Android Local Service

// The service is in the same process as the visitor, so it is called the local service // Visitor: package cn.com. localquery; import cn.com. service. ILocalQuery; import cn.com. service. localQueryService; import android. app. activity; import android. content. componentName; import android. content. intent; import android. content. serviceConnection; import android. OS. bundle; import android. OS. IBinder; import android. view. view; import android. view. view. onClickListener; import android. widget. Button; import android. widget. textView; // visitor (client) Summary: // core objective of the client (MainActivity here): To get the Binder object returned by the service, then use this Binder object to call the related methods in the service // steps: // 1 Write A LocalQueryServiceConnection class to implement the ServiceConnection interface // LocalQueryServiceConnection implements ServiceConnection // 2 create the LocalQueryServiceConnection Class Object conn. then use Context to activate the service and establish a connection with the service // that is, this. bindService (service, conn, this. BIND_AUTO_CREATE); // 3 LocalQueryServiceConnection class Public void onServiceConnected (ComponentName name, IBinder service) // The method is a callback Method !!!! After a connection is established between the client and the service, the public IBinder onBind (Intent intent) () method // returns an IBinder object to the client. this IBinder object is the service in method // public void onServiceConnected (ComponentName, IBinder service) // 4 call the method in the service using the IBinder object returned by the server // note: // 1 the conn object is used for binding and unbinding. Its class implements the ServiceConnection interface. // 2 note that you should not only rewrite the onCreate () of MainActivity to establish a connection with the service, and rewrite the onDestroy () method of the Activity! So that when the Activity exits, close the connection with the service // 3. Why do I need to define an interface in this small application? // Because the service returns a Binder object to MainActivity, MainActivity receives this object. This object is an internal class object in the service. // But generally, internal classes are private. Therefore, in MainActivity, it is impossible to add an internal class object to receive this object. // Therefore, an interface is defined here ---> used to receive the Binder object. in this way, the business is abstracted as an interface. public class MainActivity extends Activity {TextView numberTextView; TextView resultTextView; Button button; LocalQueryServiceConnection conn = new LocalQueryServiceConnection (); ILocalQuery localBinder; // The Binder object public void onCreate (Bundle savedInstanceState) {super. onCreate (savedInstanceState); setCont EntView (R. layout. main); numberTextView = (TextView) findViewById (R. id. number); resultTextView = (TextView) findViewById (R. id. result); button = (Button) findViewById (R. id. button); button. setOnClickListener (new ButtonOnClickListener (); Intent service = new Intent (this, LocalQueryService. class); // use Intent to activate the service bindService (service, conn, this. BIND_AUTO_CREATE); // start the service when the Activity starts} private class ButtonOnClic KListener implements OnClickListener {public void onClick (View v) {String number = numberTextView. getText (). toString (); String result = localBinder. queryByNumber (Integer. valueOf (number); resultTextView. setText (result) ;}// rewrite the onDestroy () method of the Activity to close the connection to the service when the Activity exits. protected void onDestroy () {unbindService (conn ); super. onDestroy ();} // receives the bound service and disconnects the private final class LocalQueryServiceConnection im Plements ServiceConnection {public void onServiceConnected (ComponentName, IBinder service) {localBinder = (ILocalQuery) service;} public void onServiceDisconnected (ComponentName name) {// when the Activity executes onDestroy, this method calls localBinder = null ;}}// server: package cn.com. service; import android. app. service; import android. content. intent; import android. OS. binder; import android. OS. IBinder; // Local SERVICE Summary: // 1 Custom Service class Local QueryService inherits from Service // 2 to write a custom internal class LocalQueryBinder to implement the business interface, and inherits from Binder // 3 to override the public IBinder onBind (Intent intent) method of the Service, returns an IBinder object. that is, the LocalQueryBinder class Object public class LocalQueryService extends Service {private String [] names = new String [] {"Xiao Ming", "Xiao Wang", "Xiao Yang", "Xiao Li "}; localQueryBinder localQueryBinder = new LocalQueryBinder (); @ Overridepublic IBinder onBind (Intent intent) {return localQueryBind Er;} // queryByNumber is the method in the service. Generally, the service is abstracted as an interface and then implemented, for example, here. Private final class LocalQueryBinder extends Binder implements ILocalQuery {// Binder implements the IBinder interface public String queryByNumber (int number) {return query (number ); // call the internal method of the Service} public String query (int I) {// internal method of the service if (I> 0 & I <5) {return names [I-1];} return "query error. Enter" ;}}// API: package cn.com. service; public interface ILocalQuery {public String queryByNumber (int number );}