如何使用应用程序类或服务类在多个活动中主动实现蓝牙连接

Question

我是蓝牙连接处理流程的新手。 我正在为我的android应用程序使用小型热敏打印机设备。 设备具有自己的SDK。

活动结束或被破坏后，我与设备的连接将丢失。 我如何修改以下代码以防止这种情况发生。

PrintDemo Activity

package com.zj.printdemo;
import com.zj.printdemo.R;
import android.content.Intent;
import com.zj.btsdk.BluetoothService;
import com.zj.btsdk.PrintPic;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import android.util.Log;


public class PrintDemo extends Activity {
    Button btnSearch;
    Button btnSendDraw;
    Button btnSend;
    Button btnClose;
    EditText edtContext;
    EditText edtPrint;
    private static final int REQUEST_ENABLE_BT = 2;
    BluetoothService mService = null;
    BluetoothDevice con_dev = null;
    private static final int REQUEST_CONNECT_DEVICE = 1;  //��ȡ�豸��Ϣ



/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    mService = new BluetoothService(this, mHandler);
    //�����������˳�����
    if( mService.isAvailable() == false ){
        Toast.makeText(this, "Bluetooth is not available", Toast.LENGTH_LONG).show();
        finish();
    }       
}

@Override
public void onStart() {
    super.onStart();
    //����δ�򿪣�������
    if( mService.isBTopen() == false)
    {
        Intent enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
        startActivityForResult(enableIntent, REQUEST_ENABLE_BT);
    }
    try {
        btnSendDraw = (Button) this.findViewById(R.id.btn_test);
        btnSendDraw.setOnClickListener(new ClickEvent());
        btnSearch = (Button) this.findViewById(R.id.btnSearch);
        btnSearch.setOnClickListener(new ClickEvent());
        btnSend = (Button) this.findViewById(R.id.btnSend);
        btnSend.setOnClickListener(new ClickEvent());
        btnClose = (Button) this.findViewById(R.id.btnClose);
        btnClose.setOnClickListener(new ClickEvent());
        edtContext = (EditText) findViewById(R.id.txt_content);
        btnClose.setEnabled(false);
        btnSend.setEnabled(false);
        btnSendDraw.setEnabled(false);
    } catch (Exception ex) {
        Log.e("������Ϣ",ex.getMessage());
    }
}

@Override
protected void onDestroy() {
    super.onDestroy();
    if (mService != null) 
        mService.stop();
    mService = null; 
}

class ClickEvent implements View.OnClickListener {
    public void onClick(View v) {
        if (v == btnSearch) {           
            Intent serverIntent = new Intent(PrintDemo.this,DeviceListActivity.class);      //��������һ����Ļ
            startActivityForResult(serverIntent,REQUEST_CONNECT_DEVICE);
        } else if (v == btnSend) {
            String msg = edtContext.getText().toString();
            if( msg.length() > 0 ){
                mService.sendMessage(msg+"\n", "GBK");
            }
        } else if (v == btnClose) {
            mService.stop();
        } else if (v == btnSendDraw) {
            String msg = "";
            String lang = getString(R.string.strLang);
            //printImage();

            byte[] cmd = new byte[3];
            cmd[0] = 0x1b;
            cmd[1] = 0x21;
            if((lang.compareTo("en")) == 0){    
                cmd[2] |= 0x10;
                mService.write(cmd);           //��������ģʽ
                mService.sendMessage("Congratulations!\n", "GBK"); 
                cmd[2] &= 0xEF;
                mService.write(cmd);           //ȡ�����ߡ�����ģʽ
                msg = "  You have sucessfully created communications between your device and our bluetooth printer.\n\n"
                      +"  the company is a high-tech enterprise which specializes" +
                      " in R&D,manufacturing,marketing of thermal printers and barcode scanners.\n\n";


                mService.sendMessage(msg,"GBK");
            }else if((lang.compareTo("ch")) == 0){
                cmd[2] |= 0x10;
                mService.write(cmd);           //��������ģʽ
                mService.sendMessage("��ϲ����\n", "GBK"); 
                cmd[2] &= 0xEF;
                mService.write(cmd);           //ȡ�����ߡ�����ģʽ
                msg = "  ���Ѿ��ɹ��������������ǵ�������ӡ����\n\n"
                + "  ����˾��һ��רҵ�����з�����������������Ʊ�ݴ�ӡ��������ɨ���豸��һ��ĸ߿Ƽ���ҵ.\n\n";

                mService.sendMessage(msg,"GBK");    
            }
        }
    }
}

/**
 * ����һ��Handlerʵ�������ڽ���BluetoothService�෵�ػ�������Ϣ
 */
private final  Handler mHandler = new Handler() {
    @Override
    public void handleMessage(Message msg) {
        switch (msg.what) {
        case BluetoothService.MESSAGE_STATE_CHANGE:
            switch (msg.arg1) {
            case BluetoothService.STATE_CONNECTED:   //������
                Toast.makeText(getApplicationContext(), "Connect successful",
                        Toast.LENGTH_SHORT).show();
                btnClose.setEnabled(true);
                btnSend.setEnabled(true);
                btnSendDraw.setEnabled(true);
                break;
            case BluetoothService.STATE_CONNECTING:  //��������
                Log.d("��������","��������.....");
                break;
            case BluetoothService.STATE_LISTEN:     //�������ӵĵ���
            case BluetoothService.STATE_NONE:
                Log.d("��������","�ȴ�����.....");
                break;
            }
            break;
        case BluetoothService.MESSAGE_CONNECTION_LOST:    //�����ѶϿ�����
            Toast.makeText(getApplicationContext(), "Device connection was lost",
                           Toast.LENGTH_SHORT).show();
            btnClose.setEnabled(false);
            btnSend.setEnabled(false);
            btnSendDraw.setEnabled(false);
            break;
        case BluetoothService.MESSAGE_UNABLE_CONNECT:     //�޷������豸
            Toast.makeText(getApplicationContext(), "Unable to connect device",
                    Toast.LENGTH_SHORT).show();
            break;
        }
    }

};

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {    
    switch (requestCode) {
    case REQUEST_ENABLE_BT:      //���������
        if (resultCode == Activity.RESULT_OK) {   //�����Ѿ���
            Toast.makeText(this, "Bluetooth open successful", Toast.LENGTH_LONG).show();
        } else {                 //�û������������
            finish();
        }
        break;
    case  REQUEST_CONNECT_DEVICE:     //��������ijһ�����豸
        if (resultCode == Activity.RESULT_OK) {   //�ѵ�������б��е�ij���豸��
            String address = data.getExtras()
                                 .getString(DeviceListActivity.EXTRA_DEVICE_ADDRESS);  //��ȡ�б������豸��mac��ַ
            con_dev = mService.getDevByMac(address);   

            mService.connect(con_dev);
        }
        break;
    }
} 

//��ӡͼ��
@SuppressLint("SdCardPath")
private void printImage() {
    byte[] sendData = null;
    PrintPic pg = new PrintPic();
    pg.initCanvas(384);     
    pg.initPaint();
    pg.drawImage(0, 0, "/mnt/sdcard/icon.jpg");
    sendData = pg.printDraw();
    mService.write(sendData);   //��ӡbyte������
}
}

DeviceListActivity

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

// 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);   //��ʾ�б����

    // 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);
    scanButton.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {
            doDiscovery();
            v.setVisibility(View.GONE);
        }
    });

    // 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() {   //����б�������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("���ӵ�ַ", 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);
            }
        }
    }
};

 }

我试图删除onDestroy ，但似乎不起作用。

Answer 1

Android中的活动旨在提供用户界面。 因此，一旦活动进入后台，系统可能会随时将其停止。 当活动停止时，它所做的任何事情也将被停止。

如果您不需要任何用户交互，而只需要在后台维护蓝牙连接，则应使用一项服务。 该活动需要启动服务并使其运行。 即使活动在此之后停止，该服务仍将继续运行。

保持无限期运行服务有两件事： 使用startService（）创建服务，然后从onStartCommand（）返回START_STICKY。 通过这两个步骤，服务可能会被系统关闭，但几乎应立即重新启动。

Google文档提供了实现此示例的示例：

http://developer.android.com/guide/components/services.html#ExtendingService