Dagger 2构造函数注入在调用模块之前没有发生

Question

我正在学习 Dagger 2 并且正在开发一个应用程序。我有一个设置模块，它依赖于一个依赖于共享首选项管理器的设置管理器。我的问题是我的设置模块在被调用之前没有被注入设置管理器。该设置管理器需要一个 SharedPrefsManager ，它也没有被注入任何地方。

我做错了什么？

按依赖顺序排列的片段：

@Module
public class SettingsModule {   
    @Inject SettingsManager manager;

    @Provides
    @TimeControl
    int[] provideResetTime(){
        return manager.getResetTime();
    }

    @Provides
    @ThemeControl
    int provideThemeID(){
        return manager.getTheme();
    }
}

取决于设置管理器：

public class SettingsManager{
    private SharedPreferencesManager manager;
    @Inject
    SettingsManager(SharedPreferencesManager manager){
        this.manager = manager;
    }
}

取决于共享首选项管理器：

public class SharedPreferencesManager {
    private static SharedPreferencesManager instance = null;
    public static SharedPreferencesManager getInstance(){return instance;}
    String prefsKey = "SHAREDPREFSKEY";
    SharedPreferences sharedPrefs = null;
    Context applicationContext = null;

    @Inject
    SharedPreferencesManager(@ApplicationContext Context applicationContext){
        this.prefsKey = prefsKey;
        this.applicationContext = applicationContext;
        sharedPrefs = applicationContext.getSharedPreferences(prefsKey,Context.MODE_PRIVATE);
        instance = this;
    }
}

Answer 1

我认为你不应该在模块中有 @Inject 注释，因为它们被构建为创建依赖关系并且只能通过对象图或简单构造函数接收其他依赖关系。

下面是一个示例，说明如何避免模块中的 @Inject 注释及其后的构造函数注入器。

SettingsModule.java

@Module
public class SettingsModule {

    @Provides
    @TimeControl
    int[] provideResetTime(SettingsManager manager) {
        return manager.getResetTime();
    }

    @Provides
    @ThemeControl
    int provideThemeID(SettingsManager manager) {
        return manager.getTheme();
    }

    @Provides
    SettingsManager provideSettingsManager(SharedPreferencesManager sharedPreferencesManager) {
        return new SettingsManager(sharedPreferencesManager);
    }

    @Provides
    SharedPreferencesManager provideSharedPreferencesManager(@ApplicationContext Context context) {
        return new SharedPreferencesManager(context);
    }
}

SettingsManager.java

public class SettingsManager {
    private SharedPreferencesManager manager;

    SettingsManager(SharedPreferencesManager manager) {
        this.manager = manager;
    }
}

SharedPreferencesManager.java

public class SharedPreferencesManager {
    private static SharedPreferencesManager instance = null;
    private SharedPreferences sharedPrefs = null;
    String prefsKey = "SHAREDPREFSKEY";
    Context applicationContext = null;

    SharedPreferencesManager(Context applicationContext) {
        this.applicationContext = applicationContext;
        sharedPrefs = applicationContext.getSharedPreferences(prefsKey, Context.MODE_PRIVATE);
        instance = this;
    }

    public static SharedPreferencesManager getInstance() {
        return instance;
    }
}

有了这个，您可以将所有注入逻辑留给您的模块，具体类不必担心自己注入类。

Answer 2

@Module
public class SettingsModule {   
    @Inject SettingsManager manager;

    @Provides
    @TimeControl
    int[] provideResetTime(){
        return manager.getResetTime();
    }

    @Provides
    @ThemeControl
    int provideThemeID(){
        return manager.getTheme();
    }
}

应该是

@Module
public class SettingsModule {   
    @Provides
    @TimeControl
    int[] resetTime(SettingsManager manager) {
        return manager.getResetTime();
    }

    @Provides
    @ThemeControl
    int themeId(SettingsManager manager) {
        return manager.getTheme();
    }
}

请注意，您的提供者没有限定范围，因此（据我所知）获得 themeId() 的调用和获得 resetTime() 的调用很可能每次都会创建一个新的 SettingsManager .

所以你可能想把@Singleton放在你提供的类上。

@Singleton
public class SharedPreferencesManager {
    private SharedPreferences sharedPrefs = null;
    String prefsKey = "SHAREDPREFSKEY";
    Context applicationContext = null;

    @Inject
    SharedPreferencesManager(Context applicationContext) {
        this.applicationContext = applicationContext;
        sharedPrefs = applicationContext.getSharedPreferences(prefsKey, Context.MODE_PRIVATE); // why isn' this in a module?
    }
}

@Singleton
public class SettingsManager{
    private SharedPreferencesManager manager;
    @Inject
    SettingsManager(SharedPreferencesManager manager){
        this.manager = manager;
    }
}

Dagger 2构造函数注入在调用模块之前没有发生

Dagger 2 Constructor Injection not happening before module called

android

dependency-injection

dagger

dagger-2