Android Service学习之本地服务
2015-08-28 12:37 指针空间 阅读(229) 评论(0) 编辑 收藏 举报Service是在一段不定的时间运行在后台，不和用户交互应用组件。每个Service必须在manifest中 通过<service>来声明。可以通过contect.startservice和contect.bindserverice来启动。
Service和其他的应用组件一样，运行在进程的主线程中。这就是说如果service需要很多耗时或者阻塞的操作，需要在其子线程中实现。
service的两种模式（startService()/bindService()不是完全分离的）：
本地服务 Local Service 用于应用程序内部
它可以启动并运行，直至有人停止了它或它自己停止。在这种方式下，它以调用Context.startService()启动，而以调用 Context.stopService()结束。它可以调用Service.stopSelf() 或 Service.stopSelfResult()来自己停止。不论调用了多少次startService()方法，你只需要调用一次 stopService()来停止服务。
用于实现应用程序自己的一些耗时任务，比如查询升级信息，并不占用应用程序比如Activity所属线程，而是单开线程后台执行，这样用户体验比较好
用于实现应用程序自己的一些耗时任务，比如查询升级信息，并不占用应用程序比如Activity所属线程，而是单开线程后台执行，这样用户体验比较好
远程服务 Remote Service 用于android系统内部的应用程序之间
它可以通过自己定义并暴露出来的接口进行程序操作。客户端建立一个到服务对象的连接，并通过那个连接来调用服务。连接以调用 Context.bindService()方法建立，以调用 Context.unbindService()关闭。多个客户端可以绑定至同一个服务。如果服务此时还没有加载，bindService()会先加载 它。
可被其他应用程序复用，比如天气预报服务，其他应用程序不需要再写这样的服务，调用已有的即可
可被其他应用程序复用，比如天气预报服务，其他应用程序不需要再写这样的服务，调用已有的即可
服务不能自己运行，需要通过调用Context.startService()或Context.bindService()方法启动服务。这两个方法都可以启动Service，但是它们的使用场合有所不同。
1. 使用startService()方法启用服务，调用者与服务之间没有关连，即使调用者退出了，服务仍然运行。
如果打算采用Context.startService()方法启动服务，在服务未被创建时，系统会先调用服务的onCreate()方法，接着调用onStart()方法。
如果调用startService()方法前服务已经被创建，多次调用startService()方法并不会导致多次创建服务，但会导致多次调用onStart()方法。
采用startService()方法启动的服务，只能调用Context.stopService()方法结束服务，服务结束时会调用onDestroy()方法。
2. 使用bindService()方法启用服务，调用者与服务绑定在了一起，调用者一旦退出，服务也就终止，大有“不求同时生，必须同时死”的特点。
onBind()只有采用Context.bindService()方法启动服务时才会回调该方法。该方法在调用者与服务绑定时被调用，当调用者与服务已经绑定，多次调用Context.bindService()方法并不会导致该方法被多次调用。
采用Context.bindService()方法启动服务时只能调用onUnbind()方法解除调用者与服务解除，服务结束时会调用onDestroy()方法。
否则启动服务时会提示new Intent找不到"com.demo.SERVICE_DEMO"。
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。
1. 使用startService()方法启用服务，调用者与服务之间没有关连，即使调用者退出了，服务仍然运行。
如果打算采用Context.startService()方法启动服务，在服务未被创建时，系统会先调用服务的onCreate()方法，接着调用onStart()方法。
如果调用startService()方法前服务已经被创建，多次调用startService()方法并不会导致多次创建服务，但会导致多次调用onStart()方法。
采用startService()方法启动的服务，只能调用Context.stopService()方法结束服务，服务结束时会调用onDestroy()方法。
2. 使用bindService()方法启用服务，调用者与服务绑定在了一起，调用者一旦退出，服务也就终止，大有“不求同时生，必须同时死”的特点。
onBind()只有采用Context.bindService()方法启动服务时才会回调该方法。该方法在调用者与服务绑定时被调用，当调用者与服务已经绑定，多次调用Context.bindService()方法并不会导致该方法被多次调用。
采用Context.bindService()方法启动服务时只能调用onUnbind()方法解除调用者与服务解除，服务结束时会调用onDestroy()方法。
看看官方给出的比较流程示意图：
官方文档告诉我们，一个service可以同时start并且bind，在这样的情况，系统会一直保持service的运行状态如果service已经 start了或者BIND_AUTO_CREATE标志被设置。如果没有一个条件满足，那么系统将会调用onDestory方法来终止service.所 有的清理工作（终止线程，反注册接收器）都在onDestory中完成
本地service
1.不需和Activity交互的本地服务
public class LocalService 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);
}
}
@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);
}
}
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"));
}
});
}
}
@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"));
}
});
}
}
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>
<intent-filter>
<action android:name="com.demo.SERVICE_DEMO" />
<category android:name="android.intent.category.default" />
</intent-filter>
</service>
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 {
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);
}
}
* 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 {
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);
}
}
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();
}
// 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).
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;
}
}
};
}
* <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();
}
// 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).
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;
}
}
};
}
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" />
<activity android:name=".app.LocalServiceBinding" android:label="@string/activity_local_service_binding">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.SAMPLE_CODE" />
</intent-filter>
</activity>
<activity android:name=".app.LocalServiceBinding" android:label="@string/activity_local_service_binding">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.SAMPLE_CODE" />
</intent-filter>
</activity>
运行时，发现调用次序是这样的：
bindService:
1.LocalService : onCreate
2.LocalService : onBind
3.Activity: onServiceConnected
2.LocalService : onBind
3.Activity: onServiceConnected
unbindService: 只是调用onDestroy
