cordova plugin add https://github.com/rossmartin/phonegap-dropbox-sync-android.git

function dropbox_linked() { }
// Called from the onActivityResult method in the plugin when linking is successful.

function dropbox_onSyncStatusChange(status) { }
// Called by observer in the plugin when there's a change 
// to the status of background synchronization (download/upload).
// status is a string variable that will be 'sync' or 'none'.

function dropbox_fileChange() { }
// Called by observer in the plugin when a file is changed.

DropboxSync.link();

DropboxSync.checkLink(function() { // success
    // User is already authenticated with Dropbox.
}, function() { // fail
    // User is not authenticated with Dropbox.
});
// Authentication status will persist between runs of your app.

var dropboxPath = '/';

DropboxSync.addObserver(dropboxPath);
// When an observer is added to a path, JavaScript callbacks
// 'dropbox_fileChange' and 'dropbox_onSyncStatusChange'
// will get invoked when a file/folder is changed or when
// a background synchronization (download/upload) occurs.
// The observer watches changes in child directories also.

var dropboxFolderPath = '/'; // root app dir in this case

DropboxSync.listFolder(dropboxFolderPath, function(files) { // success
    // Each object in files have properties: path, modifiedTime, size, and isFolder.
}, function() { // fail
    // Handle error in fail callback.
});

DropboxSync.uploadFile({
    filePath: 'file:///storage/sdcard0/DCIM/Camera/SomeVideo.mp4', // required, local URI
    dropboxPath: '/someFolder' // optional, defaults to root ('/')
}, function() { // success
    // dropboxPath is the Dropbox folder you want to upload the file into.
}, function() { // fail
    // Handle error in fail callback.
});

DropboxSync.uploadFolder({
    folderPath: 'file:///storage/sdcard0', // required
    dropboxPath: '/someFolder', // optional, defaults to root ('/')
    doRecursive: true // optional, defaults to false
}, function() { // success
    // dropboxFolderPath is the Dropbox folder you want to upload the files/folders into.
    // The folder upload can be done recursively by setting doRecursive to true.
}, function() { // fail
    // Handle error in fail callback.
});

var filePath = '/foo/bar.jpg';

DropboxSync.openFile(filePath, function() { // success
    // Android device will either open the file with the proper external application
    // installed on your device or ask you which application to use.
}, function() { // fail
    // Handle error in fail callback.
});

var folderPath = '/foo/bar';

DropboxSync.createFolder(folderPath, function() { // success
    // Creates a new folder, including parent folders if necessary.
}, function() { // fail
    // Handle error in fail callback.
});

var filePath = '/foo/bar.json';

DropboxSync.deleteFile(filePath, function() { // success
    // Deletes a file, or recursively deletes a folder.
}, function() { // fail
    // Handle error in fail callback.
});

var filePath = '/foo/bar.json';

DropboxSync.readString(filePath, function(result) { // success
    // Reads the contents of a file (result is a string).
}, function() { // fail
    // Handle error in fail callback.
});

var filePath = '/foobar.jpg';

DropboxSync.getImageBase64String(filePath, function(result) { // success
    $('#image').attr('src', 'data:image/jpeg;base64,' + result);
    // result is the Base64-encoded string.
}, function() { // fail
    // Handle error in fail callback.
});

DropboxSync.unlink(function() { // success
    // Do something here after unlinked.
}, function() { // fail
    // Handle error in fail callback.
});