官网项目Jetpack Startup库学习

object Sync {
    // This method is a workaround to manually initialize the sync process instead of relying on
    // automatic initialization with Androidx Startup. It is called from the app module's
    // Application.onCreate() and should be only done once.
    fun initialize(context: Context) {
        AppInitializer.getInstance(context)
            .initializeComponent(SyncInitializer::class.java)
    }
}
internal const val SyncWorkName = "SyncWorkName"
/**
 * Registers work to sync the data layer periodically on app startup.
 */
class SyncInitializer : Initializer<Sync> {
    override fun create(context: Context): Sync {
        WorkManager.getInstance(context).apply {
            // Run sync on app startup and ensure only one sync worker runs at any time
            enqueueUniqueWork(
                SyncWorkName,
                ExistingWorkPolicy.KEEP,
                SyncWorker.startUpSyncWork(),
            )
        }
        return Sync
    }
    override fun dependencies(): List<Class<out Initializer<*>>> =
        listOf(WorkManagerInitializer::class.java)
}

public final class WorkManagerInitializer implements Initializer<WorkManager> {
    private static final String TAG = Logger.tagWithPrefix("WrkMgrInitializer");
    @NonNull
    @Override
    public WorkManager create(@NonNull Context context) {
        // Initialize WorkManager with the default configuration.
        Logger.get().debug(TAG, "Initializing WorkManager with default configuration.");
        //这个地方已经完成了单例的构建，后面再调用WorkManager.getInstance(context)获取实例，否则报错
        WorkManager.initialize(context, new Configuration.Builder().build());
        return WorkManager.getInstance(context);
    }
    @NonNull
    @Override
    public List<Class<? extends androidx.startup.Initializer<?>>> dependencies() {
        //这里WorkManager的初始化不需要其他初始化构造器，所以返回的是个空集合
        return Collections.emptyList();
    }
}

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools">
    <application>
        <provider
            android:name="androidx.startup.InitializationProvider"
            android:authorities="${applicationId}.androidx-startup"
            android:exported="false"
            tools:node="merge">
            <!--  TODO: b/2173216 Disable auto sync startup till it works well with instrumented tests   -->
            <meta-data
                android:name="com.google.samples.apps.nowinandroid.sync.initializers.SyncInitializer"
                android:value="androidx.startup"
                tools:node="remove" />
        </provider>
    </application>
</manifest>

@HiltAndroidApp 
class NiaApplication : Application(), ImageLoaderFactory {
    override fun onCreate() {
        super.onCreate()
        // Initialize Sync; the system responsible for keeping data in the app up to date.
        Sync.initialize(context = this)
    }
    /**
     * Since we're displaying SVGs in the app, Coil needs an ImageLoader which supports this
     * format. During Coil's initialization it will call `applicationContext.newImageLoader()` to
     * obtain an ImageLoader.
     *
     * @see <a href="https://github.com/coil-kt/coil/blob/main/coil-singleton/src/main/java/coil/Coil.kt" rel="external nofollow" >Coil</a>
     */
    override fun newImageLoader(): ImageLoader {
        return ImageLoader.Builder(this)
            .components {
                add(SvgDecoder.Factory())
            }
            .build()
    }
}

object Sync {
    // This method is a workaround to manually initialize the sync process instead of relying on
    // automatic initialization with Androidx Startup. It is called from the app module's
    // Application.onCreate() and should be only done once.
    fun initialize(context: Context) {
        AppInitializer.getInstance(context)
            .initializeComponent(SyncInitializer::class.java)
    }
}