使用 Dagger 的应用程序上下文？

Question

我正在尝试使用 Dagger 将 Context 引入到一个类中，这就是我所拥有的以及随之而来的错误：

@Module(injects = { MyApp.class, TransportModule.class }, library = true, includes = { TransportModule.class })
public class AppModule {

    private final MyApp remoteApp;

    public AppModule(MyApp remoteApp) {
        this.remoteApp = remoteApp;
    }

    @Provides
    @Singleton
    Context provideApplicationContext() {
        return remoteApp;
    }

}

应用程序类：

    @Override
    public void onCreate() {
        instance = this;
        super.onCreate();

        objectGraph = ObjectGraph.create(getModules().toArray());
        objectGraph.inject(this);

        mContext = getApplicationContext();
        private List<Object> getModules() {
        return Arrays.<Object>asList(new AppModule(this));
    }

    public ObjectGraph createScopedGraph(Object... modules) {
        return objectGraph.plus(modules);
    }

    public static Context getContext() {
        return mContext;
    }

    public static LoQooApp getInstance() {
        return instance;
    }

}

DeviceInfo.java：

public class DeviceInfo {
    static LoQooApp baseApp;
    @Inject
    static Context mContext;

    public DeviceInfo() {

    }

    public static boolean checkPlayServices() {
        int resultCode = GooglePlayServicesUtil
                .isGooglePlayServicesAvailable(mContext);
        if (resultCode != ConnectionResult.SUCCESS) {
            if (GooglePlayServicesUtil.isUserRecoverableError(resultCode)) {
                Log.v(TAG, Integer.toString(resultCode));
            } else {
                Log.i(TAG + "NOPE", "This device is not supported.");
            }
            return false;
        }
        return true;
    }

}

LogCat 错误：

     Caused by: java.lang.NullPointerException: Attempt to invoke 
     virtual method 'android.content.pm.PackageManager 
     android.content.Context.getPackageManager()' on a null object   reference at com.google.android.gms.common.GooglePlayServicesUtil.isGooglePlayServicesAvai lable(Unknown Source)


     Caused by: java.lang.NullPointerException: Attempt to invoke 
     virtual method 'android.content.pm.PackageManager 
     android.content.Context.getPackageManager()' on a null object   
     reference
     at com.google.android.gms.common.GooglePlayServicesUtil.isGooglePlayServicesAvai lable(Unknown Source)

DeviceInfo 中有一大堆需要上下文的方法，它们都失败了。 如何通过 Dagger 甚至不使用 Dagger 将上下文带入该类？

Answer 1

可以进行静态注入 (How to inject into static classes using Dagger?)，但这应该是个例外。您应该让方法和字段都不是静态的。

所以，DeviceInfo 看起来像

@Inject public DeviceInfo(Context context) {
    mContext = context;
}
public boolean checkPlayServices() { //not static

然后，DeviceInfo 被注入

public class MyApp {
    @Inject DeviceInfo deviceInfo;

由 objectGraph.inject(this); 设置在 onCreate 中。

如果你在activites中需要DeviceInfo，你也可以在onCreate中调用inject

MyApp app = (MyApp) getApplication();
app.getObjectGraph().inject(this);

您还需要将活动添加到 AppModule 的注入部分。