Android connection Bluetooth process (complete code at the end)
- Declare permissions
1) Declare permissions in the AndroidManifest manifest file (Note: Searching for Bluetooth requires location permission!!)
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />
<uses-permission android:name="android.permission.BLUETOOTH_SCAN" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
2) Apply for runtime permissions
if (ContextCompat.checkSelfPermission(this, Manifest.permission.BLUETOOTH_SCAN) != PackageManager.PERMISSION_GRANTED ) {<!-- -->
ActivityCompat.requestPermissions(this, new String[]{<!-- -->
Manifest.permission.ACCESS_FINE_LOCATION,
Manifest.permission.ACCESS_COARSE_LOCATION,
Manifest.permission.BLUETOOTH_SCAN,
Manifest.permission.BLUETOOTH_CONNECT}, 0);
}
// Process the results of the permission request in the onRequestPermissionsResult method
@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {<!-- -->
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
if (requestCode == 0) {<!-- -->
if (grantResults.length > 0 & amp; & amp; grantResults[0] == PackageManager.PERMISSION_GRANTED) {<!-- -->
// The user has granted Bluetooth connection permission and performs operations related to Bluetooth connection.
// Get the pairing list
for (BluetoothDevice bondedDevice : bluetoothAdapter.getBondedDevices()) {<!-- -->
deviceListAdapter.add(bondedDevice.getName() + "\
" + bondedDevice.getAddress());
}
} else {<!-- -->
// The user has denied the Bluetooth connection permission. You may need to display a prompt message or provide an explanation.
Toast.makeText(this, "Please grant Bluetooth permissions", Toast.LENGTH_LONG).show();
}
}
}
- Get a Bluetooth adapter
bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
if (bluetoothAdapter == null) {<!-- -->
Toast.makeText(MainActivity.this, "This device does not support Bluetooth!", Toast.LENGTH_SHORT).show();
}
- Activate Bluetooth
//Start Bluetooth
if (!bluetoothAdapter.isEnabled()) {<!-- -->
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, 1);
}
- Create a Bluetooth display list
deviceListView = findViewById(R.id.deviceListView); deviceListAdapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1); deviceListView.setAdapter(deviceListAdapter);
- Register a Bluetooth broadcast receiver (for receiving results of Bluetooth searches)
//Register Bluetooth broadcast receiver
IntentFilter filter = new IntentFilter();
filter.addAction(BluetoothDevice.ACTION_FOUND);
filter.addAction(BluetoothDevice.ACTION_ACL_CONNECTED);
filter.addAction(BluetoothDevice.ACTION_ACL_DISCONNECTED);
registerReceiver(new BroadcastReceiver() {<!-- -->
public void onReceive(Context context, Intent intent) {<!-- -->
String action = intent.getAction();
if (BluetoothDevice.ACTION_FOUND.equals(action)) {<!-- -->
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
deviceListAdapter.add(device.getName() + "\
" + device.getAddress());
}
}
}, filter);
- Search bluetooth
if (bluetoothAdapter.isDiscovering()) {<!-- -->
bluetoothAdapter.cancelDiscovery();
}
deviceListAdapter.clear();
bluetoothAdapter.startDiscovery();
- Connect Bluetooth (executed in asynchronous code)
// Connect to Bluetooth
deviceListView.setOnItemClickListener((parent, view, position, id) -> {<!-- -->
String deviceInfo = (String) parent.getItemAtPosition(position);
String deviceAddress = deviceInfo.substring(deviceInfo.length() - 17);
BluetoothDevice myDevice = bluetoothAdapter.getRemoteDevice(deviceAddress);
new Thread(new Runnable() {<!-- -->
@Override
public void run() {<!-- -->
try {<!-- -->
Looper.prepare();
if (mySocket != null) {<!-- -->
Toast.makeText(MainActivity.this, "Disconnect connected Bluetooth", Toast.LENGTH_SHORT).show();
mySocket.close();
}
mySocket = myDevice.createRfcommSocketToServiceRecord(UUID.fromString("00001101-0000-1000-8000-00805F9B34FB")); // uuid is universal
mySocket.connect();
myOutStream = mySocket.getOutputStream();
myInStream = mySocket.getInputStream();
Toast.makeText(MainActivity.this, "Bluetooth connected:" + myDevice.getName(), Toast.LENGTH_SHORT).show();
} catch (Exception e2) {<!-- -->
Toast.makeText(MainActivity.this, "Bluetooth connection failed" + e2.getMessage(), Toast.LENGTH_SHORT).show();
myInStream = null;
myOutStream = null;
mySocket = null;
}
Looper.loop();
}
}).start();
});
Key API
// Get Bluetooth adapter
BluetoothAdapter.getDefaultAdapter();
// Whether Bluetooth is enabled
bluetoothAdapter.isEnabled();
// Turn on Bluetooth
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, 1);
// Is Bluetooth searching?
bluetoothAdapter.isDiscovering();
//Search for Bluetooth
bluetoothAdapter.startDiscovery();
// Stop searching for Bluetooth
bluetoothAdapter.cancelDiscovery();
// Get Bluetooth device
bluetoothAdapter.getRemoteDevice();
// Get Bluetooth socket
BluetoothSocket mySocket = myDevice.createRfcommSocketToServiceRecord(UUID.fromString("00001101-0000-1000-8000-00805F9B34FB"));
// Connect Bluetooth
mySocket.connect();
// Get the input stream and output stream
myOutStream = mySocket.getOutputStream();
myInStream = mySocket.getInputStream();
Complete code
MainActivity
package com.example.bluetoothdemo;
import android.Manifest;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.os.Looper;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.UUID;
public class MainActivity extends AppCompatActivity {<!-- -->
private BluetoothAdapter bluetoothAdapter; // Bluetooth
private ArrayAdapter<String> deviceListAdapter;
private ListView deviceListView;
private static BluetoothSocket mySocket = null;
private static OutputStream myOutStream = null;
private static InputStream myInStream = null;
// runtime permissions
public static final String[] PERMISSIONS = new String[]{<!-- -->
Manifest.permission.ACCESS_FINE_LOCATION,
Manifest.permission.ACCESS_COARSE_LOCATION,
Manifest.permission.BLUETOOTH_SCAN,
Manifest.permission.BLUETOOTH_CONNECT,
};
@Override
protected void onCreate(Bundle savedInstanceState) {<!-- -->
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Check Bluetooth scanning permissions
if (ContextCompat.checkSelfPermission(this, Manifest.permission.BLUETOOTH_SCAN) != PackageManager.PERMISSION_GRANTED
|| ContextCompat.checkSelfPermission(this, Manifest.permission.BLUETOOTH_CONNECT) != PackageManager.PERMISSION_GRANTED
|| ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED
|| ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {<!-- -->
ActivityCompat.requestPermissions(this, new String[]{<!-- -->
Manifest.permission.ACCESS_FINE_LOCATION,
Manifest.permission.ACCESS_COARSE_LOCATION,
Manifest.permission.BLUETOOTH_SCAN,
Manifest.permission.BLUETOOTH_CONNECT}, 0);
}
// Get Bluetooth
bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
if (bluetoothAdapter == null) {<!-- -->
Toast.makeText(MainActivity.this, "This device does not support Bluetooth!", Toast.LENGTH_SHORT).show();
return;
}
//Set Bluetooth list
deviceListView = findViewById(R.id.deviceListView);
deviceListAdapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1);
deviceListView.setAdapter(deviceListAdapter);
// Start Bluetooth
if (!bluetoothAdapter.isEnabled()) {<!-- -->
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, 1);
}
//Register Bluetooth broadcast receiver
IntentFilter filter = new IntentFilter();
filter.addAction(BluetoothDevice.ACTION_FOUND);
filter.addAction(BluetoothDevice.ACTION_ACL_CONNECTED);
filter.addAction(BluetoothDevice.ACTION_ACL_DISCONNECTED);
registerReceiver(new BroadcastReceiver() {<!-- -->
public void onReceive(Context context, Intent intent) {<!-- -->
String action = intent.getAction();
if (BluetoothDevice.ACTION_FOUND.equals(action)) {<!-- -->
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
deviceListAdapter.add(device.getName() + "\
" + device.getAddress());
}
}
}, filter);
Button startScanBluetooth = findViewById(R.id.start_scan_bluetooth); // Search for Bluetooth
Button stopScanBluetooth = findViewById(R.id.stop_scan_bluetooth); // Stop searching for Bluetooth
startScanBluetooth.setOnClickListener(new View.OnClickListener() {<!-- -->
@Override
public void onClick(View view) {<!-- -->
if (bluetoothAdapter.isDiscovering()) {<!-- -->
bluetoothAdapter.cancelDiscovery();
}
deviceListAdapter.clear();
bluetoothAdapter.startDiscovery();
}
});
stopScanBluetooth.setOnClickListener(new View.OnClickListener() {<!-- -->
@Override
public void onClick(View view) {<!-- -->
bluetoothAdapter.cancelDiscovery();
}
});
// Connect Bluetooth
deviceListView.setOnItemClickListener((parent, view, position, id) -> {<!-- -->
String deviceInfo = (String) parent.getItemAtPosition(position);
String deviceAddress = deviceInfo.substring(deviceInfo.length() - 17);
BluetoothDevice myDevice = bluetoothAdapter.getRemoteDevice(deviceAddress);
new Thread(new Runnable() {<!-- -->
@Override
public void run() {<!-- -->
try {<!-- -->
Looper.prepare();
if (mySocket != null) {<!-- -->
Toast.makeText(MainActivity.this, "Disconnect connected Bluetooth", Toast.LENGTH_SHORT).show();
mySocket.close();
}
mySocket = myDevice.createRfcommSocketToServiceRecord(UUID.fromString("00001101-0000-1000-8000-00805F9B34FB")); // uuid is universal
mySocket.connect();
myOutStream = mySocket.getOutputStream();
myInStream = mySocket.getInputStream();
Toast.makeText(MainActivity.this, "Bluetooth connected:" + myDevice.getName(), Toast.LENGTH_SHORT).show();
} catch (Exception e2) {<!-- -->
Toast.makeText(MainActivity.this, "Bluetooth connection failed" + e2.getMessage(), Toast.LENGTH_SHORT).show();
myInStream = null;
myOutStream = null;
mySocket = null;
}
Looper.loop();
}
}).start();
});
}
// Process the results of the permission request in the onRequestPermissionsResult method
@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {<!-- -->
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
if (requestCode == 0) {<!-- -->
if (grantResults.length > 0 & amp; & amp; grantResults[0] == PackageManager.PERMISSION_GRANTED) {<!-- -->
// The user has granted Bluetooth connection permission and performs operations related to Bluetooth connection.
//Paired list
for (BluetoothDevice bondedDevice : bluetoothAdapter.getBondedDevices()) {<!-- -->
deviceListAdapter.add(bondedDevice.getName() + "\
" + bondedDevice.getAddress());
}
} else {<!-- -->
// The user has denied the Bluetooth connection permission. You may need to display a prompt message or provide an explanation.
Toast.makeText(this, "Please grant Bluetooth permissions", Toast.LENGTH_LONG).show();
}
}
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<Button
android:id="@ + id/start_scan_bluetooth"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Search Bluetooth" />
<Button
android:id="@ + id/stop_scan_bluetooth"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Stop searching for Bluetooth" />
<ListView
android:id="@ + id/deviceListView"
android:layout_marginTop="30dp"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>