设计并实现一个LogService，应用开发时可以打印log到视图（TextView）中显示
本文将设计并实现项目LogService，通过LogService，在开发应用时可以打印log到窗口中显示。
项目源码下载地址：http://download.csdn.net/detail/guggy/4998148
Log Watcher窗口截图：
LogService包括以下3个部分：
1. service 它负责接收客户应用的log信息，并把它发给activity显示。支持多个客户应用同时打log。在AndroidManifest.xml中声明为：
public class LogService 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>(); NotificationManager mNM; @Override public void onCreate() { mNM = (NotificationManager)getSystemService(NOTIFICATION_SERVICE); // Display a notification about us starting. showNotification(); } @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(LOG_PRINT); } protected void sendMessage(int msgType, String obj) { Message msg = Message.obtain(mHandler, msgType); msg.obj = obj; msg.sendToTarget(); }// BEGIN_INCLUDE(exposing_a_service) @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 (ILogy.class.getName().equals(intent.getAction())) { return mLogyBinder; } 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 Log interface to the service. */ private final ILogy.Stub mLogyBinder = new ILogy.Stub() { public void printf(String text) { sendMessage(LOG_PRINT, text); } };// END_INCLUDE(exposing_a_service) @Override public void onTaskRemoved(Intent rootIntent) { Toast.makeText(this, "Task removed: " + rootIntent, Toast.LENGTH_LONG).show(); } private static final int LOG_PRINT = 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) { case LOG_PRINT: { // Up it goes. String text = (String)msg.obj; // Broadcast to all clients the new value. final int N = mCallbacks.beginBroadcast(); for (int i=0; i<N; i++) { try { mCallbacks.getBroadcastItem(i).printCallback(text); } catch (RemoteException e) { // The RemoteCallbackList will take care of removing // the dead object for us. } } mCallbacks.finishBroadcast(); } 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, Binding.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); } // ---------------------------------- /** * 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. */ // BEGIN_INCLUDE(calling_a_service) public static class Binding extends Activity { /** The primary interface we will be calling on the service. */ IRemoteService mService = null; 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.log_service_binding); mCallbackText = (TextView)findViewById(R.id.callback); bindService(new Intent(IRemoteService.class.getName()), mConnection, Context.BIND_AUTO_CREATE); mIsBound = true; } /** * 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); // 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_started, 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; // As part of the sample, tell the user what happened. Toast.makeText(Binding.this, R.string.remote_service_stopped, Toast.LENGTH_SHORT).show(); } }; 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); mIsBound = true; } }; 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); mIsBound = false; } } }; // ---------------------------------- // Code showing how to deal with callbacks. // ---------------------------------- /** * This implementation is used to receive callbacks from the remote * service. */ private IRemoteServiceCallback mCallback = new IRemoteServiceCallback.Stub() { public void printCallback(String text) { mHandler.sendMessage(mHandler.obtainMessage(LOG_PRINT, text)); } }; private static final int LOG_PRINT = 1; private Handler mHandler = new Handler() { @Override public void handleMessage(Message msg) { switch (msg.what) { case LOG_PRINT: String text = mCallbackText.getText().toString(); mCallbackText.setText(text + (String)msg.obj); break; default: super.handleMessage(msg); } } }; }// END_INCLUDE(calling_a_service)}