
    public SessionKeyExchangerService(AESCipherService cipherService) {
        this.cipherService = cipherService;
    }

    public void sendEncryptedKeyToServer () {

        // the next line is almost certainly part of the problem
        // but I don't know how to fix!!!
        AppComponent component = DaggerAppComponent.builder().appModule(new AppModule()).build();

        AESCipherService cipherService = component.provideCipherService();

        Long sessionID = cipherService.getSessionId();
        Log.d(Constants.TAG, "singleton verification: " + (Long.toString(sessionID)));
    }
 
 这是一些示例输出： 
 
 
 
 会议ID：217186720 
 单身验证：790090968 
 
 
 显然，我没有访问同一个对象。 我意识到至少部分问题源于我在尝试获取AppComponent类的引用时在AESCipherService调用new运算符的方式，但我不知道如何获取此引用另一种方式。 
 
 我该如何解决？ 谢谢！ 

I've been working to understand and set up Dagger to handle dependency injections for my Android project. My single (no pun intended) objective is to create singleton objects that I can access across my application. I have successfully set up the objects in the initial activity. Where I am stuck is in accessing those objects from other classes. Here is my setup thus far:
 
Initial App Activity
 
public class SplashScreenActivity extends AppCompatActivity {

    @Inject SessionKeyExchangerService exchangerService;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_splash_screen);

        AppComponent component = DaggerAppComponent.builder().appModule(new AppModule()).build();

        // establish the session id as a singleton object
        exchangerService = component.provideSessionKeyExchangerService();

        // test whether I can access the singleton from another class
        exchangerService.sendEncryptedKeyToServer();
    } 
 
Component Class
 
@Singleton
@Component(modules = {AppModule.class})
public interface AppComponent {

    SessionKeyExchangerService provideSessionKeyExchangerService();

    AESCipherService provideCipherService();
}
 
Module Class
 
@Module
public class AppModule {

    @Provides @Singleton
    AESCipherService provideCipherService() {
        return new AESCipherService();
    }

    @Provides @Singleton
    SessionKeyExchangerService provideSessionKeyExchangerService(AESCipherService service) {
        return new SessionKeyExchangerService(service);
    }
}
 
AESCipherService
 
public class AESCipherService {

    private Long sessionId;

    public AESCipherService() {
        sessionId = makeSessionId();
        Log.d(Constants.TAG, "Session ID: " + Long.toString(sessionId));
    }

    private Long makeSessionId() {
        // this generates a random unsigned integer in the space {0, 2^32-1)
        Random random = new Random();
        return random.nextLong() & 0xffffffffL;
    }

    public Long getSessionId() {
        return sessionId;
    }
}
 
SessionKeyExchanger Class
 
public class SessionKeyExchangerService {

    private static SessionKeyExchangerService exchanger;
    private AESCipherService cipherService;

    @Inject
    public SessionKeyExchangerService(AESCipherService cipherService) {
        this.cipherService = cipherService;
    }

    public void sendEncryptedKeyToServer () {

        // the next line is almost certainly part of the problem
        // but I don't know how to fix!!!
        AppComponent component = DaggerAppComponent.builder().appModule(new AppModule()).build();

        AESCipherService cipherService = component.provideCipherService();

        Long sessionID = cipherService.getSessionId();
        Log.d(Constants.TAG, "singleton verification: " + (Long.toString(sessionID)));
    }
 
Here is some sample output:
 
 
 
Session ID: 217186720 
singleton verification: 790090968
 
 
Clearly I'm not accessing the same object. I realize that at least part of the part of the issue stems from the way that I call the new operator in the AESCipherService when I am attempting to get a reference to the AppComponent class, but I don't know how to get this reference any other way. 
 
How do I fix this? Thanks!

原文：https://stackoverflow.com/questions/32211930