Support Blob provider on detached Expo apps

BlobProvider.java

/**
 * Copyright (c) 2015-present, Facebook, Inc. All rights reserved.
 *
 * <p>This source code is licensed under the BSD-style license found in the LICENSE file in the root
 * directory of this source tree. An additional grant of patent rights can be found in the PATENTS
 * file in the same directory.
 */
package kim.adoan.modules.blob;

import android.content.ContentProvider;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.ParcelFileDescriptor;
import android.support.annotation.Nullable;

import com.facebook.react.modules.blob.BlobModule;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.OutputStream;

public final class BlobProvider extends ContentProvider {

    @Override
    public boolean onCreate() {
        return true;
    }

    @Override
    public @Nullable Cursor query(
            Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
        return null;
    }

    @Override
    public @Nullable String getType(Uri uri) {
        return null;
    }

    @Override
    public @Nullable Uri insert(Uri uri, ContentValues values) {
        return null;
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        return 0;
    }

    @Override
    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
        return 0;
    }

    @Override
    public ParcelFileDescriptor openFile(Uri uri, String mode) throws FileNotFoundException {
        if (!mode.equals("r")) {
            throw new FileNotFoundException("Cannot open " + uri.toString() + " in mode '" + mode + "'");
        }

        BlobModule blobModule;

        if (BlobProviderModule.mContext == null) {
            throw new RuntimeException("blob provider context is null!");
        }

        blobModule = BlobProviderModule.mContext.getNativeModule(BlobModule.class);

        if (blobModule == null) {
            throw new RuntimeException("No blob module associated with BlobProvider");
        }

        byte[] data = blobModule.resolve(uri);

        if (data == null) {
            throw new FileNotFoundException("Cannot open " + uri.toString() + ", blob not found.");
        }

        ParcelFileDescriptor[] pipe;
        try {
            pipe = ParcelFileDescriptor.createPipe();
        } catch (IOException exception) {
            return null;
        }
        ParcelFileDescriptor readSide = pipe[0];
        ParcelFileDescriptor writeSide = pipe[1];

        OutputStream outputStream = new ParcelFileDescriptor.AutoCloseOutputStream(writeSide);
        try {
            outputStream.write(data);
            outputStream.close();
        } catch (IOException exception) {
            return null;
        }

        return readSide;
    }
}

BlobProviderModule.java

package kim.adoan.modules.blob;

import com.facebook.react.bridge.ReactApplicationContext;
import com.facebook.react.bridge.ReactContextBaseJavaModule;

public class BlobProviderModule extends ReactContextBaseJavaModule {
    public static ReactApplicationContext mContext = null;
    public BlobProviderModule(ReactApplicationContext reactContext) {
        super(reactContext);

        mContext = reactContext;
    }

    @Override
    public String getName() {
        return BlobProviderModule.class.getName();
    }
}

BlobProviderPackage.java

package kim.adoan.modules.blob;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import com.facebook.react.ReactPackage;
import com.facebook.react.bridge.NativeModule;
import com.facebook.react.bridge.ReactApplicationContext;
import com.facebook.react.uimanager.ViewManager;

public class BlobProviderPackage implements ReactPackage {

    @Override
    public List<NativeModule> createNativeModules(ReactApplicationContext reactApplicationContext) {
        ArrayList<NativeModule> modules = new ArrayList<>();
        modules.add(new BlobProviderModule(reactApplicationContext));
        return modules;
    }

    @Override
    public List<ViewManager> createViewManagers(ReactApplicationContext reactApplicationContext) {
        return Collections.emptyList();
    }
}

And don't forget to import and add the BlobProviderPackage to the packages list in the MainApplication class.

import kim.adoan.modules.blob.BlobProviderPackage; 

public class MainApplication extends ExpoApplication {
///.....
 public List<ReactPackage> getPackages() {
    return Arrays.<ReactPackage>asList(
          /// other packages...
          new BlobProviderPackage()
    );
  }
//.....
}