Using the Google Drive API for Android and some answers on Stack Overflow, I have managed to implement Google Sign-In into my app, and backup the SQLite database stored on the user's device to Google Drive.
For reference, here is how I save the database to Google Drive (this is done in a final class called DriveDbHandler):
private static final String LOG_TAG = "DriveDbHandler";
private static final String PACKAGE_NAME = "com.package.example";
private static final String DATABASE_PATH =
"/data/data/" + PACKAGE_NAME + "/databases/" + DbHelper.DATABASE_NAME;
private static final String FILE_NAME = DbHelper.DATABASE_NAME;
private static final String MIME_TYPE = "application/x-sqlite-3";
private DriveDbHandler() {
}
public static void tryCreatingDbOnDrive(final GoogleApiClient googleApiClient) {
// We need to check if the database already exists on Google Drive. If so, we won't create
// it again.
Query query = new Query.Builder()
.addFilter(Filters.and(
Filters.eq(SearchableField.TITLE, FILE_NAME),
Filters.eq(SearchableField.MIME_TYPE, MIME_TYPE)))
.build();
DriveFolder appFolder = Drive.DriveApi.getAppFolder(googleApiClient);
appFolder.queryChildren(googleApiClient, query).setResultCallback(
new ResultCallback<DriveApi.MetadataBufferResult>() {
@Override
public void onResult(@NonNull DriveApi.MetadataBufferResult metadataBufferResult) {
if (!metadataBufferResult.getStatus().isSuccess()) {
Log.e(LOG_TAG, "Query for " + FILE_NAME + " unsuccessful!");
return;
}
int count = metadataBufferResult.getMetadataBuffer().getCount();
Log.d(LOG_TAG, "Successfully ran query for " + FILE_NAME + " and found " +
count + " results");
if (count > 1) {
Log.e(LOG_TAG, "App folder contains more than one database file! " +
"Found " + count + " matching results.");
return;
}
// Create the database on Google Drive if it doesn't exist already
if (count == 0) {
Log.d(LOG_TAG, "No existing database found on Google Drive");
saveToDrive(googleApiClient);
}
}
});
}
private static void saveToDrive(final GoogleApiClient googleApiClient) {
Log.d(LOG_TAG, "Starting to save to drive...");
// Create content from file
Drive.DriveApi.newDriveContents(googleApiClient).setResultCallback(
new ResultCallback<DriveApi.DriveContentsResult>() {
@Override
public void onResult(@NonNull DriveApi.DriveContentsResult driveContentsResult) {
if (!driveContentsResult.getStatus().isSuccess()) {
Log.w(LOG_TAG, "Drive contents result not a success! " +
"Not saving data to drive.");
return;
}
Log.d(LOG_TAG, "Created drive contents for file");
createNewFile(googleApiClient, driveContentsResult.getDriveContents());
}
});
}
private static void createNewFile(GoogleApiClient googleApiClient, DriveContents driveContents) {
// Write file to contents (see http://stackoverflow.com/a/33610727/4230345)
File file = new File(DATABASE_PATH);
OutputStream outputStream = driveContents.getOutputStream();
try {
InputStream inputStream = new FileInputStream(file);
byte[] buf = new byte[4096];
int c;
while ((c = inputStream.read(buf, 0, buf.length)) > 0) {
outputStream.write(buf, 0, c);
outputStream.flush();
}
outputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
Log.d(LOG_TAG, "Written file to output stream of drive contents");
// Create metadata
MetadataChangeSet metadataChangeSet = new MetadataChangeSet.Builder()
.setTitle(FILE_NAME)
.setMimeType(MIME_TYPE)
.build();
// Create the file on Google Drive
DriveFolder folder = Drive.DriveApi.getAppFolder(googleApiClient);
folder.createFile(googleApiClient, metadataChangeSet, driveContents).setResultCallback(
new ResultCallback<DriveFolder.DriveFileResult>() {
@Override
public void onResult(@NonNull DriveFolder.DriveFileResult driveFileResult) {
if (!driveFileResult.getStatus().isSuccess()) {
Log.w(LOG_TAG, "File did not get created in Google Drive!");
return;
}
Log.i(LOG_TAG, "Successfully created file in Google Drive");
}
});
}
So here's my issue:
I can save the database to Google Drive, but how do I update the Google Drive version with any changes made locally?
For example, I can delete 3 rows from table A and then add 5 rows to table B locally (to the device's SQLite database), but how do I update the Google Drive version with this change?
I have considered deleting the entire Drive file and re-uploading it, but this would result in a different DriveId for that file, to my understanding.
I'm wondering if I would be able to take advantage of the API's modification handling (explained here), where changes are queued for upload if the device has no internet connection.
