Android 绑定类型服务---其他注意事项

以下是关于绑定的重要注意事项：
1. 你应该始终捕获DeadObjectException异常，当连接被中断时这个异常被抛出。这是由远程方法抛出的唯一异常。

2. 对象的引用计数是跨进程的。

3. 通常绑定和解除绑定应该成对使用，而且要跟客户端的生命周期的启动和退出时刻匹配。例如：

如果你只需要在Activity可见的时候跟服务交互，那么就应该在onStart()期间绑定在onStop()期间解绑；

如果你想要Activity在终止的时候也能在后台接收响应事件，那么可以在onCreate()期间绑定，在onDestroy()期间解绑。这就意味着你的Activity需要在Activity的整个生命时都要使用这个服务，这样做要小心了，因为如果服务是在另一个进程中，那么你会增加这个进程的权重，是它变的更容易被系统杀死。

注意：通常在Activity的onResume()和onPause()期间不应该绑定和解除绑定服务，因为这些回调发生在每个生命周期的过渡期，并且应该保持在这些过渡期发生最低限度的处理。如果应用程序中多个Activity绑定了同一个服务，并且在这些Activity的其中两个之间有这样的过渡发生，那么这个服务就可以在当前Activity绑定解除（暂停期间）下一个Activity绑定之前（恢复期间）来销毁和创建。

绑定服务的示例代码：RemoteService.java

/*

* Copyright (C) 2007 The Android Open Source Project

*

* Licensed under the Apache License, Version 2.0 (the "License");

* you may not use this file except in compliance with the License.

* You may obtain a copy of the License at

*

* http://www.apache.org/licenses/LICENSE-2.0
*

* Unless required by applicable law or agreed to in writing, software

* distributed under the License is distributed on an "AS IS" BASIS,

* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

* See the License for the specific language governing permissions and

* limitations under the License.

*/

package com.example.android.apis.app;

import android.app.Activity;

import android.app.Notification;

import android.app.NotificationManager;

import android.app.PendingIntent;

import android.app.Service;

import android.content.ComponentName;

import android.content.Context;

import android.content.Intent;

import android.content.ServiceConnection;

import android.os.Bundle;

import android.os.RemoteException;

import android.os.Handler;

import android.os.IBinder;

import android.os.Message;

import android.os.Process;

import android.os.RemoteCallbackList;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.TextView;

import android.widget.Toast;

// Need the following import to get access to the app resources, since this

// class is in a sub-package.

import com.example.android.apis.R;

/**

* This is an example of implementing an application service that runs in a

* different process than the application. Because it can be in another

* process, we must use IPC to interact with it. The

* {@link Controller} and {@link Binding} classes

* show how to interact with the service.

*

* <p>Note that most applications <strong>do not</strong> need to deal with

* the complexity shown here. If your application simply has a service

* running in its own process, the {@link LocalService} sample shows a much

* simpler way to interact with it.

*/

public class RemoteService extends Service {

/**

* This is a list of callbacks that have been registered with the

* service. Note that this is package scoped (instead of private) so

* that it can be accessed more efficiently from inner classes.

*/

final RemoteCallbackList<IRemoteServiceCallback> mCallbacks

= new RemoteCallbackList<IRemoteServiceCallback>();

int mValue = 0;

NotificationManager mNM;

@Override

public void onCreate() {

mNM = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);

// Display a notification about us starting.

showNotification();

// While this service is running, it will continually increment a

// number. Send the first message that is used to perform the

// increment.

mHandler.sendEmptyMessage(REPORT_MSG);

}

@Override

public void onDestroy() {

// Cancel the persistent notification.

mNM.cancel(R.string.remote_service_started);

// Tell the user we stopped.

Toast.makeText(this, R.string.remote_service_stopped, Toast.LENGTH_SHORT).show();

// Unregister all callbacks.

mCallbacks.kill();

// Remove the next pending message to increment the counter, stopping

// the increment loop.

mHandler.removeMessages(REPORT_MSG);

}

@Override

public IBinder onBind(Intent intent) {

// Select the interface to return. If your service only implements

// a single interface, you can just return it here without checking

// the Intent.

if (IRemoteService.class.getName().equals(intent.getAction())) {

return mBinder;

}

if (ISecondary.class.getName().equals(intent.getAction())) {

return mSecondaryBinder;

}

return null;

}

/**

* The IRemoteInterface is defined through IDL

*/

private final IRemoteService.Stub mBinder = new IRemoteService.Stub() {

public void registerCallback(IRemoteServiceCallback cb) {

if (cb != null) mCallbacks.register(cb);

}

public void unregisterCallback(IRemoteServiceCallback cb) {

if (cb != null) mCallbacks.unregister(cb);

}

};

/**

* A secondary interface to the service.

*/

private final ISecondary.Stub mSecondaryBinder = new ISecondary.Stub() {

public int getPid() {

return Process.myPid();

}

public void basicTypes(int anInt, long aLong, boolean aBoolean,

float aFloat, double aDouble, String aString) {

}

};

@Override

public void onTaskRemoved(Intent rootIntent) {

Toast.makeText(this, "Task removed: " + rootIntent, Toast.LENGTH_LONG).show();

}

private static final int REPORT_MSG = 1;

/**

* Our Handler used to execute operations on the main thread. This is used

* to schedule increments of our value.

*/

private final Handler mHandler = new Handler() {

@Override public void handleMessage(Message msg) {

switch (msg.what) {

// It is time to bump the value!

case REPORT_MSG: {

// Up it goes.

int value = ++mValue;

// Broadcast to all clients the new value.

final int N = mCallbacks.beginBroadcast();

for (int i=0; i<N; i++) {

try {

mCallbacks.getBroadcastItem(i).valueChanged(value);

} catch (RemoteException e) {

// The RemoteCallbackList will take care of removing

// the dead object for us.

}

}

mCallbacks.finishBroadcast();

// Repeat every 1 second.

sendMessageDelayed(obtainMessage(REPORT_MSG), 1*1000);

} break;

default:

super.handleMessage(msg);

}

}

};

/**

* 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.remote_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, Controller.class), 0);

// Set the info for the views that show in the notification panel.

notification.setLatestEventInfo(this, getText(R.string.remote_service_label),

text, contentIntent);

// Send the notification.

// We use a string id because it is a unique number. We use it later to cancel.

mNM.notify(R.string.remote_service_started, notification);

}

// ----------------------------------------------------------------------

/**

* <p>Example of explicitly starting and stopping the remove service.

* This demonstrates the implementation of a service that runs in a different

* process than the rest of the application, which is explicitly started and stopped

* as desired.</p>

*

* <p>Note that this is implemented as an inner class only keep the sample

* all together; typically this code would appear in some separate class.

*/

public static class Controller extends Activity {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.remote_service_controller);

// Watch for button clicks.

Button button = (Button)findViewById(R.id.start);

button.setOnClickListener(mStartListener);

button = (Button)findViewById(R.id.stop);

button.setOnClickListener(mStopListener);

}

private OnClickListener mStartListener = new OnClickListener() {

public void onClick(View v) {

// Make sure the service is started. It will continue running

// until someone calls stopService().

// We use an action code here, instead of explictly supplying

// the component name, so that other packages can replace

// the service.

startService(new Intent(

"com.example.android.apis.app.REMOTE_SERVICE"));

}

};

private OnClickListener mStopListener = new OnClickListener() {

public void onClick(View v) {

// Cancel a previous call to startService(). Note that the

// service will not actually stop at this point if there are

// still bound clients.

stopService(new Intent(

"com.example.android.apis.app.REMOTE_SERVICE"));

}

};

}

// ----------------------------------------------------------------------

/**

* Example of binding and unbinding to the remote service.

* This demonstrates the implementation of a service which the client will

* bind to, interacting with it through an aidl interface.</p>

*

* <p>Note that this is implemented as an inner class only keep the sample

* all together; typically this code would appear in some separate class.

*/

public static class Binding extends Activity {

/** The primary interface we will be calling on the service. */

IRemoteService mService = null;

/** Another interface we use on the service. */

ISecondary mSecondaryService = null;

Button mKillButton;

TextView mCallbackText;

private boolean mIsBound;

/**

* Standard initialization of this activity. Set up the UI, then wait

* for the user to poke it before doing anything.

*/

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.remote_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);

mKillButton = (Button)findViewById(R.id.kill);

mKillButton.setOnClickListener(mKillListener);

mKillButton.setEnabled(false);

mCallbackText = (TextView)findViewById(R.id.callback);

mCallbackText.setText("Not attached.");

}

/**

* Class for interacting with the main interface of the service.

*/

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. We are communicating with our

// service through an IDL interface, so get a client-side

// representation of that from the raw service object.

mService = IRemoteService.Stub.asInterface(service);

mKillButton.setEnabled(true);

mCallbackText.setText("Attached.");

// We want to monitor the service for as long as we are

// connected to it.

try {

mService.registerCallback(mCallback);

} catch (RemoteException e) {

// In this case the service has crashed before we could even

// do anything with it; we can count on soon being

// disconnected (and then reconnected if it can be restarted)

// so there is no need to do anything here.

}

// As part of the sample, tell the user what happened.

Toast.makeText(Binding.this, R.string.remote_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.

mService = null;

mKillButton.setEnabled(false);

mCallbackText.setText("Disconnected.");

// As part of the sample, tell the user what happened.

Toast.makeText(Binding.this, R.string.remote_service_disconnected,

Toast.LENGTH_SHORT).show();

}

};

/**

* Class for interacting with the secondary interface of the service.

*/

private ServiceConnection mSecondaryConnection = new ServiceConnection() {

public void onServiceConnected(ComponentName className,

IBinder service) {

// Connecting to a secondary interface is the same as any

// other interface.

mSecondaryService = ISecondary.Stub.asInterface(service);

mKillButton.setEnabled(true);

}

public void onServiceDisconnected(ComponentName className) {

mSecondaryService = null;

mKillButton.setEnabled(false);

}

};

private OnClickListener mBindListener = new OnClickListener() {

public void onClick(View v) {

// Establish a couple connections with the service, binding

// by interface names. This allows other applications to be

// installed that replace the remote service by implementing

// the same interface.

bindService(new Intent(IRemoteService.class.getName()),

mConnection, Context.BIND_AUTO_CREATE);

bindService(new Intent(ISecondary.class.getName()),

mSecondaryConnection, Context.BIND_AUTO_CREATE);

mIsBound = true;

mCallbackText.setText("Binding.");

}

};

private OnClickListener mUnbindListener = new OnClickListener() {

public void onClick(View v) {

if (mIsBound) {

// If we have received the service, and hence registered with

// it, then now is the time to unregister.

if (mService != null) {

try {

mService.unregisterCallback(mCallback);

} catch (RemoteException e) {

// There is nothing special we need to do if the service

// has crashed.

}

}

// Detach our existing connection.

unbindService(mConnection);

unbindService(mSecondaryConnection);

mKillButton.setEnabled(false);

mIsBound = false;

mCallbackText.setText("Unbinding.");

}

}

};

private OnClickListener mKillListener = new OnClickListener() {

public void onClick(View v) {

// To kill the process hosting our service, we need to know its

// PID. Conveniently our service has a call that will return

// to us that information.

if (mSecondaryService != null) {

try {

int pid = mSecondaryService.getPid();

// Note that, though this API allows us to request to

// kill any process based on its PID, the kernel will

// still impose standard restrictions on which PIDs you

// are actually able to kill. Typically this means only

// the process running your application and any additional

// processes created by that app as shown here; packages

// sharing a common UID will also be able to kill each

// other's processes.

Process.killProcess(pid);

mCallbackText.setText("Killed service process.");

} catch (RemoteException ex) {

// Recover gracefully from the process hosting the

// server dying.

// Just for purposes of the sample, put up a notification.

Toast.makeText(Binding.this,

R.string.remote_call_failed,

Toast.LENGTH_SHORT).show();

}

}

}

};

// ----------------------------------------------------------------------

// Code showing how to deal with callbacks.

// ----------------------------------------------------------------------

/**

* This implementation is used to receive callbacks from the remote

* service.

*/

private IRemoteServiceCallback mCallback = new IRemoteServiceCallback.Stub() {

/**

* This is called by the remote service regularly to tell us about

* new values. Note that IPC calls are dispatched through a thread

* pool running in each process, so the code executing here will

* NOT be running in our main thread like most other things -- so,

* to update the UI, we need to use a Handler to hop over there.

*/

public void valueChanged(int value) {

mHandler.sendMessage(mHandler.obtainMessage(BUMP_MSG, value, 0));

}

};

private static final int BUMP_MSG = 1;

private Handler mHandler = new Handler() {

@Override public void handleMessage(Message msg) {

switch (msg.what) {

case BUMP_MSG:

mCallbackText.setText("Received from service: " + msg.arg1);

break;

default:

super.handleMessage(msg);

}

}

};

}

// ----------------------------------------------------------------------

/**

* Examples of behavior of different bind flags.</p>

*/

public static class BindingOptions extends Activity {

ServiceConnection mCurConnection;

TextView mCallbackText;

class MyServiceConnection implements ServiceConnection {

final boolean mUnbindOnDisconnect;

public MyServiceConnection() {

mUnbindOnDisconnect = false;

}

public MyServiceConnection(boolean unbindOnDisconnect) {

mUnbindOnDisconnect = unbindOnDisconnect;

}

public void onServiceConnected(ComponentName className,

IBinder service) {

if (mCurConnection != this) {

return;

}

mCallbackText.setText("Attached.");

Toast.makeText(BindingOptions.this, R.string.remote_service_connected,

Toast.LENGTH_SHORT).show();

}

public void onServiceDisconnected(ComponentName className) {

if (mCurConnection != this) {

return;

}

mCallbackText.setText("Disconnected.");

Toast.makeText(BindingOptions.this, R.string.remote_service_disconnected,

Toast.LENGTH_SHORT).show();

if (mUnbindOnDisconnect) {

unbindService(this);

mCurConnection = null;

Toast.makeText(BindingOptions.this, R.string.remote_service_unbind_disconn,

Toast.LENGTH_SHORT).show();

}

}

}

/**

* Standard initialization of this activity. Set up the UI, then wait

* for the user to poke it before doing anything.

*/

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.remote_binding_options);

// Watch for button clicks.

Button button = (Button)findViewById(R.id.bind_normal);

button.setOnClickListener(mBindNormalListener);

button = (Button)findViewById(R.id.bind_not_foreground);

button.setOnClickListener(mBindNotForegroundListener);

button = (Button)findViewById(R.id.bind_above_client);

button.setOnClickListener(mBindAboveClientListener);

button = (Button)findViewById(R.id.bind_allow_oom);

button.setOnClickListener(mBindAllowOomListener);

button = (Button)findViewById(R.id.bind_waive_priority);

button.setOnClickListener(mBindWaivePriorityListener);

button = (Button)findViewById(R.id.bind_important);

button.setOnClickListener(mBindImportantListener);

button = (Button)findViewById(R.id.bind_with_activity);

button.setOnClickListener(mBindWithActivityListener);

button = (Button)findViewById(R.id.unbind);

button.setOnClickListener(mUnbindListener);

mCallbackText = (TextView)findViewById(R.id.callback);

mCallbackText.setText("Not attached.");

}

private OnClickListener mBindNormalListener = new OnClickListener() {

public void onClick(View v) {

if (mCurConnection != null) {

unbindService(mCurConnection);

mCurConnection = null;

}

ServiceConnection conn = new MyServiceConnection();

if (bindService(new Intent(IRemoteService.class.getName()),

conn, Context.BIND_AUTO_CREATE)) {

mCurConnection = conn;

}

}

};

private OnClickListener mBindNotForegroundListener = new OnClickListener() {

public void onClick(View v) {

if (mCurConnection != null) {

unbindService(mCurConnection);

mCurConnection = null;

}

ServiceConnection conn = new MyServiceConnection();

if (bindService(new Intent(IRemoteService.class.getName()),

conn, Context.BIND_AUTO_CREATE | Context.BIND_NOT_FOREGROUND)) {

mCurConnection = conn;

}

}

};

private OnClickListener mBindAboveClientListener = new OnClickListener() {

public void onClick(View v) {

if (mCurConnection != null) {

unbindService(mCurConnection);

mCurConnection = null;

}

ServiceConnection conn = new MyServiceConnection();

if (bindService(new Intent(IRemoteService.class.getName()),

conn, Context.BIND_AUTO_CREATE | Context.BIND_ABOVE_CLIENT)) {

mCurConnection = conn;

}

}

};

private OnClickListener mBindAllowOomListener = new OnClickListener() {

public void onClick(View v) {

if (mCurConnection != null) {

unbindService(mCurConnection);

mCurConnection = null;

}

ServiceConnection conn = new MyServiceConnection();

if (bindService(new Intent(IRemoteService.class.getName()),

conn, Context.BIND_AUTO_CREATE | Context.BIND_ALLOW_OOM_MANAGEMENT)) {

mCurConnection = conn;

}

}

};

private OnClickListener mBindWaivePriorityListener = new OnClickListener() {

public void onClick(View v) {

if (mCurConnection != null) {

unbindService(mCurConnection);

mCurConnection = null;

}

ServiceConnection conn = new MyServiceConnection(true);

if (bindService(new Intent(IRemoteService.class.getName()),

conn, Context.BIND_AUTO_CREATE | Context.BIND_WAIVE_PRIORITY)) {

mCurConnection = conn;

}

}

};

private OnClickListener mBindImportantListener = new OnClickListener() {

public void onClick(View v) {

if (mCurConnection != null) {

unbindService(mCurConnection);

mCurConnection = null;

}

ServiceConnection conn = new MyServiceConnection();

if (bindService(new Intent(IRemoteService.class.getName()),

conn, Context.BIND_AUTO_CREATE | Context.BIND_IMPORTANT)) {

mCurConnection = conn;

}

}

};

private OnClickListener mBindWithActivityListener = new OnClickListener() {

public void onClick(View v) {

if (mCurConnection != null) {

unbindService(mCurConnection);

mCurConnection = null;

}

ServiceConnection conn = new MyServiceConnection();

if (bindService(new Intent(IRemoteService.class.getName()),

conn, Context.BIND_AUTO_CREATE | Context.BIND_ADJUST_WITH_ACTIVITY

| Context.BIND_WAIVE_PRIORITY)) {

mCurConnection = conn;

}

}

};

private OnClickListener mUnbindListener = new OnClickListener() {

public void onClick(View v) {

if (mCurConnection != null) {

unbindService(mCurConnection);

mCurConnection = null;

}

}

};

}

}