android– 如何在Google云端硬盘中替换文件？

概述使用以下代码(取自android-quickstart),如果您拍摄多张照片,此代码可以生成多个具有相同名称的文件.如何修改以确保替换具有相同名称的文件？publicclassMainActivityextendsActivityimplementsConnectionCallbacks,OnConnectionFailedListener{privatestat

使用以下代码(取自android-quickstart),如果您拍摄多张照片,此代码可以生成多个具有相同名称的文件.如何修改以确保替换具有相同名称的文件？

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");    }}

解决方法:

我按如下方式打开驱动文件进行写入：

writeDrivefile(Drivefile file, Handler handler){    //see query task below to get a drive file by its name. Be careful you can get multiple data elements in the MetadataBuffer below if you have uploaded multiple files with the same name.    Task<DriveContents> openfileTask = myDriveResourceClIEnt.openfile(file, Drivefile.MODE_WRITE_ONLY);

然后用该任务将一些对象字节写入流someObject.getBytes(),这里没有魔法.然后提交结果.

openfileTask            .continueWithTask(task -> {                DriveContents contents = task.getResult();                // Process contents...                try (OutputStream writer = contents.getoutputStream()) {                    writer.write(someObject.getBytes());                    writer.close();                }                //Add whatever Metadata you want here                MetadataChangeSet changeSet = new MetadataChangeSet.Builder()                        .setLastVIEwedByMeDate(new Date())                        .build();                //commit the file to Google Drive                Task<VoID> commitTask = myDriveResourceClIEnt.commitContents(contents, changeSet);                handler.onWriteResults();                return commitTask;            })            .addOnFailureListener(e -> {                // Handle failure                Log.e(TAG, "Unable to read contents", e);                handler.onDriveError(e);            });

处理程序只是我为Drive API执行后要处理的错误或结果定义的接口.您还可以添加addOnCompleteListener()以在写入完成后处理某些内容.

file是Drivefile的一个实例,可以通过查询任务获取.在任务代码块中找到的元数据有一个getDriveID()方法,它有一个asDriveffile()方法来获取上面需要的Drive文件.

query query = new query.Builder()            .addFilter(Filters.eq(SearchableFIEld.Title, "file name"))            .build();Task<MetadataBuffer> queryTask = mDriveResourceClIEnt.query(query);

然后处理MetadataBuffer

queryTask.continueWithTask(                    task -> {                        MetadataBuffer MetadataBuffer = task.getResult() ;                        //I have this loop because I wanted to kNow if there were other versions of the file on the drive                        for(Metadata data : MetadataBuffer) {                            Log.d(TAG, "******************* MetadataBuffer Title is " + data.getTitle());                            if(data.getTitle().equals("file name")){                                //this is just a method I defined that encapsulates the drive writing code above.                                writeDrivefile(data.getDriveID().asDrivefile(), JsonContent, handler);                            }                        }                        return task;                    })            .addOnCompleteListener(task -> {                //some complete tasks                }            })            .addOnFailureListener(e -> {                Log.e(TAG, "************************** Error searching for " + filename, e);                handler.onDriveError(e);            });

此代码全部用于写入App文件夹,但您只需在创建资源客户端时设置正确的范围.

删除驱动器文件可以按如下方式完成.

 public voID deleteDrivefile(DriveResource file){    Task<VoID> deleteTask = mDriveResourceClIEnt.delete(file);    deleteTask            .continueWith(task -> {                Log.d(TAG, "************* Deleted drive file: " + file.getDriveID().toInvariantString());                return task;            })            .addOnFailureListener(e -> {                //log some sort of error for yourself            });}

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