如何解决应用程序关闭时蓝牙设备断开连接
我不熟悉应用中的 BLE 实现，但我能够连接到应用中的 BLE 设备。
当应用程序关闭时，连接断开，但即使应用程序关闭，我也需要能够连接，因为我将从微控制器接收数据。
谁能给我建议或帮助我解决问题？
是否只是因为正在等待数据发送而被连接，而当应用程序关闭时我遇到了问题？
package com.example.Pillwoah;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;
import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothGatt;
import android.bluetooth.BluetoothGattCallback;
import android.bluetooth.BluetoothGattCharacteristic;
import android.bluetooth.BluetoothGattService;
import android.bluetooth.BluetoothManager;
import android.bluetooth.BluetoothProfile;
import android.bluetooth.BluetoothSocket;
import android.bluetooth.le.BluetoothLeScanner;
import android.bluetooth.le.ScanCallback;
import android.bluetooth.le.ScanResult;
import android.bluetooth.le.ScanSettings;
import android.content.broadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import java.io.IOException;
import java.lang.reflect.Method;
import java.util.List;
import java.util.Set;
import java.util.UUID;
import static android.bluetooth.BluetoothDevice.ACTION_BOND_STATE_CHANGED;
import static android.bluetooth.BluetoothDevice.BOND_BONDED;
import static android.bluetooth.BluetoothDevice.BOND_BONDING;
import static android.bluetooth.BluetoothDevice.BOND_NONE;
import static android.bluetooth.BluetoothDevice.EXTRA_BOND_STATE;
public class MainActivity4 extends AppCompatActivity {
protected static final String TAG = "TAG";
TextView phoneName,deviceList;
private Handler mHandler;
private BluetoothAdapter bluetoothAdapter;
private Set<BluetoothDevice> pairedDevices;
private ArrayAdapter<String> BAarray,BANewArray;
private ListView DeviceList,NewDevice;
private boolean mScanning;
private BluetoothGatt mGatt;
private BluetoothLeScanner bluetoothLeScanner = BluetoothAdapter.getDefaultAdapter().getBluetoothLeScanner();
private BluetoothSocket BTSocket = null;
private BluetoothDevice device = null;
private final static UUID BTMODULEUUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
private final static int REQUEST_ENABLE_BT = 1;
private final static int REQUEST_CONNECT_DEVICE = 2;
private final static int REQUEST_COARSE_LOCATION = 1;
private static final long SCAN_PERIOD = 10000;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main4);
Button mEnable = (Button) findViewById(R.id.enable);
Button mOff = (Button) findViewById(R.id.off);
Button mPaired = (Button) findViewById(R.id.paired);
Button mdiscover = (Button) findViewById(R.id.discover);
deviceList = findViewById(R.id.deviceTitle);
deviceList.setText(null);
phoneName = findViewById(R.id.name);
phoneName.setText(getLocalBtName());
mHandler = new Handler();
//BA = BluetoothAdapter.getDefaultAdapter();
// Initializes Bluetooth adapter.
final BluetoothManager bluetoothManager = (BluetoothManager) getSystemService(Context.BLUetoOTH_SERVICE);
bluetoothAdapter = bluetoothManager.getAdapter();
// Ensures Bluetooth is available on the device and it is enabled. If not,// displays a dialog requesting user permission to enable Bluetooth.
if (bluetoothAdapter == null || !bluetoothAdapter.isEnabled()) {
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent,REQUEST_ENABLE_BT);
}
// Build ScanSetting
ScanSettings.Builder scanSetting = new ScanSettings.Builder()
.setScanMode(ScanSettings.SCAN_MODE_LOW_POWER)
.setReportDelay(5000);
scanSetting.build();
BAarray = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1);
BANewArray = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1);
DeviceList = (ListView)findViewById(R.id.deviceListView);
DeviceList.setAdapter(BAarray);
DeviceList.setonItemClickListener(DeviceClickListener);
NewDevice = (ListView)findViewById(R.id.newDeviceView);
NewDevice.setAdapter(BANewArray);
NewDevice.setonItemClickListener(DeviceClickListener);
if (bluetoothAdapter == null) {
Toast.makeText(this,"Bluetooth not supported",Toast.LENGTH_SHORT).show();
finish();
} else {
mEnable.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
checkLocationPermission();
bluetoothOn(v);
}
});
mOff.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
bluetoothOff(v);
}
});
mPaired.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
checkLocationPermission();
listPairedDevices(v);
}
});
mdiscover.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
checkLocationPermission();
discover(v);
}
});
}
};
protected void checkLocationPermission() {
if (ContextCompat.checkSelfPermission(this,android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
ActivityCompat.requestPermissions(this,new String[]{android.Manifest.permission.ACCESS_FINE_LOCATION},REQUEST_COARSE_LOCATION);
}
}
@Override
public void onRequestPermissionsResult(int requestCode,String permissions[],int[] grantResults) {
switch (requestCode) {
case REQUEST_COARSE_LOCATION: {
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
Toast.makeText(getApplicationContext(),"Permission on",Toast.LENGTH_SHORT).show();
} else {
Toast.makeText(getApplicationContext(),"Permission off",Toast.LENGTH_SHORT).show();
}
break;
}
}
}
public String getLocalBtName(){
if(bluetoothAdapter == null){
bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
}
String name = bluetoothAdapter.getName();
if(name == null){
name = bluetoothAdapter.getAddress();
}
return name;
}
@Override
protected void onResume() {
super.onResume();
// Ensures Bluetooth is enabled on the device. If Bluetooth is not currently enabled,// fire an intent to display a dialog asking the user to grant permission to enable it.
if (!bluetoothAdapter.isEnabled()) {
if (!bluetoothAdapter.isEnabled()) {
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent,REQUEST_ENABLE_BT);
}
}else {
if (Build.VERSION.SDK_INT >= 21) {
bluetoothLeScanner = bluetoothAdapter.getBluetoothLeScanner();
ScanSettings scanSetting = new ScanSettings.Builder()
.setScanMode(ScanSettings.SCAN_MODE_LOW_POWER)
.build();
}
//scanLeDevice(true);
}
}
@Override
protected void onActivityResult(int requestCode,int resultCode,Intent data) {
// User chose not to enable Bluetooth.
if (requestCode == REQUEST_ENABLE_BT && resultCode == Activity.RESULT_CANCELED) {
finish();
return;
}
super.onActivityResult(requestCode,resultCode,data);
}
@Override
protected void onPause() {
super.onPause();
scanLeDevice(false);
BANewArray.clear();
BAarray.clear();
}
@Override
public void onDestroy() {
if (mGatt == null) {
return;
}
Log.i("destroy ","ble destroy");
BANewArray.clear();
BAarray.clear();
mGatt.close();
mGatt = null;
super.onDestroy();
System.out.println("BLE// destroy");
}
private void scanLeDevice(final boolean enable) {
if (enable) {
// Stops scanning after a pre-defined scan period.
mHandler.postDelayed(new Runnable() {
@Override
public void run() {
mScanning = false;
bluetoothLeScanner.stopScan(leScanCallback);
System.out.println("BLE// bluetoothLeScanner.stopScan(leScanCallback)");
}
},SCAN_PERIOD);
mScanning = true;
bluetoothLeScanner.startScan(leScanCallback);
System.out.println("BLE// bluetoothLeScanner.startScan(leScanCallback)");
} else {
mScanning = false;
bluetoothLeScanner.stopScan(leScanCallback);
System.out.println("BLE// bluetoothLeScanner.stopScan(leScanCallback)");
}
}
// Device scan callback.
private ScanCallback leScanCallback = new ScanCallback() {
@Override
public void onScanResult(int callbackType,ScanResult result) {
super.onScanResult(callbackType,result);
Log.i("callbackType",String.valueOf(callbackType));
Log.i("result",result.toString());
//Log.i("Device Name: ",result.getDevice().getName());
System.out.println("Signal: " + result.getRSSi());
BluetoothDevice btDevice = result.getDevice();
System.out.println("name: " + btDevice);
BANewArray.add(btDevice.getName() + "\n" + btDevice.getAddress());
}
@Override
public void onBatchScanResults(List<ScanResult> results) {
System.out.println("BLE// onBatchScanResults");
for (ScanResult sr : results) {
Log.i("ScanResult - Results",sr.toString());
}
}
@Override
public void onScanFailed(int errorCode) {
System.out.println("BLE// onScanFailed");
Log.e("Scan Failed","Error Code: " + errorCode);
}
};
private void bluetoothOn(View view){
if(!bluetoothAdapter.isEnabled()){
Intent enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableIntent,REQUEST_ENABLE_BT);
Toast.makeText(getApplicationContext(),"Bluetooth turned on",Toast.LENGTH_SHORT).show();
}
else{
Toast.makeText(getApplicationContext(),"Bluetooth is already on",Toast.LENGTH_SHORT).show();
}
}
private void bluetoothOff(View view){
bluetoothAdapter.disable();
BAarray.clear();
BANewArray.clear();
Toast.makeText(getApplicationContext(),"Bluetooth turned off",Toast.LENGTH_SHORT).show();
}
public void connectToDevice(BluetoothDevice device) {
Toast.makeText(getApplicationContext(),"BLE// connectToDevice()",Toast.LENGTH_SHORT).show();
//System.out.println("BLE// connectToDevice()");
bluetoothAdapter.canceldiscovery();
if (mGatt == null) {
mGatt = device.connectGatt(this,true,gattCallback); //Connect to a GATT Server
scanLeDevice(false);// will stop after first device detection
}
else{
//mGatt.discoverServices();
Toast.makeText(getApplicationContext(),"Error",Toast.LENGTH_SHORT).show();
}
}
private final BluetoothGattCallback gattCallback = new BluetoothGattCallback() {
@Override
public void onConnectionStateChange(BluetoothGatt gatt,int status,int newState) {
System.out.println("BLE// BluetoothGattCallback");
Log.i("onConnectionStateChange","Status: " + status);
switch (newState) {
case BluetoothProfile.STATE_CONNECTED:
Log.i("gattCallback","STATE_CONNECTED");
gatt.discoverServices();
break;
case BluetoothProfile.STATE_CONNECTING:
Log.i("gattCallback","STATE_CONNECTING");
break;
case BluetoothProfile.STATE_disCONNECTED:
Log.e("gattCallback","STATE_disCONNECTED");
//gatt.close();
break;
default:
Log.e("gattCallback","STATE_OTHER");
}
}
@Override
//New services discovered
public void onServicesdiscovered(BluetoothGatt gatt,int status) {
List<BluetoothGattService> services = gatt.getServices();
Log.i("onServicesdiscovered",services.toString());
gatt.readCharacteristic(services.get(1).getcharacteristics().get(0));
}
@Override
//Result of a characteristic read operation
public void onCharacteristicRead(BluetoothGatt gatt,BluetoothGattCharacteristic characteristic,int status) {
Log.i("onCharacteristicRead",characteristic.toString());
gatt.disconnect();
}
};
private void listPairedDevices(View view){
BANewArray.clear();
BAarray.clear();
deviceList.setText("PrevIoUsly Connected Devices");
pairedDevices = bluetoothAdapter.getBondedDevices();
if(bluetoothAdapter.isEnabled()){
BANewArray.clear();
BAarray.clear();
for(BluetoothDevice device : pairedDevices)
BAarray.add(device.getName() + "\n" + device.getAddress());
Toast.makeText(getApplicationContext(),"Show paired devices","Bluetooth not on",Toast.LENGTH_SHORT).show();
}
}
private void discover(View view) {
deviceList.setText("Available Devices");
BANewArray.clear();
BAarray.clear();
scanLeDevice(true);
}
private AdapterView.OnItemClickListener DeviceClickListener = new AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView<?> av,View v,int arg2,long arg3) {
//BTSocket = null;
String info = ((TextView) v).getText().toString();
final String address = info.substring(info.length() - 17);
final String name = info.substring(0,info.length() - 17);
device = bluetoothAdapter.getRemoteDevice(address);
Log.d(TAG,"You clicked");
Log.d(TAG,"Device name" + name);
Log.d(TAG,"Address" + address);
Toast.makeText(getApplicationContext(),address,Toast.LENGTH_SHORT).show();
connectToDevice(device);
}
};
}解决方法
您可以使用 FroegroundService 在后台工作，在您的应用关闭后，将有不可关闭的通知，您的应用将继续工作。这是Android新版本中最好的解决方案，因为简单的服务会被Android杀死。您可以在 this article 中找到有关使用 FroegroundService 的更多信息。
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