原文地址： http://stackoverflow.com/questions/4300291/example-communication-between-activity-and-service-using-messaging

I couldn't find any examples of how to send messages between an activity and a service, and I have spent far too many hours figuring this out. Here is an example project for others to reference.

This example allows you to start or stop a service directly, and separately bind/unbind from the service. When the service is running, it increments a number at 10?Hz. If the activity is bound to theService, it will display the current value. Data is transferred as an Integer and as a String so you can see how to do that two different ways. There are also buttons in the activity to send messages to the service (changes the increment-by value).

Screenshot:

AndroidManifest.xml:

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android"package="com.exampleservice"android:versionCode="1"android:versionName="1.0"><application android:icon="@drawable/icon" android:label="@string/app_name"><activity android:name=".MainActivity"android:label="@string/app_name"><intent-filter><action android:name="android.intent.action.MAIN" /><category android:name="android.intent.category.LAUNCHER" /></intent-filter></activity><service android:name=".MyService"></service></application><uses-sdk android:minSdkVersion="8" /> </manifest>

res\values\strings.xml:

<?xml version="1.0" encoding="utf-8"?> <resources><string name="app_name">ExampleService</string><string name="service_started">Example Service started</string><string name="service_label">Example Service Label</string> </resources>

res\layout\main.xml:

<RelativeLayoutandroid:id="@+id/RelativeLayout01"android:layout_width="fill_parent"android:layout_height="wrap_content" ><Buttonandroid:id="@+id/btnStart"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="Start Service" ></Button><Buttonandroid:id="@+id/btnStop"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_alignParentRight="true"android:text="Stop Service" ></Button> </RelativeLayout><RelativeLayoutandroid:id="@+id/RelativeLayout02"android:layout_width="fill_parent"android:layout_height="wrap_content" ><Buttonandroid:id="@+id/btnBind"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="Bind to Service" ></Button><Buttonandroid:id="@+id/btnUnbind"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_alignParentRight="true"android:text="Unbind from Service" ></Button> </RelativeLayout><TextViewandroid:id="@+id/textStatus"android:layout_width="fill_parent"android:layout_height="wrap_content"android:text="Status Goes Here"android:textSize="24sp" /><TextViewandroid:id="@+id/textIntValue"android:layout_width="fill_parent"android:layout_height="wrap_content"android:text="Integer Value Goes Here"android:textSize="24sp" /><TextViewandroid:id="@+id/textStrValue"android:layout_width="fill_parent"android:layout_height="wrap_content"android:text="String Value Goes Here"android:textSize="24sp" /><RelativeLayoutandroid:id="@+id/RelativeLayout03"android:layout_width="fill_parent"android:layout_height="wrap_content" ><Buttonandroid:id="@+id/btnUpby1"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="Increment by 1" ></Button><Buttonandroid:id="@+id/btnUpby10"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_alignParentRight="true"android:text="Increment by 10" ></Button> </RelativeLayout>

src\com.exampleservice\MainActivity.java:

package com.exampleservice;import android.app.Activity; import android.content.ComponentName; import android.content.Context; import android.content.Intent; import android.content.ServiceConnection; import android.os.Bundle; import android.os.Handler; import android.os.IBinder; import android.os.Message; import android.os.Messenger; import android.os.RemoteException; import android.util.Log; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.TextView;public class MainActivity extends Activity {Button btnStart, btnStop, btnBind, btnUnbind, btnUpby1, btnUpby10;TextView textStatus, textIntValue, textStrValue;Messenger mService = null;boolean mIsBound;final Messenger mMessenger = new Messenger(new IncomingHandler());class IncomingHandler extends Handler {@Overridepublic void handleMessage(Message msg) {switch (msg.what) {case MyService.MSG_SET_INT_VALUE:textIntValue.setText("Int Message: " + msg.arg1);break;case MyService.MSG_SET_STRING_VALUE:String str1 = msg.getData().getString("str1");textStrValue.setText("Str Message: " + str1);break;default:super.handleMessage(msg);}}}private ServiceConnection mConnection = new ServiceConnection() {public void onServiceConnected(ComponentName className, IBinder service) {mService = new Messenger(service);textStatus.setText("Attached.");try {Message msg = Message.obtain(null, MyService.MSG_REGISTER_CLIENT);msg.replyTo = mMessenger;mService.send(msg);}catch (RemoteException e) {// In this case the service has crashed before we could even do anything with it}}public void onServiceDisconnected(ComponentName className) {// This is called when the connection with the service has been unexpectedly disconnected - process crashed.mService = null;textStatus.setText("Disconnected.");}};@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);btnStart = (Button)findViewById(R.id.btnStart);btnStop = (Button)findViewById(R.id.btnStop);btnBind = (Button)findViewById(R.id.btnBind);btnUnbind = (Button)findViewById(R.id.btnUnbind);textStatus = (TextView)findViewById(R.id.textStatus);textIntValue = (TextView)findViewById(R.id.textIntValue);textStrValue = (TextView)findViewById(R.id.textStrValue);btnUpby1 = (Button)findViewById(R.id.btnUpby1);btnUpby10 = (Button)findViewById(R.id.btnUpby10);btnStart.setOnClickListener(btnStartListener);btnStop.setOnClickListener(btnStopListener);btnBind.setOnClickListener(btnBindListener);btnUnbind.setOnClickListener(btnUnbindListener);btnUpby1.setOnClickListener(btnUpby1Listener);btnUpby10.setOnClickListener(btnUpby10Listener);restoreMe(savedInstanceState);CheckIfServiceIsRunning();}@Overrideprotected void onSaveInstanceState(Bundle outState) {super.onSaveInstanceState(outState);outState.putString("textStatus", textStatus.getText().toString());outState.putString("textIntValue", textIntValue.getText().toString());outState.putString("textStrValue", textStrValue.getText().toString());}private void restoreMe(Bundle state) {if (state!=null) {textStatus.setText(state.getString("textStatus"));textIntValue.setText(state.getString("textIntValue"));textStrValue.setText(state.getString("textStrValue"));}}private void CheckIfServiceIsRunning() {//If the service is running when the activity starts, we want to automatically bind to it.if (MyService.isRunning()) {doBindService();}}private OnClickListener btnStartListener = new OnClickListener() {public void onClick(View v){startService(new Intent(MainActivity.this, MyService.class));}};private OnClickListener btnStopListener = new OnClickListener() {public void onClick(View v){doUnbindService();stopService(new Intent(MainActivity.this, MyService.class));}};private OnClickListener btnBindListener = new OnClickListener() {public void onClick(View v){doBindService();}};private OnClickListener btnUnbindListener = new OnClickListener() {public void onClick(View v){doUnbindService();}};private OnClickListener btnUpby1Listener = new OnClickListener() {public void onClick(View v){sendMessageToService(1);}};private OnClickListener btnUpby10Listener = new OnClickListener() {public void onClick(View v){sendMessageToService(10);}};private void sendMessageToService(int intvaluetosend) {if (mIsBound) {if (mService != null) {try {Message msg = Message.obtain(null, MyService.MSG_SET_INT_VALUE, intvaluetosend, 0);msg.replyTo = mMessenger;mService.send(msg);}catch (RemoteException e) {}}}}void doBindService() {bindService(new Intent(this, MyService.class), mConnection, Context.BIND_AUTO_CREATE);mIsBound = true;textStatus.setText("Binding.");}void doUnbindService() {if (mIsBound) {// If we have received the service, and hence registered with it, then now is the time to unregister.if (mService != null) {try {Message msg = Message.obtain(null, MyService.MSG_UNREGISTER_CLIENT);msg.replyTo = mMessenger;mService.send(msg);}catch (RemoteException e) {// There is nothing special we need to do if the service has crashed.}}// Detach our existing connection.unbindService(mConnection);mIsBound = false;textStatus.setText("Unbinding.");}}@Overrideprotected void onDestroy() {super.onDestroy();try {doUnbindService();}catch (Throwable t) {Log.e("MainActivity", "Failed to unbind from the service", t);}} }

src\com.exampleservice\MyService.java:

package com.exampleservice;import java.util.ArrayList; import java.util.Timer; import java.util.TimerTask;import android.app.Notification; import android.app.NotificationManager; import android.app.PendingIntent; import android.app.Service; import android.content.Intent; import android.os.Bundle; import android.os.Handler; import android.os.IBinder; import android.os.Message; import android.os.Messenger; import android.os.RemoteException; import android.util.Log;public class MyService extends Service {private NotificationManager nm;private Timer timer = new Timer();private int counter = 0, incrementby = 1;private static boolean isRunning = false;ArrayList<Messenger> mClients = new ArrayList<Messenger>(); // Keeps track of all current registered clients.int mValue = 0; // Holds last value set by a client.static final int MSG_REGISTER_CLIENT = 1;static final int MSG_UNREGISTER_CLIENT = 2;static final int MSG_SET_INT_VALUE = 3;static final int MSG_SET_STRING_VALUE = 4;final Messenger mMessenger = new Messenger(new IncomingHandler()); // Target we publish for clients to send messages to IncomingHandler.@Overridepublic IBinder onBind(Intent intent) {return mMessenger.getBinder();}class IncomingHandler extends Handler { // Handler of incoming messages from clients.@Overridepublic void handleMessage(Message msg) {switch (msg.what) {case MSG_REGISTER_CLIENT:mClients.add(msg.replyTo);break;case MSG_UNREGISTER_CLIENT:mClients.remove(msg.replyTo);break;case MSG_SET_INT_VALUE:incrementby = msg.arg1;break;default:super.handleMessage(msg);}}}private void sendMessageToUI(int intvaluetosend) {for (int i=mClients.size()-1; i>=0; i--) {try {// Send data as an IntegermClients.get(i).send(Message.obtain(null, MSG_SET_INT_VALUE, intvaluetosend, 0));//Send data as a StringBundle b = new Bundle();b.putString("str1", "ab" + intvaluetosend + "cd");Message msg = Message.obtain(null, MSG_SET_STRING_VALUE);msg.setData(b);mClients.get(i).send(msg);}catch (RemoteException e) {// The client is dead. Remove it from the list; we are going through the list from back to front so this is safe to do inside the loop.mClients.remove(i);}}}@Overridepublic void onCreate() {super.onCreate();Log.i("MyService", "Service Started.");showNotification();timer.scheduleAtFixedRate(new TimerTask(){ public void run() {onTimerTick();}}, 0, 100L);isRunning = true;}private void showNotification() {nm = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);// In this sample, we'll use the same text for the ticker and the expanded notificationCharSequence text = getText(R.string.service_started);// Set the icon, scrolling text and timestampNotification notification = new Notification(R.drawable.icon, text, System.currentTimeMillis());// The PendingIntent to launch our activity if the user selects this notificationPendingIntent contentIntent = PendingIntent.getActivity(this, 0, new Intent(this, MainActivity.class), 0);// Set the info for the views that show in the notification panel.notification.setLatestEventInfo(this, getText(R.string.service_label), text, contentIntent);// Send the notification.// We use a layout id because it is a unique number. We use it later to cancel.nm.notify(R.string.service_started, notification);}@Overridepublic int onStartCommand(Intent intent, int flags, int startId) {Log.i("MyService", "Received start id " + startId + ": " + intent);return START_STICKY; // run until explicitly stopped.}public static boolean isRunning(){return isRunning;}private void onTimerTick() {Log.i("TimerTick", "Timer doing work." + counter);try {counter += incrementby;sendMessageToUI(counter);}catch (Throwable t) { //you should always ultimately catch all exceptions in timer tasks.Log.e("TimerTick", "Timer Tick Failed.", t);}}@Overridepublic void onDestroy() {super.onDestroy();if (timer != null) {timer.cancel();}counter=0;nm.cancel(R.string.service_started); // Cancel the persistent notification.Log.i("MyService", "Service Stopped.");isRunning = false;} }

Comment:

1. Great example! Another nice feature: If you put?android:process=:myservicename?attribute to theservice?tag of your service in your manifest.xml, like:?<service android:name="sname" android:process=":myservicename" />, then it will run your service as a different process - thus in a different thread. This means, that any heavy calculation done/long request by the service wont hang your UI thread.

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