下载适用于Google Drive API Android的数据库文件

Question

I am using the drive api to create a database file in the hidden app folder on google drive. The database file is called notes.db I have been able to successfully upload the database file to google drive but I have no idea how to download it back to the user's device. This is what i'm trying to do. My app makes a folder on the user's device called School Binder. in that folder is another folder called Note backups. Here is where I backup the database. The directory is

 Environment.getExternalStorageDirectory() + "/School Binder/Note Backups/Notes.db"

Google drive takes this file and uploads it to the hidden app folder. Now I want to get this notes.db file stored in that app folder on google drive and download it back to this directory on the phone.

 Environment.getExternalStorageDirectory() + "/School Binder/Note Backups/Notes.db"

How do I do this. Thanks. Here is my code for uploading the database to drive this works correctly

        // Define And Instantiate Variable DriveContents driveContents//
        DriveContents driveContents = result.getStatus().isSuccess() ? result.getDriveContents() : null;

        // Gets The Data for The File//
        if (driveContents != null) try {

            // Define And Instantiate Variable OutputStream outputStream//
            OutputStream outputStream = driveContents.getOutputStream();

            // Start Writing Data To File//
            if (outputStream != null) try {

                // Define And Instantiate Variable InputStream inputStream//
                InputStream inputStream = new FileInputStream(dbFile);

                // Define And Instantiate Variable Byte buffer//
                byte[] buffer = new byte[5000];

                // Define Variable Int data//
                int data;

                // Run Code While data Is Bigger Then Zero//
                while ((data = inputStream.read(buffer, 0, buffer.length)) > 0) {

                    // Write To outputStream//
                    outputStream.write(buffer, 0, data);

                    // Flush outputStream//
                    outputStream.flush();
                }

            } finally {

                // Close outputStream//
                outputStream.close();
            }

        } catch (Exception e) {e.printStackTrace(); Toast.makeText(getApplicationContext(), "Failed To Upload: No Backup File Found", Toast.LENGTH_LONG).show(); return;}

How do I change this to make it work for downloading data to a file from google drive

Answer 1

In Lifecycle of a Drive file , Drive Android API lets your app access files even if the device is offline. To support offline cases, the API implements a sync engine, which runs in the background to upstream and downstream changes as network access is available and to resolve conflicts. Perform an initial download request if the file is not yet synced to the local context but the user wants to open the file. The API handles this automatically when a file is requested.

In downloading a file , you make an authorized HTTP GET request to the file's resource URL and include the query parameter alt=media . However, please note that downloading the file requests the user to have at least read access.

Sample HTTP Request:

GET https://www.googleapis.com/drive/v3/files/0B9jNhSvVjoIVM3dKcGRKRmVIOVU?alt=media Authorization: Bearer ya29.AHESVbXTUv5mHMo3RYfmS1YJonjzzdTOFZwvyOAUVhrs

For the coding part, this SO post might be of help too.

Answer 2

I figured it out this is my code to redownload a database back to the phone

        //<editor-fold desc="Create Drive Db File On Device">

        // Log That The File Was Opened//
        Log.d("TAG", "File contents opened");

        // Define And Instantiate Variable DriveContents driveContents//
        DriveContents driveContents = result.getStatus().isSuccess() ? result.getDriveContents() : null;

        // Gets The Data for The File//
        if (driveContents != null) try {

            // Define And Instantiate Variable OutputStream outputStream//
            OutputStream outputStream = new FileOutputStream(dbFile);

            // Define And Instantiate Variable InputStream inputStream//
            InputStream inputStream = driveContents.getInputStream();

            // Define And Instantiate Variable Byte buffer//
            byte[] buffer = new byte[5000];

            // Define Variable Int data//
            int data;

            // Run Code While data Is Bigger Then Zero//
            while ((data = inputStream.read(buffer, 0, buffer.length)) > 0) {

                // Write To outputStream//
                outputStream.write(buffer, 0, data);

                // Flush outputStream//
                outputStream.flush();
            }

            // Close outputStream//
            outputStream.close();

            // Discard Drive Contents//
            driveContents.discard(googleApiClient);

        } catch (Exception e) {e.printStackTrace(); Toast.makeText(getApplicationContext(), "File Failed To Download", Toast.LENGTH_LONG).show(); }

        //</editor-fold>

Answer 3

here is a complete class to upload an internal database, download it and delete it from Google Drive.

Only need to call functions asynchronously and show user a progressbar. DownloadFromGoogleDrive function saves the database in the internal database folder to the app with the name "database2"

Hope it's helpful.

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.common.api.GoogleApiClient.ConnectionCallbacks;
import com.google.android.gms.common.api.GoogleApiClient.OnConnectionFailedListener;
import com.google.android.gms.common.api.ResultCallback;
import com.google.android.gms.common.api.Status;
import com.google.android.gms.drive.Drive;
import com.google.android.gms.drive.DriveApi;
import com.google.android.gms.drive.DriveApi.MetadataBufferResult;
import com.google.android.gms.drive.DriveFile.DownloadProgressListener;
import com.google.android.gms.drive.DriveId;
import com.google.android.gms.drive.DriveResource;
import com.google.android.gms.drive.Metadata;
import com.google.android.gms.drive.DriveApi.DriveContentsResult;
import com.google.android.gms.drive.DriveContents;
import com.google.android.gms.drive.DriveFile;
import com.google.android.gms.drive.DriveFolder.DriveFileResult;
import com.google.android.gms.drive.MetadataChangeSet;
import com.google.android.gms.drive.query.Filters;
import com.google.android.gms.drive.query.Query;
import com.google.android.gms.drive.query.SearchableField;

import android.app.Activity;
import android.content.Intent;
import android.content.IntentSender.SendIntentException;
import android.os.Bundle;
import android.util.Log;
import android.webkit.MimeTypeMap;
import android.widget.Toast;

public class BackupDatabaseActivity extends Activity implements ConnectionCallbacks, OnConnectionFailedListener {

private static final String TAG = "BackupDatabaseActivity";
private GoogleApiClient api;
private boolean mResolvingError = false;
private static final int DIALOG_ERROR_CODE =100;
private static final String DATABASE_NAME = "database";
private static final String GOOGLE_DRIVE_FILE_NAME = "database_backup";

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // Create the Drive API instance
    api = new GoogleApiClient.Builder(this).addApi(Drive.API).addScope(Drive.SCOPE_FILE).
            addConnectionCallbacks(this).addOnConnectionFailedListener(this).build();
}



final private ResultCallback<DriveApi.DriveContentsResult> contentsCallback = new ResultCallback<DriveApi.DriveContentsResult>() {

    @Override
    public void onResult(DriveApi.DriveContentsResult result) {
        if (!result.getStatus().isSuccess()) {
            Log.v(TAG, "Error while trying to create new file contents");
            return;
        }
        CreateFileOnGoogleDrive(result);
        //OR DownloadFromGoogleDrive(result);
        //OR DeleteFromGoogleDrive(result);
    }

};


final private ResultCallback<DriveFileResult> fileCallback = new ResultCallback<DriveFileResult>() {

    @Override
    public void onResult(DriveFileResult result) {
        if (!result.getStatus().isSuccess()) {
            Log.v(TAG, "Error while trying to create the file");
            return;
        }

        Log.v(TAG, "File created: "+result.getDriveFile().getDriveId());
    }
};

/**
 * Create a file in root folder using MetadataChangeSet object.
 * @param result
 */
public void CreateFileOnGoogleDrive(DriveContentsResult result){
    final DriveContents driveContents = result.getDriveContents();

    // Perform I/O off the UI thread.
    new Thread() {
        @Override
        public void run() {
            try {
                FileInputStream is = new FileInputStream(getDbPath());
                BufferedInputStream in = new BufferedInputStream(is);
                byte[] buffer = new byte[8 * 1024];
                BufferedOutputStream out = new BufferedOutputStream(driveContents.getOutputStream());
                int n = 0;
                while( ( n = in.read(buffer) ) > 0 ) {
                    out.write(buffer, 0, n);
                }
                out.flush();
                out.close();
                in.close();
            } catch (FileNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            String mimeType = MimeTypeMap.getSingleton().getExtensionFromMimeType("db");
            MetadataChangeSet changeSet = new MetadataChangeSet.Builder()
                    .setTitle(GOOGLE_DRIVE_FILE_NAME) // Google Drive File name
                    .setMimeType(mimeType)
                    .setStarred(true).build();

            // create a file in root folder
            Drive.DriveApi.getRootFolder(api)
                    .createFile(api, changeSet, driveContents)
                    .setResultCallback(fileCallback);
        }
    }.start();
}

/**
 * Download File from Google Drive
 * @param result
 */
public void DownloadFromGoogleDrive(DriveContentsResult result){
    final DriveContents driveContents = result.getStatus().isSuccess() ? result.getDriveContents() : null;
    if(driveContents!=null){
        Query query = new Query.Builder().addFilter(Filters.eq(SearchableField.TITLE, GOOGLE_DRIVE_FILE_NAME)).build();
        Drive.DriveApi.query(api, query).setResultCallback(new ResultCallback<MetadataBufferResult>() {

            @Override
            public void onResult(MetadataBufferResult result) {
                try{
                    DriveId driveId = result.getMetadataBuffer().get(0).getDriveId();
                    DriveFile driveFile =  driveId.asDriveFile();
                    //mProgressBar.setProgress(0);
                    DownloadProgressListener listener = new DownloadProgressListener() {
                        @Override
                        public void onProgress(long bytesDownloaded, long bytesExpected) {
                            // Update progress dialog with the latest progress.
                            int progress = (int)(bytesDownloaded*100/bytesExpected);
                            Log.d(TAG, String.format("Loading progress: %d percent", progress));
                           // mProgressBar.setProgress(progress);
                        }
                    };

                    driveFile.open(api, DriveFile.MODE_READ_ONLY, listener).setResultCallback(driveContentsCallback);

                }catch(Exception e){
                    Toast.makeText(getApplicationContext(), "File Failed To Download", Toast.LENGTH_LONG).show(); 
                }
            }
        });
    }else{
        Toast.makeText(getApplicationContext(), "File Failed To Download", Toast.LENGTH_LONG).show(); 
    }
}

private ResultCallback<DriveContentsResult> driveContentsCallback =
        new ResultCallback<DriveContentsResult>() {
    @Override
    public void onResult(DriveContentsResult result) {
        if (!result.getStatus().isSuccess()) {
            Log.d(TAG, "Error while opening the file contents");
            return;
        }
        Log.d(TAG, "Downloaded");
        DriveContents dc = result.getDriveContents();            
        try {
            InputStream inputStream = dc.getInputStream();

            OutputStream outputStream = new FileOutputStream(getDbPath()+"2");

            byte[] buffer = new byte[8 * 1024];
            //BufferedOutputStream out = new BufferedOutputStream(dc.getOutputStream());
            int n = 0;
            while( ( n = inputStream.read(buffer) ) > 0 ) {
                outputStream.write(buffer, 0, n);
            }
            outputStream.flush();
            outputStream    .close();
            //inputStream.close();
            dc.discard(api);    
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
};


/**
 * Delete File from Google Drive
 * @param result
 */
public void DeleteFromGoogleDrive(DriveContentsResult result){
    Query query = new Query.Builder()
        .addFilter(Filters.eq(SearchableField.TITLE, GOOGLE_DRIVE_FILE_NAME))
        .build();
    Drive.DriveApi.query(api, query)
            .setResultCallback(new ResultCallback<MetadataBufferResult>() {

        @Override
        public void onResult(MetadataBufferResult result) {
            try{
                Metadata metadata = result.getMetadataBuffer().get(0);
                /*String a = metadata.getTitle();
                String b = metadata.getDescription();
                long c = metadata.getFileSize();*/
                DriveResource driveResource = metadata.getDriveId().asDriveResource();
                 if (metadata.isTrashable()) {
                     if (metadata.isTrashed()) {
                         driveResource.untrash(api).setResultCallback(trashStatusCallback);
                     } else {
                         driveResource.trash(api).setResultCallback(trashStatusCallback);
                     }
                 } else {
                     Log.d(TAG, "Error trying delete");
                 }
            }catch(Exception e){
                Log.d(TAG, "Error: metadata doesn't exist");
            }

        }
    });
}

/**
 * Callback when call to trash or untrash is complete.
 */
private final ResultCallback<Status> trashStatusCallback =
        new ResultCallback<Status>() {
            @Override
            public void onResult(Status status) {
                if (!status.isSuccess()) {
                    Log.e(TAG, "Error trying delete: " + status.getStatusMessage());
                    return;
                }else{
                    Log.e(TAG, "Deleted: " + status.getStatusMessage());
                }
            }
        };




private File getDbPath() {
    return this.getDatabasePath(DATABASE_NAME);
}


@Override
public void onConnectionSuspended(int cause) {
    // TODO Auto-generated method stub
    Log.v(TAG, "Connection suspended");

}


@Override
public void onStart() {
    super.onStart();
    if(!mResolvingError) {
        api.connect(); // Connect the client to Google Drive
    }
}

@Override
public void onStop() {
    super.onStop();
    api.disconnect(); // Disconnect the client from Google Drive
}

@Override
public void onConnectionFailed(ConnectionResult result) {
    Log.v(TAG, "Connection failed");
    if(mResolvingError) { // If already in resolution state, just return.
        return;
    } else if(result.hasResolution()) { // Error can be resolved by starting an intent with user interaction
        mResolvingError = true;
        try {
            result.startResolutionForResult(this, DIALOG_ERROR_CODE);
        } catch (SendIntentException e) {
            e.printStackTrace();
        }
    } else { // Error cannot be resolved. Display Error Dialog stating the reason if possible.
        Toast.makeText(this, "Error: Connection failed", Toast.LENGTH_SHORT).show();
    }
}



@Override
public void onConnected(Bundle connectionHint) {
    Log.v(TAG, "Connected successfully");

    /* Connection to Google Drive established. Now request for Contents instance, which can be used to provide file contents.
       The callback is registered for the same. */
    Drive.DriveApi.newDriveContents(api).setResultCallback(contentsCallback);
}

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    if(requestCode == DIALOG_ERROR_CODE) {
        mResolvingError = false;
        if(resultCode == RESULT_OK) { // Error was resolved, now connect to the client if not done so.
            if(!api.isConnecting() && !api.isConnected()) {
                api.connect();
            }
        }
    }
}

}