如何使用Drive.API从Google Drive下载文件？
我正在使用Google Drive.Api，以便让用户的应用数据与用户帐号同步。
用户数据库是sqlite数据库格式。 我已成功将文件以二进制方式上传到驱动器，但未能从应用程序内下载文件。
我如何获得文件URl：
final GoogleAccountCredential credential = GoogleAccountCredential.usingOAuth2(this, Arrays.asList(DriveScopes.DRIVE_FILE));
credential.setSelectedAccountName(accountName);
service = new com.google.api.services.drive.Drive.Builder(AndroidHttp.newCompatibleTransport(), new GsonFactory(), credential).build();
Query query = new Query.Builder()
.addFilter(Filters.eq(SearchableField.TITLE, "BackupFile"))
.build();
final DriveFolder folder = Drive.DriveApi.getRootFolder(mGoogleApiClient);
folder.queryChildren(mGoogleApiClient, query).setResultCallback(new ResultCallback<DriveApi.MetadataBufferResult>() {
@Override
public void onResult(DriveApi.MetadataBufferResult metadataBufferResult) {
final MetadataBuffer metadataBuffer = metadataBufferResult.getMetadataBuffer();
int iCount = metadataBuffer.getCount();
if (iCount == 1) {
Log.i("Tag", "file was found");
final DriveId myFileId = metadataBuffer.get(0).getDriveId();
final DriveFile file = Drive.DriveApi.getFile(mGoogleApiClient, myFileId);
new Thread(new Runnable() {
@Override
public void run() {
DriveResource.MetadataResult mdRslt = file.getMetadata(mGoogleApiClient).await();
if (mdRslt != null && mdRslt.getStatus().isSuccess()) {
String link = mdRslt.getMetadata().getWebContentLink();
Log.d("TAG", "Link to File:" + link);
DownloadBackup(link);
}
}
}).start();
}
metadataBuffer.release();
}
});
试图通过以下方式下载文件：
public void DownloadBackup(String url){
InputStream mInput=null;
FileOutputStream mOutput=null;
if(url != null && url.length() > 0 ){
try {
GoogleAccountCredential crd = GoogleAccountCredential.usingOAuth2(this, Arrays.asList(DriveScopes.DRIVE_FILE));
crd.setSelectedAccountName(accountName);
com.google.api.services.drive.Drive srv = new com.google.api.services.drive.Drive.Builder(AndroidHttp.newCompatibleTransport(), new GsonFactory(), crd).build();
mInput = srv.getRequestFactory().buildGetRequest(new GenericUrl(url)).execute().getContent();
String outFileName = getApplicationContext().getDatabasePath(DatabaseHandler.DATABASE_NAME).getPath();
mOutput = new FileOutputStream(outFileName);
byte[] mBuffer = new byte[1024];
int mLength;
while ((mLength = mInput.read(mBuffer)) > 0) {
mOutput.write(mBuffer, 0, mLength);
}
mOutput.flush();
Log.d("TAG", "Successfully Downloaded contents");
} catch (IOException e) {
e.printStackTrace();
}finally {
try {
//Close the streams
if(mOutput != null){
mOutput.close();
}
if(mInput != null){
mInput.close();
}
} catch (IOException e) {
Log.e("Tag", "failed to close databases");
}
}
} else {
// The file doesn't have any content stored on Drive.
// return null;
Log.e("Tag", "No content on Drive");
}
}
错误日志：
W/System.err﹕ com.google.api.client.http.HttpResponseException: 401 Unauthorized
W/System.err﹕ <HTML>
W/System.err﹕ <HEAD>
W/System.err﹕ <TITLE>Unauthorized</TITLE>
W/System.err﹕ </HEAD>
W/System.err﹕ <BODY BGCOLOR="#FFFFFF" TEXT="#000000">
W/System.err﹕ <H1>Unauthorized</H1>
W/System.err﹕ <H2>Error 401</H2>
W/System.err﹕ </BODY>
W/System.err﹕ </HTML>
W/System.err﹕ [ 06-12 11:01:05.447 26208:26236 W/System.err ]
at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:1061)
W/System.err﹕ at com.example.app.activities.Main.DownloadBackup(Main.java:487)
W/System.err﹕ at com.example.app.activities.Main$15$1.run(Main.java:332)
W/System.err﹕ at java.lang.Thread.run(Thread.java:841)
这是我如何成功地做到这一点。 我不保存'getWebContentLink'的结果，而是保存一个文件/文件夹ID（它是一个字符串）。 并将此ID传递给此类方法：
/*************************************************************************
* 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;
}
检索“downloadURL”并获取内容。 这个方法的全部内容可以在这里看到。
祝你好运
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