我是Android开发的新手,DI的新手。我在一个个人项目中使用Kotlin,其中我正在试验Dagger 2。我设法将它设置为一个util类,但是我需要一个上下文来使用它来注入一个需要上下文的类(一个sharedpref管理器类),我失败了。这是我的代码,这是我得到的错误( NPE )。提前谢谢你。
我的模块类
package com.android.pine
import android.content.Context
import com.android.pine.utils.SharedPreferencesManager
import dagger.Module
import dagger.Provides
import javax.inject.Singleton
@Module
class AppModule {
@Provides
@Singleton
fun context(pineApplication: PineApplication): Context = pineApplication.applicationContext
@Provides
@Singleton
fun provideSharedPrefManager(context: Context): SharedPreferencesManager = SharedPreferencesManager(context)
}
我的组件类:
package com.android.pine
import com.android.pine.home.HomePresenter
import com.android.pine.home.categories.CategoryAdapter
import dagger.Component
import javax.inject.Singleton
@Singleton
@Component(modules = arrayOf(AppModule::class))
interface AppComponent {
fun inject(categoryAdapter: CategoryAdapter)
fun inject(homePresenter: HomePresenter)
}
编辑:添加如下信息,如何调用sharedPreferencesManager的inject:
class HomePresenter : BasePresenter<HomeView>() {
@Inject
lateinit var sharedPreferencesManager: SharedPreferencesManager
.
.
.
同样在我的HomePresenter类中,在onAttached方法覆盖中:
DaggerAppComponent.create().inject(this)
我的pineApplication类和SharedPrefManager类如下所示:
class PineApplication @Inject constructor(): Application()
SharedPref:
class SharedPreferencesManager @Inject constructor(context: Context) {
.
.
.
崩溃,无法获取pineApplication.getContext() (已编辑,添加了完整堆栈跟踪)
06-02 11:57:01.028 14840-14840/com.android.pine.debug E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.android.pine.debug, PID: 14840
java.lang.RuntimeException: Unable to resume activity {com.android.pine.debug/com.android.pine.home.HomeActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.content.Context.getApplicationContext()' on a null object reference
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3429)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3469)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2732)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.content.Context.getApplicationContext()' on a null object reference
at android.content.ContextWrapper.getApplicationContext(ContextWrapper.java:106)
at com.android.pine.AppModule.context(AppModule.kt:12)
at com.android.pine.AppModule_ContextFactory.proxyContext(AppModule_ContextFactory.java:34)
at com.android.pine.DaggerAppComponent.getContext(DaggerAppComponent.java:29)
at com.android.pine.DaggerAppComponent.getSharedPreferencesManager(DaggerAppComponent.java:34)
at com.android.pine.DaggerAppComponent.injectHomePresenter(DaggerAppComponent.java:59)
at com.android.pine.DaggerAppComponent.inject(DaggerAppComponent.java:49)
at com.android.pine.home.HomePresenter.onAttached(HomePresenter.kt:31)
at com.android.pine.home.HomePresenter.onAttached(HomePresenter.kt:10)
at com.android.pine.core.BaseActivity.onResume(BaseActivity.kt:34)
at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1269)
at android.app.Activity.performResume(Activity.java:6783)
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3406)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3469)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2732)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
发布于 2018-06-02 19:10:02
不能使用class PineApplication @Inject constructor(): Application()
创建PineApplication
。它是一个框架类,必须由Android框架创建。
这样做,Dagger将创建PineApplication
,但applicationContext
将返回null
,因为它从未初始化(由系统)。
不要为框架类使用构造函数注入,也不要自己创建。使用@Bindsintance
将对象通过其构建器添加到组件,或使用模块提供该对象。
发布于 2019-08-16 22:49:04
这就是它是如何完成的。在您的组件中使用@BindsInstance会将应用程序注入到您的所有modules.In中,您只需将其注入到AppModule即可
@Singleton
@Component(modules = arrayOf(AppModule::class))
interface AppComponent {
@Component.Builder
interface Builder() {
fun build(): AppComponent
@BindsInstance
fun application(application: Application): Builder
}
}
**删除APP模块中“提供应用程序”函数的代码,并确保传递应用程序上下文以创建sharedPreferences。
@Module
class AppModule {
@Provides
@Singleton
fun provideSharedPrefManager(context: Application): SharedPreferencesManager =
SharedPreferencesManager(context)
}
现在在你的onCreate of applicationClass中
DaggerAppComponent.builder().application(this).build()
可选:如果要向applicationClass注入某些内容,请执行以下操作
DaggerAppComponent.builder().application(this).build().inject(this)
发布于 2018-06-02 20:06:27
为了提供应用程序上下文,您可以使用以下命令创建类,如ComponentsManager
:
public class ComponentsManager {
private Context context;
private AppComponent appComponent;
public ComponentsManager(Context context) {
this.context = context.getApplicationContext();
}
public AppComponent getAppComponent(){
if (appComponent == null){
appComponent = DaggerAppComponent.builder()
.appModule(new AppModule(context))
.build();
}
return appComponent;
}
}
在你的应用程序类中,像这样初始化这个ComponentsManager
:
public class YourApp extends Application {
private static ComponentsManager componentsManager;
@Override
public void onCreate() {
super.onCreate();
initComponentsManager();
initAppComponent();
}
public static ComponentsManager getComponentsManager(){
return componentsManager;
}
private void initComponentsManager(){
componentsManager = new ComponentsManager(this);
}
private void initAppComponent(){
componentsManager.getAppComponent();
}
}
https://stackoverflow.com/questions/50655722
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