# nearby_connections

An **android** flutter plugin for the [Nearby Connections API](https://developers.google.com/nearby/connections/overview)
Currently supports Bytes and Files.

**Transfer Data between multiple connected devices using fully offline peer to peer networking**

[![pub package](https://img.shields.io/pub/v/nearby_connections.svg)](https://pub.dartlang.org/packages/nearby_connections)

## Table of Content
* [Setup](#setup)
* [Work Flow](#work-flow)
    * [Advertise For connections](#advertise-for-connection)
    * [Discover Advertisers](#discover-advertisers)
    * [Request Connection](#request-connection)
    * [Accept Connection](#accept-connection)
* [Sending Data](#sending-data)
    * [Sending Bytes Payload](#sending-bytes-payload)
    * [Sending Files](#sending-file-payload)

## Setup

### Note regarding Location(GPS)
While using this,
**Location/GPS service must be turned on** or devices may disconnect
more often, some devices may disconnect immediately.

### Set Permissions
Add these to AndroidManifest.xml
```xml
<!-- Required for Nearby Connections -->
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

<!-- Optional: only required for FILE payloads-->
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
```
Since ACCESS_FINE_LOCATION and READ_EXTERNAL_STORAGE is considered to be dangerous system permissions, in addition to adding them to your manifest, you must request these permissions at runtime.

#### As a **convinience** this library provides methods to check and request location and external read/write permissions
```dart
// returns true/false asynchronously 
bool a = await Nearby().checkLocationPermissions()
// asks for permission only if its not given
Nearby().askLocationPermission()

// OPTIONAL: if you need to transfer files and rename it on device
bool b = Nearby().checkExternalStoragePermission()
// asks for READ + WRTIE EXTERNAL STORAGE permission only if its not given
Nearby().askExternalStoragePermission() 

Nearby().askLocationAndExternalStoragePermission() // for all permissions in one go..
```

## Work Flow

The work flow is similar to the [Android Nearby Connections library](https://developers.google.com/nearby/connections/overview)

## NOTE

**Location/GPS service must be turned on** or devices may disconnect
more often, some devices may disconnect immediately.

For convinience this library provides methods to check and enable location
```dart
bool b = await Nearby().checkLocationEnabled();

// opens settings where user can enable it
Nearby().enableLocationServices();
``` 
### Advertise for connection
```dart
try {
    bool a = await Nearby().startAdvertising(
        userName,
        strategy,
        onConnectionInitiated: (String id,ConnectionInfo info) {
        // Called whenever a discoverer requests connection 
        },
        onConnectionResult: (String id,Status status) {
        // Called when connection is accepted/rejected
        },
        onDisconnected: (String id) {
        // Callled whenever a discoverer disconnects from advertiser
        },
        serviceId: "com.yourdomain.appname", // uniquely identifies your app
    );
} catch (exception) {
    // platform exceptions like unable to start bluetooth or insufficient permissions 
}
```
### Discover Advertisers
```dart
try {
    bool a = await Nearby().startDiscovery(
        userName,
        strategy,
        onEndpointFound: (String id,String userName, String serviceId) {
            // called when an advertiser is found
        },
        onEndpointLost: (String id) {
            //called when an advertiser is lost (only if we weren't connected to it )
        },
        serviceId: "com.yourdomain.appname", // uniquely identifies your app
    );
} catch (e) {
    // platform exceptions like unable to start bluetooth or insufficient permissions
}
```
### Stopping Advertising and Discovery
```dart
Nearby().stopAdvertising();
Nearby().stopDiscovery();
// endpoints already discovered will still be available to connect
// even after stopping discovery
// You should stop discovery once you have found the intended advertiser
// this will reduce chances for disconnection
```
### Request Connection
```dart
// to be called by discover whenever an endpoint is found
// callbacks are similar to those in startAdvertising method
try{ 
    Nearby().requestConnection(
        userName,
        id,
        onConnectionInitiated: (id, info) {
        },
        onConnectionResult: (id, status) {
        },
        onDisconnected: (id) {
        },
    );
}catch(exception){
    // called if request was invalid
}
```
### Accept Connection
```dart
Nearby().acceptConnection(
    id,
    onPayLoadRecieved: (endpointId, payload) {
        // called whenever a payload is recieved.
    },
    onPayloadTransferUpdate: (endpointId, payloadTransferUpdate) {
        // gives status of a payload
        // e.g success/failure/in_progress
        // bytes transferred and total bytes etc
    }
);
```
## Sending Data
### Sending Bytes Payload

```dart
Nearby().sendBytesPayload(endpointId, bytes_array);

// payloads are recieved by callback given to acceptConnection method.
```
### Sending File Payload
You need to send the File Payload and File Name seperately.

File is stored in DOWNLOAD_DIRECTORY and given a generic name
So you would need to rename the file on receivers end.

```dart
//creates file with generic name (without extension) in Downloads Directory
//its your responsibility to rename the file properly
Nearby().sendFilePayload(endpointId, filePath);

//Send filename as well so that receiver can rename the file
Nearby().sendBytesPayload(endpointId,fileNameEncodedWithPayloadId);
//e.g send a string like "payloadId:FileExtensionOrFullName" as bytes

//payloads are recieved by callback given to acceptConnection method.
```
Every payload has an **ID** which is same for sender and receiver.

You can get the absolute FilePath from Payload in *onPayloadReceived* function

Checkout the [**Example**](https://github.com/mannprerak2/nearby_connections/tree/master/example) in Repository for more details