我尝试使用Google Drive REST API Overview上的指南设置可以操作存储在个人Google云端硬盘帐户中的文件的Android应用。
我已按照示例代码允许用户连接到该帐户，但是＆＃34;选择一个帐户＆＃34;无论是选择了帐户名还是按下了取消按钮，对话框都会不断重新出现。
我认为问题是即使在从帐户选择器对话框中选择了帐户名后，refreshResults()方法在测试mCredential.getSelectedAccountName()时仍会返回null。但是，不知道为什么会发生这种情况或如何解决它。如果有经验的人能告诉我，我会非常感激。感谢。
我的代码如下：
import android.accounts.AccountManager;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.AsyncTask;
import android.preference.PreferenceManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GoogleApiAvailability;
import com.google.api.client.extensions.android.http.AndroidHttp;
import com.google.api.client.googleapis.extensions.android.gms.auth.GoogleAccountCredential;
import com.google.api.client.googleapis.extensions.android.gms.auth.GooglePlayServicesAvailabilityIOException;
import com.google.api.client.googleapis.extensions.android.gms.auth.UserRecoverableAuthIOException;
import com.google.api.client.http.HttpTransport;
import com.google.api.client.json.JsonFactory;
import com.google.api.client.json.jackson2.JacksonFactory;
import com.google.api.client.util.ExponentialBackOff;
import com.google.api.services.drive.DriveScopes;
import com.google.api.services.drive.model.File;
import com.google.api.services.drive.model.FileList;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class HomeActivity extends AppCompatActivity{
GoogleAccountCredential mCredential;
ProgressDialog mProgress;
static final int REQUEST_ACCOUNT_PICKER = 1000;
static final int REQUEST_AUTHORIZATION = 1001;
static final int REQUEST_GOOGLE_PLAY_SERVICES = 1002;
private static final String PREF_ACCOUNT_NAME = "accountName";
private static final String[] SCOPES = { DriveScopes.DRIVE_METADATA_READONLY };
public TextView mOutputText;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Initialize credentials and service object.
SharedPreferences settings = getPreferences(Context.MODE_PRIVATE);
mCredential = GoogleAccountCredential.usingOAuth2(
getApplicationContext(), Arrays.asList(SCOPES))
.setBackOff(new ExponentialBackOff())
.setSelectedAccountName(settings.getString(PREF_ACCOUNT_NAME, null));
mProgress = new ProgressDialog(this);
mProgress.setMessage("Calling Drive API ...");
setContentView(R.layout.activity_home);
mOutputText = (TextView) findViewById(R.id.textStatus);
@Override
protected void onResume() {
super.onResume();
if (isGooglePlayServicesAvailable()) {
refreshResults();
} else {
mOutputText.setText("Google Play Services required: " +
"after installing, close and relaunch this app.");
}
}
/**
* Called when an activity launched here (specifically, AccountPicker
* and authorization) exits, giving you the requestCode you started it with,
* the resultCode it returned, and any additional data from it.
* @param requestCode code indicating which activity result is incoming.
* @param resultCode code indicating the result of the incoming
* activity result.
* @param data Intent (containing result data) returned by incoming
* activity result.
*/
@Override
protected void onActivityResult(
int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
switch(requestCode) {
case REQUEST_GOOGLE_PLAY_SERVICES:
if (resultCode != RESULT_OK) {
isGooglePlayServicesAvailable();
}
break;
case REQUEST_ACCOUNT_PICKER:
if (resultCode == RESULT_OK && data != null &&
data.getExtras() != null) {
String accountName =
data.getStringExtra(AccountManager.KEY_ACCOUNT_NAME);
if (accountName != null) {
mCredential.setSelectedAccountName(accountName);
SharedPreferences settings =
getPreferences(Context.MODE_PRIVATE);
SharedPreferences.Editor editor = settings.edit();
editor.putString(PREF_ACCOUNT_NAME, accountName);
editor.apply();
}
} else if (resultCode == RESULT_CANCELED) {
mOutputText.setText("Account unspecified.");
}
break;
case REQUEST_AUTHORIZATION:
if (resultCode != RESULT_OK) {
chooseAccount();
}
break;
}
super.onActivityResult(requestCode, resultCode, data);
}
/**
* Attempt to get a set of data from the Drive API to display. If the
* email address isn't known yet, then call chooseAccount() method so the
* user can pick an account.
*/
private void refreshResults() {
if (mCredential.getSelectedAccountName() == null) {
chooseAccount();
} else {
if (isDeviceOnline()) {
new MakeRequestTask(mCredential).execute();
} else {
mOutputText.setText("No network connection available.");
}
}
}
/**
* Starts an activity in Google Play Services so the user can pick an
* account.
*/
private void chooseAccount() {
startActivityForResult(
mCredential.newChooseAccountIntent(), REQUEST_ACCOUNT_PICKER);
}
/**
* Checks whether the device currently has a network connection.
* @return true if the device has a network connection, false otherwise.
*/
private boolean isDeviceOnline() {
ConnectivityManager connMgr =
(ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
return (networkInfo != null && networkInfo.isConnected());
}
/**
* Check that Google Play services APK is installed and up to date. Will
* launch an error dialog for the user to update Google Play Services if
* possible.
* @return true if Google Play Services is available and up to
* date on this device; false otherwise.
*/
private boolean isGooglePlayServicesAvailable() {
final int connectionStatusCode =
//GooglePlayServicesUtil.isGooglePlayServicesAvailable(this);
GoogleApiAvailability.getInstance().isGooglePlayServicesAvailable(this);
if (GoogleApiAvailability.getInstance().isUserResolvableError(connectionStatusCode)) {
showGooglePlayServicesAvailabilityErrorDialog(connectionStatusCode);
return false;
} else if (connectionStatusCode != ConnectionResult.SUCCESS ) {
return false;
}
return true;
}
/**
* Display an error dialog showing that Google Play Services is missing
* or out of date.
* @param connectionStatusCode code describing the presence (or lack of)
* Google Play Services on this device.
*/
void showGooglePlayServicesAvailabilityErrorDialog(
final int connectionStatusCode) {
//Dialog dialog = GooglePlayServicesUtil.getErrorDialog(
Dialog dialog = GoogleApiAvailability.getInstance().getErrorDialog(
HomeActivity.this,
connectionStatusCode,
REQUEST_GOOGLE_PLAY_SERVICES);
dialog.show();
}
/**
* An asynchronous task that handles the Drive API call.
* Placing the API calls in their own task ensures the UI stays responsive.
*/
private class MakeRequestTask extends AsyncTask<Void, Void, List<String>> {
private com.google.api.services.drive.Drive mService = null;
private Exception mLastError = null;
public MakeRequestTask(GoogleAccountCredential credential) {
HttpTransport transport = AndroidHttp.newCompatibleTransport();
JsonFactory jsonFactory = JacksonFactory.getDefaultInstance();
mService = new com.google.api.services.drive.Drive.Builder(
transport, jsonFactory, credential)
.setApplicationName("Media Vault")
.build();
}
/**
* Background task to call Drive API.
* @param params no parameters needed for this task.
*/
@Override
protected List<String> doInBackground(Void... params) {
try {
return getDataFromApi();
} catch (Exception e) {
mLastError = e;
cancel(true);
return null;
}
}
/**
* Fetch a list of up to 10 file names and IDs.
* @return List of Strings describing files, or an empty list if no files
* found.
* @throws IOException
*/
private List<String> getDataFromApi() throws IOException {
// Get a list of up to 10 files.
List<String> fileInfo = new ArrayList<String>();
FileList result = mService.files().list()
.setPageSize(10)
.setFields("nextPageToken, items(id, name)")
.execute();
List<File> files = result.getFiles();
if (files != null) {
for (File file : files) {
fileInfo.add(String.format("%s (%s)\n",
file.getName(), file.getId()));
}
}
return fileInfo;
}
@Override
protected void onPreExecute() {
mOutputText.setText("");
mProgress.show();
}
@Override
protected void onPostExecute(List<String> output) {
mProgress.hide();
if (output == null || output.size() == 0) {
mOutputText.setText("No results returned.");
} else {
output.add(0, "Data retrieved using the Drive API:");
mOutputText.setText(TextUtils.join("\n", output));
}
}
@Override
protected void onCancelled() {
mProgress.hide();
if (mLastError != null) {
if (mLastError instanceof GooglePlayServicesAvailabilityIOException) {
showGooglePlayServicesAvailabilityErrorDialog(
((GooglePlayServicesAvailabilityIOException) mLastError)
.getConnectionStatusCode());
} else if (mLastError instanceof UserRecoverableAuthIOException) {
startActivityForResult(
((UserRecoverableAuthIOException) mLastError).getIntent(),
HomeActivity.REQUEST_AUTHORIZATION);
} else {
mOutputText.setText("The following error occurred:\n"
+ mLastError.getMessage());
}
} else {
mOutputText.setText("Request cancelled.");
}
}
}
}
答案 0 :(得分：4)
我遇到了完全相同的问题，在我的情况下，循环是因为我没有为我的应用程序创建凭据......
详情如下：https://developers.google.com/drive/android/get-started
您必须检索调试和生产环境的SHA-1密钥，并按照指南中的说明将其添加到Google Developers Console中的凭据中。
一旦我添加了这些凭据，循环就会立即停止。
答案 1 :(得分：1)
我能想到的一件事是，如果没有检索到setSelectedAccountName，null的值将默认为PREF_ACCOUNT_NAME，因此这可能会导致此问题。
我能看到的唯一区别就是你如何实例化mCredential。尝试查看适用于Android的Authorizing requests（使用GoogleApiClient代替GoogleAccountCredential。
答案 2 :(得分：0)