本地service

　　1.不需和Activity交互的本地服务

public class LocalService extends Service {

private static final String TAG = "LocalService";

@Override
public IBinder onBind(Intent intent) {
Log.i(TAG, "onBind");
return null;
}

@Override
public void onCreate() {
Log.i(TAG, "onCreate");
super.onCreate();
}

@Override
public void onDestroy() {
Log.i(TAG, "onDestroy");
super.onDestroy();
}

@Override
public void onStart(Intent intent, int startId) {
Log.i(TAG, "onStart");
super.onStart(intent, startId);
}
}
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　　Activity:
public class ServiceActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.servicedemo);

((Button) findViewById(R.id.startLocalService)).setOnClickListener(
new View.OnClickListener(){

@Override
public void onClick(View view) {
// TODO Auto-generated method stub
startService(new Intent("com.demo.SERVICE_DEMO"));
}
});

((Button) findViewById(R.id.stopLocalService)).setOnClickListener(
new View.OnClickListener(){

@Override
public void onClick(View view) {
// TODO Auto-generated method stub
stopService(new Intent("com.demo.SERVICE_DEMO"));
}
});
}

}
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　　在AndroidManifest.xml添加：
<service android:name=".LocalService">
<intent-filter>
<action android:name="com.demo.SERVICE_DEMO" />
<category android:name="android.intent.category.default" />
</intent-filter>
</service>
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　　否则启动服务时会提示new Intent找不到"com.demo.SERVICE_DEMO"。

　　对于这类不需和Activity交互的本地服务，是使用startService/stopService的最好例子。

　　运行时可以发现第一次startService时，会调用onCreate和onStart，在没有stopService前，无论点击多少次startService，都只会调用onStart。而stopService时调用onDestroy。再次点击stopService，会发现不会进入service的生命周期的，即不会再调用onCreate，onStart和onDestroy。

　　而onBind在startService/stopService中没有调用。

　　2.本地服务和Activity交互

　　对于这种case，官方的sample(APIDemo\app.LocalService)是最好的例子:

/**
* This is an example of implementing an application service that runs locally
* in the same process as the application. The {@link LocalServiceController}
* and {@link LocalServiceBinding} classes show how to interact with the
* service.
*
* <p>Notice the use of the {@link NotificationManager} when interesting things
* happen in the service. This is generally how background services should
* interact with the user, rather than doing something more disruptive such as
* calling startActivity().
*/
public class LocalService extends Service {
private NotificationManager mNM;

/**
* Class for clients to access. Because we know this service always
* runs in the same process as its clients, we don't need to deal with
* IPC.
*/
public class LocalBinder extends Binder {
LocalService getService() {
return LocalService.this;
}
}

@Override
public void onCreate() {
mNM = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);

// Display a notification about us starting. We put an icon in the status bar.
showNotification();
}

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
Log.i("LocalService", "Received start id " + startId + ": " + intent);
// We want this service to continue running until it is explicitly
// stopped, so return sticky.
return START_STICKY;
}

@Override
public void onDestroy() {
// Cancel the persistent notification.
mNM.cancel(R.string.local_service_started);

// Tell the user we stopped.
Toast.makeText(this, R.string.local_service_stopped, Toast.LENGTH_SHORT).show();
}

@Override
public IBinder onBind(Intent intent) {
return mBinder;
}

// This is the object that receives interactions from clients. See
// RemoteService for a more complete example.
private final IBinder mBinder = new LocalBinder();

/**
* Show a notification while this service is running.
*/
private void showNotification() {
// In this sample, we'll use the same text for the ticker and the expanded notification
CharSequence text = getText(R.string.local_service_started);

// Set the icon, scrolling text and timestamp
Notification notification = new Notification(R.drawable.stat_sample, text,
System.currentTimeMillis());

// The PendingIntent to launch our activity if the user selects this notification
PendingIntent contentIntent = PendingIntent.getActivity(this, 0,
new Intent(this, LocalServiceController.class), 0);

// Set the info for the views that show in the notification panel.
notification.setLatestEventInfo(this, getText(R.string.local_service_label),
text, contentIntent);

// Send the notification.
// We use a layout id because it is a unique number. We use it later to cancel.
mNM.notify(R.string.local_service_started, notification);
}
}
复制代码
　　这里可以发现onBind需要返回一个IBinder对象。也就是说和上一例子LocalService不同的是，

　　1. 添加了一个public内部类继承Binder，并添加getService方法来返回当前的Service对象；

　　2. 新建一个IBinder对象--new那个Binder内部类；

　　3. onBind方法返还那个IBinder对象。

　　Activity:

/**
* <p>Example of binding and unbinding to the {@link LocalService}.
* This demonstrates the implementation of a service which the client will
* bind to, receiving an object through which it can communicate with the service.</p>
*/
public class LocalServiceBinding extends Activity {
private boolean mIsBound;
private LocalService mBoundService;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

setContentView(R.layout.local_service_binding);

// Watch for button clicks.
Button button = (Button)findViewById(R.id.bind);
button.setOnClickListener(mBindListener);
button = (Button)findViewById(R.id.unbind);
button.setOnClickListener(mUnbindListener);
}

private ServiceConnection mConnection = new ServiceConnection() {
public void onServiceConnected(ComponentName className, IBinder service) {
// This is called when the connection with the service has been
// established, giving us the service object we can use to
// interact with the service. Because we have bound to a explicit
// service that we know is running in our own process, we can
// cast its IBinder to a concrete class and directly access it.
mBoundService = ((LocalService.LocalBinder)service).getService();

// Tell the user about this for our demo.
Toast.makeText(LocalServiceBinding.this, R.string.local_service_connected,
Toast.LENGTH_SHORT).show();
}

public void onServiceDisconnected(ComponentName className) {
// This is called when the connection with the service has been
// unexpectedly disconnected -- that is, its process crashed.
// Because it is running in our same process, we should never
// see this happen.
mBoundService = null;
Toast.makeText(LocalServiceBinding.this, R.string.local_service_disconnected,
Toast.LENGTH_SHORT).show();
}
};

private OnClickListener mBindListener = new OnClickListener() {
public void onClick(View v) {
// Establish a connection with the service. We use an explicit
// class name because we want a specific service implementation that
// we know will be running in our own process (and thus won't be
// supporting component replacement by other applications).
bindService(new Intent(LocalServiceBinding.this,
LocalService.class), mConnection, Context.BIND_AUTO_CREATE);
mIsBound = true;
}
};

private OnClickListener mUnbindListener = new OnClickListener() {
public void onClick(View v) {
if (mIsBound) {
// Detach our existing connection.
unbindService(mConnection);
mIsBound = false;
}
}
};
}
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　　明显看出这里面添加了一个名为ServiceConnection类，并实现了onServiceConnected(从IBinder获取Service对象)和onServiceDisconnected(set Service to null)。

　　而bindService和unbindService方法都是操作这个ServiceConnection对象的。

　　AndroidManifest.xml里添加:

　　<service android:name=".app.LocalService" />
复制代码
　　这里没什么特别的，因为service没有需要什么特别的action，所以只是声明service而已，而activity和普通的没差别。

　　运行时，发现调用次序是这样的：

　　bindService:

　　1.LocalService : onCreate

　　2.LocalService : onBind

　　3.Activity: onServiceConnected

　　unbindService: 只是调用onDestroy

　　可见，onStart是不会被调用的，而onServiceDisconnected没有调用的原因在上面代码的注释有说明。

本地service

　　1.不需和Activity交互的本地服务

public class LocalService extends Service {

private static final String TAG = "LocalService";

@Override
public IBinder onBind(Intent intent) {
Log.i(TAG, "onBind");
return null;
}

@Override
public void onCreate() {
Log.i(TAG, "onCreate");
super.onCreate();
}

@Override
public void onDestroy() {
Log.i(TAG, "onDestroy");
super.onDestroy();
}

@Override
public void onStart(Intent intent, int startId) {
Log.i(TAG, "onStart");
super.onStart(intent, startId);
}
}
复制代码
　　Activity:
public class ServiceActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.servicedemo);

((Button) findViewById(R.id.startLocalService)).setOnClickListener(
new View.OnClickListener(){

@Override
public void onClick(View view) {
// TODO Auto-generated method stub
startService(new Intent("com.demo.SERVICE_DEMO"));
}
});

((Button) findViewById(R.id.stopLocalService)).setOnClickListener(
new View.OnClickListener(){

@Override
public void onClick(View view) {
// TODO Auto-generated method stub
stopService(new Intent("com.demo.SERVICE_DEMO"));
}
});
}

}
复制代码
　　在AndroidManifest.xml添加：
<service android:name=".LocalService">
<intent-filter>
<action android:name="com.demo.SERVICE_DEMO" />
<category android:name="android.intent.category.default" />
</intent-filter>
</service>
复制代码
　　否则启动服务时会提示new Intent找不到"com.demo.SERVICE_DEMO"。

　　对于这类不需和Activity交互的本地服务，是使用startService/stopService的最好例子。

　　运行时可以发现第一次startService时，会调用onCreate和onStart，在没有stopService前，无论点击多少次startService，都只会调用onStart。而stopService时调用onDestroy。再次点击stopService，会发现不会进入service的生命周期的，即不会再调用onCreate，onStart和onDestroy。

　　而onBind在startService/stopService中没有调用。

　　2.本地服务和Activity交互

　　对于这种case，官方的sample(APIDemo\app.LocalService)是最好的例子:

/**
* This is an example of implementing an application service that runs locally
* in the same process as the application. The {@link LocalServiceController}
* and {@link LocalServiceBinding} classes show how to interact with the
* service.
*
* <p>Notice the use of the {@link NotificationManager} when interesting things
* happen in the service. This is generally how background services should
* interact with the user, rather than doing something more disruptive such as
* calling startActivity().
*/
public class LocalService extends Service {
private NotificationManager mNM;

/**
* Class for clients to access. Because we know this service always
* runs in the same process as its clients, we don't need to deal with
* IPC.
*/
public class LocalBinder extends Binder {
LocalService getService() {
return LocalService.this;
}
}

@Override
public void onCreate() {
mNM = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);

// Display a notification about us starting. We put an icon in the status bar.
showNotification();
}

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
Log.i("LocalService", "Received start id " + startId + ": " + intent);
// We want this service to continue running until it is explicitly
// stopped, so return sticky.
return START_STICKY;
}

@Override
public void onDestroy() {
// Cancel the persistent notification.
mNM.cancel(R.string.local_service_started);

// Tell the user we stopped.
Toast.makeText(this, R.string.local_service_stopped, Toast.LENGTH_SHORT).show();
}

@Override
public IBinder onBind(Intent intent) {
return mBinder;
}

// This is the object that receives interactions from clients. See
// RemoteService for a more complete example.
private final IBinder mBinder = new LocalBinder();

/**
* Show a notification while this service is running.
*/
private void showNotification() {
// In this sample, we'll use the same text for the ticker and the expanded notification
CharSequence text = getText(R.string.local_service_started);

// Set the icon, scrolling text and timestamp
Notification notification = new Notification(R.drawable.stat_sample, text,
System.currentTimeMillis());

// The PendingIntent to launch our activity if the user selects this notification
PendingIntent contentIntent = PendingIntent.getActivity(this, 0,
new Intent(this, LocalServiceController.class), 0);

// Set the info for the views that show in the notification panel.
notification.setLatestEventInfo(this, getText(R.string.local_service_label),
text, contentIntent);

// Send the notification.
// We use a layout id because it is a unique number. We use it later to cancel.
mNM.notify(R.string.local_service_started, notification);
}
}
复制代码
　　这里可以发现onBind需要返回一个IBinder对象。也就是说和上一例子LocalService不同的是，

　　1. 添加了一个public内部类继承Binder，并添加getService方法来返回当前的Service对象；

　　2. 新建一个IBinder对象--new那个Binder内部类；

　　3. onBind方法返还那个IBinder对象。

　　Activity:

/**
* <p>Example of binding and unbinding to the {@link LocalService}.
* This demonstrates the implementation of a service which the client will
* bind to, receiving an object through which it can communicate with the service.</p>
*/
public class LocalServiceBinding extends Activity {
private boolean mIsBound;
private LocalService mBoundService;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

setContentView(R.layout.local_service_binding);

// Watch for button clicks.
Button button = (Button)findViewById(R.id.bind);
button.setOnClickListener(mBindListener);
button = (Button)findViewById(R.id.unbind);
button.setOnClickListener(mUnbindListener);
}

private ServiceConnection mConnection = new ServiceConnection() {
public void onServiceConnected(ComponentName className, IBinder service) {
// This is called when the connection with the service has been
// established, giving us the service object we can use to
// interact with the service. Because we have bound to a explicit
// service that we know is running in our own process, we can
// cast its IBinder to a concrete class and directly access it.
mBoundService = ((LocalService.LocalBinder)service).getService();

// Tell the user about this for our demo.
Toast.makeText(LocalServiceBinding.this, R.string.local_service_connected,
Toast.LENGTH_SHORT).show();
}

public void onServiceDisconnected(ComponentName className) {
// This is called when the connection with the service has been
// unexpectedly disconnected -- that is, its process crashed.
// Because it is running in our same process, we should never
// see this happen.
mBoundService = null;
Toast.makeText(LocalServiceBinding.this, R.string.local_service_disconnected,
Toast.LENGTH_SHORT).show();
}
};

private OnClickListener mBindListener = new OnClickListener() {
public void onClick(View v) {
// Establish a connection with the service. We use an explicit
// class name because we want a specific service implementation that
// we know will be running in our own process (and thus won't be
// supporting component replacement by other applications).
bindService(new Intent(LocalServiceBinding.this,
LocalService.class), mConnection, Context.BIND_AUTO_CREATE);
mIsBound = true;
}
};

private OnClickListener mUnbindListener = new OnClickListener() {
public void onClick(View v) {
if (mIsBound) {
// Detach our existing connection.
unbindService(mConnection);
mIsBound = false;
}
}
};
}
复制代码


　　明显看出这里面添加了一个名为ServiceConnection类，并实现了onServiceConnected(从IBinder获取Service对象)和onServiceDisconnected(set Service to null)。

　　而bindService和unbindService方法都是操作这个ServiceConnection对象的。

　　AndroidManifest.xml里添加:

　　<service android:name=".app.LocalService" />
复制代码
　　这里没什么特别的，因为service没有需要什么特别的action，所以只是声明service而已，而activity和普通的没差别。

　　运行时，发现调用次序是这样的：

　　bindService:

　　1.LocalService : onCreate

　　2.LocalService : onBind

　　3.Activity: onServiceConnected

　　unbindService: 只是调用onDestroy

　　可见，onStart是不会被调用的，而onServiceDisconnected没有调用的原因在上面代码的注释有说明。