Question

我正在尝试使用Dagger 2进行注射，但它总是返回null。我想我做得很好，但无论如何它都行不通。

这是应用程序类：

public class ApplicationSA extends Application {

private static AppComponent appComponent;

@Override
public void onCreate() {
    super.onCreate();
    appComponent = DaggerAppComponent.create();
}

public static AppComponent getComponent() {
    return appComponent;
}

}

组件界面：

@Component(modules = {
        SnoreDetectorClass.class,
        AudioRecorderClass.class
})

public interface AppComponent {
    void injectsMainFunctionalityActivity(Activity activity);
}

我想要获取对象的主要类：

public class MainFunctionalityActivity extends AppCompatActivity {

    @Inject
    AudioRecorderClass audioRecorderClass;
    @Inject
    SnoreDetectorClass snoreDetectorClass;

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        ApplicationSA.getComponent().injectsMainFunctionalityActivity(this);

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Log.d("TESTING","audioRecorderClass= "+audioRecorderClass); // always null
        Log.d("TESTING","snoreDetectorClass= "+snoreDetectorClass); // always null
...
}

以下是模块类：

@Module
public class AudioRecorderClass {

    public interface AudioRecorderInterface {
        void AudioRecorder_hasUpdate(double amplitude_in_dB);
    }
    public AudioRecorderInterface delegate = null;

    @Provides
    AudioRecorderClass provideAudioRecorderClass(Activity activity) {
        delegate = (AudioRecorderInterface)activity;
        return new AudioRecorderClass();
    }
...

@Module
public class SnoreDetectorClass {

    @Provides
    SnoreDetectorClass provideSnoreDetectorClass() {
        return new SnoreDetectorClass();
    }
...

我做错了什么？为什么对象总是为空？

Answer 1

你必须明确告诉dagger这里会注入哪些活动，而不是使用超类Activity，而是使用自己的Activity类实现：

void injectsMainFunctionalityActivity(Activity activity);

更改为：

void injectsMainFunctionalityActivity(MainFunctionalityActivity activity);

Answer 2

啊，我看到这里发生了什么。你不能注入子类。所以在AppComponent你不能拥有

 void injectsMainFunctionalityActivity(Activity activity);

你必须注入

 void injectsMainFunctionalityActivity(MainFunctionalityActivity activity);

作为旁注，我建议不要将注射器和模型类组合在一起。最好分开关注点。将它们分开

注射后Dagger 2返回null

2 个答案: