Android Service和Activity基于串口蓝牙模块的双向通信

一直以来都想利用手机来控制一些东西,比如电灯,电风扇等家电或者智能小车等.
驱动蓝牙模块可以在Activity中直接调用,也可以在多线程下直接使用,但这样会存在一个缺陷:当你按下手机的Home或者Back键的时候.程序退出了,下次你重新启动软件的时候又需要重新建立蓝牙的链接了.
为了克服以上问题,我把蓝牙模块的调用放到Service里面使用.首先对Service说明下:(来源于http://tianrui-wang-163-com.iteye.com/blog/983099)
Service介绍
Android中的服务和windows中的服务是类似的东西，服务一般没有用户操作界面，它运行于系统中不容易被用户发觉，可以使用它开发如监控之类的程序。

由于没有可视化界面，Service都是从其它程序组件中启动、停止和控制，这些组件包括其它的Service、Activity和Broadcast Receiver。如果你的应用程序正常且不间断的运行，而不直接依赖于用户输入，Service是你最佳的选择。

Service生命周期

服务常用生命周期回调方法如下：
onCreate() 该方法在服务被创建时调用，该方法只会被调用一次，无论调用多少次startService()或bindService()方法，服务也只被创建一次。
onDestroy()该方法在服务被终止时调用。

Service对象不能自己启动，需要通过某个Activity、Service或者其他Context对象来启动。启动的方法有两种，Context.startService和Context.bindService()。两种方式的生命周期是不同的，具体如下所示。
Context.startService方式的生命周期：
启动时，startService –> onCreate() –> onStart()
停止时，stopService –> onDestroy()
Context.bindService方式的生命周期：
绑定时,bindService -> onCreate() –> onBind()
解绑定时,unbindService –>onUnbind() –> onDestory()

Service实现
定义一个Service只需要如下两步：

第一步：继承Service类
public class SMSService extends Service { } 这里可以选择要实现的方法
第二步：在AndroidManifest.xml文件中的<application>节点里对服务进行配置:
<service android:name=".SMSService" ”></service>

好了,废话少说,下面从我的代码直接开始:

package com.lxx;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.UUID;

import android.app.Service;
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.os.IBinder;
import android.util.Log;

public class MyService extends Service{

public boolean threadFlag = true;
MyThread myThread;
CommandReceiver cmdReceiver;//继承自BroadcastReceiver对象，用于得到Activity发送过来的命令

/**************service 命令*********/
static final int CMD_STOP_SERVICE = 0x01;
static final int CMD_SEND_DATA = 0x02;
static final int CMD_SYSTEM_EXIT =0x03;
static final int CMD_SHOW_TOAST =0x04;

private BluetoothAdapter mBluetoothAdapter = null;
private BluetoothSocket btSocket = null;
private OutputStream outStream = null;
private InputStream  inStream = null;
public  boolean bluetoothFlag  = true;
private static final UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
private static String address = "00:19:5D:EE:9B:8F"; // <==要连接的蓝牙设备MAC地址

@Override
public IBinder onBind(Intent intent) {
// TODO Auto-generated method stub
return null;
}

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

}

//前台Activity调用startService时，该方法自动执行
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
// TODO Auto-generated method stub
cmdReceiver = new CommandReceiver();
IntentFilter filter = new IntentFilter();//创建IntentFilter对象
//注册一个广播，用于接收Activity传送过来的命令，控制Service的行为，如：发送数据，停止服务等
filter.addAction("android.intent.action.cmd");
//注册Broadcast Receiver
registerReceiver(cmdReceiver, filter);
doJob();//调用方法启动线程
return super.onStartCommand(intent, flags, startId);

}

@Override
public void onDestroy() {
// TODO Auto-generated method stub
super.onDestroy();
this.unregisterReceiver(cmdReceiver);//取消注册的CommandReceiver
threadFlag = false;
boolean retry = true;
while(retry){
try{
myThread.join();
retry = false;
}catch(Exception e){
e.printStackTrace();
}

}
}

public class MyThread extends Thread{
@Override
public void run() {
// TODO Auto-generated method stub
super.run();
connectDevice();//连接蓝牙设备
while(threadFlag){
int value = readByte();
if(value != -1){
DisplayToast(value + "");
}

try{
Thread.sleep(50);
}catch(Exception e){
e.printStackTrace();
}
}
}
}

public void doJob(){
mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
if (mBluetoothAdapter == null) {
DisplayToast("蓝牙设备不可用，请打开蓝牙！");
bluetoothFlag  = false;
return;
}

if (!mBluetoothAdapter.isEnabled()) {
DisplayToast("请打开蓝牙并重新运行程序！");
bluetoothFlag  = false;
stopService();
showToast("请打开蓝牙并重新运行程序！");
return;
}
showToast("搜索到蓝牙设备!");
threadFlag = true;
myThread = new MyThread();
myThread.start();

}
public  void connectDevice(){
DisplayToast("正在尝试连接蓝牙设备，请稍后····");
BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address);
try {
btSocket = device.createRfcommSocketToServiceRecord(MY_UUID);
} catch (IOException e) {
DisplayToast("套接字创建失败！");
bluetoothFlag = false;
}
DisplayToast("成功连接蓝牙设备！");
mBluetoothAdapter.cancelDiscovery();
try {
btSocket.connect();
DisplayToast("连接成功建立，可以开始操控了!");
showToast("连接成功建立，可以开始操控了!");
bluetoothFlag = true;
} catch (IOException e) {
try {
btSocket.close();
bluetoothFlag = false;
} catch (IOException e2) {
DisplayToast("连接没有建立，无法关闭套接字！");
}
}

if(bluetoothFlag){
try {
inStream = btSocket.getInputStream();
} catch (IOException e) {
e.printStackTrace();
} //绑定读接口

try {
outStream = btSocket.getOutputStream();
} catch (IOException e) {
e.printStackTrace();
} //绑定写接口

}
}

public void sendCmd(byte cmd, int value)//串口发送数据
{
if(!bluetoothFlag){
return;
}
byte[] msgBuffer = new byte[5];
msgBuffer[0] = cmd;
msgBuffer[1] = (byte)(value >> 0  & 0xff);
msgBuffer[2] = (byte)(value >> 8  & 0xff);
msgBuffer[3] = (byte)(value >> 16 & 0xff);
msgBuffer[4] = (byte)(value >> 24 & 0xff);

try {
outStream.write(msgBuffer, 0, 5);
outStream.flush();
} catch (IOException e) {
e.printStackTrace();
}
}

public int readByte(){//return -1 if no data
int ret = -1;
if(!bluetoothFlag){
return ret;
}
try {
ret = inStream.read();
} catch (IOException e) {
e.printStackTrace();
}
return ret;
}

public void stopService(){//停止服务
threadFlag = false;//停止线程
stopSelf();//停止服务
}

public void showToast(String str){//显示提示信息
Intent intent = new Intent();
intent.putExtra("cmd", CMD_SHOW_TOAST);
intent.putExtra("str", str);
intent.setAction("android.intent.action.lxx");
sendBroadcast(intent);
}

public void DisplayToast(String str)
{
Log.d("Season",str);
}

//接收Activity传送过来的命令
private class CommandReceiver extends BroadcastReceiver{
@Override
public void onReceive(Context context, Intent intent) {
if(intent.getAction().equals("android.intent.action.cmd")){
int cmd = intent.getIntExtra("cmd", -1);//获取Extra信息
if(cmd == CMD_STOP_SERVICE){
stopService();
}

if(cmd == CMD_SEND_DATA)
{
byte command = intent.getByteExtra("command", (byte) 0);
int value =  intent.getIntExtra("value", 0);
sendCmd(command,value);
}

}
}
}

}

主界面Activity只有一个按钮,就是通过Broadcast来想Service发送数据,Service收到数据进行命令等的解析,然后调用相应的函数,相当于直接调用了Service中的函数.因为Activity和Service是运行在不同的进程中的,两者不能进行直接的通讯,必须通过一个"桥梁"建立起联系才行.

package com.lxx;

import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.os.IBinder;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class BroadcastActivity extends Activity {
/** Called when the activity is first created. */

TextView myTextView;
Button sendButton;
MyReceiver receiver;
IBinder serviceBinder;
MyService mService;
Intent intent;
int value = 0;

/**************service 命令*********/
static final int CMD_STOP_SERVICE = 0x01;
static final int CMD_SEND_DATA = 0x02;
static final int CMD_SYSTEM_EXIT =0x03;
static final int CMD_SHOW_TOAST =0x04;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

myTextView = (TextView)findViewById(R.id.myTextView);
myTextView.setText("Season");
sendButton = (Button)findViewById(R.id.sendButton);
sendButton.setOnClickListener(new SendButtonClickListener());

intent = new Intent(BroadcastActivity.this,MyService.class);
startService(intent);
}

public class SendButtonClickListener implements OnClickListener{

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
byte command = 45;
int value = 0x12345;
sendCmd(command,value);
}
}

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

if(receiver!=null){
BroadcastActivity.this.unregisterReceiver(receiver);
}
}

@Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
receiver = new MyReceiver();
IntentFilter filter=new IntentFilter();
filter.addAction("android.intent.action.lxx");
BroadcastActivity.this.registerReceiver(receiver,filter);
}

public void showToast(String str){//显示提示信息
Toast.makeText(getApplicationContext(), str, Toast.LENGTH_SHORT).show();
}

public class MyReceiver extends BroadcastReceiver{
@Override
public void onReceive(Context context, Intent intent) {
// TODO Auto-generated method stub
if(intent.getAction().equals("android.intent.action.lxx")){
Bundle bundle = intent.getExtras();
int cmd = bundle.getInt("cmd");

if(cmd == CMD_SHOW_TOAST){
String str = bundle.getString("str");
showToast(str);
}

else if(cmd == CMD_SYSTEM_EXIT){
System.exit(0);
}

}
}
}

public void sendCmd(byte command, int value){
Intent intent = new Intent();//创建Intent对象
intent.setAction("android.intent.action.cmd");
intent.putExtra("cmd", CMD_SEND_DATA);
intent.putExtra("command", command);
intent.putExtra("value", value);
sendBroadcast(intent);//发送广播
}

}

以下主要对代码部分进行详细的说明:
1.为了方便Activity和Service简历起良好的通信关系,需要在各自发送的数据进行命令的解释,这些命令在两者之间是一致的,能够相互读懂对方发送过来的数据.

/**************service 命令*********/
static final int CMD_STOP_SERVICE = 0x01;//停止服务
static final int CMD_SEND_DATA = 0x02;//发送数据
static final int CMD_SYSTEM_EXIT =0x03;//退出程序
static final int CMD_SHOW_TOAST =0x04;//界面上显示toast

2.Service传送数据到Activity:
要接收Broadcast首先的有个Receiver:

//接收Activity传送过来的命令
private class CommandReceiver extends BroadcastReceiver{
@Override
public void onReceive(Context context, Intent intent) {
if(intent.getAction().equals("android.intent.action.cmd")){
int cmd = intent.getIntExtra("cmd", -1);//获取Extra信息
if(cmd == CMD_STOP_SERVICE){
stopService();
}

if(cmd == CMD_SEND_DATA)
{
byte command = intent.getByteExtra("command", (byte) 0);
int value =  intent.getIntExtra("value", 0);
sendCmd(command,value);
}

}
}
}

为了能够接收到数据,首先得把这个Receiver注册:

public class MyReceiver extends BroadcastReceiver{
@Override
public void onReceive(Context context, Intent intent) {
// TODO Auto-generated method stub
if(intent.getAction().equals("android.intent.action.lxx")){
Bundle bundle = intent.getExtras();
int cmd = bundle.getInt("cmd");

if(cmd == CMD_SHOW_TOAST){
String str = bundle.getString("str");
showToast(str);
}

else if(cmd == CMD_SYSTEM_EXIT){
System.exit(0);
}

}
}
}

其中doJob是启动一个线程,定时的去读取蓝牙串口的数据,然后根据里面的数据解析就可以实现不同的操作了,这个反过来就是外设直接控制手机了.因为这个线程是一直在后台运行着的,只要不结束Service,它就一直保持这与外设串口蓝牙模块的通讯.

public class MyThread extends Thread{
@Override
public void run() {
// TODO Auto-generated method stub
super.run();
connectDevice();//连接蓝牙设备
while(threadFlag){
int value = readByte();//从蓝牙模块读取一个字节的数据,解释命令用
if(value != -1){
DisplayToast(value + "");
}

try{
Thread.sleep(50);
}catch(Exception e){
e.printStackTrace();
}
}
}
}

3.Activity传送数据到Service:

Activity上有一个按钮,点击一下就可以发送数据到蓝牙串口模块,工作原理是这样的:界面上实现按钮的点击事件

public class SendButtonClickListener implements OnClickListener{

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
byte command = 45;
int value = 0x12345;
sendCmd(command,value);
}
}

这里的sendCmd是关键,里面通过建立起一个广播消息,Service里会负责接收他

public void sendCmd(byte command, int value){
Intent intent = new Intent();//创建Intent对象
intent.setAction("android.intent.action.cmd");
intent.putExtra("cmd", CMD_SEND_DATA);
intent.putExtra("command", command);
intent.putExtra("value", value);
sendBroadcast(intent);//发送广播
}

Service中

//前台Activity调用startService时，该方法自动执行
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
// TODO Auto-generated method stub
cmdReceiver = new CommandReceiver();
IntentFilter filter = new IntentFilter();//创建IntentFilter对象
//注册一个广播，用于接收Activity传送过来的命令，控制Service的行为，如：发送数据，停止服务等
filter.addAction("android.intent.action.cmd");
//注册Broadcast Receiver
registerReceiver(cmdReceiver, filter);
doJob();//调用方法启动线程
return super.onStartCommand(intent, flags, startId);

}

通过以上步骤就可以建立起蓝牙模块发送数据到Activity,Activity也可以发送数据到蓝牙模块了;