android - 蓝牙连接在 Android 中丢失

Question

当我打开一个 Activity 时，我可以将蓝牙打印机连接到我的应用程序，但是一旦我导航到另一个 Activity/屏幕并再次返回该屏幕，连接就会丢失。我想要的是，在我从手机禁用蓝牙之前，我只需要连接到蓝牙设备一次。

代码如下:

public class Activity_Payment extends ActionBarActivity 
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_payment);
    mActivity = Activity_Payment.this;
// To start bluetooth for printing receipts.....
            mService = new BluetoothService(this, mHandler);
            //À¶ÑÀ²»¿ÉÓÃÍ˳ö³ÌÐò
            if( mService.isAvailable() == false ){
                Toast.makeText(this, "Bluetooth is not available", 
Toast.LENGTH_LONG).show();
                finish();
            }
}


@Override
protected void onStart() {
// TODO Auto-generated method stub
super.onStart();

if( mService.isBTopen() == false)
{
    Intent enableIntent = new    
Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
    startActivityForResult(enableIntent, REQUEST_ENABLE_BT);
}
}

public void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == REQUEST_ENABLE_BT) {    //ÇëÇó´ò¿ªÀ¶ÑÀ
        System.out.println("====inresltttt11");
        if (resultCode == Activity.RESULT_OK) {   //À¶ÑÀÒѾ­´ò¿ª
            Toast.makeText(this, "Bluetooth open successful", Toast.LENGTH_LONG).show();
            Intent serverIntent = new Intent(Activity_Payment.this,DeviceListActivity.class);      //ÔËÐÐÁíÍâÒ»¸öÀàµÄ»î¶¯
            startActivityForResult(serverIntent,REQUEST_CONNECT_DEVICE);
        } else {                 //Óû§²»ÔÊÐí´ò¿ªÀ¶ÑÀ
            finish();
        }
        }
    else if (requestCode == REQUEST_CONNECT_DEVICE){

        if (resultCode == Activity.RESULT_OK) {   

            String address = data.getExtras()

.getString(DeviceListActivity.EXTRA_DEVICE_ADDRESS);  

            con_dev = mService.getDevByMac(address);   

            mService.connect(con_dev);

            Toast.makeText(this, "Bluetooth connected", 
   Toast.LENGTH_LONG).show();
        }
        }
  }


  @Override
public void handleMessage(Message msg) {
    switch (msg.what) {

    case BluetoothService.MESSAGE_STATE_CHANGE:
        switch (msg.arg1) {
        case BluetoothService.STATE_CONNECTED:   //ÒÑÁ¬½Ó
            Toast.makeText(getApplicationContext(), "Connect successful",
                    Toast.LENGTH_SHORT).show();
            deviceConnected = true;
            break;
        case BluetoothService.STATE_CONNECTING:  //ÕýÔÚÁ¬½Ó
            Log.d("À¶ÑÀµ÷ÊÔ","ÕýÔÚÁ¬½Ó.....");
            break;
        case BluetoothService.STATE_LISTEN:     //¼àÌýÁ¬½ÓµÄµ½À´
        case BluetoothService.STATE_NONE:
            Log.d("À¶ÑÀµ÷ÊÔ","µÈ´ýÁ¬½Ó.....");
            break;
        }
        break;
    case BluetoothService.MESSAGE_CONNECTION_LOST:    //À¶ÑÀÒѶϿªÁ¬½Ó
        Toast.makeText(getApplicationContext(), "Device connection was lost, 
 Please try again.",
                       Toast.LENGTH_SHORT).show();

        break;
    case BluetoothService.MESSAGE_UNABLE_CONNECT:     //ÎÞ·¨Á¬½ÓÉ豸
        Toast.makeText(getApplicationContext(), "Unable to connect device, 
Please try again.",
                Toast.LENGTH_SHORT).show();
         serverIntent = new     
 Intent(Activity_Payment.this,DeviceListActivity.class); 
        startActivityForResult(serverIntent,REQUEST_CONNECT_DEVICE);
        break;
    }
}


};
}

public class DeviceListActivity extends Activity {
// Return Intent extra
public static String EXTRA_DEVICE_ADDRESS = "device_address";
public static String EXTRA_DEVICE_UUID = "device_uuid";

// Member fields
BluetoothService mService = null;
private ArrayAdapter<String> mPairedDevicesArrayAdapter;
private ArrayAdapter<String> mNewDevicesArrayAdapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // Setup the window
    requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
    setContentView(R.layout.device_list);   //ÏÔʾÁбí½çÃæ

    // Set result CANCELED incase the user backs out
    setResult(Activity.RESULT_CANCELED);

    // Initialize the button to perform device discovery
    Button scanButton = (Button) findViewById(R.id.button_scan);
    Button cancelButton = (Button) findViewById(R.id.button_cancel);
    scanButton.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {
            doDiscovery();
//                v.setVisibility(View.GONE);
        }
    });
    cancelButton.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {
             Intent intent = new Intent();
             // Set result and finish this Activity
             setResult(Activity.RESULT_CANCELED, intent);
           finish();
        }
    });

    // Initialize array adapters. One for already paired devices and
    // one for newly discovered devices
    mPairedDevicesArrayAdapter = new ArrayAdapter<String>(this, R.layout.device_name);
    mNewDevicesArrayAdapter = new ArrayAdapter<String>(this, R.layout.device_name);

    // Find and set up the ListView for paired devices
    ListView pairedListView = (ListView) findViewById(R.id.paired_devices);
    pairedListView.setAdapter(mPairedDevicesArrayAdapter);
    pairedListView.setOnItemClickListener(mDeviceClickListener);

    // Find and set up the ListView for newly discovered devices
    ListView newDevicesListView = (ListView) findViewById(R.id.new_devices);
    newDevicesListView.setAdapter(mNewDevicesArrayAdapter);
    newDevicesListView.setOnItemClickListener(mDeviceClickListener);

    // Register for broadcasts when a device is discovered
    IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
    this.registerReceiver(mReceiver, filter);

    // Register for broadcasts when discovery has finished
    filter = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
    this.registerReceiver(mReceiver, filter);

    mService = new BluetoothService(this, null);

    // Get a set of currently paired devices
    Set<BluetoothDevice> pairedDevices = mService.getPairedDev();

    // If there are paired devices, add each one to the ArrayAdapter
    if (pairedDevices.size() > 0) {
        findViewById(R.id.title_paired_devices).setVisibility(View.VISIBLE);
        for (BluetoothDevice device : pairedDevices) {
            mPairedDevicesArrayAdapter.add(device.getName() + "\n" + device.getAddress());
        }
    } else {
        String noDevices = getResources().getText(R.string.none_paired).toString();
        mPairedDevicesArrayAdapter.add(noDevices);
    }
}

@Override
protected void onDestroy() {
    super.onDestroy();
    if (mService != null) {
        mService.cancelDiscovery();
    }
    mService = null;
    this.unregisterReceiver(mReceiver);
}

/**
 * Start device discover with the BluetoothAdapter
 */
private void doDiscovery() {

    // Indicate scanning in the title
    setProgressBarIndeterminateVisibility(true);
    setTitle(R.string.scanning);

    // Turn on sub-title for new devices
    findViewById(R.id.title_new_devices).setVisibility(View.VISIBLE);

    // If we're already discovering, stop it
    if (mService.isDiscovering()) {
        mService.cancelDiscovery();
    }

    // Request discover from BluetoothAdapter
    mService.startDiscovery();
}

// The on-click listener for all devices in the ListViews
private OnItemClickListener mDeviceClickListener = new OnItemClickListener() {   //µã»÷ÁбíÏÁ¬½ÓÉ豸
    public void onItemClick(AdapterView<?> av, View v, int arg2, long arg3) {
        // Cancel discovery because it's costly and we're about to connect
        mService.cancelDiscovery();

        // Get the device MAC address, which is the last 17 chars in the View
        String info = ((TextView) v).getText().toString();
        String address = info.substring(info.length() - 17);

        // Create the result Intent and include the MAC address
        Intent intent = new Intent();
        intent.putExtra(EXTRA_DEVICE_ADDRESS, address);
        Log.d("Á¬½ÓµØÖ·", address);
        System.out.println("=====address: "+address);

        // Set result and finish this Activity
        setResult(Activity.RESULT_OK, intent);
        finish();
    }
};

// The BroadcastReceiver that listens for discovered devices and
// changes the title when discovery is finished
private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();

        // When discovery finds a device
        if (BluetoothDevice.ACTION_FOUND.equals(action)) {
            // Get the BluetoothDevice object from the Intent
            BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
            // If it's already paired, skip it, because it's been listed already
            if (device.getBondState() != BluetoothDevice.BOND_BONDED) {
                mNewDevicesArrayAdapter.add(device.getName() + "\n" + device.getAddress());
            }
        // When discovery is finished, change the Activity title
        } else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {
            setProgressBarIndeterminateVisibility(false);
            setTitle(R.string.select_device);
            if (mNewDevicesArrayAdapter.getCount() == 0) {
                String noDevices = 
getResources().getText(R.string.none_found).toString();
                mNewDevicesArrayAdapter.add(noDevices);
            }
        }
    }
};

}

Answer 1

我建议将所有蓝牙连接管理代码移到 Service 中.使用 BroadCastReceiver 捕获蓝牙打开或关闭等事件，然后您的接收器可以通过在 Intent 中发送信息来调用该服务。即使 Activity 未处于 Activity 状态，服务也可以在后台运行。