android - 如何替换 Google 云端硬盘中的文件？

Question

使用以下摘自android-quickstart 的代码，如果您拍摄多张照片，此代码可以生成多个同名文件。如何修改才能保证替换同名文件？

public class MainActivity extends Activity implements ConnectionCallbacks,
        OnConnectionFailedListener {

    private static final String TAG = "android-drive-quickstart";
    private static final int REQUEST_CODE_CAPTURE_IMAGE = 1;
    private static final int REQUEST_CODE_CREATOR = 2;
    private static final int REQUEST_CODE_RESOLUTION = 3;

    private GoogleApiClient mGoogleApiClient;
    private Bitmap mBitmapToSave;

    /**
     * Create a new file and save it to Drive.
     */
    private void saveFileToDrive() {
        // Start by creating a new contents, and setting a callback.
        Log.i(TAG, "Creating new contents.");
        final Bitmap image = mBitmapToSave;
        Drive.DriveApi.newContents(mGoogleApiClient).setResultCallback(new ResultCallback<ContentsResult>() {

            @Override
            public void onResult(ContentsResult result) {
                // If the operation was not successful, we cannot do anything
                // and must
                // fail.
                if (!result.getStatus().isSuccess()) {
                    Log.i(TAG, "Failed to create new contents.");
                    return;
                }
                // Otherwise, we can write our data to the new contents.
                Log.i(TAG, "New contents created.");
                // Get an output stream for the contents.
                OutputStream outputStream = result.getContents().getOutputStream();
                // Write the bitmap data from it.
                ByteArrayOutputStream bitmapStream = new ByteArrayOutputStream();
                image.compress(Bitmap.CompressFormat.PNG, 100, bitmapStream);
                try {
                    outputStream.write(bitmapStream.toByteArray());
                } catch (IOException e1) {
                    Log.i(TAG, "Unable to write file contents.");
                }
                // Create the initial metadata - MIME type and title.
                // Note that the user will be able to change the title later.
                MetadataChangeSet metadataChangeSet = new MetadataChangeSet.Builder()
                        .setMimeType("image/jpeg")
                        .setTitle("Android Photo.png")
                        .build();
                // Create an intent for the file chooser, and start it.
                IntentSender intentSender = Drive.DriveApi
                        .newCreateFileActivityBuilder()
                        .setInitialMetadata(metadataChangeSet)
                        .setInitialContents(result.getContents())
                        .build(mGoogleApiClient);
                try {
                    startIntentSenderForResult(
                            intentSender, REQUEST_CODE_CREATOR, null, 0, 0, 0);
                } catch (SendIntentException e) {
                    Log.i(TAG, "Failed to launch file chooser.");
                }
            }
        });
    }

    @Override
    protected void onResume() {
        super.onResume();
        if (mGoogleApiClient == null) {
            // Create the API client and bind it to an instance variable.
            // We use this instance as the callback for connection and connection
            // failures.
            // Since no account name is passed, the user is prompted to choose.
            mGoogleApiClient = new GoogleApiClient.Builder(this)
                    .addApi(Drive.API)
                    .addScope(Drive.SCOPE_FILE)
                    .addConnectionCallbacks(this)
                    .addOnConnectionFailedListener(this)
                    .build();
        }
        // Connect the client. Once connected, the camera is launched.
        mGoogleApiClient.connect();
    }
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addApi(Drive.API)
                .addScope(Drive.SCOPE_FILE)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .build();
    }
    @Override
    protected void onStart() {
        super.onStart();
        mGoogleApiClient.connect();
    }
    @Override
    protected void onPause() {
        if (mGoogleApiClient != null) {
            mGoogleApiClient.disconnect();
        }
        super.onPause();
    }

    @Override
    protected void onActivityResult(final int requestCode, final int resultCode, final Intent data) {
        switch (requestCode) {
            case REQUEST_CODE_CAPTURE_IMAGE:
                // Called after a photo has been taken.
                if (resultCode == Activity.RESULT_OK) {
                    // Store the image data as a bitmap for writing later.
                    mBitmapToSave = (Bitmap) data.getExtras().get("data");
                }
                break;
            case REQUEST_CODE_CREATOR:
                // Called after a file is saved to Drive.
                if (resultCode == RESULT_OK) {
                    Log.i(TAG, "Image successfully saved.");
                    mBitmapToSave = null;
                    // Just start the camera again for another photo.
                    startActivityForResult(new Intent(MediaStore.ACTION_IMAGE_CAPTURE),
                            REQUEST_CODE_CAPTURE_IMAGE);
                }
                break;
        }
    }

    @Override
    public void onConnectionFailed(ConnectionResult result) {
        // Called whenever the API client fails to connect.
        Log.i(TAG, "GoogleApiClient connection failed: " + result.toString());
        if (!result.hasResolution()) {
            // show the localized error dialog.
            GooglePlayServicesUtil.getErrorDialog(result.getErrorCode(), this, 0).show();
            return;
        }
        // The failure has a resolution. Resolve it.
        // Called typically when the app is not yet authorized, and an
        // authorization
        // dialog is displayed to the user.
        try {
            result.startResolutionForResult(this, REQUEST_CODE_RESOLUTION);
        } catch (SendIntentException e) {
            Log.e(TAG, "Exception while starting resolution activity", e);
        }
    }

    @Override
    public void onConnected(Bundle connectionHint) {
        Log.i(TAG, "API client connected.");
        if (mBitmapToSave == null) {
            // This activity has no UI of its own. Just start the camera.
            startActivityForResult(new Intent(MediaStore.ACTION_IMAGE_CAPTURE),
                    REQUEST_CODE_CAPTURE_IMAGE);
            return;
        }
        saveFileToDrive();
    }

    @Override
    public void onConnectionSuspended(int cause) {
        Log.i(TAG, "GoogleApiClient connection suspended");
    }
}

Answer 1

我们可以使用 Google Drive API 来:
- 查找现有文件
- 获取其 ID
- 删除文件
- 写一个新文件