如何以编程方式从Android中的Google驱动器所选文件下载并保存在本地目录中?

Question

我在我的应用程序中使用谷歌驱动器API，我能够从谷歌云端硬盘中选择(.doc/docx/.pdf)文件，到目前为止一切都很好。但是我想下载选定的文件，并且需要使用Multipart将该文件发送到我们的服务器。 我尝试了多种方法，我得到了DriveId和DriveFile但不幸的是我无法下载下载选定的文件。

我已经浏览了安卓开发者文档

我正在使用以下代码

import android.accounts.Account;
import android.accounts.AccountManager;
import android.app.Activity;
import android.content.Intent;
import android.content.IntentSender;
import android.os.Bundle;
import android.util.Log;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GoogleApiAvailability;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.drive.Drive; 
import com.google.android.gms.drive.DriveFile;
import com.google.android.gms.drive.DriveId;
import com.google.android.gms.drive.DriveResource;
import com.google.android.gms.drive.OpenFileActivityBuilder;
import com.google.api.client.extensions.android.http.AndroidHttp;
import com.google.api.client.http.HttpTransport;
import com.google.api.client.json.JsonFactory;
import com.google.api.client.json.gson.GsonFactory; 
import com.google.api.services.drive.DriveScopes;
public class DriveActivity extends Activity implements GoogleApiClient.ConnectionCallbacks,
GoogleApiClient.OnConnectionFailedListener {
/**
* DriveId of an existing folder to be used as a parent folder in
* folder operations samples.
*/
public static final String EXISTING_FOLDER_ID = "0B2EEtIjPUdX6MERsWlYxN3J6RU0";
/**
* DriveId of an existing file to be used in file operation samples..
*/
public static final String EXISTING_FILE_ID = "0ByfSjdPVs9MZTHBmMVdSeWxaNTg";
/**
* Extra for account name.
*/
protected static final String EXTRA_ACCOUNT_NAME = "account_name";
/**
* Request code for auto Google Play Services error resolution.
*/
protected static final int REQUEST_CODE_RESOLUTION = 1;
/**
* Next available request code.
*/
protected static final int NEXT_AVAILABLE_REQUEST_CODE = 2;
private static final String TAG = "===GoogleDriveActivity";
private static final int REQUEST_CODE_OPENER = 2;
/**
* Google API client.
*/
private GoogleApiClient mGoogleApiClient;
private static final String[] SCOPES = {DriveScopes.DRIVE_FILE};
final HttpTransport transport = AndroidHttp.newCompatibleTransport();
final JsonFactory jsonFactory = GsonFactory.getDefaultInstance();
private String accountName;
DriveResource.MetadataResult metadataResult;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
connect();
}
@Override
protected void onStop() {
if (mGoogleApiClient != null) {
mGoogleApiClient.disconnect();
}
super.onStop();
}
@Override
protected void onRestart() {
super.onRestart();
connect();
}

private void connect() {
if (mGoogleApiClient == null) {
mGoogleApiClient = new GoogleApiClient.Builder(this)
.addApi(Drive.API)
.addScope(Drive.SCOPE_FILE)
.addScope(Drive.SCOPE_APPFOLDER) // required for App Folder sample
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.build();
}
mGoogleApiClient.connect();
}
/**
* Called when {@code mGoogleApiClient} is disconnected.
*/
@Override
public void onConnectionSuspended(int cause) {
Log.i(TAG, "GoogleApiClient connection suspended");
}
/**
* Called when {@code mGoogleApiClient} is trying to connect but failed.
* Handle {@code result.getResolution()} if there is a resolution is
* available.
*/
@Override
public void onConnectionFailed(ConnectionResult result) {
Log.i(TAG, "GoogleApiClient connection failed: " + result.toString());
if (!result.hasResolution()) {
// show the localized error dialog.
GoogleApiAvailability.getInstance().getErrorDialog(this, result.getErrorCode(), 0).show();
return;
}
try {
result.startResolutionForResult(this, REQUEST_CODE_RESOLUTION);
} catch (IntentSender.SendIntentException e) {
Log.e(TAG, "Exception while starting resolution activity", e);
}
}

/**
* Getter for the {@code GoogleApiClient}.
*/
public GoogleApiClient getGoogleApiClient() {
return mGoogleApiClient;
}
@Override
public void onConnected(Bundle connectionHint) {
IntentSender intentSender = Drive.DriveApi
.newOpenFileActivityBuilder()
.setMimeType(new String[]{"application/msword", " application/vnd.openxmlformats-officedocument.wordprocessingml.document", "application/vnd.google-apps.document", "application/pdf"})
.build(getGoogleApiClient());
AccountManager manager = (AccountManager) getSystemService(ACCOUNT_SERVICE);
Account[] list = manager.getAccountsByType("com.google");
//Getting the first account because that is the primary account for that user
accountName = list[0].name;
try {
startIntentSenderForResult(
intentSender, REQUEST_CODE_OPENER, null, 0, 0, 0);
} catch (IntentSender.SendIntentException e) {
Log.w(TAG, "Unable to send intent", e);
}
}
/**
* Handles resolution callbacks.
*/
@Override
protected void onActivityResult(int requestCode, int resultCode,
Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode == RESULT_OK) {
switch (requestCode) {
case REQUEST_CODE_OPENER:
Intent intent = null;
if (resultCode == RESULT_OK) {
DriveId driveId = data.getParcelableExtra(
OpenFileActivityBuilder.EXTRA_RESPONSE_DRIVE_ID);
String resourceId = driveId.getResourceId();
DriveFile file = driveId.asDriveFile();
}
break;
case REQUEST_CODE_RESOLUTION:
mGoogleApiClient.connect();
break;
default:
super.onActivityResult(requestCode, resultCode, data);
}
}
}
}

请有人帮我以编程方式从谷歌云端硬盘下载选定的文件吗？

提前谢谢。

Answer 1

有两种方法可以下载它，通过REST或使用GDAA。您可以根据编码的舒适位置使用其中任何一个。

使用 REST 时：

/*************************************************************************
* get file contents
* @param resId  file driveId
* @return       file's content  / null on fail
*/
static InputStream read(String resId) {
if (mGOOSvc != null && mConnected && resId != null) try {
File gFl = mGOOSvc.files().get(resId).setFields("downloadUrl").execute();
if (gFl != null){
String strUrl = gFl.getDownloadUrl();
return mGOOSvc.getRequestFactory()
.buildGetRequest(new GenericUrl(strUrl)).execute().getContent();
}
} catch (Exception e) { /* error handling */ }
return null;
}

使用 GDAA 时：

/************************************************************************************************
* get file contents
* @param id file driveId
* @return file's content  / null on fail
*/
static byte[] read(String id) {
byte[] buf = null;
if (mGAC != null && mGAC.isConnected() && id != null) try {
DriveFile df = Drive.DriveApi.getFile(mGAC, DriveId.decodeFromString(id));
DriveContentsResult rslt = df.open(mGAC, DriveFile.MODE_READ_ONLY, null).await();
if ((rslt != null) && rslt.getStatus().isSuccess()) {
DriveContents cont = rslt.getDriveContents();
buf = UT.is2Bytes(cont.getInputStream());
cont.discard(mGAC);    // or cont.commit();  they are equiv if READONLY
}
} catch (Exception e) { UT.le(e); }
return buf;
}

查看此 SO 帖子以了解 GDAA 中驱动器休息的区别。

1 GDAA 的主要标识符 DriveId 仅存在于 GDAA (GooPlaySvcs) 中，不存在于 REST API 中。您必须检索"ResourceId"，这是 REST API 中的主标识符(请参阅 SO 29030110)。

2 只有在 GDAA 提交(上传)文件/文件夹后，才能从 DriveId 获取资源 ID(请参阅 SO 22874657)

3 由于 GDAA 按照自己的计划(系统优化)"缓冲"网络请求，而 REST API 让您的应用程序控制响应的等待，因此您会遇到很多计时问题。一般来说，如果你浏览这些SO问题，你会发现很多关于这些问题的喋喋不休(虽然这是一团糟)。

希望这有帮助。

Answer 2

只需传递上传文件的驱动器ID和下载时要提供的文件名

public void DownloadFile(final DriveId driveId, final File filename, final GoogleApiClient mGoogleApiClient) {
if (!filename.exists()) {
try {
filename.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
}
final DriveFile file = Drive.DriveApi.getFile(mGoogleApiClient, driveId);
file.getMetadata(mGoogleApiClient).setResultCallback(metadataRetrievedCallback);
DriveFolder folder = Drive.DriveApi.getFolder(mGoogleApiClient, driveId);
folder.getMetadata(mGoogleApiClient).setResultCallback(metadataRetrievedCallback1);
new Thread(new Runnable()
{
@Override
public void run()
{
DriveApi.DriveContentsResult driveContentsResult = file.open(mGoogleApiClient,DriveFile.MODE_READ_ONLY, null).await();
DriveContents driveContents = driveContentsResult.getDriveContents();
InputStream inputstream = driveContents.getInputStream();
try
{
FileOutputStream fileOutput = new FileOutputStream(filename);
byte[] buffer = new byte[1024];
int bufferLength = 0;
while ((bufferLength = inputstream.read(buffer)) > 0)
{
fileOutput.write(buffer, 0, bufferLength);
}
fileOutput.close();
inputstream.close();
}
catch (IOException e) {
e.printStackTrace();
}
}
}).start();
}