问使用消息传递的活动和服务之间的通信？

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 the Service, 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:

<RelativeLayout

    android:id=""@+id/RelativeLayout01""

    android:layout_width=""fill_parent""

    android:layout_height=""wrap_content"" >

    <Button

        android:id=""@+id/btnStart""

        android:layout_width=""wrap_content""

        android:layout_height=""wrap_content""

        android:text=""Start Service"" >

    </Button>

    <Button

        android:id=""@+id/btnStop""

        android:layout_width=""wrap_content""

        android:layout_height=""wrap_content""

        android:layout_alignParentRight=""true""

        android:text=""Stop Service"" >

    </Button>

</RelativeLayout>

<RelativeLayout

    android:id=""@+id/RelativeLayout02""

    android:layout_width=""fill_parent""

    android:layout_height=""wrap_content"" >

    <Button

        android:id=""@+id/btnBind""

        android:layout_width=""wrap_content""

        android:layout_height=""wrap_content""

        android:text=""Bind to Service"" >

    </Button>

    <Button

        android:id=""@+id/btnUnbind""

        android:layout_width=""wrap_content""

        android:layout_height=""wrap_content""

        android:layout_alignParentRight=""true""

        android:text=""Unbind from Service"" >

    </Button>

</RelativeLayout>

<TextView

    android:id=""@+id/textStatus""

    android:layout_width=""fill_parent""

    android:layout_height=""wrap_content""

    android:text=""Status Goes Here""

    android:textSize=""24sp"" />

<TextView

    android:id=""@+id/textIntValue""

    android:layout_width=""fill_parent""

    android:layout_height=""wrap_content""

    android:text=""Integer Value Goes Here""

    android:textSize=""24sp"" />

<TextView

    android:id=""@+id/textStrValue""

    android:layout_width=""fill_parent""

    android:layout_height=""wrap_content""

    android:text=""String Value Goes Here""

    android:textSize=""24sp"" />

<RelativeLayout

    android:id=""@+id/RelativeLayout03""

    android:layout_width=""fill_parent""

    android:layout_height=""wrap_content"" >

    <Button

        android:id=""@+id/btnUpby1""

        android:layout_width=""wrap_content""

        android:layout_height=""wrap_content""

        android:text=""Increment by 1"" >

    </Button>

    <Button

        android: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 {

        @Override

        public 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."");

        }

    };

    @Override

    public 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();

    }

    @Override

    protected 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."");

        }

    }

    @Override

    protected 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.

    @Override

    public IBinder onBind(Intent intent) {

        return mMessenger.getBinder();

    }

    class IncomingHandler extends Handler { // Handler of incoming messages from clients.

        @Override

        public 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 Intege

                mClients.get(i).send(Message.obtain(null, MSG_SET_INT_VALUE, intvaluetosend, 0));

                //Send data as a String

                Bundle 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);

            }

        }

    }

    @Override

    public 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 notification

        CharSequence text = getText(R.string.service_started);

        // Set the icon, scrolling text and timestamp

        Notification notification = new Notification(R.drawable.icon, text, System.currentTimeMillis());

        // The PendingIntent to launch our activity if the user selects this notification

        PendingIntent 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);

    }

    @Override

    public 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);

        }

    }

    @Override

    public 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;

    }

}