RxAWSDownloadUtil

AWSDownloadUtil.java

package com.sample.awsutils;

import android.annotation.SuppressLint;
import android.content.Context;
import android.util.Log;

import com.amazonaws.ClientConfiguration;
import com.amazonaws.auth.CognitoCachingCredentialsProvider;
import com.amazonaws.mobileconnectors.s3.transferutility.TransferListener;
import com.amazonaws.mobileconnectors.s3.transferutility.TransferObserver;
import com.amazonaws.mobileconnectors.s3.transferutility.TransferState;
import com.amazonaws.mobileconnectors.s3.transferutility.TransferUtility;
import com.amazonaws.services.s3.AmazonS3Client;

import java.io.File;
import java.util.List;
import java.util.concurrent.Callable;

import io.reactivex.Observable;
import io.reactivex.ObservableEmitter;
import io.reactivex.ObservableOnSubscribe;
import io.reactivex.ObservableSource;
import io.reactivex.functions.Function;

public class AWSDownloadUtil implements ObservableOnSubscribe<String> {

    private String COGNITO_POOL_ID = "";
    private String COGNITO_POOL_REGION = "";
    private String BUCKET_NAME = "";

    private static final String TAG = "AWSDownloadUtil";
    private AmazonS3Client sS3Client;
    private CognitoCachingCredentialsProvider sCredProvider;
    private TransferUtility sTransferUtility;

    private static final AWSDownloadUtil ourInstance = new AWSDownloadUtil();
    private Context context;
    private String fileToDownload;

    public static AWSDownloadUtil getInstance() {
        return ourInstance;
    }

    private AWSDownloadUtil() {
    }

    private AWSDownloadUtil(Context context, String fileToDownload) {
        this.context = context;
        this.fileToDownload = fileToDownload;
    }

    /**
     * Gets an instance of a S3 client which is constructed using the given
     * Context.
     *
     * @param context An Context instance.
     * @return A default S3 client.
     */
    public AmazonS3Client getS3Client(Context context) {
        if (sS3Client == null) {
            ClientConfiguration clientConfiguration = new ClientConfiguration();
            clientConfiguration.setMaxErrorRetry(10);
            clientConfiguration.setConnectionTimeout(50 * 1000); // default is 10 secs
            clientConfiguration.setSocketTimeout(100 * 1000); // default is 50 secs

            sS3Client = new AmazonS3Client(getCredProvider(context.getApplicationContext()), clientConfiguration);

        }
        return sS3Client;
    }

    /**
     * Gets an instance of CognitoCachingCredentialsProvider which is
     * constructed using the given Context.
     *
     * @param context An Context instance.
     * @return A default credential provider.
     */
    private CognitoCachingCredentialsProvider getCredProvider(Context context) {
        if (sCredProvider == null) {
            sCredProvider = new CognitoCachingCredentialsProvider(
                    context.getApplicationContext(),
                    COGNITO_POOL_ID,
                    COGNITO_POOL_REGION);
        }
        return sCredProvider;
    }

    /**
     * Gets an instance of the TransferUtility which is constructed using the
     * given Context
     *
     * @param context
     * @return a TransferUtility instance
     */
    public TransferUtility getTransferUtility(Context context) {
        if (sTransferUtility == null) {
            sTransferUtility = TransferUtility.builder()
                    .context(context.getApplicationContext())
                    .s3Client(getS3Client(context.getApplicationContext()))
                    .defaultBucket(BUCKET_NAME)
                    .build();
        }

        return sTransferUtility;
    }

    @Override
    public void subscribe(final ObservableEmitter<String> e) throws Exception {
        if (e.isDisposed()) {
            return;
        }
        final TransferUtility transferUtility = getTransferUtility(context);
        String storagePath = context.getCacheDir();
        ;

        File destinationFile = new File(storagePath + fileToDownload);
        if (destinationFile.exists()) {
            e.onNext(destinationFile.toString());
            return;
        }

        TransferObserver uploadObserver = transferUtility.download(fileToDownload, destinationFile);
        uploadObserver.setTransferListener(new TransferListener() {
            @Override
            public void onStateChanged(int id, TransferState state) {
                TransferObserver transferObserver = transferUtility.getTransferById(id);
                String keyName = "";
                if (transferObserver != null) {
                    keyName = transferObserver.getKey();
                }

                if (TransferState.COMPLETED == state) {
                    String file = storagePath + fileToDownload;
                    e.onNext(file);
                }
            }

            @Override
            public void onProgressChanged(int id, long bytesCurrent, long bytesTotal) {
                float percentDonef = ((float) bytesCurrent / (float) bytesTotal) * 100;
                int percentDone = (int) percentDonef;
                Log.d(TAG, "ID:" + id + " bytesCurrent: " + bytesCurrent + " bytesTotal: " + bytesTotal + " " + percentDone + "%");
            }

            @Override
            public void onError(int id, Exception ex) {
                ex.printStackTrace();
                e.onError(ex);
            }
        });
    }

    public static Observable<String> create(final Context context, final String fileName) {
        return Observable.defer(new Callable<ObservableSource<? extends String>>() {
            @Override
            public ObservableSource<? extends String> call() throws Exception {
                return Observable.create(new AWSDownloadUtil(context, fileName));
            }
        });
    }

    public static Observable<String> create(final Context context, final List<String> fileNameList) {
        return Observable.defer(new Callable<ObservableSource<? extends String>>() {
            @SuppressLint("CheckResult")
            @Override
            public ObservableSource<? extends String> call() throws Exception {
                return Observable.fromIterable(fileNameList).flatMap(new Function<String, ObservableSource<String>>() {
                    @Override
                    public ObservableSource<String> apply(String fileName) throws Exception {
                        return Observable.create(new AWSDownloadUtil(context, fileName));
                    }
                });
            }
        });
    }
}