[英]Mobile Backend Starter - Upload to AppEngine Blobstore
如何使用Mobile Backend Starter或Google Cloud Endpoints將文件從Android上傳到Google App Engine Blobstore?
與Mobile Backend Starter分享我的經驗。
要獲取上傳和下載網址,您需要將這兩種方法添加到CloudBackend.java
類,以便從活動中訪問網址:
public String getUploadBlobURL(String bucketName, String path, String accessMode) {
String url = null;
try {
url = getMBSEndpoint().blobEndpoint()
.getUploadUrl(bucketName, path, accessMode).execute()
.getShortLivedUrl();
} catch (IOException e) {
e.printStackTrace();
}
return url;
}
public String getDownloadBlobURL(String bucketName, String path) {
String url = null;
try {
url = getMBSEndpoint().blobEndpoint()
.getDownloadUrl(bucketName, path).execute()
.getShortLivedUrl();
} catch (IOException e) {
e.printStackTrace();
}
return url;
}
然后,您可以使用網址通過標准客戶端庫將字節流式傳輸到Google雲端存儲。
下面我將舉例說明如何使用它們。
要將文件上傳到Google雲端存儲,您可以使用與此類似的內容:
活動
File fileUp = new File(Environment.getExternalStorageDirectory(), fileName);
new AsyncBlobUploader(this, mProcessingFragment.getCloudBackend()).execute(fileUp);
的AsyncTask
public class AsyncBlobUploader extends AsyncTask<File, Void, String> {
private Context context;
private ProgressDialog pd;
private CloudBackend cb;
public AsyncBlobUploader(Context context, CloudBackend cb) {
this.context = context;
this.cb = cb;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
pd = ProgressDialog.show(context, null,
"Loading... Please wait...");
pd.setProgressStyle(ProgressDialog.STYLE_SPINNER);
pd.setIndeterminate(true);
pd.setCancelable(true);
pd.show();
}
protected String doInBackground(File... files) {
File file = files[0];
String uploadUrl = cb.getUploadBlobURL(bucketName, file.getName(),"PUBLIC_READ_FOR_APP_USERS");
String url = uploadUrl.split("&Signature")[0]; // url without Signature
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(url);
FileBody filebody = new FileBody(file,ContentType.create(getMimeType(file
.toString())), file.getName());
MultipartEntityBuilder multipartEntity = MultipartEntityBuilder.create();
multipartEntity.setMode(HttpMultipartMode.BROWSER_COMPATIBLE);
multipartEntity.addPart("file", filebody);
httppost.setEntity(multipartEntity.build());
System.out.println( "executing request " + httppost.getRequestLine( ) );
try {
HttpResponse response = httpclient.execute( httppost );
Log.i("response", response.getStatusLine().toString());
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
httpclient.getConnectionManager( ).shutdown( );
return (String) uploadUrl;
}
protected void onPostExecute(String result) {
pd.dismiss();
Log.d("BlobUrl", result);
}
public static String getMimeType(String url) {
String type = null;
String extension = MimeTypeMap.getFileExtensionFromUrl(url);
if (extension != null) {
MimeTypeMap mime = MimeTypeMap.getSingleton();
type = mime.getMimeTypeFromExtension(extension);
}
return type;
}
}
MultipartEntityBuilder
類不包含在android標准庫中,因此您需要下載httpclient並將其包含到您的項目中。
注意這一行String url = uploadUrl.split("&Signature")[0];
我在哪里切斷網址簽名。 (使用url簽名我得到503 Internal Server Error
但沒有它一切都按預期工作。我不知道為什么會發生這種情況。)
要下載,您可以使用以下代碼段:
活動
File fileDown = new File(Environment.getExternalStorageDirectory(),
fileName); //file to create
new AsyncBlobDownloader(imageView, mProcessingFragment.getCloudBackend())
.execute(fileDown);
的AsyncTask
public class AsyncBlobDownloader extends AsyncTask<File, Integer, File> {
private ImageView imageView;
private ProgressDialog pd;
private CloudBackend cb;
public AsyncBlobDownloader(ImageView imageView, CloudBackend cb) {
this.imageView = imageView;
this.cb = cb;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
pd = ProgressDialog.show(imageView.getContext(), null,
"Loading... Please wait...");
pd.setProgressStyle(ProgressDialog.STYLE_SPINNER);
pd.setCancelable(true);
pd.show();
}
protected File doInBackground(File... files) {
File file = files[0];
String downloadUrl = cb.getDownloadBlobURL(bucketName,
file.getName());
InputStream input = null;
OutputStream output = null;
HttpURLConnection connection = null;
try {
URL url = new URL(downloadUrl);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
if (connection.getResponseCode() != HttpURLConnection.HTTP_OK) {
Log.i("Response",
"Server returned HTTP " + connection.getResponseCode()
+ " " + connection.getResponseMessage());
}
int fileLength = connection.getContentLength();
input = connection.getInputStream();
output = new FileOutputStream(file);
byte data[] = new byte[4096];
int count;
while ((count = input.read(data)) != -1) {
if (isCancelled()) {
input.close();
return null;
}
output.write(data, 0, count);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (output != null)
output.close();
if (input != null)
input.close();
} catch (IOException ignored) {
}
if (connection != null)
connection.disconnect();
}
return file;
}
protected void onPostExecute(File result) {
pd.dismiss();
imageView.setImageURI(Uri.fromFile(result));
}
}
注意:要使用Google雲端存儲,您需要啟用結算功能。 您還需要在GCS中創建存儲桶。
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