android 主件之 Service

/Files/tt_mc/MyService.rar

 

一、Service的概念

Service是Android程序中四大基础组件之一，它和Activity一样都是Context的子类，只不过它没有UI界面，是在后台运行的组件。

二、Service的生命周期

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。

使用context.startService() 启动Service是会会经历:
context.startService()  ->onCreate()- >onStart()->Service running
context.stopService() | ->onDestroy() ->Service stop 
 
如果Service还没有运行，则android先调用onCreate()然后调用onStart()；如果Service已经运行，则只调用onStart()，所以一个Service的onStart方法可能会重复调用多次。 
 
stopService的时候直接onDestroy，如果是调用者自己直接退出而没有调用stopService的话，Service会一直在后台运行。该Service的调用者再启动起来后可以通过stopService关闭Service。
 
所以调用startService的生命周期为：onCreate --> onStart(可多次调用) --> onDestroy
 
使用使用context.bindService()启动Service会经历：
context.bindService()->onCreate()->onBind()->Service running
onUnbind() ->onDestroy() ->Service stop
 
onBind将返回给客户端一个IBind接口实例，IBind允许客户端回调服务的方法，比如得到Service运行的状态或其他操作。这个时候把调用者（Context，例如Activity）会和Service绑定在一起，Context退出了，Srevice就会调用onUnbind->onDestroy相应退出。 
      
所以调用bindService的生命周期为：onCreate --> onBind(只一次，不可多次绑定) --> onUnbind --> onDestory。
 
在Service每一次的开启关闭过程中，只有onStart可被多次调用(通过多次startService调用)，其他onCreate，onBind，onUnbind，onDestory在一个生命周期中只能被调用一次。

使用context.startService()

 

public class MyService extends Activity implements OnClickListener {    /** Called when the activity is first created. */    Button buttonStart, buttonStop,buttonBind,buttonUnbind,buttonCount;    private static final String TAG = "ServicesDemo";     @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);                buttonStart = (Button) findViewById(R.id.bt1);           buttonStop = (Button) findViewById(R.id.bt2);           buttonBind = (Button) findViewById(R.id.bt3);           buttonUnbind = (Button) findViewById(R.id.bt4);        buttonCount = (Button) findViewById(R.id.bt5);                 buttonStart.setOnClickListener(this);           buttonStop.setOnClickListener(this);         buttonBind.setOnClickListener(this);           buttonUnbind.setOnClickListener(this);        buttonCount.setOnClickListener(this);                   }    //////////////////////    //通过ServiceConnection的内部类实现来连接Service和Activity    ///////////////////////        private ICountService countService=null;        private ServiceConnection serviceConnection = new ServiceConnection() {        @Override        public void onServiceConnected(ComponentName name, IBinder service) {            countService = (ICountService) service;            Log.v("CountService", "on serivce connected, count is "                    + countService.getCount());        }        @Override        public void onServiceDisconnected(ComponentName name) {            countService = null;        }    };            @Override    public void onClick(View v) {        switch (v.getId()) {            case R.id.bt1:              Log.d(TAG, "onClick: starting srvice");          //activity传递值给service，service里的onStart()方法有个intent参数，可以接收到activity传递的值           Intent intent1= new Intent();           Bundle bundle1=new Bundle();           bundle1.putString("activity-to-service","i come from activity");           intent1.putExtras(bundle1);              intent1.setClass(this, CountService.class);           this.startService(intent1);           break;            case R.id.bt2:              Log.d(TAG, "onClick: stopping srvice");              this.stopService(new Intent(this, CountService.class));              break;           case R.id.bt3:                  Log.d(TAG, "onClick: bind srvice");                //bindservice启动的时候不会调用onstart方法               //activity传递值给service，service里的onbind()方法有个intent参数，可以接收到activity传递的值               Intent intent2= new Intent();               Bundle bundle2=new Bundle();               bundle2.putString("activity-to-bindservice","i come from activity");               intent2.putExtras(bundle2);                  intent2.setClass(this, BindCountService.class);               this.bindService(intent2,this.serviceConnection, BIND_AUTO_CREATE);                  break;          case R.id.bt4:                  Log.d(TAG, "onClick: unbind srvice");                  this.unbindService(serviceConnection);                  break;          case R.id.bt5:                //随时和service通信，让activity获取到service里count的值是多少               if(countService!=null)               Log.d(TAG, "onClick: getCount="+countService.getCount());                  break;          }       }    } 

public class CountService extends Service{    private boolean threadDisable;    private String activityValue=null;    private int count;    @Override    public IBinder onBind(Intent intent) {        Log.v("CountService", "on bind");        return null;    }    @Override    public void onCreate() {        super.onCreate();        Log.v("CountService", "on create");        new Thread(new Runnable() {            @Override            public void run() {                while (!threadDisable) {                    try {                        Thread.sleep(1000);                    } catch (InterruptedException e) {                    }                    count++;                    Log.v("CountService", "Count is " + count);                }            }        }).start();    }        @Override    public void onRebind(Intent intent) {        // TODO Auto-generated method stub        super.onRebind(intent);        Log.v("CountService", "on rebind");    }    @Override    public void onStart(Intent intent, int startId) {        // TODO Auto-generated method stub        super.onStart(intent, startId);        Log.v("CountService", "on start");        //接收activity传递过来的值        Bundle b=intent.getExtras();        activityValue=b.getString("activity-to-service");        Log.v("CountService", activityValue);    }    @Override    public boolean onUnbind(Intent intent) {        // TODO Auto-generated method stub        Log.v("CountService", "on unbind");        return super.onUnbind(intent);            }            @Override    public void onDestroy() {        super.onDestroy();        this.threadDisable = true;        Log.v("CountService", "on destroy");    }    public int getCount() {        return count;    }}

 

 

使用context.bindService()

public interface ICountService {    public abstract int getCount();} 

 

public class BindCountService extends Service  {    private int count;    private boolean threadDisable;    private String activityValue=null;        @Override    public IBinder onBind(Intent intent) {        // TODO Auto-generated method stub        Log.v("BindCountService", "on bind");        //接收activity传递过来的值        Bundle b=intent.getExtras();        activityValue=b.getString("activity-to-bindservice");        Log.v("BindCountService", activityValue);        return serviceBinder;    }    private ServiceBinder serviceBinder=new ServiceBinder();        public class ServiceBinder extends Binder implements ICountService{        @Override        public int getCount() {            return count;        }    }        @Override    public void onCreate() {        super.onCreate();        Log.v("BindCountService", "on create");        new Thread(new Runnable() {            @Override            public void run() {                while (!threadDisable) {                    try {                        Thread.sleep(1000);                    } catch (InterruptedException e) {                    }                    count++;                    Log.v("BindCountService", "Count is " + count);                }            }        }).start();    }         @Override        public void onRebind(Intent intent) {            // TODO Auto-generated method stub            super.onRebind(intent);            Log.v("BindCountService", "on rebind");        }        @Override        public void onStart(Intent intent, int startId) {            // TODO Auto-generated method stub            super.onStart(intent, startId);            Log.v("BindCountService", "on start");        }        @Override        public boolean onUnbind(Intent intent) {            // TODO Auto-generated method stub            Log.v("BindCountService", "on unbind");            return super.onUnbind(intent);                    }            @Override    public void onDestroy() {        super.onDestroy();        this.threadDisable = true;        Log.v("BindCountService", "on destroy");    }}